Guide to Protective Coatings: Inspection and Maintenance Tom N. Bortak
United States Department of the Interior Bureau of Reclamation Technical Service Center
September 2002
Acknowledgments Several Reclam ation em p loyees help ed p r ep a r e t h is g u id e, a n d th eir con tr ib u tio n is gr ea tly ap p re ciate d . The se p eo p le ar e Ku rt F. von Fay, m aterials engineer , w ho set u p fu n d in g an d s h ow e d g re at p a tie n ce ov er th e w r i tin g i n t erv al; D . Th o m as (T o m ) Jo h n son, m ater ials en gine er, for h is corr osion exp ertise co n t r ib u t i on ; G r e g o r y J. M y e r s a n d R ich a r d A . Pe p in , m a t e rials en g in eerin g tech n ician s, for th eir initial rev iew in ferretin g ou t obv iou s
er r or s; an d Ro b er t Ro od , ed ito r , for h is n u m e r o u s “ I d o n ' t u n d e r s ta n d ” co m m e n t s th a t forced m e into w riting a clearer, m ore concise, a n d u n d er st a n d a b le d ocu m en t. A d e b t o f g r a tit u d e is ex p r e ss ed t o N A C E Inter n ation al, Society of Pro tective Co ating s, a n d U n iv er sit y of M iss ou r i-Ro lla, C oa tin g In s t it u t e fo r p r o v id in g a l l t h e co u r s e s a n d references that m ad e this guid e p ossible.
Preface
In r e c en t y e a r s , co a t in g t e ch n o lo g y h a s ch an g ed d ra m at ically . Th e d riv in g for ce b e h i n d t h e ch an g e h as b een reg u latio n s affecting the en vironm ent an d p ersonn el h e a l t h a n d s afety . F o r ex am p le, reg u lations r e la t ed t o d u s t p a r t icle s fr o m a b r a siv e b la s tin g , vo latile org an ic com p ou n d (VOC ) em ission s, a n d h a z a r d o u s m a t e r ia ls su ch a s le a d , ch r o m a t e, a n d o t h er h e av y m e t a ls h av e chan ged . Before the late 1980s, coating m aterials w ere m or e t ole ra n t o f less th an op tim u m su rfa ce p r ep a r a tio n con d itio n s b eca u se p a in t form u lation contained high VOC s to allow the m ater ial to w et or p en etr ate st eel su rfaces. The m o s t su cce ssfu l w e r e r ed le ad p r im e r s a n d v in y l r es in s ; h o w e v e r , r eg u la tio n s h a v e d isco u r a g ed th e u se of t h es e m a te r ials . Pa in t m an u factu rers reform u lated their coatings to com p ly w ith ne w regu lation s. This has led to th e d ev elo p m en t o f a w id e v ar iety of h igh -tech co a tin g m a te r ials th a t a r e m u ch m or e s en sit iv e t o su r fa ce p r e p a r a t io n a n d e n v i r o n m e n t a l a p p lica t io n p r a ct ice s . T h e Fe d e r a l H ig h w a y A d m in ist r a tio n h a s e st im a te d th a t u p to 80 p e r c en t o f all p rem atu r e co atin g failu res on
b r id g e s tr u ctu r es ar e p a r tia lly or com p let ely c a us e d by d e fic ie nt s ur fa c e p re p a ra tion or a p p lic a tion p ra c tic es . Se ve ra l orga niz a tion s s u c h a s th e A m e r ica n S ocie t y fo r T es t in g a n d M aterials, N A CE Intern ational, and the Society for Protective Co atings hav e issued con se n su s st an d ar d s to m in im ize su rfa ce p rep ara tion a n d ap p lication ina d equ acies. Th is g u id e is n ot in te n d ed to b e a ll e n c o m p a s sin g ; r a t h e r , it is in t e n d e d t o b e an in t r o d u ct io n t o sp e c ific r e fe r e n ce st a n d a r d s an d te st p ro ced u re s r ela te d to su rfa ce p r e p a r a t i on , a p p lica t io n , te s tin g , a n d m a in t e n a n c e o f co a t in g s . E xp la n a t io n s a n d p r oc ed u r es of r efe r en ce s ta n d a r d s cit ed w ith in this gu id e a re a bbre via te d to d e ve lop a w o r k in g b a s i s. T h e u s e r is e n co u r a g e d t o r e ad r e fe r e n ce st a n d a r d s a n d c o a tin g m a n u a ls fo r a m or e t h or ou g h u n d er st a n d in g . Th e g u id e focu se s o n n ew con st r u ctio n coa tin g s, ex ist in g in f r a st r u c t u r e co a t in g m a in t e n a n c e , a n d ga lva niz e d c oa tings of fe rrou s s ubs tra te s for m et a lw or k ite m s co a te d in th e fie ld . In ge ne ra l, this gu id e follow s the Bu re a u of Re clam a tio n ’s (Re clam a tio n ) coa tin g g u id e sp ecifications.
Contents
Page Ch ap te r I— In tro d u cti o n an d Back g ro u n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. St a n d a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Coating References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. T er m in o lo g y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. C o r ro s io n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Se r v ice Ex p o s u r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 1 1 1 1 5
Cha pte r II— M a terials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. C o m p o n e n t s o f C o a t in g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Coating Typ es . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. G e n e r ic C o a t in g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 5 7 7
C h ap te r III— S p e ci f icati o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. Con stru ction Sp ecification Institu te . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10. R e clam atio n C o atin g S p ecificatio ns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. Coating Tabu lations an d Categor ies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. M an u factu rer's Prod u ct Data an d Ap p lication She ets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13. A d d e n d u m s a n d M o d ifica tio n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11 11 11 12 13 14
Cha pte r IV — I n s p ecto r's R o le . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14. Prim ary Resp onsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15. Daily Respo nsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16. M a t e r ia l A p p r o v a l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17. Do c u m en tatio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18. In st r u m en ts , Ga u g es , an d To ols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19. Su b s trate In s p ectio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20. Coating Insp ection Ch ecklist Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21. P re coa tin g C on fer en ce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15 15 15 16 16 17 17 17 17
Ch ap te r V — M ate rial S to rag e , Co n tain e rs, an d S h e lf Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22. St o r ag e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23. C o n t a in e r s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24. Sh elf Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19 19 19 19
C h ap te r V I — S u rf ace Pre p arati o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25. Su rface Conta m inan ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26. P re su r fa ce Tr ea tm e n t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27. A b r a s i v e Bla s t M a t e r ia l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28. N ozz le Blast Pressu re . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29. Su r f ace P rep aratio n M eth o d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30. P h o t o g r a p h i c In s p e c tio n St a n d a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31. Al t ern ativ e Su rface P rep aratio n M e thod s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21 21 23 23 24 25 27 30
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Page C h ap te r V I I— En v i ro n m e n t al Co n d i ti o n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 32. E n v ir o n m e n t a l Fa ct o r s A f fe ct in g C o a t in g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Cha pte r VI II— A p p licatio n a n d C u rin g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33. Ap p licatio n T em p eratu re an d H u m id ity R e stric tions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34. C o a t in g L a y er s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35. M ixin g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36. Ap p licatio n M eth o d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37. A p p l ica t io n T ech n i q u e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38. D r y in g , Reco atin g , an d C u r in g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35 35 35 36 36 39 39
Cha pte r IX— Field I n s p ectio n a n d T es ti ng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39. Su rface Prep aration Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40. W et Film Th ickn es s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41. H ard ened Painted Su rfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42. De stru ctiv e T es t M eth o d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
41 41 42 42 45
C h ap te r X— M a i n te n an c e C o ati n g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43. De f in itio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44. Pu rp ose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45. R isk E v alu atio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46. In sp ectio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47. Toxic-Based Paints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48. W ork er Pr otection from Toxic-Based Paints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49. L e a d E x p o s u re L ev els b y Rem o v a l M e thod s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50. C o r rectiv e A ctio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51. M a t e r ia l Se le ct io n F act o r s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52. Sch ed u lin g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47 47 47 47 47 49 50 50 51 52 52
Cha pte r XI— G a lv a n izin g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53. Ga l v an izin g M eth o d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54. Z in c C or r os ion an d Ser v ice L ife . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55. Z in c C h em i ca l Re actio n s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56. Con tam inan ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57. Su r f ace P rep aratio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58. C o a t in g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
53 53 54 54 54 55 57
Ch ap te r XII— Co ati n g Failu res . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59. M a t e rial Selectio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60. Fo r m u latio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61. Ad hes io n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62. Su bstrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63. Ap p licatio n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64. D e s ig n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65. Exterior Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
59 59 59 61 61 62 63 67
Bi b li o grap h y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
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Appendices A B C D E F G H I J K L M
Or gan izationa l Sou rces for Stan d ard s and References Read ing Sources Insp ection Ch ecklist Re fer en ce St a n d a r d s C ite d in G u id e Inspection Equ ipm ent Exam p le of Insp ection Daily Ch eck Sheet P r oc ed u r e fo r D et ect in g M ois tu r e a n d O il in C om p r es se d A ir (A STM D 4285) Pr o c e du re fo r D etectin g C h lo rid es and Solu ble Sa lts in A bra s ive s by C on d u c tivity M e thod Proced u res for Detecting Ch lorid e Ion in W ater P r o ce d u r e s fo r D e te r m i n in g Bla s t C le a n in g A i r P r es su r e D e t er m in a t io n o f E n v ir o n m e n t a l Fa ct o r s Proced u res for Detecting Ch lorid e Salts on P rep ared or Existing Su rfaces D eter m inin g Su rface P ro file of Blast-Clean ed Steel Usin g Rep lica Tap e (N A C E RP 0 28 7 o r A S T M D 4 41 7, M e thod C ) P r oc ed u r es for M ea su r in g W et Film Th ick n es s (A STM D 4414) W e t Film T h ick n es s F o rmu las an d Exa m p le C a lcu la tions P r oc ed u r es for D r y Film Th ick n es s G a u g es (SSPC -P A 2) an d Exa m p le P r oc ed u r es for D isco n tin u ity (H olid a y ) Tes tin g (N A C E RP 0188) P r oc ed u r e fo r M ech a n ical (P u lloff) A d h es ion Te st in g (A STM D 4541; An n ex A 2) P r oc ed u r e fo r H y d r a u lic A d h es ion Te st in g (A STM D 4541; An n ex A 3) P r o ce d u r e fo r M e a s u r in g D r y F ilm T h ick n e s s b y D e s tr u c t iv e M e a n s W i th T o o k e G a u g e (A STM D 4138) Pr o c e du res fo r SSP C-V IS 2 (2 00 0 R evis ion) P r o ce d u r e to D e t er m in e t h e P r es en c e o f So lu b l e Le a d a n d In s o lu b l e Le a d C h r o m a t e in C o a t in g s P r o ce d u r e to D e t er m in e t h e P r es en c e o f C h r o m a t e in C o a t in g s D et er m in a tio n of T ox ic M et a ls in H a r d en ed P a in t
N O P Q R S T U V W X
Figures Figure 1
Page C o m p o n e n t s o f co a t in g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Tables T able 1 2 3 4 5 6 7 8 9 10
Page N u m ber of spot m easu rem ents based on total coated sur face area . . . . . . . . . . . . . . . . . . . Typ ical and m axim u m lead exposu re levels in m icrogra m s per cubic meter b y rem o v al m eth o d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G alv an izin g m eth o d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fo r m u l a tio n -r e la t ed fa ilu r e s fo r o r g a n ic co a t in g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fo r m u l a tio n -r e la t ed fa ilu r e s fo r in o r g a n i c co a t in g s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ad hesion-related failu res . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Su bstrate-related failu res . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ap p lication-related failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design-related failu res . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Failures related to exterior forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44 51 53 60 61 62 63 64 66 67
ix
Chapter I Introduction and Background Pro tective or ind u strial coating s are th e p r i m a r y m ean s em p lo y ed b y th e Bu reau of R e cla m a t io n (Reclam atio n ) to co n tro l co r r os ion . H y d r a u lic st r u ctu r es ar e t y p ically co n s t ru c t ed w it h fe r r o u s m e t a ls a n d a r e su b je ct t o co rro s io n . M an y Reclam atio n s tr u c t u r e s a r e 50 y e a r s o ld , a n d s o m e a r e a p p r o a ch i n g 100 y e a r s. T h e se st r u c tu r e s a r e exp ected to continu e fun ction ing into th e fo r e se e ab le fu t u r e . P r o te ct iv e co a t in g s in flu en ce t h e life, sa fety , op er at in g efficien cy , ap p ear an ce, an d econo m y of th ese stru ctu res. A coa tin g 's e ffect iv en es s d ep en d s o n se lect in g coating m aterial that correctly m atches th e in te n d ed se r v ice ex p o su r e fo r th e m eta lw or k . In t h e p a s t, co a t in g m a t e r ia l s e le ct io n w a s b a se d o n Fed eral, m ilitary , o r R eclam ation form u lations; how ev er, nea rly all these fo r m u l a tio n s h a v e b e en w it h d r a w n . T od a y , s e le ct io n i s b a s e d o n s e r v i ce e xp o s u r e t y p e a n d th e r es u lts of a ccele r a te d p er for m a n ce t es tin g of com m ercially av ailable p rod u cts.
1. Standards.— F o rm erly , Reclam atio n p r o v i d e d n arra tiv e s tan d ard s an d d efin i tions fo r sp e c ify i n g m aterials, s u rface p r ep aration, a p p lica t io n , a n d in s p e c tio n . H o w e v e r , Reclam ation n ow ad op ts ind u strial stand ard s, w h e r e a p p licab le. T h e fo llo w in g o r g an iz a tions (se e a p p e n d ix A fo r ad d res s es , telep h o n e nu m bers, and w eb sites) are referenced thro u gh ou t this guid e: •
A m e rica n So cie ty fo r Te stin g an d M a te r ials (A STM ).
•
N AC E Intern ational (form erly called N atio n al A s s o ciatio n o f C o rro s ion En g in ee r s) (N A C E).
•
So cie t y fo r P r o te ct iv e C o a tin g s (form erly called Steel Stru ctures P a in tin g C ou n cil) (SSPC ).
2. Coating References.— Th e co atin g insp ector is no t exp ected to h av e th e exp ertise of a coa tin g ch em ical fo r m u lat or or a co a tin g e n g i n e e r , b u t sh o u ld b e r e a so n a b l y fa m ilia r w ith th e m a te r ials b ein g ap p lied . Th is g u id e is in te n d ed to p r ov id ed th e m os t b a sic b ack g ro u n d on g en er ic m at er ial ty p es , su rfa ce p re p a ra tion, a pp lic a tion, a nd ins p e ction m eth od s. The r ead er is en cou rag ed to p u rsu e r ela ted co a tin g r efe r en ce s lis ted in ap p en d ix B.
3. Terminology.— The w ord “coating ” is a gen eric term an d inclu d es “p aint.” In th e m os t ge ne ra l te rm s , a “ c oa ting” is prote c tion a g a in s t co r r o s io n , w h e r e a s a “ p a i n t ” m a y ha v e a d d itiona l prop e rtie s su c h a s color or u l t ra v io le t s cr e e n in g p ig m e n t s. T h e te r m s “coating ” an d “p aint” are u sed interchang eably throu gh ou t this guid e. O th er ter m s often u sed toge th er a re “ coating s” an d “linin gs.” In g en eral, w he n d escribing the interior su rfaces of p ipes or tan ks, the term “ linings ” is u s e d to ide n tify the inte rior su rfaces an d “coatings” is u sed to iden tify th e ext er io r su r fa ce s.
4. Corrosion.— The p rima ry re a s on for c oa ting s te e l is to pre ve n t corros ion. C orrosion o f m e t a ls is a n e le ct r o ch e m ica l r e a ct io n t h a t c a n be controlle d by inte rfe ring w ith on e or m or e o f th e fo u r r eq u ir ed ele m en ts of a co r r os ion cell: (1) an od e (co r r od in g ar ea ); (2) cath od e (non corrod ing ar ea); (3) electrolyte (w a te r or m ois ture in a tm os ph e re , im m e rs ion, or soil); an d (4) m etallic p ath (betw een tw o d iffe r en t m eta ls o r w ith in th e sa m e m eta l). Eliminate an y on e of the four requ ired e le m e nts a nd the c orros ion p roc e ss w ill s to p. The m os t com m on typ e s of c orrosion e nc oun te re d on R e cla m a tion fe rrous m etalw ork ar e:
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Guide to Protective Coatings: Inspection and Maintenance (a) U niform Co rrosio n.— C o r r o s io n t h a t oc cu r s m or e o r les s u n ifor m ly an d r es u lts in ru st and m etal loss over th e m etal sur face. (b) G alvanic C orro sion.— C o r r o s io n t h a t occu rs on the m ore active m etal of tw o d issim ilar m etals that are electrically coup led to g eth er in th e sa m e electr o ly te (e.g ., w a te r ). The m ore active m etal w ill corrod e. (c) Crevice Co rrosio n.— C rev ice co r ros ion is a for m of lo ca lize d cor r os ion th a t o ccu r s in c r e v ic es w h ere th e en v iro n m en t d iffers from th e su r r ou n d in g bu lk en v ir on m e n t . Th e d iffe r e n t e n v iro n m en ts res u lt in co rro s ion b e c a u se o f d ifferen ces in co n cen tratio n (e.g ., oxy g en , p H , an d fer r ic ion s). If th er e is a n o x y g e n co n cen tratio n d ifferen ce, co rrosion w ill pr oceed at crev ices w h ere th ere is less o xy g en th a n in th e en v ir on m e n t su r r ou n d in g the crev ice. Crev ices are form ed w he n tw o su rfa ces ar e in p ro xim ity to on e a n ot h er , su ch a s w h e n t w o m etal s u rfaces are ag ain s t one a n o t h e r , w h en a g as k et is ag ain s t a s u rfa ce , or w h en an g le ir o n s a r e p la ce d b a ck to b a ck . Cre vice corro sion can occu r u nd er d ep osits (e .g ., b a r n acles , d irt, g reas e, an d s lim e) on a m et al s u rfa ce. (d) Pittin g corrosio n.— A form of localized co r r os ion w h er e t h e d ep th of p en et r a tio n is g r e a t er t h a n t h e d ia m e t er o f t h e a ffe ct e d a r e a .
red ep osit of th e cath od ic con stitu en t. The elem en t rem ove d is alw ays an od ic to the m atrix. With d ealloying , there is n o m etal loss, d im en sion ch an ges, cracks, or gr oov es; how ever, the affected area m ay be ev iden t because of a color cha ng e. The affected area b e co m e s lig h t e r , p o r o u s , a n d lo s e s it s o r ig in a l m ech a n ical p r op er tie s (i.e., it b eco m es b r itt le a nd los e s te ns ile s trength ). Tw o c omm on form s of d ealloying ar e: De zincifica tion.— The s e le ctive d is s olu t ion of zinc from brass alloys. It is recognized by a c olor c ha nge (e .g., from its origina l ye llow b r a s s co lo r t o a d i st in c tly r e d , co p p e r y a p p ea r a n ce). De grap hitization.— Th e se le ct iv e d issolu tion o f iron from som e cast iron s, u su ally gra y cast iron s. It norm ally p roceeds u n ifo r m ly in w a r d f r o m t h e s u r fa ce , le a v in g a p orou s m a trix a lloy tha t is c omp os e d m os t ly of ca r b o n . D e g r a p h i t iz a t io n c an b e r e co g n iz e d b y a c ha nge from a n origina l s ilve r-gra y c olor t o a d ar k g ra y . Th e a ffecte d m et al ca n b e e as ily cu t or p ierced w ith a k nife.
5. Service Exposure.— Coatings are sp ecified by ser vice exposu re or th e env ironm en t the co a t in g w ill b e su b je ct to . T h e fo llo w in g a r e t h e b a sic s er v ice e xp o s u r e s d e fin e d b y R e cla m a tion:
(e) Cavita tion corro sion.— The m etal loss c a u se d b y th e fo rm atio n an d co llap s e o f va p or bu bb les in a liqu id n ear a m etal su rface. The a p p e a r a n ce o f ca v it a tio n is sim ila r t o p i t tin g , e x ce p t t h a t p i t te d a r e a s a r e clo s e ly s p a c e d a n d the su rface is consid erably rou gh ened .
•
•
Bu r ia l
(f) Erosion-corro sion.— The accelerated m etal loss from an initial corro sion m echa n ism a s so cia t e d w it h h i g h - v e lo cit y flo w s a n d abrasion. Erosion-corrosion is cha racterized by g roov es, gu llies, w aves, and rou nd ed r id g e s o r v a lle y s a n d e x h ib it s a d ir e ct io n a l flo w p a t t e r n .
•
Im m e rs ion
•
C om p let e, p a r tia l, or flu ctu a tin g im m ersion cond ition s
•
A tm osp he ric exp osu re su bject to cond en sation , high h u m id ity, sp lash, or spray
•
The follow ing s u be xpos u re cond it ions m ay ap p ly to any of the abov e:
(g) Dealloying o r Selective L eaching.— Th e s e le ct iv e r e m o v a l o f o n e o f t h e e le m e n t s o f a n alloy b y either p referen tial attack or com p lete d is so lu t i on o f t h e m a t r ix , fo llo w e d b y
2
A tm os p h er ic
N N
In d o o r s Ou tdoors
Introduction and Background
N
D i r ect su n l ig h t o r U V : s e v e r a l co a tin g s, su ch as ep ox ies , w ill d eteriorate by cha lking w hen exp osed to su nlight.
N
Ch em ical resistance: exposu res m a y in clu d e acid ic o r a lk alin e co n c en t r a t io n s , in d u s t r ia l s m o g , a cid r a in , sew a g e, o r sp ecific chem icals.
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Chapter II Materials C o a t i n g fo rm u latio n is g en erally b as ed on organ ic, inorgan ic, p olym er, an d co-p olym er ch em ist r y . It is n ot th e in te n tio n of t h is chap ter to d iscu ss coating chem istry b u t, r a th er , to p r ov id e a b a sic k n ow led g e o f coa tin g com p onen ts and gen eric coating typ es sp e c ifie d b y R eclam atio n .
6. Components of Coatings.— A ll or g a n ic co a tin g s co n sis t of t h r ee b a sic co m p o n en ts: (1) so lv en t, (2) r es in , an d (3) p ig m en t. N ot all coating s contain solven t and p igm ented co m p on en ts . Th er e a r e s olv en t-fr ee (100 p ercent solids) coating s an d clear, p igm en tfree coating s, bu t n ot resin -free coat ings. C oa tin g ch em ical fo r m u lat or s co m m on ly gro u p solvent, resin, and p igm en t com p on en ts in t o t w o g e n e r a l ca t eg o r ie s. T h e fir s t ca t eg o r y co m b in es t h e so lv en t a n d th e r esin to g eth er . Th e s olv en t p or tio n is ca lled th e “ v ola tile veh icle,” an d the r esin p ortion is called th e “n on volatile veh icle.” The com bination of the so lv en t a n d th e r es in , w h er e t h e r es in is d is so lv e d in t h e s o lv e n t , is ca lle d t h e “ v e h i cle .” The secon d category is the p igm en t. Pigm en ts are ad d itives th at im p art sp ecific pr op erties to the coating an d are su bd ivided into tw o
So lv en t (Volatile)
Re sin (No nv olatile)
g e n e r a l ca t e g o r ie s : (1) co lo r a n d (2) in e r t a n d r ein for ced . Figu r e 1 illu st r a te s t h e r ela tio n sh ip of these com p on en ts. W hen a coating is ap p lied , the solvent ev a p or a te s d u r in g th e cu r in g p r oc es s, lea v in g only the re s in a n d the p igm e nt c omp one n ts on t h e s u b s t r a te . T h e r e m a i n in g r e s in a n d p ig m en ts ar e s om et im es calle d th e “ co a tin g s olid s ,” a nd the y form the p rote ctive film for co rr osio n p r ote ctio n . (a) So lvent.— Or gan ic solven ts are form u lated in t o co a t in g s t o p e r f or m t h r e e e ss e n t ia l fun ction s: (1) dissolve the r esin com p on en t; (2) co n t r o l e v a p o r a t i o n fo r film fo r m a t io n ; a n d (3) re d u c e the c oa ting v is cos ity for e a s e of a p p licat ion . Solv en ts w ill als o a ffect d r y film a d h es ion an d d u r a b ility coa tin g p r op er tie s. In g e n e r a l, r e sin s t h a t a r e le ss so lu b l e w i ll r e q u i re either m ore solven ts or stron ger solven ts to d issolve th e resin s. T h e te r m s “ s o lv e n t s ” a n d “ t h in n e r s ” a r e o ft e n u s e d i n t er ch a n g e a b ly , b u t t h e r e ar e d ist in ctio n s w ith in an d b etw een th e tw o te r m s. The term “solvent” can im p ly tw o d ifferen t u sa g es : (1) th e s olv en t o r so lv en t b len d s in the coating form u lation a t p red eterm ined
C olor Pigm en ts
Ve h icle
In e rt a n d Reinforced
P ig m e n t
C oa tin g Figure 1.—Com ponents of coatings.
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Guide to Protective Coatings: Inspection and Maintenance co n cen tr a tio n lev els ; or (2) clea n in g so lv en ts in st r on g con cen tr a tio n st r en g th for clea n in g b r u sh es, r o lle r s, h o se s, a n d oth er eq u ip m en t. The u sage of the ter m “th inn er” (a thin n er is a solven t) is m ost often associated w ith the c o a tin g a p p licato r ad d in g a th in n er to a co a tin g con ta in er (n or m a lly ab ou t 1 p in t thin ne r to 1 gallon of coating ) to red u ce the v isco sit y for ea se of a p p licat ion . A d d in g thinn er to a coating in the field is often called “ fie ld th in n in g .” Th e m a n u fact u r er ’s p r od u ct d a ta sh ee t w ill s p e cify a t h in n e r a n d a m a x im u m a m o u n t to b e u sed for each coating typ e. Use of a thinner n o t r e co m m e n d e d b y t h e m a n u fa ct u r e r c a n c a u se n u m ero u s ap p licatio n p ro b lems o r p r e m a t u r e failu res s u ch as s ep aratio n o f c o m p o n e n ts , co ag u latio n , to o fas t o r to o s low d r y i n g , c h a n g es in flo w ch aracteris tics, or liftin g of p r ev iou s co a ts . Th e fo llow in g com m on th inners ar e u sed w ith th e associated gen eric coatin g ty p es: T h in n e r s
C o a t in g s
M ineral sp irits
O ils an d alk y d s
Ar om atics (ben zene, xylol, tolu ole)
Co al tar ep oxies, alkyd s, chlorina ted rubbers
Keton es (MEK, M IBK)
Vinyls, ep oxies, u rethan es
A lcoh ols (iso p r op y l)
P h en olics , in or g a n ic zin cs
W ater
A cry lics, s o m e in or g an ic zin cs
So lv e n t s p r o d u ce v a p o r s t h a t a r e h e a v ie r t h a n air and w ill collect in tank b ottom s or confined a r ea s. Th e k et on es h a v e t h e lo w es t fla sh p oin t of the or gan ic solven ts; how ever, any solven t in t h e r i g h t co m b in a t io n w it h a ir ca n c r e a te a n e x p l o siv e co m b in atio n . Fed er a l, Stat e, co u n ty , city , an d loca l air q u a l it y co n tro l d is tricts reg u late th e am ou nt of v o la tile or g a n ic so lv en ts (VO C ) in co a tin g s. A s the coating cures, VOC s evap orate into the
6
a tm os p h er e a n d r ea ct w ith su n lig h t a n d air p o llu t a n t s to fo r m o z o n e , a k n o w n h u m a n h ea lth h a z a r d . In r es p on se , coa tin g m a n u fact u r er ’s h a v e r efo r m u lat ed th eir p rod u cts w ith low er solvent content to m eet cu rre n t VO C r egu lations. R ecla m a t io n s p e cifica t io n s r eq u i r e th e co a t in g s to m e e t the V O C re gu la tions “ in-the -ca n” or “ a s-m a n u fact u r ed ” b efo r e fie ld th in n in g . Field thin nin g of a coating tha t w ill exceed the r eg u la te d VO C m a xim u m is n ot p er m itte d . Reclam ation sp ecifies coating s based on the cu rr en t En v iro n m en ta l Pr ot ect ion A g en cy (EPA) VO C lim its. (b) Resin.— The resin (frequ ently called b in d er ) is th e film for m in g com p on en t o f a co a t in g . Re s in s a r e t y p i ca lly a h i g h m o le cu la r w e ig h t s olid p o l y m e r t h a t fo r m s la r g e rep eatin g m olecu les in th e cu red film . The p rim ary p u rp ose of the resin is to w et the p igm ent p articles and bind the p igm ent p articles together a nd to the su bstrate (hen ce, the te rm “ bind e r” ). The re s in im p a rts m ost of the c oa ting p rop e rtie s . The va rious typ e s o f r e s in s fo r m u la t e d i n a co a t in g w ill d is p l a y d istinct p rop erties. These p rop erties are: • • • • • • •
M e ch a n ism a n d t im e o f cu r in g P e r fo r m a n c e in s e r v ice e xp o s u r e ty p e P e r fo r m a n c e o n s u b s t r at e t y p e C o m p a t ib ilit y w i t h o th e r co a t in g s Flexibility an d tou gh n ess Ext er ior w ea th er in g A d he s ion
N o s ingle re s in c a n a c hie ve a high d e gre e o f su cces s in m ee tin g th e a b ov e co a tin g p rop erties w ith w ide v ariations associated w ith ea ch p r op er ty . Th er efo r e, g en er ic coa tin g t y p e s a re g e n e r ally cla s sifie d b y t h e p r im a r y r esin ty p e u se d in th e co a tin g fo r m u la tion . Typ ical resin s ar e acry lics, alky d s, and ep oxy p olym ers. (c) Pigm ent.— P ig m e n t s a r e in s o lu b l e an d a r e t h e h e a v i er s o lid p o r t io n o f a co a t in g t h a t ty p ica lly se tt les t o th e b ott om of th e co n ta in er . P ig m en ts ar e a d d itiv es to th e co a tin g form u la tion th a t im p a rt s pe c ific prop e rtie s t o
Materials ach ieve t h e d esired film p ro p ert ies. Th e fo llo w in g p r o p e r t ie s a r e acco r d e d b y p igm ents, and a brief d escription is prov ided fo r e ach . Co lor.— N a tu r a l ea r th p ig m en ts (k a olin clay, m agn esiu m silicate, calciu m carbona te) p rov id e color stab ility from u ltrav iolet (UV) su nlight d eterioration. N atu ral earth p igm en ts a r e m or e U V s ta b le t h a n sy n th et ic or g a n ic p igm en ts. Opacity.— Titan ium oxide h ides th e s u b s t r a t e o r p r e v i o u s c oa t in g c o lo r a n d p r o t e ct s t h e b in d e r fr o m U V s u n l ig h t d e te rio ra tio n . Wet pa int.— Silica an d talc co n tro l v isco sit y , w et film lev elin g , an d se tt lin g b u t p r o v i d e lit tle h id in g ( op a c it y ) p o w e r . Weath er an d m oisture resistance.— A lu m in u m lea fs a n d m icac eo u s ir on ox id e (M IO ) in cre as e b ar rie r t h ickn es s a n d for ce m o is tu r e t o d e t o u r a r o u n d t h e se p l at e -lik e ad d itive s. Co rrosio n resistance.— Pigm en ts ad d ed to in h ib i tiv e (p rim er) co atin g s im p ed e co rr os ion o f fe r r o u s s u b s trates . P as t fo rm u latio n s in clu d ed ch r o m a te an d lea d p ig m en ts , b u t t h e y a r e se ld o m u s ed to d ay b ecau s e o f en vir on m en tal an d h ealth con cern s. The fo llo w in g c h r o m a t e a n d le a d p ig m e n t s a r e rar ely u sed in cu rre n t coating form u lations: • • • • •
R ed le a d W h i te le a d Basic lead silico-chrom ate Stron tium chrom ate Zinc chrom ate
Th e fo llow in g ar e a ccep ta b le a lte r n a tiv e inh ibitive p igm en ts: • • • • • •
Bariu m m etabor ate Calciu m p ho sp ho silicate Z in c ox id e Zinc p ho sp ha te Zinc m olybd ate Zinc p ho sp ho silicate
Mildew resistance.— M ild e w c id e s p r ev en t m ild e w g r o w t h o n t h e d r y f ilm co a t in g . Skid or slip resistan ce.— A lu m in u m oxid e o r m i n er al a gg re ga te is a d d e d in th e form u lation or ap p lied to the w et film to a ch iev e n on slip su r face s. A lu m in u m ox id e is the b etter choice because m ineral agg rega te m a y b e cr u sh e d u n d e r w e ig h t, p r o vid in g m o istu r e a cce ss to th e su b str ate , a n d p r o m o t in g f u r t h e r c o a tin g d e g r a d a t io n a n d co rr osio n .
7. Coating Types.— The follow ing are th ree ba sic typ es of coatings: (a) Ba rrier.— A coating th at form s a bar rier betw een the m etal sur face an d the electr oly te an d electr ica lly iso la te s t h e m eta l. Exam p les are ep oxies an d coal tar ep oxies. (b) Inh ibitive.— P ig m e n t in a co atin g p r im e r t h a t is slig h t l y so lu b le in w a t e r th a t for m s a ch em ical in h ib ito r an d effe ctiv ely in t e r fe r e s w it h t h e e le ct r o ly t e . E xa m p le s a r e red lead and chrom ate p rim ers (no long er a ccep ta b le). (c) Ga lvanic.— Z in c -r ich p r im e r co a t in g s tha t p rov ide g alvan ic or catho d ic p rotection to fer ro u s m et al (z in c sa crifices itse lf to p ro te ct t h e fe r r o u s m e t a l). G a lv a n i c co a t in g s a r e effe ctiv e o n ly if ap p lied d ir ect ly to b a r e m et a l.
8. Generic Coatings.— Th e fo llow in g g en er ic co a tin g s a n d g en er a l d es cr ip tio n s a r e t y p ically s pe c ifie d by R e cla m a tion: (a) Acrylics.— In w a te r -b or n e a cr y lic coating s, the r esin is d ispersed in w ater to for m a w at er em u lsion . W at er -bo rn e a cry lics are sp ecified for atm osp h eric expo su res as a p r im e r o r t op co a t a n d h a v e e x ce lle n t co lo r a n d gloss retention. Acrylics cure by coalescence. (b) Alkyds.— A l k y d s a r e n o r m a lly n a t u r a l oils (soya, tu ng , styrenate) that h ave been chem ically m od ified to im p rove cu re rate, ch em ical r es ista n ce, an d h ar d n es s. Ph en olicm o d ifie d a lk y d s a r e s p e c ifie d a s a p r i m e r , a n d s ilic one a lkyd s a re s pe c ifie d a s the topc oa t for a tm os ph e ric se rvice e xpos u re s . The y a re not
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Guide to Protective Coatings: Inspection and Maintenance s u i ta b le fo r a lk a lin e (co n c re t e o r m a s on r y ) su r face s o r en v ir on m en ts . A lk y d s cu r e b y air oxid ation of d ry ing o ils. (c) Bitumin ous.— Bit u m in o u s co a t in g s a r e h ea v y -bo d ied m at er ials a p p lied w ith a cu tb ack solven t. They h ave go od m oistu re barr ier re sist an ce a n d fair to g oo d ch em ical r es ista n ce b u t a r e n o t r es is t an t t o so lv e n t s . C o m m e r cia l bitum inou s pr od u cts are sp ecified on a lim ited b a sis b y R e clam atio n fo r p ro tectio n o f alum inu m su rfaces in contact w ith cem en tit iou s m a te r ial o r st ee l an d cop p er cab le w e ld co n n e c tio n s . Bit u m in o u s co a t in g s cu r e b y so lv en t e va p o ra tio n . (d) Ep oxy, Am ine.— A m in e e p o x ie s a r e tw o-com p onen t coatings that are catalyzed (hard en ed ) by an am ine cur ing ag en t to p r o d u ce a h a r d , t ig h t l y b o n d e d , ch e m ica l r esis ta n t (a lk a li, a cid , an d so lv en t) p r o d u ct, b u t t h ey a re m o is tu r e a n d t em p e r a tu r e se n sit iv e d u r i n g a p p licatio n . Th ey are s p ecified for b u r i a l a n d im m e r sio n s e rv ice e xp o s u r e s, b u t th ey w ill fa d e an d ch a lk in d ir ect su n lig h t. Am in e e p o x ies cu re b y ch em ical reactio n. (e) Ep oxy, Polyam ide.— Polyam ide ep oxies are tw o com p onen t coatings that are catalyzed b y a p oly am id e cu rin g ag en t to p ro d u ce su p erior r esistance to w ater an d salt solution s, b u t t h e y d o n o t p r o v i d e t h e c h e m ica l resistance of the am ine ep oxy. Polyam ides h a v e a g r ea te r flexib ility th a n th e a m in e e p o x ie s . T h e y a r e sp e cifie d fo r b u r ia l a n d im m er sio n se r v ice e xp os u r es , bu t t h ey w ill fad e a n d ch a lk in d ir ect su n lig h t. P oly a m id e e p o x ie s cu re b y ch em ical reactio n . (f) Epo xy, Coal Tar.— C o a l t a r ep o x ie s a r e ge n era lly a n am ine o r p olya m id e ep oxy m od ified w ith coal tar pitch r esin to p rod u ce a h i g h -b u ild film t h a t h a s g o o d c h e m ica l resistance and excellent w ater resistance. They h a v e a t e n d e n c y to b e co m e b r it t le w it h a g e a n d d ela m in a te b et w ee n coa ts or b en ea th r ep a ir p a t ch e s . T h e y a r e sp e cifie d fo r b u r ia l a n d im m er sio n se r v ice e xp os u r es , bu t t h ey w ill fa d e a n d ch a l k in d ir e ct su n l ig h t . C o a l t a r e p o x ie s cu re b y ch em ical reactio n .
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(g) Epoxy, Fusio n-Bo nde d.— Fus ionbon d ed ep oxies (com m only called p ow d er coating s) are com p lete coating s in p ow d er form . The re a re tw o ap p lication m eth od s, flu idized -bed an d electrostatic. In the flu i d i z ed -b e d m e t h o d , t h e m e t a l it e m s a r e p r eh e ate d to a fu s io n te m p e r atu r e a n d im m er se d in th e p ow d er -ep ox y so lu tio n . In the electrostatic meth od , the ep oxy p ow d er p a r t icle s a r e ch a r g e d w it h h i g h v o l ta g e , a n d t h e m e t a l it e m i s t h e n s p r a y e d . A ft e r s p r a y in g , the ite m is pla ce d in a n ove n to c ure a t a bo u t 350 to 650 d e gre e s Fa hre n he it (F). Fus ionb o n d e d e p o x ie s a r e s p e c ifie d fo r b u r ia l a n d im m er sio n se r v ice e xp os u r es , bu t t h ey w ill fa d e a n d c h a lk in d ir e ct su n lig h t a n d a r e brittle. A n ew m aterial is fu sion-bon d ed nylon. This ma te ria l is s up e rior to the fu s io nbon d ed ep oxy an d w ill be incorp orated into Re clam a tio n 's sp ecifica tio n . Po w d er coa tin g s cu r e b y fu sio n (h ea t). (h) Ino rgan ic Zinc Prim ers.— In or g a n ic z in c s a r e p r im e r s t h a t in c o rp o r a t e a h ig h loa d ing (p ou nd s pe r ga llon) of m e ta llic z in c for p ig m e n t a t io n ( h e n c e, t h e t er m “ z in c -r ich ” ) a n d a r e e ith er so lv en t o r w a te r b a se d . D ep en d in g on th e s olv en t a n d r es in s u se d , th e co a tin g m ay be a zinc-rich ep oxy o r u reth an e. Th ese coating s are exclusively p rim ers because th ey p rovid e galvan ic or cathod ic p rotection to steel s ub s tra te. Inorg a nic z inc s a re sp e cifie d for atm osp h eric and im m ersion serv ice exp osu res, b u t t h ey can b e t op co a te d to ex te n d th eir s e rvic e life . Su ita ble topc oa t m a te ria l s e le ct ion is requ ired to p rev en t ou t-gassing from the in or g a n ic zin c th a t p r od u ces sm a ll p in h ole s in th e t op co a t. Re clam a tio n sp ecifie s in or g a n ic zinc coatings only to fraying su rfaces or heated tre ated m etalw or k (A STM A 325 or A STM A 4 90). A p p lica t io n r e q u ir e s sp e cia l s k ills a n d kn ow ledge. Inor gan ic zincs cure by either re a c tion to w a te r (s olve n t re du c ible ) or r ea ctio n to car b on d iox id e (w a te r r ed u cib le). (i) Organic Zinc Prim ers.— O rg an ic zin cs a r e p r im er s t h a t in cor p or a te a h ig h loa d in g (p ou nd s pe r ga llon) of m e ta llic z inc for p igm en tation w ith a w ide v ariety of solven ts a n d r esin s. D ep e n d in g on th e so lv en t a n d
Materials re sin s u se d , th e co at in g m ay b e a zin c-rich alkyd , d rying oil, ep oxy, or m oistu re-cu red u r et h a n e. Th es e co a tin g s a r e e xclu siv ely p r im er s b eca u se th ey p r ov id e g a lv a n ic p rotection to steel substr ate or th ey ar e u sed to rep air da m aged galvan ized coatings on steel su b st r a t es. O rg an ic zin cs are sp ecified for at m os p h er ic, bu ria l, an d im m er sio n se rv ice exp osu res bu t are n orm ally top coated to ex te n d th e s er v ice life of t h e co a tin g . Su ita b le top coat m aterial selection is requ ired to p r ev en t o u t-g a ss in g fr o m th e or g a n ic z in c. O u t-gassing p rod u ces sm all p inh oles in th e top coat. The w ay org an ic zincs cure d ep end s on th e coating typ e. (j) Polyu rethane .— T ech n i ca lly , p o ly u r e t h an e is a s u b clas s o f u reth an e. A tw oco m p o n e n t p o ly u r e t h a n e is cr e a te d b y ch e m ica lly c om b in i n g a p o ly is o y a n a t e a n d a p o ly o l to p r o d u ce an is o cy an ate th at h as a tw om o d e cu r e m e ch a n ism o f so lv en t e va p o ra tio n
an d chem ical reaction. Reclam ation specifies p oly u r eth a n es fo r to p co a tin g co m p a tib le (i.e., sa m e m a n u fact u r er ) am in e a n d p oly a m id e e p o x ie s t o p r o t ect a g ain s t d i r ect su n lig h t or U V a n d to p r ov id e sp ecific co lo r s. P oly u r et h a n es ar e s p ecifie d for at m os p h er ic an d p ar tia l or flu ctu at in g im m er sio n se rv ice exp osu res. (k) Urethane .— U r e t h a n e co a t in g s v a r y w id ely in for m u lat ion s for sp ecific ser v ice en v ir on m en ts an d ap p lica tion r eq u ir em en ts . Reclam ation sp ecifies sing le-com p on en t, m ois ture -cu re d u re tha n e s . The y c ure from m oistu re in the atm osp her e and can be ap p lied to d am p sur faces that d o no t hav e free m o is tu r e p r e se n t . T h e se u r e t h a n e s a r e fo r m u la t e d w it h v a r i o u s p i g m e n t a t io n s a n d a r e s p ecifie d in se v er a l com b in a tio n s t o s u it th e inten d ed serv ice exp osu re. These u r et h a n es ar e s p ecifie d for at m os p h er ic, bu r ial, an d im m ersion exp osu res.
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Chapter III Specifications Reclam ation constru ction jobs are ad vertised t o co n t r a ct o r s t o p e r fo r m t h e r eq u i r e d w o r k , a n d con tr a cto r se lect ion is m a d e b y a b id p r o c e ss. T h e m o s t co m m o n b id ty p es are low p r ice , n eg o tia te d , fixe d co st , an d so le so u r ce . O n ce Re cla m a tio n acce p ts a co n tr a cto r ’s b id , a contra ct exists betw een Reclam ation an d the contractor. The contract is often called a sp ecification. The sp ecification can be d efined a s a w r i tt e n , d etailed , tech n ical d es crip tion of w o rk to be p er fo rm e d , d e scr ib in g th e m a te r ia ls, q u a n tities, a n d m o d e of co n str u ctio n . Sp e cific a tio n s are d iv id ed in to m an y d ivis ions t o d e s cr ib e t h e v a r io u s jo b r e q u i r e m e n t s a n d m a y in clu d e ge n er al jo b d e scr ip t io n , su bm ittals, p re-existin g con d ition s, e n v i r o n m e n t a l r e q u i r e m e n t s , a n d t e ch n ica l a r ch ite ctu r a l, civil, e lect r ical, m ech a n ical, co a tin g , an d ca th o d ic p r o te ctio n d isc ip lin es. E a ch d iv i sio n i s s o m e t im e s ca lle d a t e ch n ica l p a r ag ra p h o r se ctio n .
9. Construction Specification Institute.— Re clam a tio n h a s ch a n g ed fro m a n a r r a tiv e p a r a g r a p h fo rm at to th e C o n s tru ctio n Sp e cific a tio n In s titu te (CSI) fo rm at fo r sp ecifications. CSI form at style is m ore concise an d u se s im p er at iv e la n g u ag e. Refe re n ce st a n d a r d s a re s p ecified to d es crib e q u ality of m a t e r ia ls , w o r k m o d e , t e st m e t h o d s , a n d accep tance criteria tha t are a recognized in d u st r y p r actice, th u s red u cin g th e n eed for len g th y v er b iag e. Th e m os t co m m on re fer en ce s ta n d a r d s u s ed in t h e co a t in g s in d u s t r y a r e A ST M , N A C E , a n d SSP C . C SI sp e c ificatio n s are d iv id ed in to 1 6 d ivis ions fo r a l l t h e bu ild in g trad es , an d each d iv i s ion m a y b e fu r th er d iv id ed in to sp ecia lity se ctio n s. F in i sh e s a r e D iv i sio n 9 , a n d p a in t a n d p ro te ctiv e co at in g s a re Sectio n 09900. Ea ch se ctio n is su b d iv id ed in to th e fo llow in g b a sic p arts:
P a rt 1 : G e nera l.—Includ es cost, r efer en ce s, s u b m itta ls, q u a lity ass u r a n ce , d elive ry , stora ge, ha n d lin g, an d restr ictions. P a rt 2: P rod uct .—Includ es requ irem en ts for m aterials to be u sed P a rt 3 : Execut i o n.—Inclu d e s m od e of co n s t r u c t io n , te s t m e t h o d s , a cce p t a n c e cr it e r ia , and repair
10. Reclamation Coating Specifications.— The Techn ical Service Cen ter (TSC) in D env er m a in ta in s C SI g u id elin e co a tin g sp ecifica tion s. The g u ideline coating sp ecification s are th e b a s is fo r s p e c ific p r o je ct r e q u i r em e n t s a n d a r e b a se d on h ist or ica l Re cla m a tion st r u ctu r es. Th e g u id elin e s p ecifica tio n s co n ta in instru ction al notes an d footnotes to aid the sp ecification w riter in p rep aring the sp ecificat ion s to m ee t sp ecific p ro ject r eq u ir em en ts . Th e g u id elin e co a tin g sp ecifica tion s ar e av a ila b le on Recla m a tion ’s in tr a n et w eb sit e: . Reclam ation u ses the follow ing sp eciality sections for coating s and haz ard ou s based p aints: Sect io n 09902.—C oa tin g s fo r n ew m et a llic su b st r a te s t h a t in clu d e: st ee l, cas t o r d u ctile iron; ga lva n iz e d , a lu m inu m ; bra s s ; bron z e ; or copp er Sect io n 09908.—M a inte na nc e coa tings f or p r e v io u s l y co a t e d m e t a llic s u b s t r a t es th a t inclu d e: steel, cast or d u ctile iron; galvan ized, alum inu m ; brass; bron ze; or copp er Sect io n 09980.— C o a t in g s fo r co n c r e te a n d m asonr y su bstrates Sect io n 13283.— H a n d lin g an d d isp o sin g of p a in t con ta in in g h ea v y m eta ls (i.e., ch r om a te , lea d , et c. . .)
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Guide to Protective Coatings: Inspection and Maintenance (a) Pa rt 1: G ene ral.— P ar t 1 in clu d e s th e follow ing gen eral outline: •
C os t p ro v is io n s fo r eith er lu m p s um or bid item
•
Su rfa ce pr e p a ra tion m e thod s
•
A p p lica tio n eq u ip m e n t
•
Coa ting ap p lication requ irem en ts
•
R efe r e n ce s fo r in d u s t r ia l s ta n d a r d s u se d in th e s p ecificatio n s ectio n
•
In sp ect ion m et h od s a n d acce p ta n ce cr ite r ia
•
Su bm ittals are req u ired to en su re th e contractor is sup p lying the sp ecified m a te r ials . Th e fo llow in g su b m itt a ls a r e e ss en tia l:
•
Re p a ir of d a m a g ed an d n on a ccep ta b le co a t e d a r e a s
•
Coating tab u lations an d categories (see follow ing s e c tion)
•
C olo r sch ed u le
" M a n u fa ctu r er ’s p r o d u ct d a ta an d ap p lication sheets
" M an u factu rer’s certificatio n of co m p lian ce, s ta tin g th a t m a te r ials w er e m an u fact u re d in acco rd an ce w ith qu ality assu ran ce and qu ality p ro g ra m s to in clu d e b at ch n u m b ers , q u an tity , an d co lor
" P u r ch a se or d e rs, e n su r in g th a t th e contractor u sing ap p roved m at er ials t o in clu d e b at ch n u m b ers , q u an tity , an d co lor •
Q u ality as su ra n ce
•
D eliv er y , sto r a g e, a n d h a n d lin g
•
En v iro n m en ta l re str iction s for su rfa ce p r e p aratio n an d ap p licatio n
(b) Pa rt 2: P rod ucts.— P ar t 2 in clu d e s th e follow ing m aterial requ irem ents ou tline: • • •
11. Coating Tabulations and Categories.— T h e fo r m a t o f t h e co a t in g t a b u la t io n s a n d ca t eg o r ie s in t h e C SI s p e cifica t io n s w ill b e sim ila r to th e old n a r r a tiv e p a r a g r a p h fo r m a t. T h e co a t in g t a b u l a tio n s a n d ca t eg o r ie s ch a n g e ov er tim e becau se of low er VO C r egu lations, lead- and chrom ate-free requirem ents, new coating techn ology d evelopm ents, and other factors. The follow ing section s d escribe th e tab u lations an d categor ies. (a) Coating Tabulatio ns.— Th e co atin g ta bu la tions a re ba s e d on R e cla m a tion’s h i st o r ica l e xp e r i en c e w it h co a t in g m e t alw o r k ite m s, se r v ice e xp os u r e, a n d m a te r ials u se d in d a m s a n d w a t er co n v ey an ce p ro je cts. Th e tabu lation s are in th e follow ing tab le form at: •
Item s to be coated are iden tified .
•
Coa ting m aterials are id en tified in the first colum n b y an alph an u m eric label fo r a m a n u f a ct u r e r ’s b r an d n a m e o r a Fe d er a l/ m ilit a r y sp ecifica tion n u m b er . Sev er a l eq u iv a len t co a tin g m a te r ials m a y b e lis t ed w it h in t h e s a m e m a t e r ia l o p tio n n u m b e r. M o r e th a n on e coating m aterial op tion m ay be listed in the tabu lation . For sm all jobs, the co lor m a y b e s p ecifie d in th is co lu m n .
•
N u m ber of coats (p rim er, inter m ed iate, an d top coat), thickn ess
Ab rasives M IO C o a t in g s
(c) Part 3: E xecu tion.— P ar t 3 in clu d e s th e follow ing ou tline requ irem en ts to com p lete w ork: •
•
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P r ot ect ion an d r ep a ir of e xist in g su rfaces Em bed d ed m etalw ork in concrete
Specifications of e a ch ap p lied coa t, a n d to ta l d r y film thickn ess (DFT) of the coating system a r e id en tifie d in th e s eco n d colu m n . •
•
Su r f a ce p r e p a r a t io n m e t h o d s a r e id en tifie d b y let te r or alp h a n u m er ic la b e l in t h e t h ir d co lu m n a n d a r e d e fin ed in th e ex ecu tio n p art fo r su r face p r ep aratio n . In s t r u c t io n a l n o t es , if s p e c ifie d , a r e located at either tab le front or en d .
(b) C oating C ategories.— Th e co atin g categories spe cify, by a lph an u m eric labels, the m a n u fa c tu r er’s b ran d n am e o r th e F ed er a l or m ilita r y sp ecifica tio n n u m b er of t h e co a tin g m a t er ia l liste d in th e ta bu la tio n s. Th e categories are su bd ivided accord ing to th e follow ing th ree esse n tial ch ara cteristics: C o m p o s i t i o n.— L is t t h e g e n e r ic ch e m ica l co a t in g n a m e P hy si ca l cha ract eris t ics .—W eight p er g a l lo n , VOC co n ten t, m in im u m ap p lication te m p er a tu r e, cu r in g tim es at sp ecific te m p er at u re an d h u m id ity , etc.
(a) Pro duc t Da ta Sh eet.— T h e fo llo w in g a r e the m ost com m on item s on th e p rod u ct da ta sh eets: •
G e n e r i c ch e m ica l co a t in g n a m e (acrylic, alkyd , ep oxy, p olyur ethan e)
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Typ ical u ses, such as on br id ges, p i p e s , o r w a t er t a n k s
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Ser v ice ex p os u re for at m os p h er ic, b u r ial, im m er sio n (fre sh w a te r or sa lt w at er ), an d ch em ical r es ista n ce
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Color an d gloss availability
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P h y sica l or te ch n ical p ro p er ties , su ch a s w e ig h t p e r g a llo n , s o lid s b y volu m e, VOC content, pigm ent ad d itiv es , flash p oin t, an d se rv ice te m p er at u re re sist an ce
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Re co m m en d ed d r y or w et film th ickn ess
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The ore tic a l c ove ra ge ra te pe r ga llon
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M ix r a tio (if m u ltico m p on en t s y st em ), p ot life, a n d in d u ctio n or sw ea t-in tim e (elap sed tim e interv al to allow the c he m ic a l re a c tion to be gin for m u l t ico m p o n e n t m a t e r ia ls b efo r e a p p lica tio n )
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D r y , re co a t, cu r in g , an d fu ll cu r e t im e p eriod s at tem p eratu re an d hu m idity ran ges
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Perform an ce test results (accelerated A S TM t e s ts th a t m a y o r m a y n o t b e listed )
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Sh elf life
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Sa fe ty pre c a u tions
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Sh ip p in g d ata
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W arr an ty an d lim itation s of liability
P erform ance requi rement s .— A ccelerated A STM te st in g an d acc ep ta n ce cr ite r ia
12. Manufacturer's Product Data and Application Sheets.— Reclam atio n sp ecification s requ ire the su bm ittal of the coating m an u factu rer’s p rod u ct da ta (s o m e t i m e s ca lle d t e ch n ica l d a t a ) a n d a p p licat ion sh ee ts . Th es e s h ee ts sp ecify t h e m a n u fa ct u r e r ’s in s t r u c t io n s a n d r eco m m en d a tio n s. Th e m a n u fact u r er 's in s t r u c t io n s a n d r e co m m e n d a t io n s h a v e becom e sp ecification requ irem en ts, u nless the sp ecificat ion s a re m or e r es tr ictiv e. P ro d u ct d a t a a n d a p p licatio n s h eets s h o u ld b e k ep t for fu t u r e r efe r e n ce to v e r ify t h e m a t e r ia l t y p e a p p lie d . T he p r o d u ct d ata an d ap p lication sh e e t s v a r y in co n ten t an d fo rm at fro m m a n u fa c tu r er to m an u factu re. So m e m a n u f actu r er s co m b in e p ro d u ct d a ta an d ap p lication into on e sheet. H ow ever , the sheets p rov ide u seful inform ation for th e sp ecific m a te r ial.
(b) Applica tion S hee t.— The follow ing ar e the m ost com m on item s on th e ap p lication sheet:
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Guide to Protective Coatings: Inspection and Maintenance
14
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Su b st r a te ty p es th a t a r e co m p a tib le w ith th e co a tin g m a te r ia l (e .g ., a lu m in u m , con cr et e, g a lv a n ize d , ste el, cast iron , or existin g coated su rfaces)
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Su r face p r ep a r a tio n m et h od , n or m a lly list ed as a m in im u m
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Thinn er p rod u ct nam e an d am ou nt to be ad d ed
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Pot-life-tim e of m u lticom p on en t c o a tin g m aterial at v ario u s tem p eratu re an d hu m idity ran ges
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Lo w e r a n d u p p e r te m p e r atu r e a n d h u m id ity ra n ge re str ictio n s d u r in g a p p lica tio n
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M o st m a n u fa ctu r er ’s sta te th a t th e coating is to be ap p lied only w hen the su bs tr at e te m p er at u re is 5 d eg re es F, m i n im u m , a bo v e th e d ew p o in t
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D r y i n g , r e co a t , a n d cu r in g t i m e s a t va riou s tem p eratu re an d hu m idity ran ges
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A p p l ica t io n m e t h o d : b r u s h , ro lle r , conv en tiona l airless sp ray , or airless sp r a y . M a y in clu d e s p ecific equ ipm en t at re com m en d ed p ressu res, h os e d iam et er siz es , sp r a y g u n , n oz z le tip siz es , etc.
13. Addendums and Modifications.— Sp ecifications ar e som etim es cha ng ed to alter d esig n s, co r r ect er r or s, o r r ed r ess om iss io n s. The follow ing tw o gen eral m etho d s are u sed to rev ise spe cifications: (1) ad d en d u m s (also called a m en d m en ts) are w ritten p age inser ts t h a t ch a n g e p a r t (s ) o f t h e sp e c ifica t io n b e fo r e b id d in g o c cu r ; a n d (2) m o d i fica t io n s a r e w ritten p age inser ts that m od ify p art(s) of the sp ecifica tion after th e co n tr a ct is a w a r d ed . M o d ifica tio n s ca n in cu r co st a d ju s tm e n t s to th e contr act an d are often called chan ge o rd ers.
Chapter IV Inspector's Role The coating insp ector ensu res th at: (1) the w or k is a cco m p lish ed in a t im ely m a n n er in a c co r d a n c e w ith th e s p ecificatio n s ; (2 ) w ork a ctiv itie s a r e d oc u m en te d ; an d (3) w or k is p erform ed safely. The coating insp ector at the jobsite is eithe r th e contra cting officer’s or th e field en gineer’s rep resentative. The insp ector shou ld n ot ver bally cha ng e the r eq u ir em en ts or r eq u ir e m or e r ig id r e q u i r em e n t s o n t h e co n t r a ct o r th a n w e r e or ig in a lly sp ecifie d . Th e in sp ect or sh ou ld contact his su p erv isor for reso lution if the s p e c ifica t io n s a r e in a d e q u a t e . C o n t r a c to r s m a y r e q u e s t a v a r ia n t fr o m s p e c ifica t io n s t h a t m a y o r m a y n o t b e s ig n ifican t. R eg ard les s o f v a r ian t s ig n ifican ce, t h e in sp ect or sh ou ld inform his sup ervisor of an y requ ested c h a n g e s. If a co atin g ap p licato r is n o t fo llo w in g t h e s p ecificatio n s , th e in s p ector sh o u ld n o t co n fr o n t t h e ap p lica to r . In st ea d , h e sho u ld a sk th e coating contra ctor su p erv isor to d et er m in e w h y th e s p ecifica tio n s a r e n ot b ein g fo llo w e d . In s o m e ca s e s, a d e v ia t io n m a y h a v e b e e n a l lo w ed o r th e co atin g co n tracto r su p e r v i so r m ay n eed to co rrect h is o w n w or k er ’s p ra ctices .
14. Primary Responsibilities.— Th e fo llow in g a r e p r im a r y r esp o n sib ilit ie s of t h e in sp ect or : •
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Ve r ify in w r itin g th a t co a tin g w or k is being p erform ed in accord an ce w ith t h e s p ecificatio n s
15. Daily Responsibilities.— Th e fo llow in g is a p artial list of d aily in sp ection resp on sibilities: (a) Pre paratory.— •
En su r e s p ecifica tio n s co n ta in all a d d e n d u m s a n d m o d i fica tio n s
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E n s u r e a ll s p e c ifica t io n s u b m it t a l requ irem ents are m et
(b) Presurface P reparation.— •
E n s u r e w e a t h e r co n d it io n s a r e c ond u c ive to bla sting op e ra tions
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D e te rm ine p re bla st s urfa ce cond ition fo r r u s t g r a d e
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Ens ur e tha t the s urfa ce is fre e of irreg u larities (w eld sp atter , slag bu rrs, sharp ed ges, p its, lam inations, or other objectiona ble irreg u larities)
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Ensu re that ab rasives m eet s p e cifica t io n r e q u i r em e n t s a n d a r e w ithin contam ination lim its
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Ens ur e the a ir c omp re s s or is fre e of m ois ture a n d oil c onta m ina tion
(c) Postsurface Preparation.— •
M on itor w ork activity on a d aily basis, inclu d ing d eviations from the sp e cificatio n s
Ens ur e the s urfa ce pr e p a ra tion m e thod m e e ts s pe c ific a tions requ irem en ts
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En su r e t h e s u r face (an ch or ) p r ofile m ee ts sp ecifica tio n s r eq u ir em en ts
Rep ort an d record d eficien cies to the fie ld en g in eer fo r res o lu tio n
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Ens ur e the s urfa ce is fre e of conta m inan ts an d m eets cleanliness sp ecification s requ irem en ts
En su r e w or k is co n d u cte d in a s a fe m an ner
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Guide to Protective Coatings: Inspection and Maintenance (d) Precoating Applicatio n.— •
E n s u r e a ll co a t in g m a t er ia ls a re ap p roved
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Ch eck storage ar ea for pro p er en viron m en tal and safety requ irem en ts
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E n s u r e en v iro n m en tal co n d itio n s (am bien t an d su rface tem p era tu res, hu m idity, and d ew p oint) m eet sp ecification s requ irem en ts
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Ensu re m ixing an d thinn ing m eet m an u factu rer’s requ irem en ts
resp on sible rev iew ing office is listed in the r eq u ir ed su b m itt a l n u m b er (RSN ) ta b le in Sec tion 01330 (Su b m itta ls) of th e C SI sp ecifications. Th e co a tin g in sp ect or is n ot u su a lly r es p on sib le fo r ap p r ov in g or d isa p p r ov in g contra ctor su bm itted m aterial. H ow ever , the in s p e ct o r sh o u ld t r a ck c on t r a c to r a n d R ecla m a t io n c o r r es p o n d e n c e t o e n s u r e t h a t o n ly ap p r o v ed m a te ria ls a re u se d o n th e jobsite. If the TSC in the Den ver Office is the r es p on sib le s p ecifica tio n r ev iew in g office , it w ill p rovid e a contra c tor su bm itta l w ith on e of th e follow ing r esp on ses:
(e) Coating A pplica tion.— •
Ensu re ap p lication m ethod s m eet m an u factu rer’s requ irem en ts
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E n s u r e in t e r m e d ia t e co a t a n d t o p c o a t a p p licat ion s a r e w ith in r eco a t t im e interv al for tem p eratu re an d hu m idity r an g es a n d th a t th e y m e e t th e sp ecifica tio n s or th e m a n u fa ctu r er ’s requ irem en ts
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C h eck am b ie n t te m p e r atu r e a n d h u m id ity d u rin g cu rin g p erio d
A p p rov ed .— In d ica t es m a t e r ia l ca n b e p u rchased and ap p lied . Co nd it io na ll y a p p rov ed .—Ind icates the m at er ial se lectio n is a ccep ta b le a n d th e m a t er ia l m a y b e p u r ch a se d ; h o w e v er , th e su b m itt a l is in co m p let e o r is m iss in g d oc um e nta tion. Re s ubm itta l of inc om p le te or m iss in g d ocu m en ta tion is r eq u ir ed . C on d itio n a l ap p r ov a l d oe s n ot im p ly a c ce p ta nc e for m a te ria l a p p lic a tion. N o t a p p rov ed .—Ind icates the selected m a t er ia l is n o t a p p r ov ed fo r a p p lica tio n .
(f) Postcoating A pplica tion.— •
Ensu re th e d ry film thickness m eets sp ecification requ irem en ts
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Inspect d ry film for h olid ay (pinh ole) d efects
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E n s u r e t h a t d e fe ct iv e , d a m a g e d , a n d d eficient areas are rep aired to m eet sp ecification r equ irem en ts.
The ins p e ctor s hou ld c he ck ba tc h nu m be rs on m aterial containers against the ap p rova l letter batch n u m bers for m aterials tha t arrive o n th e jo b s it e . C o n t a in e r s w it h b a t ch n u m b e r s th a t d o n o t co r r e s p o n d t o th e a p p r o v e d m a t e r ia l b atch n u m b er s sh o u ld b e re m o v ed fr om t h e jobsite.
17. Documentation.— Th e in sp ect or sh ou ld acqu ire th e follow ing d ocu m en ts:
Fo r a m o r e co m p reh en s iv e lis t o f resp on sibilities, see ap p en d ix C.
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Sp ecifications th at includ e ad d end u m s a n d m o d i fica tio n s
16. Material Approval.— Co n tracto r su b m itt ed coa tin g m a te r ials ar e n or m a lly review ed by th e Reclam ation office that either p rep ared or issu ed the sp ecifications. The
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T h e m a n u fa ct u r e r ’s p r o d u ct d a t a , ap p lication , an d M aterial Safety Data Sh eet (M SD S)
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Inspector's R ole •
Referen ce stand ard s referred to in th e sp ecifica tio n s t h a t r ela te to th e fie ld in s p ectio n
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Re fer en ce s ta n d a r d s a r e d iscu ss ed in m or e d et a il for th e p er tin en t in sp ectio n m eth o d in oth er ch a p te r s. A p p e n d ix D lis ts r efe r e n ce st a n d a r d s cited in this docu m ent
18. Instruments, Gauges, and Tools.— Th e insp ector shou ld a cqu ire the equ ipm en t, in st r u m en ts , an d in st r u ctio n a l m a n u a ls n ece ss a r y to p er fo r m th e in sp ectio n w o r k . Sp a r e b a tt er ies sh ou ld b e a v a ilab le if e lect r on ic in st r u m e n ts are u s ed . T h e ty p es o f in st r u m en ts w ill be d iscu ss ed in th e fo llow in g cha p ter s an d ar e listed in a p p en d ix E. (a) Conflicts.— A t t im e s, t h e r e a r e d isa gr ee m e n ts b etw e en th e co n tr acto r a n d th e in s p e ct o r o v e r in s t r u m e n t r e a d i n g s s u c h a s su r fa ce an ch o r p r o file s o r d r y film th ick n ess es. Th er e m ay b e r ea so n ab le e xp lan at ion s for su ch d is cr e p a n c ie s. T h e se d i scr e p a n c ie s s h o u l d b e investigated to av oid futu re conflicts and to d evelop a w ork ing relationsh ip w ith the c o n t r a ct o r . T h e fo llo w in g ar e s o m e p ossibilities for instr u m en t d isagree m en ts: •
T h e t w o p a r t ie s a r e n o t u s i n g t h e s a m e typ e of instru m en t sets:
" O n e in s t r u m e n t m a y b e m a lfu n ctio n in g
" O n e in s tru m en t m ay b e o u t of calib ratio n •
T h e t w o p a r t ie s a r e u s in g t h e s a m e typ e of instr u m en ts bu t:
" They ar e u sing d ifferen t p roced u res
" T h e y a r e ta k in g r e a d in g s a t d iffe re n t lo ca tio n s
" O n e in s tru m en t m ay b e o u t of calib ratio n
19. Substrate Inspection.— The ins p e ctor s h o u l d i n sp e c te d t h e s u b s t r at e s u r fa ce b e fo r e su rface prep aration . Ferrou s su bstrates w ith localized ru st or m ill scale are m ore p ron e to p r em a tu r e co a tin g failu r e. Ru st an d m ill sca le a re a s s hou ld be ins p e cte d m ore thorou ghly f or clea n lin es s a fte r su r face p r ep a r a tio n . If m ill s ca le is note d a nd a bra s ive bla s ting is not sp ecified , notify the field en gine er b ecau se ab ra siv e b las tin g is r eq u ire d . For m ain te n an ce coating w ork w her e overcoating is sp ecified , t h e ex is tin g c o at in g m a t er ia l s h o u l d b e insp ected for loose coatings by scrap ing w ith a sh a r p en ed p u tt y k n ife. O v er co a tin g loo se ly a d h er in g ex ist in g coa tin g w ill re su lt in p rem atu re failure. Fo r ite m s co a te d in a s h op , th e co a tin g s s h ou ld b e in s p e ct e d a n d id e n t ifie d fo r d a m a g e a n d faile d coa tin g ar ea s t h a t w ill re q u ir e r ep a ir e ithe r be fore or a fte r ins ta lla tion.
20. Coating Inspection Checklist Sheet.— R e cla m a tion s p e cific a tion c oa ting ta bu la tions (see cha p ter III, su bsection 11) id en tify th e item s to be coated , coatin g m ater ials, the D FTs, an d th e su rface p rep ara tion m eth od s; how e ve r, the ins pe c tor ma y w is h to e xpa n d on th e co a tin g ta b u lat ion s b y cr ea tin g a co a tin g in sp ect ion ch eck list u n iqu e t o t h e job . Sin ce sp ecifica tio n coa tin g ta b u lat ion s ca n id en tify se v er a l ite m s t o b e co a te d w ith in a s in g le ta bu la tion, a n ins pe c tion s he e t c a n p rovid e for the in d ividu al coating op eration s an d for the co m p l e te d i n s p e ct io n fo r a sin g l e it e m t o b e co a t e d , s u c h a s a p i p e lin e i n t er io r o r a r a d i a l g a t e . T h e ch e c k lis t ca n b e c o m e a p e r m e a n t r e co r d o f th e jo b . A c h e ck lis t e xa m p l e ap p e a r s in ap p en d ix F.
21. Precoating Conference.— R e cla m a tion coating specifications d o no t requ ire a p r eco a tin g co n fer en ce w ith th e co n tr a ctor . H ow ever , a m eeting w ith the con tractor to d is cu s s co a t in g - r ela t ed is su e s w o u l d b e he lpful. A p re c oa ting c onfe re nc e w ill a llow the con tractor to kn ow w ha t is exp ected an d to ou tlin e t h e w or k p r og r a m . Th is m ee tin g sh ou ld es ta b lish a w or k in g r ela tio n sh ip be tw een th e con tra ctor a n d Reclam ation . The fo llo w in g a r e p o s sib le it e m s f or d is cu s sio n a t t h e m e e t in g :
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Guide to Protective Coatings: Inspection and Maintenance •
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The insp ector’s access and safety
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Th e co n tr acto r’s p r o p ose d o p er atio n , inclu d ing equ ipm ent an d p ersonn el
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The contractor’s job-specific w orker health an d safety p lan (a su bm itted w ritten p lan is req u ired fo r lead or o t h e r h a z a r d o u s m a t e r ia l r e m o v a l a n d d isp os a l)
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T h e m e t h o d o f d u s t co lle ct io n a n d d isp osal of u sed abrasives
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U nfav orab le w eath er related to p re p a re d s urfa ce s , a p p lie d c oa tings, or cu r in g
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T h e p l a n fo r co a t in g i n a cce s sib le a r e a s
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Ins p e ction m e thod s a nd the nu m ber of m easu rem en ts
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The ty p es of insp ection instru m en ts to be u sed
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T h e N A C E / SSP C r e fe r e n ce st a n d a r d s t h a t ar e sp e c ifie d , th e v is u a l s ta n d a r d s to b e m et , an d th e a ccep ta n ce cr ite r ia
T h e co n t r a ct o r ’s w o r k i n g h o u r s
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Th e m a te r ial s to r a g e a r ea , in clu d in g tem p eratu re, ven tilation, and security
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T h e ap p ro v ed s u rface p r ep aration m eth od s, ab rasiv es, coatin g m ater ials, ap p lication m ethod s, and curing tim es
Chapter V Material Storage, Containers, and Shelf Life C o a t in g m a t er ia ls a rr iv e o n t h e jo b s it e b e fo r e a p p lica tio n b eg in s, a n d th ey r eq u ir e st o r a g e. M a n u fa c tu r ers reco m m en d s p ecific p ro vis ions fo r st o r a g e to p r ev en t co a tin g d ete r io r a tion . C oa tin g m a te r ials m u st b e u se d w ith in a sp ecified tim e from m an u factu re or sh ipm en t.
22. Storage.— C o a t in g m a t er ia ls sh o u ld b e s t or e d in a c o v e r ed , w e ll-v e n t i la t e d a r e a a w a y fr o m sp a r k s, fla m es, a n d d ir ect su n lig h t. M a n y co a t in g s r e q u ir e a lim it e d t e m p e r a tu r e r a n g e f or p r o p e r s t o r a g e . C o ld s to r a g e m a y r e q u ir e a co atin g to b e ex ces s iv ely th in n ed for a p p lica t io n , r es u l tin g i n lo w s o lid s co n t e n t a n d a le ss-t h a n -in ten d ed D F T . A t o r b elo w freezing tem p eratu res, coating s (su ch as w ater b a s e d m a t e r ia ls ) ca n d e g r a d e t o th e p o in t t h a t t h e y a r e u n u s a b le . M a t e r ia ls in c o ld s to r a g e s h o u l d b e m o v e d t o a h e a te d a r e a b e fo r e a p p lica t io n . A t h i g h t e m p e r a t u r e s , a m a t e r ia l su c h a s so lv en t-b as ed co atin g m ay g el o r b e co m e fla m m a b le o r e xp lo s iv e . T h e st o r a g e sit e sh o u l d b e m o n ito red u s in g a h ig h / low t h e r m o m e t er . C o a t in g m a t er ia ls sh o u ld b e st o r ed t o g et h e r b y t h e sa m e b a tch o r lo t n u m b ers . T w o com p onen t coating system s shou ld be stored c lo se t o g e th er b u t b e d is tin g u is h ab le fro m one a n o t h e r . For sto rag e o f s ev eral m o n th s or lo n g e r , co ntain ers s h o u ld b e in v erted o n a m o n t h l y b a s is to a v o id e x ce s siv e s e tt lin g a n d for ea se of fu tu r e m ixin g . Th e o ld es t co a tin g m aterials sho u ld b e u sed first. Solvents an d thinn ers shou ld be stored se p a r a t e l y fro m co atin g m aterials. Sep ara tion o f s o lv e n t s an d t h in n e r s is a sa fe t y co n c er n because m an y of these m aterials hav e low er flash p oint tem p era tu res th an m ost coating s, a n d t h e y p o s e a p o t e n t ia l fir e h a z a r d . C o n t r a c to r s w i ll o ft e n s to r e co a t in g m a t e r ia l a t t h e jo b s it e in t r a ile r s. T ra ile r s w it h n o h e a t in g , co olin g , or v en tila tio n sy st em s a r e u n su ita b le for storage b ecause they becom e cold in w inter
an d hot in su m m er an d hav e limited v e n t ila t io n . C o a tin g m a t er ia ls sh o u ld b e st or ed in clim a te co n tr olle d en v ir on m en ts . The follow ing are gen erally accep ted reg u lations for stor ing coa ting m ater ials: Indo or sto rage.— N o m or e t h a n 25 g a llon s o u t s id e o f a p p r o v e d ca b in e t s in a s in g l e a r ea . Outdoor stora ge.— N o m or e t h a n 1,100 g a llo n s o f m a te r ia ls g r ou p ed to g eth er . N o m ore th an 60 gallon s in ind ivid u al contain ers. For fu rthe r inform a tion on the s tora ge of flam m able an d com bu stible liqu ids, refer to the m a nu fa c tu re r's M SD S a nd “ R e cla m a tio n Sa fety an d H ea lth Sta n d a r d s.”
23. Containers.— C on ta in er s v a r y lar g ely in volu m e an d com m on ly ran ge from 1 qu art to 55 gallons. Because of app lication eq u ipm ent lim ita tions , the m os t com m on c onta ine rs on a job sit e w ill b e eith er 1-g a llo n or 5-g a llo n p a ils. Single com p one n t m a te ria ls a re s hipp e d in on e co n ta in e r, a n d tw o or m o r e co m p o n e n t m ater ials are ship p ed in sep ara te con taine rs, e a ch o f w h ich h a s th e c a p a c it y t o h o l d t h e t o t a l com bined volu m e. A n y c onta ine rs tha t a re d a m a ge d , le a king, or u nlabeled sh ou ld be r ejected and rem oved from the job site.
24. Shelf Life.— Sh elf life is th e le n g th of t im e a fte r m a n u fact u r e t h a t a coa tin g m a te r ial w ill rem ain u sable w hen stored in an u nop ened co n ta in er , acco r d in g to th e m a n u fa ctu r er . M a n u fact u r er s n or m a lly sp ecify th e s h elf life o f a co a t in g o n t h e co n t a in e r o r u s e a s p e c ia l c ode or ba r c od e tha t s pe c ifie s the da te of m a nu fa c tu re or the e xpira tion d a te . For s p e c ia l co d e s or b a r co d e s , t h e in s p e ct o r m a y n eed to ca ll th e m a n u fa ctu r er to r ea d th e co d e. In ge n e ra l, m os t coa tings h a ve a s he lf life of b e t w e e n 6 a n d 12 m o n t h s a t a n o p t i m a l tem p eratu re, bu t this w ill vary w ith 19
Guide to Protective Coatings: Inspection and Maintenance m a n u fact u r er an d m a te r ial t y p e. Sh elf life is no ted on the m an u factu rer’s p rod u ct da ta sh e e t . T h e in s p ecto r s h o u ld ch eck th e d ate of m an u factu re or th e exp iration d ate to d eterm ine that the exp iration d ate has n ot been reached . Coating m aterials that h ave exceeded
20
the sh elf life sho u ld b e rem ove d from the job sit e. C on se q u en ces of e xce ed in g th e s h elf life includ e gelling, od or, cha ng es in viscosity, fo r m a t io n o f lu m p s , p ig m e n t s et t le m e n t , a n d c olor or liqu id s e pa ra tion.
Chapter VI Surface Preparation The serv ice life of a coating d ep en d s on th e d e g r e e o f s u r f a ce p r e p a r a t io n a c h ie v e d a s m u ch a s it d e p e n d s o n m a t e r ia l s e le ct io n a n d a p p licat ion . A ll coa tin g sy st em s w ill even tu ally fail; how ever, pr em atu re failures ar e o ften th e r es u lt o f in ad eq u at e s u rfa ce p r e p a r a t i on . Ev e n s u r fa ce p r e p a r a t io n s t h a t a ch i ev e a n a cce p t a b le m a r g i n o f cle a n lin e s s b u t leave contam inan ts on th e su rface w ill tend to lessen th e coating serv ice life. Thu s, cle a n l in e s s o f t h e s u b s t r a te is a n e s se n t ia l a n d integral com p onen t of a coating system .
25. Surface Contaminants .— Su rfa ce c o n t a m in a t io n is o n e o f th e m o s t co m m on cau ses of coating failur es. To achieve th e m a xim u m se r v ice life of a coa tin g sy st em , it is ess en tia l to r em ov e su r fa ce co n ta m in a n ts . (a) Types o f Surface C ontam inan ts.— Th e fo llo w in g a r e th e m o s t co m m o n ty p es o f su r f a ce co ntam in an ts an d th e co n s eq u en c es of not rem oving th em : Rust.— Ru st is th e co rr os ion b y p ro d u ct (fe r r o u s o x id e) o f s teel an d m ay b e lo o se or m a y ad h er e r ela tiv ely tig h tly to th e su b st r a te . Rust is porou s and m ay inclu d e m oistu re, o x y g e n , a n d s o lu b le s a lt s . R u s t w i ll e x p a n d u p t o e ig h t t im e s th e v o l u m e o f t h e b a s e m e t a l consu m ed and fu rther corrod e the steel su bstrate, thu s d islodg ing an y coating ap p lied ove r it. Mill scale.— M ill sca le is a h ea v y ox id e la y e r fo r m e d d u r in g h o t fa b r ica t io n o r h e a t tr ea tm en t o f m et a ls a n d is a b lu ish colo r . M ill scale will even tu ally brea k loose from the steel su b st r a te , ta k in g th e co a tin g w ith it. Ste el is a n od ic to m ill sca le (s te el h a s a low er ele ctr icalch em ical p ot en tia l d iffer en ce t h a n m ill sca le); ther efore, steel w ill corro d e (sacrifice itself) to p rotect the m ill scale. Gre ase a nd o il.—Grea se an d oil p rev en t a coating from ad her ing to the su bstrate.
Dirt and dust.— D ir t a n d d u st o n th e su rface prev en t the a p p lication of a sm ooth u n ifo rm f ilm a n d w e ak en th e ad h e sio n of th e coating to the su bstrate. Soluble sa lts.— Solu ble s a lts de p os ite d on a su rface can rem ain on th e sur face, even after ab rasiv e clean ing. Solu ble salts w ill in crease m o istu r e p e rm e a tio n th r ou g h th e co atin g (osm otic blistering) an d can accelerate th e co r r os ion r a te u n d er th e co a tin g film (u n d erfilm corr osion or u n d ercu tting ). Th e m o s t co m m o n so lu b le sa lts e n co u n te re d in th e co a t in g i n d u s t r y a r e ch l o r id e s , s u l fa t e s, a n d m et a llic sa lts . Th e ch lor id e io n is th e m os t aggr essive. Water.— W a te r w i ll p r ev en t a d h e sio n an d m a y e it h e r p r o d u c e fla s h r u s t in g b e fo r e coating ap p lication or it m ay accelerate u n d er film co r r osio n after co a tin g ap p lica tion . M ois tu r e in th e liq u id or fro z en st a te w ill p rev en t ad he sion of the coating to th e s ub s tra te a nd c a n d is rup t cu ring re a c tions of coating s. M oistu re con tam ination can cau se several typ es of failu re. Chalk.— Ch alk is the r esidu e left after the d ete r io r a tion of th e co a tin g ’s o r g a n ic b in d er . Ch alk resu lts from exp osu re of the coating to d ir ect su n lig h t o r ar tificia l U V lig h t. A ll co a t in g s ch a l k t o so m e d e g r e e , b u t e p o x ie s a r e m ore p ron e to cha lk. Ov ercoating chalked s u r f a ce s w i ll r e s u l t in p o o r a d h e s io n a n d m a y re s ult in d e la m ina tion (s e pa ra tion of one co a t in g l ay e r fr o m a n o t h e r co a t in g l ay e r ) failure. De teriorated co atings.— Old , loose, d e t er io r a t e d c o a tin g s t h a t a r e o v e r co a t e d m a y p e el, d e la m in a te , o r lift fr om t h e su b str ate an d take the n ew coating w ith th em . (b) C om pressed Air C ontam inan ts.— A ir co m p r e s so r s co n t a m in a t e d w it h m o is t u r e a n d oil can resu lt in ad h esion -related failu res. Th e 21
Guide to Protective Coatings: Inspection and Maintenance fo llo w in g a r e t w o co m m o n o p e r a t io n s t h a t tran sfer oil and w ater con tam inan ts from the com p ressed air sup p ly to the sub strate: •
Ab ras iv e s u rface p r ep aratio n o p er atio n s
•
Blow ing d ow n th e p rep ared su bstrate a ft er su r fa ce p r ep a r a tio n to r em o v e d u st b efo re ap p l yin g th e co atin g
A ir com p r es so r s s h ou ld b e e q u ip p ed w ith in lin e m ois tu r e a n d oil s ep a r a to r s (t r a p s) o n all lin e s. T h e in s p ecto r s h o u ld h av e th e co n tra c tor ch eck th e a ir su p p ly for con ta m in a n ts in accord an ce with A TM D 4285. (See a p p en d ix G for th is p r oc ed u r e.) It is r e co m m e n d e d t h a t t h e co m p r e s s ed a ir lin e s b e checked on ce every 4 h ou rs or after th e co m p r es so r h a s b ee n tu r n ed off. (c) Flash Rusting.— Flash ru sting (som etim es called flash ba ck ru sting o r ru st bloom ing) is a lig h t o x i d a tio n (co rro sio n ) o f th e ferro u s su rface after su rface p rep aration h as been co m p let ed . Flas h r u st in g d ev elo p s o n fre sh ly p r ep a r ed su r fa ce s in th e p r ese n ce of m oist u r e. A fte r th e m ois tu r e d r ies off, a n y r es u ltin g cor ro sio n is calle d flash ru stin g an d can occu r w ith in m i n u te s a fte r su r fa ce p re p ar atio n . Th e follow ing tw o circu m stan ces are th e m ost com m on m oistu re sou rces resu ltin g in flash r u s t in g : •
C on d en sa tio n is o ccu r r in g
•
W at er is u se d in th e s u rfa ce p r e p aratio n m eth o d
Con d ensation is the form ation of liquid w ater fr o m w a t e r v a p o r i n t h e su r r o u n d in g a i r a t certain am bient tem p eratu res an d hu m idity r a n g e s . C o n d e n s a t io n c a n o ccu r u s in g a n y su r face p r ep a r a tio n m et h od b eca u se it is w e a t h e r d ep en d en t. Su rface p r ep aratio n m e t h od s th a t e m p lo y w a t er ar e w a t er je ttin g a n d w et ab r a siv e b las t cle a n in g . Flas h r u st in g ca n b e m in im ize d w h en u sin g w a te r jet tin g an d w et abr asive blast clean ing b y th e follow ing m eth od s:
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Usin g an inhib itive agent.— In h ib itiv e a g en t o r w a sh p r im er , n or m a lly a p h os p h a te , is inje cte d into the w a te r or bla s t stre a m or a p p lie d a fte r cle a ning. Re cla m a tion d oe s n ot p ro h ibit th e u se of in h ibit or s, b u t th e s u rfa ce s h o u l d b e t h o r o u g h l y w a t e r w a s h e d b e fo r e co a t in g b e c a u s e h e a v y i n h i b it iv e r e s id u e s ca n a d ve rs e ly a ffe ct coa ting a d he s ion. Usin g ho t force d (blown) air.— D r y o ff th e w etted su rface im m ed iately after clean ing w ith h ot air b low ers. Using high-pressure, water-jet vacuum clean ing m etho d.— H ig h - w a t e r p r e s su r e tran sfers enorm ou s ener gy to the su rface, thu s elevating th e su rface tem p eratu re to ev ap orate an y m oistu re, an d the v acuu m rem oves e v a p o r a t e d a n d liq u i d m o is tu r e a w a y . T o p r e v e n t fla s h r u s t in g , it is a g e n e r a l in d u str ial p ra ctice n ot to p ro cee d w ith su rfa ce p rep aration u nless the steel sub strate te m p e ra ture is 5 d e gre e s F, m inim u m , a bove th e d ew p oin t. (See ch a p te r VII, “ En v ir on m en ta l C on d itio n s” .) Su r fa ce p r ep a r a tion st a n d a r d s N A C E 1/ SSP C SP -5, N A C E 2/ SSP C -SP 10, N A C E 3/ SSP C -SP 6, N A C E 4/ SSPC -SP-7, N A C E 8/ SSPC -SP14, SSPC -SP15, a nd SSPC -SP11 p rovid e for reclean ing o r re blasting to rem ov e flash r u s t in g . T h e su r f a ce p r e p a r a t io n s ta n d a r d s SSPC -SP2, SSPC -SP3, a n d N A C E 5/ SSPC -SP12 d o n o t sp e c ifica lly a d d r e ss fla s h r u s t in g b u t r eq u ir e t h a t t h e s u r face b e r ecle a n ed acc or d in g t o cle a n lin e s s r e q u i re m e n t s o f t h e st a n d a r d u s e d if ru s t form s on the s u rfa ce . R e cla m at ion s p e cifica t io n s r eq u i r e th a t a n y s u r fa ce w h e r e fla s h r u s t o r co r r o s io n b y p r o d u ct s h a v e fo r m ed b e r ecle a n ed . If flas h r u st in g is su sp ect ed an d is n ot v isib ly no ticeable, a goo d d etection m etho d is to ins p e ct the s urfa ce w ith a bright fla s hlight or sp otligh t. The ligh t shou ld b e held p arallel to the s ur fa c e a nd s hine d a c ross it. R us t bloom s w ill a p p e ar as d a r ke n in g on th e su r fa ce an d ha ve a r ed d ish or ligh t brow n tint.
Surface Preparation
26. Presurface Treatment.— P r io r t o a ct u a l su rfa ce p re p ar at ion s, all st ee l su rfa ce im p erfection s are to be corr ected . This is a Re clam a tio n sp ecifica tio n r eq u ir em en t. W eld sp atter , slag, bu rrs, p oro sity, sh arp ed ges, p its, lam in a tio n s (sliv er s), cr ev ices , or ob ject ion a b le irr eg u lar ities n ee d to b e r ep air ed . Su rfa ce d ep ressions, such as p its or crevices, can be a co lle ct io n p o in t fo r e xce s siv e co a t in g m a t e r ia l t h a t m a y n o t fu lly c u r e . P r o je ct io n s s u c h a s w e ld s la g , s la g b u r r s , o r s h a r p e d g e s th a t m a y st ick ou t t h r ou g h th e co a tin g can r es u lt in p i n p o in t co r r o sio n . A l l t h e se ir r e g u l ar it ie s a r e t o b e r e p a ir e d b y w e ld in g , s cr a p p in g , gr ind ing, or o th er sp ecified m ean s.
(a) Nonme tallic Ab rasive s.— There are th ree b a sic ty p es of n on m eta llic ab r a siv es: (1) n a tu r a lly occu r r in g ; (2) b y p r od u ct s; an d (3) m a nu fa c tu re d . The follow ing s e c tions p r o v i d e a b r ie f d e scr ip t i on o f t h e ty p i ca l u s a g e a n d t h e d e g r e e of d u s t in g p r o d u ce d b y n on m et a llic ab r a siv es d u r in g b las tin g op era tions. Na turally occu rring.— •
Nonsilica or heavy mineral sands (magnetite, olivene rutile, straurolite).— Th es e s a n d s a r e t y p ically to u g h , d en se , r ou n d -sh a p ed m a te r ia ls. Th ey ar e e ffect iv e fo r b las t cle a n in g new steel bu t are not recom m end ed for m aintenan ce coating w ork. Degree of d u s ting d u ring bla sting op e ra tions is m ed iu m .
•
Flint, garnet, novaculite (siliceous rock ), and zircon.— These are d ense, tou gh , an gu lar or cu bic abr asives tha t, because of their high costs, are u sed p r im a r ily in sp e cia l cle an in g a p p licat ion s. Th e d eg r ee of d u st in g d u r in g b las tin g op er a tio n s is m ed iu m for flint a n d ga rn e t a nd low for n o v acu lite an d z ir co n .
27. Abrasive Blast Material.— Th e a br a siv e b las t m a te r ial is im p or ta n t b eca u se it d ete r m in es t h e su r fa ce p r o file p r o d u ce d . Th er e ar e tw o g en er a l ca teg o r ie s of a b r a siv es: m etallic and non m etallic. M etallic abrasives a r e u s e d p r im a r ily t o b la s t cle a n s t ee l a n d for g ed or cas t ir on w h er e a su r face p r ofile is se ld o m cr itica l o n th e fin ish ed p r o d u ct. N o n m e t allic a b r a siv e s , d e p e n d in g o n t h e t y p e u se d , can p r od u ce t h e d es ir ed su r face p r ofile a n d clea n lin es s o n h a r d , d en se fer r ou s m et a ls o r o n so f t m etals (alu m in u m , b ras s , b ro n z e , or cop p er) w ithou t d am aging or altering th e m et al s u rfa ce. Re clam a tio n sp ecifie s SSP C -A B 1, “ A b r a siv e Sp ecifica tio n N o. 1, M in er a l an d Slag A b r a siv es,” C la ss A , eith er Ty p e I o r II. Re clam a tio n sp ecifica tio n s d o n ot p er m it a b r a s iv e m a t e r ia ls co n t a in i n g t o xic h e a v y m etals su ch as a rsen ic or so lub le salts in excess of 0.04 p ercent. Ab rasive m aterial is not to co n ta in m or e t h a n 1 p er cen t s ilica, b y v olu m e becau se silica san d p articles cau se silicosis. Re clam a tio n d oe s n ot sp ecify m et a llic a b r a siv es . M et a llic ab r a siv es ar e n ot field ap p licable because of high costs and inability t o r e cy c le . H o w ev er, Reclam atio n w ill a llow a co n tr a ct v a r ian ce, if r eq u es te d , to u se m et a llic a b r a si v e s fo r s h o p s u rface p r ep aratio n , p r o v i d e d t h a t th e m e t allic a b r a siv e is a d r y , clean , an gu lar steel grit.
Byp rod uct.— •
Slags (coal, copper, nicke l).—Sla g a b r a siv e s ar e g en e r a lly a g la s sy , hom oge ne ou s m ixture of va riou s oxid e s tha t a re sha rp ly a ng u la r or cu bic and are efficient for b last cleaning new , ru sted , or p ainted s urfa ce s . The s e a bra s ive s a re not r ecy cled . Th e d eg r ee of d u st in g d u ring bla sting op e ra tions is high f or co a l a n d n i ck e l a n d lo w fo r co p p e r .
•
Agricultural products (corncobs, pea ch pits, w alnut shells).— T h e se a r e g e n e r a lly r e g a r d e d a s to u g h b u t lig h t w e ig h t a b r a s iv e s u s e d in s p e cia l cle a n in g a p p l ica t io n s fo r r e m o v i n g
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Guide to Protective Coatings: Inspection and Maintenance p aint, fine scale, and other contam inan ts w ithou t altering the m et a l su b st r a te or d ist or tin g th in m e t als. Th e d eg re e o f d u stin g d u r in g b l a stin g o p eratio n s is lo w . Manu factured.— •
Synthe tic (aluminu m o xide, glass bea ds, silicon carbide).— The se abr asives can be p rod u ced w ith sp ecific prop erties for va rying d egrees of hard ne ss and tou gh ne ss and w ith sp ecific shap es. H igh cost restricts the u s e of t h e s e a b r a s iv e s t o s p e c ia l clean ing a p p lications, an d th ey m u st be recy cled to b e econ om ical. The m a in ad v a n ta g es of u sin g sy n th et ic abr asives are fast cu tting cap ability a n d n o n ru s tin g of th e su b str ate . Th e d eg r ee of d u st in g d u r in g b las tin g o p eratio n s is lo w .
(b) Sa mp ling an d Testing.— Ab rasive sam p les sho u ld b e retained for fu tu re referen ce in th e e v e n t of co a t in g p r o b le m s . Sa m p l e s ca n b e tested an d the resu lts retained to either confirm or r eject abr asives as a p ossible cau se of failu re. Different ab rasives u sed on the sam e m etalw ork can p rod u ce differen t a p p e a r a n c es . T estin g s h o u ld b e co n d u cte d on th e ab ra siv es b efo re u se to en su r e th a t th e m a te r ia l d o es n o t co n ta in co n ta m in a n ts . (c) Sam pling.— T h e in s p e c to r sh o u ld r e co r d t h e m a n u fa ctu rer’s b ran d n am e, b atch o r lot n u m b e rs , a n d a b r a siv e ty p e . A b r a siv e m a t er ia l s h o u l d b e s to r e d i n a d r y env ironm ent an d be clean, u niform in textu re, an d m oisture free. It is recom m en d ed tha t a sm a l l sa m p le o f each ab r as iv e b atch o r lot n u m ber be k ep t for futu re r eferen ce in case chan ges occu r in the su rface p rofile. (d) Te sting.— So lu b l e sa lt co n c en t r a t io n s a r e typ ically low for m ined m ineral abrasives (SSP C -A B1, ty p e I) a n d sla g ab r a siv es (SSP C A B1, typ e II) th a t a r e a ir coo led or q u en ch ed in p u r ifie d w a t e r . H o w e v e r , s la g a b r a s iv e s m a y b e q u e n c h e d in s eaw ater, b rack is h w ater, or o t h e r s a lt -co n t a m in a t e d w a t e r a n d , co n se q u en tly , h a v e a h ig h er so lu b le s a lt
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co n te n t. A b r a siv es w ith h ig h so lu b le s a lt conten t shou ld n ot be u sed becau se the salts ca n con ta m in a te th e s u b st r a te d u r in g b las tin g op erations and , thu s, cause coating failu re. M ine ra l a nd s la g a bra s ive s shou ld be te s te d for the p resen ce of solub le salts by a con d u ctivity m et er . Co n d u ctiv ity is th e io n ic p r op er ty of a flu id o r s o lid t h a t p e r m it s t h e p a s s a g e o f a n ele ctr ic cu r r en t. Solu b le s a lts d iss olv ed in w ater can be m easu red by a cond u ctivity m e t er . C on d u ctiv ity m e te rs m e a su r e th e cond u ctance of all salts (ch lorid es, sulfates, ferrou s, etc.) in d issolution bu t cann ot d etect a “ sp ecific” sa lt io n (e.g ., th e ch lo r id e io n ). R ecla m a t io n s p e c ifie s th a t m in e r a l a n d s la g a b r a siv es a r e to b e in acco r d a n ce w ith SSP C A B1, an d the stan d ard ’s cond u ctivity r eq u ir em en t is n ot to ex cee d 1,000 m icr os iem en s. Th e ch lor id e-s p ecific io n in a b r a siv es ca n b e te st ed u sin g a tit r a tion k it. (See ap p en d ix H for te st p r oc ed u r es .) Tes tin g fo r to xic m eta ls r eq u ir es la b or a to r y m eth od s. C e r t ifica t io n o r a n a l y s is o f a b r a s iv e m a t e r ia l co n t e n t is a v a ila b le fr o m t h e m a n u f a ct u r e r . Althou gh w ater is not consid ered an a brasive, it is us e d a s a s urfa ce pr e p a ra tion m e d iu m for p r e v io u s l y co a t e d m e t a lw o r k . W a t e r m a y contain a n excessive am ou nt o f solub le salts that, if left as resid u e on th e p rep ared sur face, can cause th e coating to blister. The w ater u s e d in w a t er je t tin g o p e r a tio n s sh o u ld b e tested for high chlorid e ion levels. (See a p p en d ix I for p r oce d u r es.)
28. Nozzle Blast Pressure.— R e cla m a tion d oe s n ot r eq u ir e ch eck in g th e b las t n oz z le p r e s su r e . In d u s t r y p r a c tice r e co m m e n d s th a t the blasting p ressur e be m aintained betw een 90 a n d 100 p ou n d s p er sq u a r e in ch (p si). R e du c ed p re s s ure s ca n re s u lt in a s ha llow su rface p rofile d ep th an d a d im inished blast r a t e efficie n c y . E xce s siv e p r e s su r e s ca n in cr ea se th e su r fa ce p r ofile d ep th . Con sequ ently, the p rim e coat ma y n ot cover t h e p e a k s of t h e p r o file a n d p in h o l e fa ilu r e m a y r e s u l t. T h e cr it ica l p o in t o f p r e s su r e is a t the blast nozzle, w her e p ressur e w ill be low er th a n at th e a ir com p r es so r b eca u se of h os e lin e p ressu re losses.
Surface Preparation If th e n oz z le b las t p r es su r e is su sp ect , it is r eco m m e n d ed t h at th e in sp e cto r r eq u e st th e coating sup ervisor to check the p ressur e. (See a p p en d ix J fo r th e p r o ce d u r e.)
29. Surface Preparation Methods.— Th e follo w in g ar e t h e fiv e b as ic ty p es of su rfa ce p r ep a r atio n : • • • • •
D e g r e a sin g . H a n d a n d p o w e r to o l cle a n in g . A b r a s iv e (w e t o r d r y ) cle a n in g . W a t e r je t tin g o r p r e s s u r e cle a n in g . C h e m ica l s tr ip p in g .
Ther e are sev eral stand ard s d escribing the a b o v e m e t h o d s ; h o w e v e r , R ecla m a t io n h a s ad op te d SSPC an d join t N A C E/ SSPC su rfa ce p r ep a r a tio n st a n d a r d s. Th e in sp ect or sh ou ld e n s u r e t h a t t h e a p p lica b le st a n d a r d s a re av aila b le o n th e job site . A fter su rfa ce p rep aration , clean line ss shall be based on the sp ecifie d st a n d a r d 's cle a n in g r eq u ir em en ts . Vis u a l st a n d a r d s b y SSPC an d join t N A C E/ SSPC ar e a su p p lem en t t o a id in d et er m in in g clea n lin es s b u t a r e n ot th e s ole con firm at ion re q u ire m en t. Su rfa ce p r ep a r a tio n st a n d a r d r eq u ir em en ts sh a ll g o v e r n w h e r e s u r f a ce p r e p a r a t io n a n d v i su a l st a n d a r d s co n flict . Th e fo llo w in g ar e th e SSP C a n d jo in t N A C E / SSP C s u rface p r ep aration st a n d a r d s, in in cr ea sin g or d er of cle a n lin ess . An a b b r e v iated s u m m atio n is p ro v id ed for each su rface prep aration stand ard an d the correspon d ing visua l stand ard to be u sed . (a) SSPC-SP1 : Solvent C leaning.— So lv en t clean ing is used to rem ove grea se, oil, d irt, d raw ing an d cutting com p ou nd s, and other contam inants by solven t w iping, w ater w a s h in g , cle a n i n g co m p o u n d s , a n d s te a m c le a n i n g . Th is p ro ced u re is a p rereq u is ite for all other su rface p rep aration m ethod s excep t N A C E 5/ SSP C -SP 12 (w a te r je ttin g ) a n d N A CE 6/ SSPC -SP13 (con crete su rfaces). Th e r e a s on f o r so lv e n t c le a n i n g is th a t co n t a m i n a n t s le ft o n th e s u r fa ce ca n b e im p a cte d in to th e s u b st r a te su r face d u r in g p rep aration u sing other m ethod s (listed b e lo w ), r e s u l tin g i n p o o r a d h e s io n a n d p rem atu re failure.
(b) SSPC-SP2 : Ha nd T ool Clea ning.— H a n d tools are u sed to rem ov e loose m ill scale, loose ru s t, loos e coa tings , w e ld flu x, w e ld s la g, or w e ld s p a t te r b y b r u s h in g , s a n d i n g , ch i p p in g , or scrapp ing. Tightly ad her ing ru st, m ill scale, a nd p a int a re a llow e d to re m a in. The us e of h an d tools is gene rally confined to sm all are as, sm a ll r ep a ir ar ea s, o r sm a ll in a cce ss ib le ar ea s. T h e v is u a l s ta n d a r d i s d e t er m in e d b y com p ar iso n to SSPC -VIS 3 refe re n ce p h otog rap h s. (c) SSP C-SP3: Pow er Tool Clea ning.— Pow er tools are u sed to rem ov e loose m ill scale, loose ru s t, loos e coa tings , w e ld flu x, w e ld s la g, or w eld sp atter. Tigh tly ad her ing ru st, m ill scale, an d coating are allow ed to rem ain if they cann ot be rem ove d by lifting w ith a d u ll p u tty k n i fe . T h e re q u i r em e n t s o f t h is m e t h o d a r e sim ilar to SSPC-SP2, excep t that, w ith p ow er t o ols , la r g e r ar e a s ca n b e cle a n e d m o r e efficiently. The visua l stand ard is d eterm ined b y com p ar iso n to SSPC -VIS 3 refe re n ce p h otog rap h s. (d) SSPC-SP15: Commercial Grade Power Tool Cleaning.— Pow er tools are u sed to rem ov e all grease, oil, dirt, d u st, m ill scale, ru st co a t in g s , o x id e s , co r r o s io n b y p r o d u ct s , a n d othe r fore ign m a tte r tha t a re vis ible w ithou t m a g n i fica t io n , e xce p t t h a t ra n d o m s ta in s a r e a llo w e d o n 3 3 p e r c en t o f e a ch 9 -in c h s q u a r e a r ea . Stain s m a y con sis t o f ligh t s h a d ow s, lig h t streaks, and m ild d iscoloration cau sed by r u st, m ill s ca le, an d p r ev io u s a p p lie d co a tin g s. Sligh t residu es of rust an d p aint are allow ed to rem ain a t th e bo ttom of corr osion p its, p r ov id ed th a t t h e or ig in a l su b st r a te w a s p itte d . Th is st an d ar d re q u ire s a m in im u m su rfa ce p rofile of not le ss tha n 1 m il be re ta ine d or p r o d u ce d . C u r r e n t ly , t h e r e is n o v i su a l r e fe r e n ce p h o t o g r a p h s fo r t h is st a n d a r d . (e) NA CE 4 /SSPC -SP7: B rushoff Blast Clea ning.— Br u s h - o ff b la s t cle a n in g e m p l o y s abr asive blasting to rem ove all grea se, oil, d irt, d u st , loo se m ill sca le, lo os e r u st , an d loo se co a tin g s t h a t a r e v isib le w ith ou t m a g n ifica tion . Tig h tly ad h er in g r u st , m ill sca le, a n d coa tin g s are allow ed to rem ain if they can not b e
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Guide to Protective Coatings: Inspection and Maintenance r em o v ed b y lift in g w ith a d u ll p u tt y k n ife . Th e v isu al s ta n d ar d is SSPC -VIS 1 refe re n ce p h otog rap h s. (f) NAC E 8/SSPC-SP 14: Ind ustrial Blast Clea ning.— In d u s t r ia l b la s t cle a n in g e m p l o y s abrasive blasting to rem ove all visible grease, o il, d ir t , a n d d u s t th at are v is ib le w ith o u t m a g n ificat ion . Tr a ces of t ig h tly ad h er in g m ill scale, ru st, an d coating resid u e are allow ed to r e m a i n o n 10 p e r c en t o f e a ch 9 in c h s q u a r e a r ea , p r o v id ed th a t t h e d ist r ib u tio n is e v en . T r a ce s of r u s t , m ill s ca le , a n d co a t in g s a r e allow ed to rem ain if they can not b e rem oved by liftin g w ith a d u ll p u tty k n ife. Sh ad ow s, st r ea k s, a n d d isco lor a tio n cau se d b y r u st , m ill s ca le , a n d p r e v i o u s ly a p p lie d c o a tin g s a r e accep table. The visua l stand ard is d eterm ined b y com p ar iso n to SSPC -VIS1 re fer en ce p h otog rap h s. (g) SSP C-SP8: Pickling.— P ick lin g r em ov es all m ill sca l e an d ru s t th at are v is ib le w ith o u t m agn ification, by chem ical reaction (acid b ath ) o r e le ct r o ly s is (an o d ic electrical cu rren t) or both . Acceptan ce criteria are to be established betw een contr acting p arties. (h) NA CE 3 /SSPC -SP6: C om me rcial Blast Clea ning.— C o m m e r cia l b la s t cle a n in g e m p l o y s abr asive blasting to rem ove all grea se, oil, d irt, d u st , m ill s cale, ru s t, co atin g s , o xid e, co rrosion b y p r o d u c t s, a n d o t h e r fo r e ig n m a t te r th a t a r e v i sib l e w it h o u t m ag n ificatio n , excep t fo r r a n d o m st a in in g . Stain in g m ay co n s is t of lig h t s h a d o w s , s lig h t s tr e a k s, o r m in o r s tr e a k s ca u se d b y r u st , m ill sca le, o r p r ev iou sly ap p lied coa tin g s. A t lea st t w o-t h ird s o f ea ch 9-in ch -sq u a r e a r ea sh a ll be fre e o f all v isib le resid u e, and only the ab ove-m entioned st a in i n g m ay b e p res en t in th e rem ain d e r of t h e a r ea . T h e v is u a l s ta n d a r d i s d e t er m in e d b y com p ar iso n to SSPC -VIS 1 refe re n ce p h otog rap h s. (i) NAC E 2/SSPC-SP 10: N ear-w hite m etal blast clean ing.— N ea r -w h ite m et a l b las t cle a n in g em p loys abrasive blasting to rem ove all grease, oil, d irt, d u st, m ill scale, ru st, coating s, oxid e, corrosion b yp rod u cts, and other foreign m atter that are v isible w ithou t m agn ification, excep t fo r r a n d o m s tain in g . Stain in g m ay co n s is t of
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lig h t s h a d o w s , s lig h t s tr e a k s, o r m in o r s tr e a k s ca u se d b y r u st , m ill sca le, o r p r ev iou sly a p p lied coa tin g s. A t le a st 95 p er cen t o f ea ch 9in ch -sq u a r e a r ea sh a ll be fre e o f all v isib le r es id u e, a n d th e r em a in d er of t h e a r ea sh a ll h av e on ly th e ab ov e-m en tion ed stain ing . The vis ua l sta nd a rd is de te rm ine d by c om p a rison to SSPC -VIS 1 referen ce p h otog rap h s. (j) NAC E 1/SSPC-SP 5: W hite M etal Blast Clea ning.— W h it e m e t al b la s t cle a n in g e m p l o y s abr asive blasting to rem ove all grea se, oil, d irt, d u s t, m ill s ca le, ru s t, c oa tings , oxid e , c orro sion b y p r o d u c t s, a n d o t h e r fo r e ig n m a t te r th a t a r e v isib le w ith ou t m a g n ificat ion . Th e r es u ltin g b la s te d s u r fa ce is g en e r a lly a u n ifo r m g r a y w hite color. Variation in color cau sed by steel typ e, origina l su rface cond ition, steel thickne s s , w e ld m e ta l, m ill or fa brica tion m ark s, h eat tr eatm en t, heat-affected zon es, blasting abr asives, or d ifferen ces in blast p a tt er n is a ccep ta b le. Th e v isu a l st a n d a r d is d ete r m in ed b y co m p a r iso n to SSP C -VIS 1 referen ce p h otog rap h s. (k) NACE 5/SSPC-SP12: Surface Preparation and C leaning of Steel and Other Hard Metals by High- and Ultra-Pressure Water Jetting Prior to R ecoating.— H igh- or ultra-high w ater jet b las tin g em p loy s w a te r b las tin g to r em ov e a ll gr ease, oil, dirt, d u st, m ill scale, ru st coating s, oxid es, corrosion b yp rod u cts, and other fore ign m a tte r tha t a re vis ible w ithou t m a g n ificat ion . Rem ov e n on v isib le s olu b le s a lt s t o a llo w a b le lim it s t h a t r e q u i r e p h y s i ca l testing to ver ify. The stand ard d efine s the fo llow in g fo u r d iffe r en t w a ter p r essu r es: (1) lo w -p r e s su r e w a t e r cle a n i n g a t le s s t h a t 5,000 p s i; (2) h i g h -p r e s su r e w a t e r cle a n i n g a t 5,000 to 10,000 psi; (3) high -pressu re w ater jet tin g at 10,000 to 25,000 p si; an d (4) u ltr a h ig h p r e s su r e w a t e r je t tin g a t g r e a t e r th a n 25,000 psi. The d egree of cleanliness is d ivid ed in t o t w o ca t e g o r ie s : v i sib le co n t a m in a n t s a n d no nv isible con tam inan ts. Visible contam inan ts are su bd ivid ed into fou r classifications, d esignated W J-1 thr ou gh W J-4 (WJ-1 is the clean est) on the b asis of allow able visible ru st, coating s, m ill scale, and foreign m atter v er ified w ith ou t m a g n ificat ion . N on v isib le contam inants are su bd ivid ed into three clas sifica tio n s, d es ig n a te d SC-1, SC -2, an d SC-3
Surface Preparation (SC-1 is th e cle a n es t) o n th e b a sis of a llow a b le so lu b l e c h lo rid e io n s , iro n -s o lu b le s alts , or su lfat e io n s. Th e v isib le a n d n on v isib le a llo w a b le co n t a m i n a n t le v e ls a re sp e c ifie d b y the d esignation W J-x/ SC-x; “x” ind icates the s p e c ifie d d e fin i tio n n u m b e r . T h e v is u a l stan d ard w ill be d eterm ined by com p arison to SSPC -VIS 4/ N A CE 7 referen ce p h otog rap h s. Re clam a tio n sp ecifie s W J-2/ SC -2 for all im m ersion serv ice exp osu res. W a te r jet tin g can n ot p r od u ce a su r face p r ofile w ithou t the ad d ition of abrasives into the jet flo w a n d , t h erefo re, is n o t s p ecified fo r su rfaces w ithou t a sur face p rofile, e.g., new co n st r u ctio n st ee l. Recla m a tio n sp ecifie s t h is stand ard only for pr eviou sly coated sur faces that h ave an existing sur face p rofile.
Th is is a n ex celle n t m et h od for r em ov in g old p aint and contam inants u sing only p ressur ized w a t er . W a t e r je t tin g e q u i p m e n t ca n b e v a cu u m s h ro u d e d t o p r e v en t sp r a y a n d h a v e in - lin e f ilt e r s t o se p a r a t e o u t o ld p a in t a n d co n t a m i n a n t s . So m e m a n u f a ct u r e r s ar e exp erim en ting w ith injecting abr asives into the w a te r -jet st r ea m th a t w ou ld b e ca p a b le o f p rod u cing a su rface p rofile. (a) SSPC-VIS 1: Visual Standard for Abrasive Blast C leaned S teel.— This guid e show s a series of ph otograp hs of un p ainted carbon steel be fore a nd a fte r a bra s ive bla s t c le a ning. Below is an abb rev iated exp lanation of the p r oc ed u r es to follo w b efo r e a n d aft er clea n in g t h e s te e l. T h e p r o c e d u r e s a r e fo llo w e d b y a n exam p le. 1.
Befor e a b ra siv e b las t clea n in g , m at ch the existing su rface con d ition w ith the “initial con d ition ” sh ow n in on e of the p h o t o g r a p h i c s ta n d a r d s . In i tia l co n d it io n s (o r r u s t g r ad e s) a r e p h o t og r a p h s A , B, C , a n d D a n d a r e d efin ed in se ctio n 4.1 o f th e st a n d a r d . V a r io u s a r e a s o f t h e su r f a ce to b e cle a n e d m a y m a t ch o n e o r m o r e in i tia l cond ition p h otog rap h s.
2.
Fr om th e s p ecifica tio n s, d et er m in e the s pe c ifie d s urfa ce pr e p a ra tion s ta nd a rd . The s urfa ce pr e p a ra tion sta n d a r d w ill b e on e of t h e fo llow in g : N A C E 1/ SSP C -SP 5, N A C E 2/ SSP C SP10, N A C E 3/ SSPC -SP6, or N A C E 4/ SSPC -SP7.
3.
Fr o m t a b le 1 in t h e v is u a l s ta n d a r d , s e le ct the s pe c ifie d s urfa ce pr e p a rat ion stan d ard an d the initial cond ition to ob ta in th e co r r ect p h ot og r a p h ic d e sig n atio n .
4.
Ev alu at e t h e fin ish ed b las t su rfa ce against the selected p hotog rap h in step 3 ab ov e t o d et er m in e if th e s u rfa ce m ee ts t h e s p ecified su rfa ce p re p a ra tion re qu ire m e nts for clean lin ess.
Th is is a n ex celle n t m et h od for r em ov in g old p aint and contam inants u sing only p ressur ized w a t er . W a t e r je t tin g e q u i p m e n t ca n b e v a cu u m s h ro u d e d t o p r e v en t sp r a y a n d h a v e in - lin e f ilt e r s t o se p a r a t e o u t o ld p a in t a n d co n t a m i n a n t s . So m e m a n u f a ct u r e r s ar e exp erim en ting w ith injecting abr asives into the w a te r -jet st r ea m th a t w ou ld b e ca p a b le o f p rod u cing a su rface p rofile.
30. Photographic Inspection Standards.— T h e in s p e c to r sh o u ld in s p e c t t h e su r f a ce b e fo r e an d after sur face p rep aration to eva luate clean line ss. SSPC an d N A CE/ SSPC stand ard visual reference ph otograp hs are a s u p p l e m e n t a l a id t o ev a lu a t in g c le a n lin e s s b u t ar e n ot in te n d ed as a s u b stit u te for su rfa ce clean line ss requ irem en ts d efine d in the su r f a ce p r ep aratio n s tan d ard u s ed . Th e re a s on for in sp ect in g th e s u rfa ce b efo re su rfa ce p r e p a r a t io n is th at d ifferen t d eg rad atio ns on th e s a m e s te el s u r face (e.g ., h ea v y m ill sca le w ith ligh t and heav ily ru sted areas) w ill have a d iffe r e n t a p p e a r a n c e a ft e r u s in g t h e s a m e su rface p rep aration m ethod . Thu s, steel s u r f a ce s th a t a r e a cce p t a b l y cle a n w ill a p p e a r d ifferen t, d ep end ing on the initial steel c o n d it io n a n d th e s u r face p rep aratio n m e thod em p loy ed . Belo w ar e t h e v isu al r efe re n ce s t an d a r d s fo r a b r a s iv e b la s t cle a n i n g , h a n d a n d p o w e r t o ol cle a n i n g , w a t e r je t cle a n i n g , a n d w et ab r a siv e b las t cle a n in g .
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Guide to Protective Coatings: Inspection and Maintenance Ex a m ple: A steel trashr ack has been d e liv er ed t o th e jo bsite u n co ate d a n d stor ed ou tsid e w itho u t p ro tection . The t r a sh r a c k is sh o w in g e v id e n ce o f u n ifo r m co r r o sio n an d n o p ittin g b efo r e co a tin g . T h e sp e cified s u rface p r ep aratio n m e thod is N A C E 2/ SSPC -SP10.
sta n d a r d w ill b e on e of t h e fo llow in g : SSPC -SP2, SSPC -SP3, o r SSPC -SP11. 3.
Step 1: Th e e xist in g su rfa ce ap p earan ce m ost closely rep resen ts r u st g r a d e “B.”
Reclam ation allow s the con tractor to c hos e the typ e of ha n d or p ow e r tool to acc om p lish th e w or k . D et er m in e th e ty p e of to ol to be u se d fr om t h e c ontra ctor. The follow ing d e s igna tion cod es are u sed in the stan d ard to id en tify v ariou s ha n d an d p ow er too ls: SP 2: H a n d w ir e b ru s h .
Step 2: Ta b le 1 sh ow s th at for su rfa ce p r e p a r a t i on N A C E 2 / SSP C - SP 10 a n d ru st gr ad e “B,” th e fin ished blast su rface sho u ld corr esp on d to p h ot og r a p h B SP 10.
SP 3/ P W D : P ow e r w i re br u sh . (R ecla m a t io n d o e s n o t p e r m it r o ta r y p ow e r w ire bru s hing be c a us e the t ool h as th e ten d en cy to bu rn ish or p olish t h e m e t a l s u r f a ce , t h u s r e m o v i n g a n y exis tin g su r fa ce p r ofile .)
Step 3: Evalu ate th e fin ished blast su r face ag a in st p h ot og r a p h B SP 10 to d eterm ine if the su rface m eets N A CE 2/ SSPC -SP10 cleanliness req u irem en ts. (b) SSPC-VIS 3: Visual Standard for Powe rand Ha nd-Tool Cleaned S teel.— Th is g u id e show s a series of p hotog rap hs of un p ainted an d p ainted carbon steel before an d after h a n d - a n d p o w e r -t o o l cle a n i n g . Be lo w is a n abb rev iated exp lanation of the p roced u res to follow befor e an d after clean ing th e stee l. Th e p roced u res are follow ed by an exam p le. 1.
2.
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Be fo r e h a n d - o r p o w e r -t o ol cle a n in g , m a tch th e ex is tin g s u rface co n d ition tha t m ost closely rep resen ts the a p p earan ce w ith th e “in itial co nd ition” sh ow n in on e o f th e p h ot og r a p h ic stan d ard s. Initial cond ition s (or ru st g r a d es ) A , B, C , an d D are fo r u n c o a te d s u r f a ce s ; co n d it io n s E , F , a n d G a re for p rev iou sly p ainte d su rfaces. In i tial co n d itio n s are d efin ed in s e c tion 4 .1 o f th e s tan d ard . V ario u s area s of th e s u rfa ce t o b e clea n ed m ay m at ch o n e o r m o re in itial co n d itio n p h otog rap h s. From the sp ecification s, d eterm ine th e sp e cified s u rface p r ep aratio n st an d ard . T h e s u rface p r ep aration
SP3/ SD: Po w er sa n d in g d isc. SP 3/ N G : P o w e r n e e d le g u n . SP11: Pow e r rota ry fla p p e e n or n ee d le g u n (to p ro d u ce a su rfa ce p r ofile ). SP11/ R: Pow er tool using n onw oven d isk s (to re sto re exis tin g su rfa ce p r ofile ). 4.
Fr o m t a b le 1 in t h e v is u a l s ta n d a r d , s e le ct the s pe c ifie d s urfa ce pr e p a rat ion stan d ard an d the initial cond ition to ob ta in th e co r r ect p h ot og r a p h ic d e sig n atio n .
5.
Evaluate th e finished han d or p ow er tool su rface against the selected p ho togr ap h in step 4 above to d e te rm i n e if th e su r fa ce m e ets th e s pe c ifie d s urfa ce pr e p a ra tion req u irem en ts for clean lin ess.
Example: An existing coated rad ial gate r e q u i r e s s p o t r e p a i r s. T h e co a t in g h a s d et er ior a te d or p ee led off in sm a ll lo ca liz e d a r e a s, a n d r u s t is ev id e n t b u t there is no visible pitting . The sp ecified su r face p r ep a r a tio n m et h od is SSPC -SP11, a n d th e co n tr acto r u s ed a n e ed le gu n .
Surface Preparation sp ecifie d d eg r ee of cle a n in g is W J-2.
Step 1: Th e e xist in g su rfa ce ap p earan ce m ost closely rep resen ts r u st g r a d e “C .”
N o t e: The d esignation SC-3 in the a b ov e e xa m p le d en ot es acc ep ta b le d eg r ee of cle a n in g for allo w a b le no nv isible solu ble salt contam inan ts a fte r w a te r jet clea n in g . Th e g u id e d oe s n ot at te m p t t o s h ow n on v isib le co n ta m in a n ts b y p h ot og r a p h ic illu st r a tio n . Ph y sica l te st in g is re qu ire d to de te rm ine c om p lia nc e for n on v isu a l con ta m in a n ts an d is d iscu s se d in su b se ctio n 28, “ Te stin g fo r C h lo r id es o n P r ep a r ed Su r fa ce s.”
St ep 2 : Select p o w er to o l d es ig na tion SP1 1 b ecau s e a n eed le g u n p o w e r tool w as u sed to p rep are the su rface. Step 3: From table 1, the finished su r fa ce p h oto gr ap h t h at co rr esp o n d s to ru st g ra d e “ C ” a n d su rfa ce p r e p aratio n S SP C -SP 1 1, an d th e tool u se d is C SP11. Step 4: Ev alu at e t h e fin ish ed su rfa ce aga inst p ho togr ap h C SP11 to d e te r m i n e if t h e su r f ace m e e ts SSP C SP11 clean lin ess req u irem en ts.
3.
Th e gu id e sh o w s p h oto gr ap h s of th e follow ing fou r d egr ees for flash ru sting : (1) no ru sting , (2) light, (3) m ed ium , and (4) heav y. These d e g re es o f fla sh r u stin g ar e th e d eg r ee s o f ru st in g allo w ed to r em a in on th e su r fa ce after w a te r jet clea n in g . T h e d e g r e es o f fla s h r u s t in g a r e d en oted in th e g u id e b y th e fo llow in g : (1) n o le t te r d e s ig n a t io n fo r n o r u s t in g , (2) L fo r lig h t , (3) M f o r m e d iu m , a n d (4) H fo r h e a v y . Fo r e xa m p l e , if lig h t flash ru sting is allow ed by th e sp ecificat ion s, a p os sib le su rfa ce p r e p a r a t io n w o u l d b e N A C E 5/ SSP C SP12 W J-2/ SC-3 L, w he re L is the a llo w a b le a m o u n t o f fla s h r u s t in g , a n d it is d e n o t e d i n t h e g u i d e p h o t o g r a p h s as W J-2 L.
4.
Fr o m t a b le 1 in t h e v is u a l s ta n d a r d , select the d egree of cleaning, den oted by W J-1, -2, -3, or -4, corresp on d ing to the in itial con d ition to obtain the c orre ct ph otogra p hic d e s igna tion.
5.
If th e s p ecifica tio n s a llow flas h r u st in g to r em a in on th e s u r face , u se ta b le 2 in th e visu a l sta n d a rd t o o bta in th e corr ect p h oto gr ap h ic d esign ation . The gu id e s how s ph otogra p hs for the four d egrees o f rusting p aired on ly w ith the in i tia l co n d it io n s C a n d D .
6.
Evaluate th e finished w ater jetted su rface against the selected
(c) NACE 7/SSPC-VIS 4: Guide and visual reference photographs for steel cleaned by water jetting.— T h is g u id e s h o w s a s eries of p h o t o g r a p hs o f u n p ain ted an d p ain ted ca rbon st eel b efo r e an d after w a te r jet clea n in g . Below is an abb rev iated exp lanation of the p r oc ed u r es to follo w b efo r e a n d aft er clea n in g t h e s te e l. T h e p r o c e d u r e s a r e fo llo w e d b y a n exam p le. 1.
2.
Before w ater jet clean ing, m atch th e existin g su rface cond ition th at m ost closely rep resen ts the ap p earan ce w ith t h e “in itial co n d itio n ” s h o w n in one of t h e p h o t o g r a p h ic s ta n d a r d s . In i tia l co n d it io n s (o r r u s t g r a d e s ) B a n d C (in i tia l co n d it io n p h o t o g r a p h s A a n d B a r e n o t in clu d ed in th e g u id e) are for u n co a te d s u r fa ce s. C o n d i tio n s E, F, G , an d H are for pr eviou sly p ainted su rfaces. Initial cond itions are d efined in s ectio n 4 .1 o f th e s tan d ard . V a riou s a r e a s o f t h e s u r f a ce t o b e cle a n e d m a y m a tch o n e o r m o re in itial co n d ition p h otog rap h s. From the sp ecification s, d eterm ine th e sp ecifie d d eg r ee of cle a n in g d esig n a ted b y on e th e fo llo w in g : W J1, W J-2, W J-3, or W J-4. A p os sib le s u r fa ce p r e p a r a t io n m e t h o d c ou l d b e N A C E 5/ SSP C -SP 12 W J-2/ SC -3; th e
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Guide to Protective Coatings: Inspection and Maintenance p ho togr ap h in step 4 and 5 above to d e te rm i n e if th e su r fa ce m e ets th e sp ecified su rface prep aration requ irem en ts for clean lin ess. Ex a m ple: T h e co atin g o n th e in terior s u r f a ce o f a n e x is t in g s t e e l p ip e h a s d e t er io r a t e d , a n d e x te n s iv e r u s t in g a n d p ittin g is ev id en t. Th e s p ecified su rfa ce p r e p a r a t io n m e th o d is N A C E 5/ SSP C SP12, WJ-2/ SC-2 L. Step 1: Th e e xist in g su rfa ce ap p earan ce m ost closely rep resen ts r u st g r a d e “D .” Step 2: From table 1, the finished su r fa ce p h oto gr ap h t h at co rr esp o n d s t o ru s t g rad e “D ” an d d eg ree o f clea n in g W J-2 is D W J-2. Ste p 3: Fro m ta b le 2, th e a llow a b le ligh t flash ru sting to rem ain on the fin ish ed su r face is p h ot og r a p h D W J-2 L, co rr esp o n d i n g to ru s t g r ad e “ D ” a n d lig h t fla sh r u st in g “L.” Step 4: Evaluate th e finished w ater je t te d s u r f a ce a g a in s t p h o t o g r a p h D W J-2 to d eterm ine if the su rface m eets N A CE 2/ SSPC -SP10 cleanliness r e q u i r e m e n t s a n d a g a in s t p h o t o g r a p h D W J-2 L fo r allo w a b le r em a in in g su rface flash ru st. N o t e: In t h e a b o v e ex a m p le , if lig h t flash ru sting is no t allow ed by th e sp ecificat ion s (i.e., th e s u rfa ce p r e p a r a t io n m e th o d is N A C E 5/ SSP C SP12 W J-2/ SC -2), sele ctio n an d ev a lu a tio n of p h ot og r a p h D W J-2 L in steps 3 and 4 are exclu d ed .
31. Alternative Surface Preparation Methods.— Ther e are altern atives to t r a d it io n a l ab ras iv e b las t clean in g m eth od s th at m ay red u ce su rface p rep ara tion costs, d u s t, o r fo u lin g o f m a ch in e r y b y sm a ll a b ra siv e p articles. These altern ative m eth od s, u n less ot h er w ise n ot ed , ass u m e a n exis tin g su rfa ce (anchor) pr ofile on th e sub strate surface does exist. If a su rface p rofile d oes not exist, or n ew
30
m a t e r ia l r e q u i r e s a d e e p e r p r o file , t r a d i t io n a l a b r a siv e b la st cle a n in g m u st b e em p lo y ed . Th e fo llow in g se ctio n s p r ov id e a lte r n a tiv e cleaning m ethod s w ith an abbr eviated d e scr ip t io n . (a) Sponge A brasive B lasting.— This m e tho d follow s th e tra d ition al abr asive b last m eth od s, e xce p t t h a t th e a b r a siv e p a r t icle s a r e en cap su lated in a sp on ge m ater ial. Th e sp ong e m aterial p reven ts abrasive pa rticles from brea king u p an d d iffusing on im p act, t h u s r e d u cin g t h e a m o u n t o f d u s t . Sp o n g e bla sting c re a te s a bou t 10 to 20 p e rc ent of t h e d u s t t h a t w o u ld b e cr e a te d b y n on en cap su lated ab ra sive m ater ials. Th e m etho d d oes create a su rface pro file, an d the su r fa ce cle a n lin ess ca n b e co m p a r ed to SSP C VIS 1. (b) So da B icarb onate B lasting.— This m e th od p rop els larg e crystals of sod a bicarbon ate (b a k in g so d a ) b y p r es su r ize d air or w a te r . It is u s ed m o stly as a str ip p e r fo r cle an in g co n ta m in a n ts an d for th in coa tin g s. Th er e is n o s u r face clea n lin es s s ta n d a r d for th is m ethod ; how ever, cleanliness can be sp ecified to m eet th e req u irem en ts of a consen su s su r face p r ep a r a tio n (e.g ., N A C E 3/ SSPC -SP6). (c) Ice Blasting.— Th is m et h od p ro p els ice p ar ticles b y p re ssu riz ed air . O n im p act , th e ice exerts a shee r force across the su bstrate su r face , re m ov in g con ta m in a n ts an d th in coating s. If d ry ice is u sed , it sho u ld n ot be u s e d in c onfine d s pa c e s be ca u s e of c a rbon d ioxid e b u ild u p . Th er e is n o s u rfa ce cleanliness stand ard for this m ethod ; how ever, clean line ss can be sp ecified to m eet the re q u ire m en ts o f a co n se n su s su rfa ce p r ep a r a tio n (e.g ., N A C E 3/ SSPC -SP6). (d) Chem ical Strip pers.— C h e m ica l s tr ip p e r s c a n be cla s s ifie d into tw o ge ne ric c omp os ition typ e s : (1) bond bre a ke rs a nd (2) c a us tic . Bond b r ea k er st r ip p er s w or k b y b r ea k in g th e p a in t's m o le cu la r b on d s b etw e en p a in t la ye rs a n d b e t w e e n t h e p a i n t a n d t h e s u b s t r a te s o t h a t p a in t w ill cr in k le u p an d b e ea sily r em ov ed . Bond break er strip p ers can contain tolu ene, m e t h yle n e ch lo rid e , o r m e th y l e th y l k eto n e th a t r em ov es p a in ts in a r ela tiv ely sh or t t im e
Surface Preparation b u t m a y b e co n sid er ed h a z a r d o u s t o w o r k er s. Le ss h a z a r d ou s b on d b r ea k er s co n ta in N m ethyl-pryr rolid one (N M P) or d ibasic ester (DBE) com p ou n d s, bu t th ese rem ov e p aint less q u ick ly . Bo n d b r e ak e r s tr ip p e rs w ill r em o v e a ll co a tin g s e xcep t o il-b a se d , in o r g a n ic, a n d m e t allic co a t in g s . C a u s t ic s tr ip p e r s w o r k b y s o ft e n in g t h e e n t i r e p a in t s y s te m r a t h e r t h a n b r e a k in g m o le cu l a r b o n d s . C a u s t ic s tr ip p e r s ca n con ta in so d iu m , calciu m , an d m a g n es iu m hy d roxid e. Cau stic strip p ers are r estricted to oil-based p aints bu t w ill not w ork on oil-based p a in ts th a t a r e p ig m en te d w ith alu m in u m flak es . Th is is b eca u se h y d r og en g a s is g en er a te d w h en cau st ic com p ou n d s co m e in contact w ith alum inu m , thu s p rev en ting th e ca u st ic st r ip p er fro m p en et r a tin g th e p a in t system .
C h e m ic a l s trip p e rs a re com m only u s e d for sm all areas w her e p ow er is not av ailable, a bra s ive a nd w a te r je t bla s ting is not e conom ic a lly fea s ible , hos e d is ta nc e is too gre a t to a chie ve ne c e ss a ry a ir p re s s ure for b las tin g op er a tio n s, o r w h er e a cces sib ility is lim ited. Ch em ical strip p ers are a lso used to m in im ize air b or n e p a in t p a r ticle s fo r or g a n ic p a in ts or h ea v y -m eta l b a se d p a in ts (e.g ., lea d ). In g e n e r a l, ch e m ica l s tr ip p e r s m a y b e m e s s y , m a y re q u ir e r ep e t it iv e ap p lica tio n s t o r em o v e a ll fo r e ig n m a t t er fr o m t h e s u b s t r a te , a n d m a y leave a resid u e on th e sub strate that requ ires so lv en t clea n in g . Th er e is n o s u rfa ce cleanliness stand ard for this m ethod ; how ever, clean line ss can be sp ecified to the re q u ire m en ts o f a co n se n su s su rfa ce p r ep a r a tio n (e.g ., N A C E 3/ SSPC -SP6).
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Chapter VII Environmental Conditions Cold w eath er, high h u m idity, w ater, fog, frost, m i st, r ain , ice , a n d sn o w a re so m e of th e en viron m en tal factors d etrim en tal to the p e r f or m a n c e o f co a t in g s . C o a tin g s s h o u l d b e a p p lie d u n d e r o p t im u m e n v i r o n m e n t a l co n d itio n s, b u t t h e w ea th er can ab r u p tly ch a n g e. Th e p r ev a ilin g en v ir on m en ta l ru le-o fth u m b is t h a t e v a p o r a tio n sh o u ld b e occu r r in g . C o m m o n s e n se , t h e m a n u f a ct u r e r ’s instru ction s, an d ind u stry p ractices ap p ear to be the m ost com m only follow ed gu idelines r eg a r d in g en v ir on m en ta l con d itio n s d u r in g co a tin g ap p lica tio n an d th e cu r in g p er io d . F a ilu r e t o co n f o r m w it h e n v i r o n m e n t a l r e st r ic tio n s res u lts in a v ariety o f ap p lica tion failu res.
32. Environmental Factors Affecting Coatings.— Th e fo llow in g ar e fiv e en v ir on m en ta l fact or s t h a t r eq u ir e m on ito r in g d u r i n g co a t in g a p p l ica t io n a n d t h e cu r e p e r io d . (Se e ap p en d ix K fo r tes t p ro ced u re s on th e fa cto r s b elo w .) (a) Amb ient T em perature.— D u r in g th e a p p lic a tio n o f co atin g s , Reclam atio n sp ecificat ion s r eq u ire th at th e a ir a n d su rfa ce t e m p e r a t u r e b e 50 d e g r e e s F o r h i g h e r a n d w it h in t h e m a n u fa ct u r e r ’s u p p e r t e m p e r a tu r e lim it or acco r d in g to th e m a n u fa ctu r e’s in st r u ctio n s, w h ich ev er is th e m or e r es tr ictiv e r e q u i r em e n t . E xce p t io n s a r e m a d e fo r co a t in g s fo r m u la te d fo r co ld w ea th er ap p lica tio n s. Am b i e n t (a ir) tem p eratu re is im p o rtan t for su c ce ssfu l film fo rm atio n an d cu rin g . Som e ep ox y coa tin g s a p p lied b elo w 50 d eg r ee s F w ill n ot cu r e, a n d cu r in g w ill n ot p r oc ee d ev en if tem p eratu res exceed 50 d egrees F at a later tim e. A g en er a l ru le-o f-th u m b in th e co a tin g ind u stry is to ap p ly coatings at am bient tem p er at u re s b etw ee n 40 an d 95 d eg re es F, d ep en d in g on th e co a tin g m a te r ial.
(b) Su rface Sub strate Tem perature.— R ecla m a t io n s p e c ifica t io n s r e q u i r e th a t co a t in g s b e a p p lie d w h e n t e m p e r a tu r e s a r e 50 d egrees F or h igher an d w ithin th e m an u factu rer’s u p p er lim it or accord ing to t h e m a n u f a ct u r e r ’s in s t r u ct io n s . T h e m o r e r est r ict iv e r eq u ir em en t w ill b e fo llo w ed . In gener al, ind u stry p ractice requires su r face te m p er a tu r e b et w ee n ab ou t 40 a n d 125 d eg r ees F. (c) Relative Hu mid ity.— R e cla m a tion d oe s not sp ecify lim its for r ela tiv e h u m id ity ; ra th er , it sp ecifies that th e coating be ap p lied w ithin th e m a n u fa ctu r er ’s r eco m m en d ed h u m id ity r a n g e. G en er a l in d u st r y p r a ctice r eq u ir es a m a xim u m relative hu m idity of abou t 80 to 85 p ercent, e xce p t fo r t h o se co a t in g s t h a t a r e le ss m o i st u r e s e n s it iv e o r a r e m o i s tu r e cu r e d . H o w e v e r , a s a gen eral ru le-of-thu m b, the closer to th e op tim u m relative h u m idity, the m ore likely to a ch iev e th e d esig n ed se r v ice life . (d) D ew Poin t.— Th e d ew p oin t d et er m in es if m o is tu r e w ill fo r m o n t h e fe r r o u s su b s t r a te s b y co n d en sa tion or if m oist u r e w ill e v a p or a te . M oisture w ill form on ferrou s su bstrate su rfaces w he n th e d ew p oint is higher tha n th e s u r fa ce te m p e r a t u r e . C o n v e r s ely , m o is tu r e w ill n ot for m w h en th e s u r face te m p er a tu r e is h ighe r th an th e d ew p oint. Dew p oint is a fun ction of am bient tem p eratu re, sub strate tem p eratu re, an d relative h u m idity. All three o f t h e se e n v ir o n m e n t a l co n d it io n s m u s t b e kn ow n to d eterm ine th e d ew p oint. Reclam ation sp ecification s requ ire that th e fer r ou s s u b st r a te te m p er a tu r e b e a m in im u m of 5 d egrees F higher th an the d ew p oint w hen co a t in g s a r e a p p lie d . Th e co a t in g i n d u s tr y im p ose s t h e sa m e d ew p oin t r est r ict io n . Reclam ation specifications requ ire su rfaces th a t a re n ot th o ro u g h ly d r y to be h ea te d o r th e e n v i r o n m e n t co n t r o lle d b y d e h u m id ify in g a n d heating equ ipm ent to d rive off m oistu re. 33
Guide to Protective Coatings: Inspection and Maintenance M oisture cond en sation w ill begin w he n th e su bstrate tem p eratu re is less than the d ew p o in t . To a llo w fo r p o s s ib le in s tru m en ta tion e r r o r o r v a riatio n , a m in im u m s afety m argin of 5 d e g re es F su b str ate te m p e r atu r e a bo v e th e d e w p o i n t is r eg a r d e d a s a g e n e r a l in d u s t r y requ irem en t. (e) W ind.— R ecla m a t io n d o e s n o t sp e c ify a m a xim u m w in d v elo city r es tr ictio n in coa tin g ap p lication s. W ind becom es a factor w he n it
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overcom es the sp raying op eration an d carries coating p articles aw ay from the intend ed s u r fa ce . T h is p r o b le m is k n o w n a s a ir b o r n e ov er sp r a y . A ir b or n e o v er sp r a y m a y r es u lt in p r e m a t u r e d r y i n g o f t h e co a t in g b e fo r e r e a ch i n g t h e in t e n d e d s u r f a ce , a lo w e r D F T a t th e sp ra y a p p lication p oin t, a h igh er D FT d o w n w in d , o r sp r a y b ein g ca rr ie d to ad ja ce n t veh icles, hom es, or oth er su rfaces not intend ed to be coated. Com m on sen se shou ld be u sed to av oid airbo rn e ov ersp ray p rob lem s.
Chapter VIII Application and Curing C o a t i n g a p p licatio n is next in imp ortan ce after su rface p rep ara tion, an d accou n ts for m ost failu re s. A coa tin g is n ot a fin ish ed p ro d u ct u ntil it ha s been su ccessfu lly ap p lied to the st ee l su b st r a te an d cu r ed . Co a tin g p e r fo r m a n c e is a ffe ct e d d u r in g a p p lica t io n a n d cu r in g b y t e m p e r a t u r e , r e la t iv e h u m id it y , a n d d e w p o in t . (Se e ch a p t e r VII, “ E n v ir o n m e n t a l C o n d it io n s .” ) M i x in g , n u m b e r o f co a t s a n d th ickn ess, and ap p lication tech n iqu e w ill also affect coating p erform an ce. N ot obser ving the env ironm ental restrictions or im p rop er ap p lication tech n iqu es can resu lt in d efects, p rem atu re failure, or red u ced serv ice life.
33. Application Temperature and Humidity Restrictions.— E n v ir o n m e n t a l co n d it io n s a r e n o t a lw a y s co n t r o lla b le . W e a t h e r m a y abr u p tly cha ng e, an d cond ition s m ay v iolate the m an u factu rer’s tem p eratu re an d hu m idity r e st r ict io n s . U n l e ss co n d it io n s ca n b e c o n t r o lle d by d eh u m id ify in g , h eatin g , o r a co m b in a tio n of b ot h , field ap p licat ion sh ou ld p r o ce ed on ly d u r in g fa v o r a b le w ea th er . Coa ting in h igh h u m idity ar eas, su ch as th e in t e r io r s o f v a u l t s o r p i p e s , s h o u l d b e p er for m ed on ly w h en th e e n v ir on m en t is co n tr o lle d b y d eh u m id ify in g , h ea tin g , or b oth . Reclam ation sp ecification s p rov ide th e follow ing tem p eratu re an d hu m idity r estr ictio n s, u n less th e m a n u fa ctu r er ’s instru ction s are m ore string en t:
•
Relative h u m idity sh all be w ithin th e m an u factur er’s lim its.
34. Coating Layers.— Re clam a tio n ty p ically sp ecifie s t h e n u m b er of co a ts to b e a p p lied in t h e co a t in g t a b u l a tio n s . T h e fo llo w in g t e r m s p rov id e a d escription of the coat ing lay ers: (a) Strip e Coat.— Stripe coats are ap p lied to p rep are d bar e m etal ed ges, bolth ead s, w e ld s , co rn e rs, a n d sim i la r e d g es b efo re th e p r i m e co a t is a p p lie d . St r ip e c o at s a r e n ece ss a r y b eca u se , as th e co a tin g d r ies , te n sile forces are created at the ed ges, forcing th e coating to p u ll aw ay from the ed ge in b oth d irections, resulting in a th inn er coating at th e e d g e . St r ip co a t s p r o v i d e a n a d d it io n a l t h ick n e s s b u i ld u p t o p r e v e n t t h i n , D F T a t ed ges. (b) Prime Co at.— Prim e coats are ap p lied ov er th e e n tir e s u r face to b e co a te d , in clu d in g strip e coated ar eas. The p rim e coat mu st cover th e p eak s of th e su rface p ro file. Th e co n se q u en ce o f n ot cov er in g th e p ea k s is p i n p o in t r u s t in g . (c) Interme diate Co at.— Interm ed iate co a ts ar e a p p lied ov er th e p r im er to p r ov id e a d d itio n a l p r ote ctio n or to se a l th e p r im er . M u ltip le inter m ed iate coats can b e ap p lied to bu ild u p th e film th ickn ess.
•
A ir an d su b st r a te te m p er a tu r es sh a ll b e a b ov e 50 d eg r ee s F d u r in g a p p lica tio n an d c u rin g an d w ith in th e m a n u fa ct u r e r ’s u p p e r t e m p e r a tu r e lim it.
(d) To pco at.— Top coats or finishe d coats are ap p lied over the p rim er or in term ed iate coat for color aesthetics or to p rotect the u n d e r lin i n g c oa t in g m a t e r ia l fr o m s u n lig h t a n d U V light.
•
Su r faces sh all b e a m in im u m o f 5 d eg r ee s F a b ov e t h e d ew p oin t te m p er a tu r e a t t h e t im e o f coa tin g a p p lica tio n .
(e) Ba se Coat.— “Base coat” is a term often u s e d t o d e s cr ib e a s elf-p r im in g m a t e r ia l ap p lied in m u ltip le coats. The ter m , “base co a ts ,” is u se d in st ea d of “ p r im er ,” “ in te r m ed iat e,” an d “t op co a t” b eca u se all
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Guide to Protective Coatings: Inspection and Maintenance thr ee coats are of the sam e m aterial. Base coats a r e n o t n o r m a lly co n s id e r e d s u n l ig h t o r U V resistant.
35. Mixing.— Befo r e a p p licat ion , th e co a tin g m a t er ia ls r eq u ir e m i xin g to m a k e th e p ain t h o m o g e n e o u s a n d u n i fo r m . L iq u id s a n d p igm ents of different d ensities m ay sep arate, se tt le, o r for m a s k in w ith in th e s h ip p in g container. M ixing is to be p erform ed accord ing to th e m an u factur er’s instru ction s. C o a t i n g s a r e eith er s in g le-co mp o n en t o r m u ltip le-co m p on en t. M os t m u ltip leco m p o n en t co a tin g s a r e tw o -co m p o n en t. Epo xies are an exam p le of a two -com p onen t co a tin g . Th ey co n ta in a r esin an d a h a r d en er . The com p onen ts of a m u ltiple-com p onen t co a tin g can b e in eq u a l p r op or tio n s (e .g., 1:1) o r u n e q u a l p ro p o rtio n s (e.g ., 1:4 ). P ro p o rtions are d eterm ined by vo lum e. Com p on en ts m u st be sh ipp ed in sep ara te con taine rs. Regard less of the p rop ortion volu m e for m u ltipleco m p on en t m a te r ials , th e m a n u fact u r er w ill ship on e container large en ou gh to ho ld a ll the co m p o n e n t s fo r m ix in g . The follow ing a re com m on m ixin g m eth od s: •
M an u ally p ad d lin g (the m ost in efficie n t m et h od ).
•
M e c h a n ica lly a g it a tin g o r p a d d lin g .
•
Sh a k i n g .
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Bo x in g ( r e q u i r es p o u r in g t h e m a t e r ia l from the original ship p ing container in to an em p ty con ta in er an d r ep ea tin g th e p rocess sev era l tim es). It is m ost often u sed for sing le-com p on en t, m oistu re-cur ed m ater ials.
If th e m an u factur er r ecom m en d s th inn ers, they are ad d ed in the r ecom m en d ed am ou nts d u ring m ixing. After m ixing, som e m u ltipleco m p on en t m a te r ials r eq u ir e a 10- to 30m in u t e in d u ct io n p e r io d t o a llo w ch e m ica l r e a c tio n s t o b eg in b efo re ap p licatio n .
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36. Application Method.— O n ce t h e s u rfa ce su b str ate h as b ee n p ro p er ly p r ep a r ed a n d env ironm ental cond itions are w ithin sp ecified to ler a n ces , th e a p p licat ion of t h e co a tin g m aterial m ay p roceed. There are severa l equ ipm en t choices from tran sferring the co a tin g fr om th e co n ta in er to th e su b st r a te . A p p lica tio n eq u ip m e n t m a y b e d icta te d b y th e m a te r ia l ty p e an d th e siz e of th e su r fa ce ar ea . Th e m a n u fact u r er ’s in st r u ctio n s w ill n or m a lly p rovid e the p re fe rre d a p p lic a tion m e thod for sm a ll a n d la r g e ar ea s. The follow ing is a de s c rip tion of a pp lic a tio n equ ipm en t an d m eth od s. (a) Brush.— The re tw o ge ne ra l type s of bru s he s : w a ll a nd s a s h. The y c ome in va riou s sizes, shap es, and bristle typ es. For steel s ub s tra tes , w a ll bru s he s a re norm a lly u s e d f or sm a ll a r ea s, r ep a ir ar ea s, a n d cr ev ice s o r g a p s. W a ll or ov a l b r u sh es ar e w ell s u ite d for st r ip e coating irregu lar su rfaces su ch as ed ges, corn ers, bolth ead s, an d sim ilar a rea s. Sash bru s he s a re be tte r s uite d for coa ting n a rrow are as. (b) M itten.— M i t te n o r p a i n t p a d s h o ld m o r e co a tin g th a n a b r u sh , b u t t h ey r eq u ir e a tr a y . Th is a p p licat ion m et h od is u se d for sm a ll, ir r e g u l a r ly s h a p e d s tr u ct u r e s s u c h a s h an d rails. (c) Ro ller.— R o lle r s co n s is t o f t w o g e n e r a l p a rts : cove r a n d c ore. The cove r is the s e ct ion th a t a p p lies th e co a tin g an d w ill v a r y in d iam eter, len gth , fabric typ e, an d fiber len gth (n a p ). R o lle r s a r e n o r m a lly u s e d f o r la r g e fla t a r e a s (h o r iz o n t a l a n d v e r t ica l s u r fa ce s) t h a t ar e t o o la r g e fo r b r u s h a p p lica t io n o r w h e r e ov er sp r a y can n ot b e t ole r a te d . Th r ee b a sic typ e s of rolle rs a re dis cu s s e d be low . Pipe roller.— Pipe rolle rs cons ists of tw o or m ore rolle rs hinge d toge the r to conform to a curv ed sur face such a s a sm all-diam eter p ipe. Fence ro ller.— Fe n ce r o lle r s h a v e a n e x tr a long n a p s o tha t w he n a p p lying a c oa ting fr om
Application and Curing o n e si d e o f a h u r rican e o r w ire fen ce, th e long n ap w ill cov er b oth sid es. Pressure roller.— Pressu re rollers feed a p e r fo r a t e d co re w ith a s tead y s u p p ly o f co a t in g m a t er ia l fr o m a p r e s su r i z ed t a n k . (d) Conventional Spray (applied cold or hot).— Equipm ent.— A n air com p r es so r , an oil a n d w a t e r s ep arato r, a p res s u re tan k (p ot) or p u m p , a ir a n d flu i d h o s es , a n d a s p r a y g u n a r e ne ed ed . For ho t sp ray , a h eater is ad d ed to h ea t th e m at er ial to ab ou t 150 to 160 d eg re es F. Working principle.— C om p r es se d air is in t r o d u ce d in t o t h e co a t in g s t r e a m a t t h e s p r a y g u n n oz z le, th u s b r ea k in g d ow n th e co a tin g in t o t in y d r o p l e t s (co a t in g a t o m iz a t io n ) a n d p rop elling the coating to the su rface sub strate. Ad van tages.— T h e co n v e n t io n a l sp r a y m et h od p r ov id es m or e fin ely at om ize d coa tin g p a r t icle s, r e su l t in g i n a sm o o th e r a n d m o r e u n ifor m film . Lar g e a r ea s ca n b e co v er ed in a relatively sh ort tim e. Op erator control of the sp ray gu n is excellen t. Th e sp ray gu n h as a high d egree of versatility regar d ing d ifferen t co a tin g m a te r ials an d sp r a y p a tt er n s. Str ip in g c a n b e a cc omp lis h ed b y th is meth o d . Fo r h ot sp r a y ap p licat ion , th e v isco sit y is low ered to im p rove a p p lication o r to m eet m inim u m m aterial tem p eratu re. Disa dva ntag es.— T h e co n v e n t io n a l sp r a y m eth o d u se s la r g e am o u n ts of a ir . C o n se q u e n tly , tran s fer efficien cy is lo w (m at er ial is lo st) b eca u se of b ou n ce b ack (rebou nd ) an d oversp ray. The rebou nd m akes it d ifficu lt t o co a t co r n er s a n d cr ev ices . Th is m et h od is n ot g en er a lly su ita b le fo r h ig h -b u ild co a tin g m a te r ia ls w ith o u t e xcess iv e th in n in g . Use .— Th is m et h od is u se d on n ea r ly all R e cla m a t io n s tru ctu res w h ere o v ers p ray is not a concern. The h ot spr ay m ethod is u sed d u r i n g co o le r w e a t h e r . (e) High-Volume, Low-Pressure (HVLP) Spra y.—
Equipm ent.— Th is m e th o d r eq u ir es a h ig h v olu m e a ir su p p ly (com p r es se d air or tu r b in e g e n e r a t o r ), a m a t e r ia l s u p p ly s y s te m , a n d a n H VLP sp r a y g u n . Working principle.— A h ig h v olu m e o f air a t o m i z es th e co a t in g m a t er ia l a t a lo w p r e s s u r e an d tran sfers the atom ized coating p articles to the su bstrate by low p ressur e. Ad van tages.— The m ethod has a b etter t r a n s fe r e fficie n c y (le s s m a t e r ia l lo s t) t h a n h a s th e co n v en tio n al s p ra y m et h od , an d b ou n ce ba ck an d ov ersp ra y a re r ed u ced . Th e H VLP sp ray g u n is m ore controllable than other sp ray gu ns. The m etho d w ork s w ell w ith h ig h -so lid s co a tin g m a te r ial. Disa dva ntag es.— The cove ra ge or p r o d u ct io n r a t e is le s s t h a n w it h o t h e r s p r a y m ethod s, and the m ethod m ay not atomize certain coa ting m ater ials. Use s.— This meth od is lim ited to sm aller a re a s or s urfa ce s tha t conta in nu m e rou s recesses. (f) Airless Spray (Ap plied Co ld or Ho t).— Equipm ent.— This m eth od req u ires a p ow er so u r ce (e lect r ic m ot or or air co m p r ess or ), a h y d r a u lic p r ess u r e p u m p , a h i g h -p r e s su r e flu id h o s e , a n d a n a i r le s s s p r a y g u n w ith a s a fet y ex te n sio n tip . Working principle.— A t om i za tio n of th e co a t in g i s a ch i e v e d b y f o r cin g t h e m a t e r ia l th r ou g h a s m a ll or ifice u sin g h y d r a u lic p r e s s u r e r a th e r t h a n a ir p r e s su r e . T h e h ig h p r e s s u r e p u m p m u l t ip l ie s t h e in p u t p r e ss u r e by a m inim u m factor of 30, su ch th at th e ou tp u t p ressur e at the sp ray g u n p rod u ces p r e s su r e s u p t o a b o u t 6,000 p s i. T h e sp r a y g u n ha s a fixed orifice size an d variou s fixed ang les t o a llo w s e v e r a l s p r a y f a n p a t t e r n s a n d t h ick n e s s e s t o b e ap p lie d w it h t h e s a m e a m ou n t o f m a te r ial. Ad van tages.— This meth od p rovid es g r ea te r cap a city for ap p ly in g h ig h b u ild coating s, gr eater su rface p en etra tion b ecau se of high a p p lic a tion p re s s ure s , high c ove ra ge or
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Guide to Protective Coatings: Inspection and Maintenance p r o d u c t io n r a t es , t h e ca p a c it y to a to m iz e h ig h v i sco s it y m a t e r ia l, r e d u ce d o v e r s p r a y a n d b ou n ce b a ck , an d th e p ot en tia l for r ed u ced oil a n d w a te r co n ta m in a tio n .
Use s.— This m e thod is s uita ble for m e d i u m t o la r g e su r f a ce a r ea s w h e r e o v er sp r a y a n d r eb ou n d a re n ot a co n ce rn . (h) Electrostatic Spray.—
Disa dva ntag es.— T h is m eth o d d o es not p rod u ce the finely atom ized coating p articles t h a t a r e p r o d u ce d b y c on v e n t io n a l sp r a y , a n d it is n ot su ited for h igh qu ality finishe s. The o p e r a t o r h a s le s s co n t r o l o f t h e s p r a y g u n t h a n w it h t h e co n v e n t io n a l s p r a y m e t h o d , a n d t h e r e is a h igher p oten tial for ap p lication d efects th an w ith th e con ve n tion al sp ra y m eth od . The h igh p ressu res ar e cau se for safety con cern s. Use s.— T h is m e t h o d is b es t s u it e d t o la r g e su r fa ce ar ea s w h er e ov er sp r a y is n o t a co n ce r n . It is u se d on n ea r ly all Re cla m a tio n st r u ctu r es. T h e h o t sp ray m eth o d is u s ed fo r ap p lication d u r i n g co o le r w e a t h e r . (g) Air-A ssisted Airless Spra y.— Air-assisted a ir le s s s p r a y a p p lica t io n e q u ip m e n t w a s d eveloped to comb ine som e of the ad van tages of con ven tional and airless spr ay sy stem s into one system . Equipm ent.— This m eth od req u ires a h y d r a u lic p r es su r e p u m p (500 to 1,000 p si), h o s e s , a n a i r co m p r e s so r (10 t o 15 p s i), a n d a sp r a y g u n . Working principle.— T h e ato m izatio n of the coating is sim ilar to th e atom ization of the airless sp ray er, bu t the p ressu re is low er at th e o r i fic e o f t he s p r ay g u n w ith th is m eth o d , n or m a lly at ab ou t 10 p si. Ad van tages.— T h is m e t h o d p r o v i d e s m o r e finely atom ized coating p articles, a low er p otential for ap p lication d efects, and better o p er ato r co n tr ol o f th e sp r a y g u n th a n th e a ir les s m et h od . A lso , tr a n sfe r efficie n cy is b e t te r th a n w it h t h e co n v e n t io n a l s p r a y e r . Disa dva ntag es.— This meth od is not su ited fo r h i g h - q u ality fin is h es b ecau s e ato miz a tion a p p r o a c h e s b u t d o es n o t eq u al ato m ization w ith th e co n v en tio n a l sp r a y er m et h od . Th is m e t h od p r od u ce s o ve rsp r a y a n d r eb ou n d .
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Equipm ent.— Th e eq u ip m e n t u s ed in th e electrostatic sp ray m etho d is sim ilar to conven tiona l, airless, and air-assisted spr ayer e q u i p m e n t , e xce p t t h a t an e le ct r o st a tic, h i g h voltage su p p ly is requ ired. Working principle.— A t o m iz e d c o at in g s a r e a p p lied to th e s u b st r a te b y con v en tio n a l, air less , or air -as sist ed sp ra y eq u ip m en t, w h ich is con n ected to an electr ost a tic p ow er so u r ce . The coating m aterial is p ositively charged , an d the su bstrate is neg atively charg ed (conv entional electrical theor y). Sp rayed , p ositively charged , atom ized coating p articles are attracted to n egatively charg ed sub strate. Ad van tages.— T h e e le ct r o st a t ic s p r a y m e thod is ca p a ble of a p p lying c oa tings to od d sh a p es a n d a ro u n d co rn e rs, a n d o ve rsp r a y a n d r e b o u n d m a t er ia l in c o n fin e d s p a ce s a r e rea ttracted to th e su bstr ate. This m eth od h as a h igh tr an sfer efficiency r ate an d p rod u ces a u n ifo rm f in ish . Disa dva ntag es.— Th e w in d m a y ca rr y th e co a tin g m a te r ial a w a y , th e m et h od allo w s o n ly on e thin coat, the cov erag e an d p rod u ction rate a r e less th a n w ith th e oth er sp r a y m eth od s, a co n d u ctiv e co a tin g for m u lat ion is u su a lly r e q u i r ed , t h e m e t h o d is u n s u it a b le fo r la r g e stru ctu res, an d th is m eth od p resen ts a p o t e n t ia l e le ct r ica l s h o ck h a z a r d . Use s.— Th is m et h od is su ite d to sm a ll a r e a s b e h i n d co r n e r s , r e ce s se d a r e a s, ir r e g u l a r a r e a s, o r a r ea s th a t ca n n o t b e co a t ed b y conv en tional-typ e ap p lication equ ipm en t. (i) Plural Comp onent S pray.— T h is sp r a y ap p lication m etho d is the m ost com p lex of the spray equipm ent group an d should be used by a p p lica t o rs w h o a r e t r a in e d a n d ce r tifie d b y the c oa ting m a nu fa c tu re r. This a pp lic a tion m e t h o d i s co m m o n ly u s e d t o ap p ly t w o o r
Application and Curing m o r e co m p o n e n t m a t e r ia ls (h e n c e, t h e te r m “ p lu r a l” ) s u c h a s p o l y u r e t h a n e s a n d p o ly u r e a s t h a t c a n h a v e an ex trem ely s h o rt s et p eriod (3 to 30 se co n d s fo r m a te r ial t o h a r d en ). Equipm ent.— This m eth od req u ires a p r o p o r t io n in g p u m p , a m i x m a n i fo ld , a m ix er , a s p r a y g u n , m a t e r ia l s u p p ly c on t a in e r s , a n d a s o lv e n t p u r g e (flu s h ) co n t a in e r . M a t e r ia l ca n b e a p p lie d b y c o n v e n t io n a l, a ir le ss , o r a ir a s sis t ed s p r a y e q u ip m e n t , b u t sp e cia l s p r a y g u n s a re re qu ir ed . Th e eq u ip m e n t a n d m at er ials m ay b e h ea te d to d ecr ea se th e cu re p e rio d a n d a llo w fo r cle an u p . Working principle.— In d iv id u a l co m p on en ts ar e m ixe d th r ou g h a m et er in g sy st em th a t in clu d es a p r op or tio n in g p u m p , if m i x r atio s a re oth e r th a n on e -to -o n e, a n d d eliv er ed at t h e sp r a y g u n or at t h e sp r a y tip . Th is m et h od elim in a te s p r em ixin g in a p ressu re p ot. Ad van tages.— W ith th is m et h od , it is p ossible to ap p ly high -bu ild , high -viscosity m a t e r ia l s in o n e p as s , elim in ate lim ited p ot life, an d m ay p rov id e red u ced cur e tim es. Disa dva ntag es.— This meth od requ ires p r e cis e p r e s e tt in g o f p r o p o r t io n i n g a n d tem p eratu re system s. It requ ires im m ed iate an d th oro u gh clean ing o f equ ipm en t after u se to p r ev en t m a te r ial fr om se tt in g u p . It is imp ractical for sm all jobs; it requ ires trained op erators fam iliar w ith th e specific equ ipm ent an d m aterial to be u sed . Use s.— It is su it a b le fo r la r g e s u r f ace s th a t a r e s u b je ct t o b u r ia l, im m e r s io n , an d ch e m ica l ex p os u r es r eq u ir in g th ick b a r r ier coa tin g m a te r ial.
37. Application Technique.— Reclam at ion d oes n ot sp ecify the p roced u re or tech niqu e to a p p ly th e co a tin g . Recla m a tio n r eq u ir es on ly tha t the coating be ap p lied in accord an ce w ith th e m an u factur er’s instru ction s. These instru ction s are p rov ided in the m a n u f actu r er ’s a p p lica tio n sh e et. Th e a p p lic a tio n tech n iq u e u s ed b y th e ap p lic a tor w ill v a ry slig h tly w ith th e ty p e of e qu ip m e n t a n d m a t er ia l. M o s t co a t in g jo b s ar e
a c com p lis he d u s ing b ru s h, rolle rs , s pra y e rs, or a co m b in a t io n o f th e s e to o ls ; h o w e v e r , s p r a y equ ipm ent is the m ost com m only u sed m e t h o d . Se v e r a l “ g o o d p r a ct ice ” t ip s fo r s p r a y a p p lic a tions a re d is cu s s e d be low . (a) Po t Pressures.— The p re s s ure p ot s hou ld ha v e tw o p re s s ure ga u ge s : one for pot p ressu re an d on e for atom ization of the c oa ting m a te ria l. The pr e s s ure p ot re gula to r s hou ld p rovid e s uffic ie nt p re s s ure to m ove co a t in g m a t e r ia l t h r o u g h t h e h o s e t o th e s p r a y gu n. The a tom iz a tion p re s s ure re gu la tor sh o u ld b e se t h ig h en o u g h to ato m iz e th e co a tin g m a te r ial. A se tt in g th a t is to o lo w w ill c a us e the m a te ria l to clu m p or p os s ibly clog th e sp r a y g u n . (b) Air Co mp resso r.— C om p r es se d air s hou ld flow a t a s te a d y ra te . Pu ls a tion of m aterial from the sp ray g u n n orm ally ind icates a n in a d e q u a t e a ir s u p p l y . (c) Spray G un T echniqu e.— T h e sp r a y g u n s hou ld be he ld p e rp e nd ic ula r to a nd a bou t 18 in ch es aw a y fro m th e s u b st r a te . Th is d is t an c e m a y v a r y s lig h t l y w i t h d iffe r e n t sp r a y a p p a r a tu s . A n g l in g , t ilt in g , o r h o ld in g t h e g u n too close or too far aw ay cou ld cau se the co a tin g to sa g or d r y b efo r e h ittin g th e su r fa ce . The s pra y p a tte rn s hou ld ove rla p the p re vious p ass by a p p roxim ately 50 p ercent, and the stroke length o f each p ass shou ld be b etw een 18 to 36 inches. The ap p licator shou ld m ake a p a ss o f th e sp r a y g u n b y m o v in g th e ar m a n d bod y, rather tha n r otating th e w rist to fan the gun.
38. Drying, Recoating, and Curing.— D r yin g a n d cu r in g a r e n o t i n t er ch a n g e a b le t er m s a s th ey r elate to coatin gs. SSPC d efin es cu re a s, “ Th e p r oc es s o f ch a n g in g th e p r op er tie s o f a p aint from its liquid state into a d ry, stable, solid p rotective film by ch em ical reaction w ith oxyge n, mois ture , or c he m ic a l a d d itive s , or by t h e a p p lica t io n o f h e a t o r r a d ia t io n . ” A c co r d i n g t o th i s d e fin i tio n , co a t in g s t h a t fo r m p rote ctive film s w ithou t che m ic a l re a c tion d o n ot cu r e, b u t o n ly d r y to for m a film . D r y in g is th e loss of solve n t or w ater , and th e p rocess m a y o r m a y n o t fo rm a p r o te ctiv e film . C u r in g w ill alw a y s p r od u ce a p r ot ect iv e film .
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Guide to Protective Coatings: Inspection and Maintenance O nce th e coating ha s been ap p lied , the in sp ect or can d o lit tle , exce p t t o p r ot ect n ew ly coated su rfaces from being d am aged an d no te te m p er a tu r e a n d h u m id ity d u r in g th e cu r in g p er io d to en su r e th a t p r o p er cu r e is o b ta in ed . M an u factu rer’s instr u ction s m ay list a va riety o f t im e p e r i o d s fo r d r y in g , r eco a t in g , a n d cur ing at v ariou s tem p eratu re an d hu m idity co m b in a t io n s . T h e se tim e p e r io d s a r e d iscu ss ed b elo w . (a) D rying.— D r yin g is th e p er io d w h e n a co a t e d i te m ca n b e m o v e d o r w h e n i t ca n a ccep t t r a ffic w ith ou t d a m a g in g th e co a tin g b e fo r e fu l l cu r e a t a r efe r e n ce d t e m p e r a t u r e an d h u m id ity . M os t m an u fact u re r’s p ro d u ct d a ta sh eets r efer to d r y in g tim es a s “ ta ck fr ee,” “t o t ou ch ,” “ to h an d le,” o r, “ to sta ck ” (t o s ta ck ite m s o n e o n to p of a n ot h er , e.g ., p ip e stacking), m eaning the tim e betw een a p p lic a tio n an d w h en th e s u r face is tack fre e or d r y en o u g h to to u ch , to h a n d le, or to st a ck . Re clam a tio n sp ecifica tio n s co n sid er a co a tin g t o b e d r y “ w h en it can n o t b e d is to rted o r r e m o v e d b y e x er t in g s u b s t a n t ia l, b u t le s s t h a n m a x im u m , p r essu r e w i th th e th u m b an d tu rn ing th e thu m b th rou gh 90 d egrees in th e p la n e of th e co a tin g film .” (b) Recoating.— This is also referred to as “to r eco a t” or “r eco a t w in d ow .” Th is is t h e t im e p e r io d w h e r e a p r e v i o u s c oa t in g c a n r e ce iv e a n interm ed iate coat or a topcoat at a referenced
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t e m p e r a t u r e a n d h u m id it y . W h e n t h e r e co a t w in d ow h a s b ee n ex cee d ed , th e co a tin g su rfa ce m ay re q u ire fu rt h er su rfa ce p r e p a r a tio n fo r w h i ch m o s t m a n u fa ct u r e r ’s recom m end abrad ing the su rface or solvent a p p lica t io n o r b o th . R eco a t w in d o w s v a r y w idely, from a few m inu tes to a m on th o r lon g er , d ep en d in g on th e t y p e o f coa tin g m a te r ial. If te m p er a tu r e a n d h u m id ity ar e n ot sho w n o r are ou tsid e the listed valu es on the m a n u fact u r er ’s in st r u ctio n s, th e co a tin g m a n u fa ctu r er sh ou ld b e co n su lted . Reclam ation sp ecification s sp ecify the m a nu fa c tu re r’s re com m e nd e d re coa t w ind ow becau se recoat w ind ow s var y gr eatly w ith m a te r ia l ty p e. (c) Cu ring.— This is the ne c e ss a ry tim e pe ri od at a referen ced tem p eratu re an d hu m idity com bination to allow the coating to com p lete t h e ch e m ica l r e a ct io n a n d t o a ch i e v e st r u c t u r a l integrity so th at it w ill be read y for th e in t e n d e d s e r v ice e xp o s u r e . E xce ss iv e m o is tu r e a n d lo w o r h i g h h u m id it y o r te m p e r a t u r e ca n stop or r etar d th e cu ring p rocess. Mo st m a n u fact u r er ’s in st r u ctio n sh ee ts p r ov id e inform ation for cu re tim e an d cur e tim e to im m e rsio n . C u r r en tly , th er e is n o a ll-en co m p a ss in g m e t h o d t o d e t e r m in e i f a co a t in g h a s com p letely cu red .
Chapter IX Field Inspection and Testing Field in sp ection an d testing is necessary to en su r e co a tin g p er for m a n ce a n d to v er ify s p e c ifica t io n a c ce p t a n c e . Fie ld in s p e ct io n a n d te st in g ar e p er for m ed in th e fo llow in g coa tin g areas: (1) su rface prep aration , (2) w et p aint, (3) h a r d e n e d p a in t , a n d (4) d e st r u c tiv e t es tin g .
39. Surface Preparation Tests.— Th e follow ing tests are perform ed on p rep ared su r face s b efo r e co a tin g ap p licat ion s a n d ar e in ad d ition to the p hotog rap hic stand ard s (see ch a p te r VI, su b se ctio n 29, “P h ot og r a p h ic In sp ect ion Sta n d a r d s” ). (a) Testing for Chlorides on Prepared Surfa ces.— Solu b le s a lts , esp ecia lly th e ch lor id e ion, if left on p rep are d su rfaces, can cau se co a tin g s t o b list er . If ch lor id e co n ta m in a tio n is s u s p e c te d , Re cla m a t io n s p e cifica t io n s r eq u i r e t e st in g t o d e t er m in e t h e p r e s en c e a n d con cen tr at ion of ch lor id e io n s a fter th e s u rfa ce p r ep a r a tio n of p r ev io u sly co a te d m eta lw or k . (See ap p en d ix L fo r p r oc ed u r es .) If N A C E 5/ SSPC-SP12 sur face p rep aration is sp ecified , th e st a n d a r d r eq u ir es t est in g fo r so lu b le sa lts. For im m ersion serv ice exp osu re, the accep tan ce criteria for chlor id es is 7 m icr og r a m s p er sq u a r e ce n tim et er or les s. (b) Su rface Profile and Adhesio n.— Su rfa ce p r o f ile (o r an ch o r p attern ) is th e to p o g ra p hy of the finished , abrasively blasted sur face. W hen view ed p erp end icu lar to the sur face p lane, ja g g ed p e ak s a n d v a lle y s ca n b e o b se rv e d . V a r io u s p e a k h e i g h ts a n d v a l le y d e p t h s ca n b e a ch ie v ed b y t h e ty p e a n d s iz e o f t h e a b ra siv e m a t er ia ls u s e d . Su r f a ce p r o file is cla s sifie d b y d e p t h an d t extu r e p r o d u ce d . D ep t h is th e m easu rem ent of the aver age d istance betw een the p eaks an d the v alleys. Textu re is the a n g u la r fin i sh e d a p p e a r a n c e o f t h e p e a k s a n d v a lle y s, r a n g in g fr o m ja g g ed to r o u n d ed . A ja g g e d t e xt u r e w ill n o r m a lly p r o d u c e b et te r a d h e sio n .
The p u rp ose of the su rface pro file is to p rom ote ad he sion of the coating to th e su b str at e. A b ra siv ely b las tin g a s u rfa ce in c r ea s es th e s u r fa ce a r ea , t h u s p r o d u cin g a gre a te r a re a for c oa ting a d he s ion. A d he s ion st r en g th is p r im a r ily ach iev ed b y ion ic b on d in g be tw e en th e co atin g an d t h e su bstrate. Intercoat ad hesion is achieved ch iefly b y cov ale n t b on d in g . In g en er al, th ick co a tin g s r eq u ir e a d ee p er p r ofile th a n th in co a tin g s. Th er e is an op tim u m su r face p r ofile d ep th for th e s p ecifie d coa tin g m a te r ial. If a p rofile is too sha llow , the c oa ting m a y not a ch iev e p r op er ad h es ion . If a su r face p r ofile is to o h ig h , th e co a tin g m a y n ot cov er th e p r ofile p eak s, resu lting in p inp oin t ru sting . The m an u factu rer’s pr od u ct d ata sheet re com m en d s th e s u rfa ce p ro file for ea ch s p e cific co a t in g p r im e r . The p rofile m ay b e m easu red w ith an y of the fo llo w in g : •
Su rfa ce pr ofile com p a ra tor
•
D i al s u r fa ce p r o file g a u g e
•
Sp rin g m icro m et er an d re p lica im p r e s sio n t a p e
Reclam ation specifies the sp ring m icrom eter a n d r ep lica im p r essio n ta p e m e th o d u s in g N AC E RP 0287, “Stand ard Recom m end ed P ra ctice fo r Fie ld M ea su re m en t o f Su rfa ce Profile of Abrasive Blast Cleaned Steel Su rfaces Using a Rep lica Tap e.” (See a p p en d ix M fo r th e p r oce d u r e.) Som e old e r ve rs ions of Re cla m a tion sp ecification s sp ecify ASTM D 4417, “Stand ard Te st M e thod s for Fie ld M e a s ure m e nt of Su rfa ce Profile of Bla s t C le a ne d Ste e l,” m e t hod C. Essen tially, N A CE RP 0287 an d A STM D 4417 ar e e q u iv ale n t, p ro v id ed th at th e co rr ect m il ran ge rep lica tape is used .
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Guide to Protective Coatings: Inspection and Maintenance D u r in g in sp ect ion s, p r ot ect iv e g lov es sh ou ld be w orn to avoid contam inating the finished p r ep a r ed su r fa ce w ith oil a n d sa lt p er sp ir a tion . W h e r e fo o t tr a ffic is u n a v o i d a b l e, s u c h a s w ithin p ipe interiors, p lastic slip cover booties are recom m end ed . (c) Dust.— U se clea r ce llop h an e t ap e (o ffice v a r i e t y ) t o d eterm in e am o u n t o f d u s t from a b r a s iv e b la s tin g a n d o t h e r s ou r ce s th a t h a s no t been blow n o r v acu u m ed off. Press th e ta p e o n th e s u r face , p ee l off, a n d v isu a lly observ e the a m ou nt o f du st that sticks to th e t a p e . C le a n th e tes t area w ith aceto n e o r a l co h o l t o r em o v e tap e ad h es iv e fro m p r ep a r ed s u r fa ce . Th e te st ta p e sh o w in g th e d u st p a r ticle s ca n be d o cu m e n te d b y a p p ly in g it t o t h e d a ily in sp ect ion r ep or t o r an ot h er field rep ort.
40. Wet Film Thickens.— Reclam ation d oes n ot req u ire testing th e w et film th ickn ess (WFT). W FT is m easu red in accord an ce w ith A STM D 4414. (Se e p p e n d ix N f or th e p r oc ed u r e.) H ow ev er , it is a u se fu l m easu rem en t for th e follow ing p u rp oses: •
To v er ify th a t a con sis te n t t h ick n es s is be in g a p p lied . A co n siste n t W FT sh ou ld d ry into an ev en DFT.
•
T o p red ict th e res u ltin g D F T. Som e m an u factu rer’s instru ctions state a w et film thickness coating a p p lied at a cer ta in n u m b er of m ils w ill re su lt in a p r ed ete r m in ed D FT. Fo r ex a m p le, a co a tin g ap p lied 10 m ils w et w ill re su lt in a D FT of 8 m ils. H ow ever , if the m a n u factu rer’s in s tru ctio n s d o n ot state the D FT that w ill result from the W FT, it can be calculated . (See a p p e n d ix O fo r fo rm u la s a n d exa m p les.)
M easu ring th e W FT on q u ick d ry ing m ater ials, s u c h a s in o r g a n ic z in c s , m a y y ie ld le s s t h a n accur ate r ead ings.
41. Hardened Painted Surfaces.— On ce a co a t in g s y s te m h a s d r i ed o r h a r d e n e d , b u t before the recoat w ind ow has exp ired, Re clam a tio n sp ecifica tio n s im p os e t w o cr ite r ia
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for accep tan ce. The first is to m eet the m i n im u m a n d m a xim u m D F T, a n d th e se co n d is to d etect and rep air an y p inh oles in th e coating or d am ag ed are as. (a) D ry Film Thickness.— Th e D FT o f a co a tin g c a n be m e a s ure d w he n the m a te ria l d ries or h a r d e n s b u t b e f or e t h e r e co a t w i n d o w h a s expired . The thickness is com m only sp ecified in m ils, a lth ou g h som e m a n u fa ctu r er ’s ins tru c tion s he e ts w ill a ls o us e m ic rome te rs (or m icr on s) in th e m et r ic sy st em . Th e fo llow in g p rov id es conv ersion s of these u n its: 1 m il = 0.001 in ch = 25.4 m icrom eters 1 m icr om et er = 0.000001 m et er = 0.039 m il Reclam ation specifies that th e har d ened coated su r face sh a ll m ee t a m in im u m an d m a xim u m s pe c ifie d thickne s s . D FT is m e a s ure d for qu ality con tr ol a n d sp ecification D FT accep tance criteria. There are n u m erou s typ es o f D F T g a u g e s a v a ila b le o n t h e co m m e r cia l m ark et. Th ese ga u ges m easu re th e th ickn ess of a n on co n d u ctiv e co a tin g on a m a g n et ic co n d u ctiv e (fe r r ou s) o r n on m a g n et ic cond u ctive (alu m inu m , brass, bron ze, copp er, et c.) su b st r a te . Th er e a r e D FT g a u g es av a ilab le th a t w ill re a d on ly m a g n et ic or n on m a g n et ic su b st r a te s a n d g a u g es t h at w ill m ea su r e b oth . Th e in sp ect or sh ou ld en su re th at th e co rr ect su b str ate ga u g e is b ein g u se d a n d th a t th e g a u g e r a n g e is w i th i n t h e film t h ick n e s s t o b e m e a su red . SSPC-PA2 .— Reclam ation sp ecifies that th e DFT is to be m easu red in accord an ce w ith SSPC -P A 2, “M ea su r em en t o f D r y C oa tin g Thickness w ith M agn etic Gag es,” w ith the e xce p t io n o f t h e fo llo w in g : •
Section 5 .2.1.— The sp ecified m in im u m p er cen ta g e t h ick n es s is chan ged from 80 to 90 p ercent.
•
Section 5 .2.2.— The sp ecified m a xim u m p er cen ta g e t h ick n es s is chan ged from 120 to 150 p ercent.
DF T gauges.— T h e ty p e s o f D F T g a u g e s a r e d eterm ined by th e specific m agn etic prop erties
Field Inspection and Testing of the instru m en t being u sed in m easu ring the c o a tin g t h ic k n es s , rath er th an b y th e read ou t m od e (an alog or d igital). The stand ard d oes not cover D FT gau ges u sing an ed d y cur ren t m e th od .
(Se e ap p e n d ix P fo r ca lib r a t io n a n d p r o c ed u r e fo r e ach g a u g e ty p e a n d a D F T p r o c ed u r e ex a m p le.). 1.
The follow ing sections d escribe DFT gaug es w it h in t h e s ta n d a r d . •
P u l l o f f g au g e s .—In g en er a l, p u lloff g a u g es u se a p er m a n en t m a g n et in co n t a ct w it h t h e co a t e d s u r f a ce a n d a calib ra te d sca le to m ea su re th e fo rce requ ired to p u ll the m agn et from the co a te d su r fa ce . Th e sca le is n o n lin ea r . Th e fo llow in g ar e t w o t y p es of p u lloff gau ges an d their ap p roxim ate thickn ess range:
" Ban a n a g a u g e (0 t o 200 m ils). " P en cil g a u g e (0 t o 30 m ils). •
C o n s tan t p re s s u re p ro b e g a u g e s.— The g en eral w ork ing p rinciple of the constan t p ressu re p rob e gau ge is that a p r o be exe rts a co n sta n t p r essu r e o n th e co a t ed s u r fa ce , a n d e le ct r o n ic cir cu i t ry c o nv erts a referen ce sig n a l in to a c o a tin g th ick n es s th at is d is p lay e d on a n an a lo g o r d ig ita l scr ee n .
Termin olog y and definition .— Th e p roced u re for d eterm ining the D FT involves t a k in g a n u m b er o f g au g e read in g s at ran d om lo c a tio n s. Th es e read in g s are called s p o t m e a su r em e n t s. It is im p o rta n t to u n d e rsta n d g au g e re ad in g an d s p o t m e a su r em e n t te r m in olo g y b eca u se w ith ou t co m p r eh en d in g th e m ea n in g o f th e te rm s, th e SSPC -PA 2 DFT p r o ce d u r e co u ld b e co n d u cted in co r r ectly . De f in i t io n s o f “g au g e read in g ” an d “s p ot m e a su r e m e n t” are p res en ted b elo w :
Take 5 sp ot m easu rem en ts (at least 3 ga u ge re a d ings p e r s pot m ea su r em en t) s p a ced r a n d om ly w ithin e a ch 100-s qu a re -foot a re a for D FT me a s u re m e nts . The nu m be r o f 100- s qua re -foot a re a s w h e re the s pot m easu rem ents are to be taken is based on th e tot al coated su rface ar ea. Th e 100-sq u a r e-fo ot ar ea s a r e r a n d om ly se lected w ith in th e to ta l co a te d ar ea . Ta ble 8.1 p rovid e s the crite ria for d et er m in in g th e n u m b er of 100s qu a re - foot a re a s for s pot m e a s u r e m e n t s co r r e s p o n d in g t o t o t al co a t e d s u r f a ce a r e a . Su r face ar ea s o f irr eg u lar ly or od d ly sh ap ed stru ctu res, su ch as tr ash racks, chan nels, and I-beam s, m ay exceed 1,000 squ are feet becau se th ese st r u ctu r a l m em b er s a r e m a n y sid ed . The insp ector shou ld r ou gh ly calcu late the area to d eterm ined the total coated s u r f a ce a r e a .
2.
Calibrate th e DFT instru m en t for the an ticip ated DFT rang e.
3.
M ea su re th e h ar d en ed coa te d su rfa ce w it h t h e ca lib r a t e d D F T in s t r u m e n t a t the n u m ber o f sp ot m easu rem en ts in d ica t e d i n t a b le 1. D i sr e g a r d in c o n s is t en t h i g h o r lo w r e a d i n g s t h a t ca n n ot b e r ep ea te d . Th e fo llow in g are th e n u m ber of gau ge r ead ings, sp ot m easu rem ents, and avera ging p er 100- s q u a r e - fo o t a r ea : a.
•
Gauge read ing.— A s in g l e r ea d in g a t on e p oint.
•
Spo t measu rem ent.— T h e a v e r a g e o f a t le a s t t h r e e g a u g e r e a d in g s t a k e n a t d iffere n t p oin ts w ith in a 1.5-in ch d ia m e t er cir cu la r a r e a .
Outline pro cedure.— T h e fo llo w in g i s a n a b b r ev ia te d ou tlin e of SSP C -P A 2 p r o ce d u r e.
D ete rm i n e th e 5 sp o t m e a su r em e n t locations requ ired p er 100-squ arefo o t a r ea .
b . Ta ke 3 ga u ge re a d ings p e r s pot m e a su r em e n t a n d a v er ag e th e 3 re a d ings . This is a tota l of 15 g a u g e r ea d in g s, m in im u m (3 ga u ge re a d ings x 5 s pot m ea su r em en t lo ca tio n s p er 100sq u a r e-fo ot ar ea ).
43
Guide to Protective Coatings: Inspection and Maintenance Table 1.—Number of spot measurements based on total coated surface area Total coated surface area
Number of 100-square-foot areas for spot measurements
Less than 300 square feet
Each 100-square-foot area within the total area.
Greater than 300 square feet but less than 1,000 square feet
Three (3) 100-square-foot areas within the total area
Equal to and greater than 1,000 square feet
Three (3) 100-square-foot areas for the first 1,000 square feet within the total area; plus One (1) 100-square-foot area for each additional 1,000 square feet of coated areas or fraction thereof
c.
A v erag e th e 5 in d iv id u al s p o t m ea su r em en ts to ob ta in a s in g le avera ged valu e for the 100-squ arefo o t a r ea .
4.
Rep eat step s 2 thr ou gh 5 for th e rem ainin g 100-squ are -foot a rea s.
5.
D et er m in e m in im u m an d m a xim u m t h ick n e s s a cce p t a n c e cr it e r ia .
6.
M inim u m accep tance. a.
A n y n u m b e r o f in d iv id u a l g a u g e r e a d i n g s m a y b e le s s t h a n 90 p ercent of the sp ecified th ickn ess.
b . N o s in g le av erag ed s p o t m eas u rem en t in 10 0-s q u are-foot area m ay b e les s th an 90 p er c ent of th e sp ecifie d th ick n ess .. W he re av erag e sp ot m easu rem en ts are less than 90 p ercent of the s p e c ifie d t h ick n e s s , a d d it io n a l m easu rem en ts m ay b e taken to red efine the n oncon form ing area 7.
M axim u m accep tance. a.
A n y n u m b e r o f in d iv id u a l g a u g e read ings m ay exceed 150 percent of the sp ecified th ickn ess.
b . N o s in g le av erag ed s p o t m easu rem en t in a 100-squ are-foot
44
area sh all exceed 150 p ercent of the sp ecified th ickn ess. W he re av erag e sp ot m easu rem en ts exceed 150 percent of the specified t h ick n e s s , a d d it io n a l m easu rem en ts m ay b e taken to r e d e fin e t h e n o n co n f o r m i n g a r e a . (b) D iscontinuity (Ho liday) T esting.— Reclam ation sp ecifies that coating s su bject to b u r i a l o r im m e r sio n s e rv ice e xp o s u r e s b e te st ed fo r h olid a y s (i.e., p in h oles a n d v oid s). H olid ays p rov ide a n a ven u e for m oisture to p enetrate th rou gh the coating to the su bstrate, le a d i n g t o g e n e r a l co r r o s io n , p it t in g , a n d u n d e rfilm c or ro sio n . The re a re tw o typ e s of holid a y te s ting: low v o lt a g e a n d h i g h v o lt a g e. T h e ap p lie d v o l ta g e is based on the coating thickness an d the co a t in g d ie le ct r ic s tr e n g t h . L ow -v o lt a g e te st er s a r e u se d on th in film s (20 m ils a n d les s), a n d h ig h -v olt a g e t es te r s a r e u se d on h ig h b u ild film s (20 m ils o r g r e a te r ) o r a s d e t er m in e d b y th e m a n u fa ctu r er to p r ev en t coa tin g d a m a g e. U sing v oltages tha t are too h igh or leaving th e in s t r u m e n t in o n e p la ce to o lo n g m a y d a m a g e the coating by sp ark ing or bu rn ing th rou gh the coating . Thin coating s are m ore su sceptible to v o l ta g e d a m a g e . T es t in g o f co a t in g s t h a t con ta in ele ctr ically con d u ctiv e p igm en ts s u ch a s a lu m inu m fla ke s , gra p hite , or z inc is not r e co m m e n d e d b e c au s e a n e le ct r ic d is ch a r g e m a y sp a r k th o u g h t h e co a tin g a t co n d u ct iv e p a r ticle s, d a m a g in g th e co a tin g or in d icat in g d iscontinu ities w her e non e exist. Su ggested
Field Inspection and Testing voltages at DFT ranges are p rovid ed in table 1 of t h e N A C E RP 0188. Re clam a tio n sp ecifie s t h a t t es tin g b e in accord an ce w ith N A CE RP 0188, except th at: •
Te st in g is n ot r eq u ir ed on con d u ctiv e co a tin g s p ig m en te d w ith alu m in u m , g r a p h ite , zin c, or ot h er ele ctr ically cond u ctive p igm en ts.
•
U sin g a d et er g en t w et tin g so lu tio n is not p erm itted (d etergen ts m ay cover ove r p inh oles after testing, leav ing th e false im p ression th at no p inholes ex ist ).
P r ev iou s v er sio n s o f Recla m a tio n coa tin g sp e c ific a tio n s referen ce A S TM D 5 16 2 for h olid ay test ing . ASTM D 5162 an d N A CE RP 0188 are essentially equivalent, but th e N AC E v er sio n is m o r e co m p lete an d ea sie r to fo llo w . (See ap p en d ix Q fo r th is p r o ce d u r e.)
Metho d B.— This m e thod is prim a rily f or laboratory u se, althou gh it is often em p loyed in th e fie ld . The m e thod is not s uita ble for co a tin g s w ith a th ick n ess g r ea te r th a n 5 m ils. A lattice pattern of 6 to 11 evenly spaced ho rizon tal and ver tical lines are cu t into the co a tin g to th e s u b st r a te . Pr es su r e-s en sit iv e t a p e i s a p p lie d o v e r t h e la t t ice p a t t e r n a n d p u lle d o f f. C o a tin g a d h e s io n is a ss es se d b y m a king the be s t m a tch to a c om p a rison s c ale of 0B (lo w e s t) t o 5B (h i g h e s t) o f n a r r a t iv e a n d p ho togr ap hic d escrip tions p rov ided in the s ta n d a r d . (b) Adhesion, Pulloff Method (ASTM D 4541).— T h is m e t h o d is m o r e q u a n t it a tiv e b u t re qu ire s a n e xpe rie nc e d op e ra tor for r e p r o d u c ib ilit y . T h e se te st e rs a re recom m end ed for flat hor izontal su rfaces u n less oth erw ise stated in th e ap p en d ix. Th e s ta nd a rd lis ts the follow ing th re e type s of tester s in th e an n ex:
42. Destructive Test Methods.— D e st ru c tiv e
Typ e I, fixed.— Typ e I testers are restricted to labora tory u se.
test m etho d s are n orm ally u sed to eva luate ov er co a tin g or aid in d et er m in in g a co a tin g failure. The follow ing sections are abbr eviated d e scr i p t io ns o f th e d es tru ctiv e tes tin g m e thod s list e d i n t h e ab o v e P h y s ical Co atin g In s p e ction Su r v e y m e th o d .
Typ e II, fixed alignm ent.— T y p e II t es te r s w e r e d e v e lo p e d fo r la b o r a to r y u s e b u t a r e em p loyed in th e field . Typ e II are th e m ost co m m on p u llo ff a d h esio n te st er s fo r fie ld u se . (See ap p en d ix R fo r th is p r oce d u r e.)
(a) Adhe sion, T ape Metho d (ASTM D 3 359).— Th is t es t is con sid er ed su b ject iv e a n d sh ou ld be p erform ed by qu alified and exper ienced p ersonn el. The choise of test m ethod d ep end s on coating th ickn ess. Metho d A.— T h is m eth o d is u s ed o n co a tin g s 5 m ils th ick or g r ea te r . A n “X” cu t is m ad e in th e coating to the su bstrate. Pressu res e n s it iv e t a p e i s a p p lie d o v e r t h e “ X” cu t a n d p u lle d o f f. C o a tin g a d h e s io n is a ss es se d b y a co m p a r iso n sca le o f 0A (low es t) t o 5A (h i g h e st ), as d es crib ed b y w ritten d efin it ions p r o v i d e d in t h e s ta n d a r d .
Typ e III, self-aligning or hyd raulic.— T y p e III testers w ere d ev elop ed for labor ator y u se bu t ar e em p loyed in th e field . (See ap p en d ix S fo r p r oce d u r e.) Dry film thickness by Tooke gauge (ASTM D 4138).— The Tooke ga ug e is us e d for m e a s u r i n g t h e n u m b e r o f co a t s a p p lie d a n d D F T if t h e co a t in g l ay e r s ca n b e id e n t ifie d b y color d ifferen ce or by a d istinctive line. (See a p p en d ix T fo r th is p r oce d u r e.)
45
Chapter X Maintenance Coatings Reclam ation infrastru ctures m ay still be coated w it h t h e o r ig in a l m a t e r ia ls fr o m t h e in i tia l in st a llat ion or th ey m a y h a v e r ece iv ed fu ll, p artial, or sp ot coating rep air in th e in te r v en in g y ea r s. O b v iou sly , an y coa tin g m a t e r ia l h a s a fin i te s er v i ce life , a n d m a in t e n a n c e co a t in g s h a v e b e co m e a n im p ortan t com p on en t in m aintaining the stru ctu ral integ rity of h igh-cap ital-cost infrastr u ctu res.
43. Definition.— A s im p lified d efin itio n of m a in t e n a n c e co a t in g s is “ th e r e co a t in g o f a n y existing coated su bstrate sur face to p reven t co r r o sio n or to m a in ta in ap p ea r a n ce .”
m a y also b e a m a jor co n sid er a tion , an d th ese asso ciated costs m ay be d ifficu lt to asse ss. To p rovid e a ba s is for risk e va lua tion, ins p e ction of the coating an d sub strate is recomm end ed .
46. Inspection.— To d e te rm in e th e co r re ct iv e a c tion re qu ire d , s truc ture s id e ntifie d for m a in t e n a n c e co a t in g s w o r k sh o u ld b e in s p e ct e d b e f or e b e g in n in g w o r k . P r e lim in a r y w o rk sh o u ld in clu d e ga th e rin g ba ck g ro u n d in for m a tio n on th e s tr u ctu r e, in clu d in g location , original installation d ate, d im en sions, d r a w in g s, s u b st r a te ty p e, an d co a tin g h ist o r y . The coating history sh ou ld includ e the follow ing inform a tion, if know n:
44. Purpose.— Th e b a sic p u r p os es of a
•
Se r v ice e xp o s u r e
c o a tin g p r o g ram to m ain tain Reclam ation st r u c t u r e s a re to :
•
Typ e of sub strate
•
P r e v e n t s ig n i fica n t lo s s o f m e t a l
•
Su r face (an ch or ) p r ofile
•
Pr ev en t s ig n ifican t d eg r ad atio n of co a t in g m a t e r ia l
•
A g e o f co atin g
•
Type of e xis ting c oa ting m a te ria l o r brand nam e
•
D FT
•
Id e ntific a tion a n d c once ntra tion of to xic m et a ls in th e e xist in g coa tin g (ca d m iu m , ch r om iu m , lea d , et c.)
•
M ain ta in ae sth et ics or th e a p p ea ra n ce of stru ctures exp osed to p u blic view
•
Id en tify b y co lo r co d e
•
M inim ize fu tu re rep air costs
45. Risk Evaluation.— Risk ev a lu a tio n is p rim ar ily a p ro ject office resp on sibility. Th e ov er r id in g or u ltim a te con sid er a tio n in ev a lu a tin g r isk s a ss oc iat ed w ith coa tin g s is w h e t h e r t h e co a t in g i s m a in t a in i n g s t r u c tu r a l in te g r ity or if coa tin g d eg r a d a tio n is a llow in g corrosion to p roceed , lead ing to th e p ossibility o f s tr u ct u r a l fa ilu r e . T h e r e is n o s ta n d a r d m eth od to ev alu ate r isks; h ow ev er, the m ost b a s ic a p p r o a ch i s t o co m p a r e e st im a t e d p a r t ia l or total m etalw ork rep lacem en t costs w ith the es tim a te d cos ts of a m a in te n a n ce co a tin g p r o g r a m . Sa fe t y t o th e p u b lic a n d w o r k e r s
(a) Insp ection Sch edu le.— Id e a lly, ins p e ctio n su rv eys sh ou ld b e cond u cted ev ery 3 to 5 y e a r s, d e p e n d in g o n t h e s er v ice e xp o s u r e a n d t h e s tr u ct u r e t y p e . T h e 3- t o 5-y e a r in te r v a l is r ea so n a b le fo r st r u ctu r es sit u a te d in atm osp her ic service exposu re. For structu res re qu iring d e w a te ring, a 5-ye a r ins pe c tion inte rva l m a y not be a c hie va ble ; how e ve r, s om e d esign ated interval shou ld be initiated . (b) Insp ection Types.— The typ e of ins p e ction su rvey d ep end s m ainly on the tim e allotted a n d acc es sib ility . Ext er ior su r face s in 47
Guide to Protective Coatings: Inspection and Maintenance a tm os p h er ic ex p os u r es ar e r ea d ily acc es sib le fo r i n sp e c t io n . In terio r in s p ectio n s o f p enstocks, p iping, scroll cases, and other w ater-bearing sur faces requ ire a plann ed o u t a g e to d e w a t er . In t e r io r in s p e c tio n s a r e consid ered confine d sp ace, an d ap p rop riate safety requ irem en ts m u st be m et.
e le m e nts (be a m s , c onne c tions , e d ge s , e tc.) o f the stru cture or facility are insp ected s ep a r a t e ly . 1.
O b se r v e a n d d oc u m en t t h e fo llow in g coating cond ition s: •
D e fe ct s: b lis te r in g , ch a l k in g , c ra cking, e ros ion, de la m ina tion, p inh ole s , p e e ling, un d e rc utting, or oth er d efects
•
A p p e a r a n c e: co a t in g o r t o p co a t lo ss , ab r a sio n st r ea k s, r u st st a in in g , fading color, w eathering , or oth er ab n or m al a p p ea ra n ce
There are fou r typ es of inspection: thr ee typ es ar e coatin g r elated an d on e is stru ctu ra l. Th e four typ es are: • • • •
Gen eral overview sur vey Detailed visual sur vey Ph ysical coating insp ection su rvey Stru ctural sur vey
F or m o s t R ecla m a t io n s t r u c t u r e s , t h e g e n e r a l o v e r v i e w a n d d etailed v isu al s u rv ey m ethod s a r e su f fic ien t to id en tify co atin g an d co r rosion d eterior ation tren d s. Genera l overview survey.— Th is qu a lit at iv e s u r v e y ca n b e a cco m p l is h e d i n a fe w h o u r s a n d is a d e qu ate to ascertain s ev ere co rro s ion cond ition s an d d egra d ed coating s. On ly the m a jo r fe a tu r e s o f t h e st r u c tu r e o r fa cilit y a r e inspected . 1.
2.
3.
•
•
T h e g en e r a l co n d it io n o f co a t in g ; ch eck fo r d efects o r d eterio r a tion
•
A n y ev id e n ce of r u stin g
D et er m in e t h e t y p e o f to xic m et a lb a se d p a in t a n d its con cen tr a tio n , if p resen t. R a t e th e co n d itio n o f th e co atin g on e a ch m ajo r s tru ctu ral featu re as good , fa ir , o r p o o r .
Type : u niform ru s te d s u rfa ce or p itt in g
" On flat or cur ved sur faces " At corn ers or ed ges " U n d e r b lis te r s •
E st im a t e t h e a m o u n t o f r u s t b y u sing SSPC -VIS 2. (See ap p en d ix U fo r p r oce d u r es.)
•
M etal loss: m inim al or significan t.
Visu ally observ e:
De tailed visua l surve y.— The time r equ ired t o co n d u c t th i s s u r v e y v a r ie s fr o m a fe w h o u r s to abo u t 1 da y, d ep en d ing on the size of the stru cture. This sem iquan titative su rvey r e q u i r e s a m o r e d e t a ile d d e s cr ip t io n a n d d o cu m e n t a t io n o f th e c o a tin g c o n d it io n a n d co r r os ion . M a jor fea tu r es an d st r u ctu r a l
48
2. By ob se r v a tio n , d oc u m en t t h e fo llow in g ru st cond ition s:
3. D et er m in e t h e t y p e o f to xic m et a lb a se d p a in t a n d its con cen tr a tio n , if p resen t. 4. Rate each stru ctural com p onen t s e p a r a t e ly a s g o o d , fa ir , o r p o o r a n d co m b in e th e r esu lts. U sin g SSP C -VIS 2 to es tim a te th e a m ou n t o f ru st is p referred m ethod . A w eighting system o r sp r e a d s h e et ca n h e lp f a cilit a te b y co m b in i n g in d iv i d u a l r a t in g s in t o a n ov era ll assessm en t, settin g p riorities, a n d d e v e lo p i n g q u a n t it ie s fo r a p relim inary cost estima te. Physical co ating inspe ction survey.— Th e tim e re qu ire d to cond u c t this s urv e y is from 1 d a y t o s ev e r a l d a y s , d e p e n d in g o n s t r u c tu r e size an d access to th e coate d su rface. The
Maintenance Coatings su rvey incorpor ates the observ ations recorded in th e D et a iled Visu a l Su r v ey w ith q u a n tit a tiv e m easu rem ents. This surv ey evalu ates w heth er a n e x ist in g co atin g can b e s p o t rep aired or ov er co a te d or if fu ll re m ov a l an d r eco a tin g is requ ired . For a h igher level of confid en ce, the su rvey shou ld be cond u cted by a certified N A CE or SSPC coating sp ecialist. 1. O b se r v e a n d d oc u m en t t h e fo llow in g coating cond ition s: •
•
D e fe ct s: b lis te r in g , ch a l k in g , crack in g , ero s io n , d elam in atio n, p in h o les , p eelin g , u n d ercu tting, or oth er d efects A p p e a r a n c e: co a t in g o r t o p co a t lo s s, a b r a sio n s tr e a k s, r u s t st a in i n g , fading color, w eathering , or oth er abn orm al app earan ce.
2. O b se r v e a n d d oc u m en t t h e fo llow in g ru st cond ition s: •
T y p e: u n ifo rm ru s ted s u rface or p itt in g
" On flat or cur ved sur faces " At corn ers or ed ges " U n d e r b lis te r s •
Rust rating b y SSPC-VIS 2. (See a p p en d ix U fo r p r o ce d u r e.)
•
M e t a l lo s s: m in i m a l o r s ig n i fica n t
3. P er for m th e fo llow in g q u a n tit a tiv e m easu rem en ts: •
Test ad he sion by on e or b oth of the follow ing m eth od s:
" P u lloff (A STM D 4541) " Ta p e (A STM D 3359) •
D et er m in e D FT (SSPC -P A 2)
•
D ete rm i n e th e p re se n ce an d co n cen tr a tio n of s olu b le s a lts , if p r ese n t
•
D ete rm i n e th e ty p e an d concentration of toxic m etal-based p a in t, if p r ese n t
•
D et er m in e t h e d ep th an d fre q u en cy of corro sion p its
•
U se a kn ife to d eterm ine th e length of u nd e rc utting c orros ion
•
U se a To ok e g au g e to d e te rm i n e th e n u m b e r o f co a t in g s
•
M easu re th e steel w all th ickn ess w it h a n u lt r a so n ic t h ick n e s s g a u g e
•
A p p ly te st p a tch es to d et er m in e if the c oa ting is com p a tible for ov er co a tin g (A STM D 5064)
Struc tural inspection.— T h e s tr u ct u r a l ins p e ction c a n be c ond u c te d in c onju nc tion w it h a n y o f th e a b o v e s u r v e y s . St r u c t u r a l m e m be rs a nd c omp one n ts a re ins p e cte d for se v er e m et a l los s, b r ok en join ts , d efe ctiv e w e ld s , b e n t m e m b e r s , o r o t h e r st r u c t u r a l d efe cts . N or m a lly , in sp ect ion s a r e b y v isu a l o bse rv a tio n .
47. Toxic-Based Paints.— D u r in g th e in sp ect ion , sa m p les of t h e e xist in g coa tin g m a t er ia l sh o u ld b e an a ly ze d to d e te rm i n e th e typ e an d con cen tra tion of toxic m etals. The co m m o n t o xic m e t als in p r e -1990s p a in t a r e ca d m iu m , ch r o m iu m , co b a lt , a n d le a d ; h ow ev er , ar se n ic, ba riu m , be ry lliu m , m er cu ry , silver, seleniu m , van ad ium , or oth er hea vy m et a ls m a y b e p r es en t in v er y low lev els . The m ost com m on h eavy m etal in p aint u sed on Re clam a tio n p r oject s is r ed lea d p r im er . It w a s a n e xce lle nt c orros ion inh ibiting p rimer on m e t a l s u r f a ce s . T h e u s e o f r e d l e a d p r im e r h a s d r a m a t ica lly d e clin e d in t h e co a t in g i n d u s tr y since the late 1980s, and Reclam ation no long er sp ecifies red lead p rim er. There is no p roblem w ith r ed le ad p r im e r as lo n g a s it r em a in s intact on th e structu re. Th e p r ob lem w ith lea d -b a se d p a in ts is co n ta m in a tio n of t h e lo ca l en v ir on m en t (s oil a n d w a t e r ) a n d e x p o s u r e t o h u m a n s . L ea d
49
Guide to Protective Coatings: Inspection and Maintenance ex p os u re n or m ally occu rs d u rin g th e s u rfa ce p r e p a r a tio n p r o ce ss , a s old co a t in g s a r e r em o v ed an d lea d p a r ticle s b eco m e air b or n e. T h e e n v i r on m e n t is co n t a m in a t e d b y le a d p a r t icle fa llo u t . H u m a n s a r e co n t a m i n a t ed b y inh aling or ing estin g th e lead p ar ticles. The m o s t s e r io u s a d v e r s e h e a lt h e ffe ct o f le a d e x p o s u r e i s p e r m a n e n t d a m a g e t o th e c en t r a l ner vou s system . (a) Te sting.— Te st in g of e xist in g coa tin g m a t er ia ls sh o u ld b e p er fo rm e d b e fo re sta rtin g con tra ct or m ain ten an ce coatin g w or k. The p u r p o s e o f t e st in g i s t h r e e fo ld : (1) t o m i n i m i z e exp osu re to en viron m en t an d w ork ers; (2) to red u ce surface p rep aration costs; an d (3) to d e te rm i n e th e ty p e an d c on ce n tr atio n of a n y toxic m etals p resen t. Th e follow ing te st m ethod s are recom m end ed : Screen te sting.— Screen tests w ill ind icate t h e p r e se n ce o f to x ic metals b u t w ill n o t in d ic a te t h e co n cen tratio n . Th es e tests a re not in t e n d e d t o e q u a l o r r ep l a ce la b o r a to r y a n a ly sis . Th e fo llow in g tw o co m m on to xic m et a ls ca n b e d et ect ed b y colo r ch a n g e u sin g p rem ixed rea gen ts: •
•
Lead at concentr ations of 2,000 par ts p e r m illio n (p p m ) (0 .2 p ercen t) o r m or e. (See ap p en d ix V fo r m a n u fact u r er 's in for m a tio n an d th is p roced u re.) C h r o m a t e (a s C r +6) at co n cen trations of 3 microgram s or m ore. (See a p p e n d ix W fo r m a n u fa ctu r e a n d p roced u re.)
Lab oratory testing.— Paint chip sam p les shou ld be tak en an d p rovid ed to an accred ited la b o r a t o r y fo r an aly s is to v erify co n cen tra tion, ev en if screen tests w ere n ot p ositive . The resu lts shou ld be ev aluated by a certified in d u st r ia l h y g ien is t. (See ap p en d ix X for sam p lin g, lab ora tory testing , estim ated costs, a n d w e b s it e s fo r a ccr e d it e d l a b o r a to r ie s a n d in d u st r ial h y g ien ist s b y city an d Sta te ).
48. Worker Protection from Toxic-Based Paints.— Blasting o p era tions a re th e m ost likely event w her e lead is inhaled or ingested
50
b eca u se th e p a r ticle s a r e t oo sm a ll to b e v isib ly s e e n. Le a d d u s t on the s kin is not ha z a rd ou s as long as it is not inh aled or ingested . Prop er r e sp i r a to r y p r o t e ct io n , co n s is tin g o f e it h e r a ir fe d re s pira tors , p os itive p re s s ure hood s , or ne ga tive pr e s s ure H EPA filte r-c a rtridge h al f or fu ll faced resp irato rs, sh ou ld be w or n . The follow ing p rov id es som e com m on sen se p r o t e ct io n b u t d o e s n o t in c lu d e a ll n e ce ss a r y req u irem en ts: •
W e a r w o r k clo t h in g d u r in g r e m o v a l o p e r a t io n s a n d h a v e c lo t h in g i n d u s t r ia l w a s h e d b y c on t r a ct o r or o w n e r .
•
W e a r re s pira tory pr ote ction a p p r o p r i a t e t o co n c e n t r a tio n l ev e l a n d e xpos u re tim e pe riod .
•
W a s h h a nd s a nd fa c e be fore e a ting or smoking.
•
A fter w ork , show er an d chan ge into street clothing to p reven t co n t a m in a t in g y o u r v e h i cle , h o m e , a n d fa m ily .
F or co m p r e h e n s iv e r e q u i r e m e n t s fo r p e r s o n a l s a fe t y , s e e t h e fo llo w in g C o d e o f F ed e r a l Re g u lat ion s (C FR): •
29 C FR 1910.1018, A r se n ic
•
29 C FR 1910.1027, C a d m iu m
•
29 CFR 1926.55, Ga ses, Vap ors, Fum es, Du sts, an d M ists
•
29 CFR 1926.62, Lead
49. Lead Exposure Levels by Removal Methods.— E n g in e e r s, m a n a g e r s, a n d w o r k e r s s hou ld be a w a re tha t s urfa ce pr e p a ra tion m eth od s w ill g en er a te air b or n e lea d p a r ticle s. The O ccu p ational Safety an d H ealth A d m in i st r a t io n ( O SH A ) m o n i to r e d s e v e r a l t y p e s o f le a d r e m o v a l o p e r a t io n s fo r t y p i ca l an d m axim u m exposu res. The m onitored r e s u l ts in d ica t e h ig h e x p o s u r e le v e ls , a n d n o su r face p r ep a r a tio n m et h od w ill n ot to ta lly elim in at e a irb or n e le ad p ar ticles . Vacu u m s hrou d e d e qu ip m e nt w ill re d u c e the a m ou nt
Maintenance Coatings of airbo rn e p articles bu t w ill not elim inate t h e m . T a b le 2 p ro v id es O SH A res u lts for t y p i ca l a n d m a x im u m le a d e x p o s u r e le v e ls b y r e m o v a l m e th o d .
Table 2.—Typical and maximum lead exposure levels in micrograms per cubic meter by removal method Typical exposure
Maximum exposure
Open blast cleaning
17,300
59,000
Blast cleaning in containment system
25,700
59,000
Welding, cutting, or burning
600
28,000
Hand tool cleaning
45
167
Power tool cleaning
735
20,600
Chemical stripping
11
476
500
2,100
Removal method
Movement (air, foot traffic, cleanup, etc.) in the containment system (causes particles to become airborne)
50. Corrective Action.— A fte r o n e o f th e a b o v e in sp ect io n su r v ey s (s ee ch a p ter X, su bsection 47(b), “Insp ection Typ es”) has been co m p l e te d a n d e v a lu a t e d , th e co a t in g m a y b e in so m e s ta te of d et er ior a tio n , th u s r eq u ir in g co r r e ct iv e a ct io n . C o r r e ct iv e a ct io n m a y r a n g e fr o m n o p a in tin g to fu ll r em o v a l a n d r eco a tin g . Th e fo llow in g se ctio n s p r ov id e a lte r n a tiv e r e m e d ia l o p tio n s b as ed o n th e in s p ectio n assessm en t. (a) No Pa inting R equ ired.— T h e in s p ection assessm en t ind icates the follow ing: (1) the c o a tin g i s in g o o d to excellen t co n d itio n ; (2) th e s er v ice e n v ir on m en t is m ild ; (3) litt le co r r os ion is e xp ect ed to p r og r es s a t co a tin g film b reaks; (4) m inor d iscoloration is noted b u t a p p e a r a n c e is n o t a n im p o r t a n t fa ct o r ; a n d (5) no significant m etal loss is noted . E sse n t i a lly , th is o p tio n m ean s “d o n o th ing for “ x” n u m b e r y ea rs.” It d o e s n o t m e a n ?d o n ot h in g for ev er .” It m ea n s t h a t t h e co a tin g m a i n t e n a n ce p ro g ram is d elay ed u n til s om e tim e in th e fo r es ee a b le fu tu r e w h en coa tin g
d e te riora tion re qu ire s a tte ntion or u ntil s om e tim e w hen coating m aintenan ce is sched u led w ith oth er m a jor m a in te n a n ce p r og r a m s. A n ot h er r ea so n for n ot p a in tin g is th a t fu n d in g m ay n ot be av ailable for “ x” n u m ber of year s. (b) Sp ot R epa irs.— Sp ot rep airs are in or d er w he n th e insp ection assessm en t ind icates the follo w in g : (1) th e co a tin g is d et er ior a tin g in localized areas; (2) the service environm ent is m ild to corrosive; (3) corro sion is exp ected to p rog ress at coa ting film br eak s; (4) d isco lor at ion is n ot ed b u t a p p ea ra n ce m a y o r m a y n o t b e a n im p o rta n t fa cto r; a n d (5) m inor m etal loss is noted . T h is o p t io n i s a p p r o p r i a t e fo r is o la t e d a n d relatively sm all areas that d o no t exceed 1 p e r ce n t o f t h e t o ta l co a t e d s u r f a ce a r e a a n d a r e n ot in a h ig h ap p ea r a n ce a r ea . If colo r is im p orta nt, s uc h a s in a pu blic a re a , ta ke color chip sam p les to th e coating m an u factu rer to m a t ch t h e e x is t in g c o lo r b e ca u s e th e o r ig in a l coating color m ay h ave fad ed . Sp ot re pa irs a re a via ble op tion for at m os p h er ic, bu ria l, an d im m er sio n se rv ice exp osu res. (c) Spo t Repairs Plus Full Recoa t.— Sp ot re p a irs a re in ord e r w he n the ins pe c tion assessm en t ind icates the follow ing: (1) the co a t in g i s d e t er io r a t in g i n lo ca liz e d a r e a s t h a t r e p r e s e n t b e t w e e n 1 a n d 3 p e r ce n t o f t h e t o ta l a r e a an d a r e ex p e ct e d t o d e t e rio r a te fu r t h e r ; (2) the service env ironm en t is m ild to corrosive, (3) corrosion is expected to p roceed a t co a tin g film b r ea k s, (4) d isco lor a tio n is note d a nd a p p e a ra nc e is a fa c tor, a nd (5) m inor to m od erate m etal loss is noted . T h is o p t io n is a p p r o p r i a te fo r co a t in g s t h a t a r e in r e l at iv e ly g o o d co n d it io n b u t d e f ect s a n d co r r os ion ar e n ot icea b le. Th e co a tin g sh ou ld still be resilient, it can still hav e a red u ced D FT, a n d a d h e sio n sh o u ld b e go od w h e re th e coating has n ot d eteriorated . W hen ov er coa tin g an exis tin g p ain t, a t es t p at ch sho u ld b e ap p lied to d eterm ine com p atibility betw een th e coating m ater ials. The test p a t ch e s s h o u l d b e e v a l u a t e d b e t w e e n 1 a n d 3 m on th s after ap p lica tion . T h e str u ctu r e’s
51
Guide to Protective Coatings: Inspection and Maintenance ap p ea ra n ce m ay b e o f ae sth et ic im p or ta n ce (s u c h a s w h e n i n p u b lic v i ew ), a n d a fu ll r e co a t w ill pr ov id e a u n iform color an d gloss. Th e s p ot r ep a ir p lu s fu ll re co a t is a v iab le op tio n for coa tin g st r u ctu r es in at m os p h er ic service exposu res, bu t it is not recom m end ed for bu rial and im m ersion serv ice exp osu res. (d) Com plete Rem ova l and Recoat.— C o m p le t ely r e m o v i n g t h e o ld co a t in g a n d r e c o a tin g i s in o rd er w h en th e in s p ectio n assessm en t ind icates the follow ing: (1) the co a t in g i s d e t er io r a tin g i n lo ca liz e d a n d la r g e areas r ep resen ting gr eater th an 3 per cent of the total area, and it is exp ected to d eteriorate furth er; (2) the service env ironm en t is m ild to corro sive; (3) corr osion is expected to p rog ress a t co a tin g film b r ea k s; (4) d isco lor a tio n is n ot ed an d m ay or m ay n ot b e a n ap p ea ra n ce fa ct o r ; a n d (5) m o d e r a t e t o sig n i fica n t m e t a l loss is noted . Th is o p tio n is co n d u civ e t o co a tin g s t h a t a r e in p oo r con d itio n an d ar e n o lo n g er p r ot ect in g th e s u b st r a te . Th is o p tio n r eq u ir es fu ll r e m o v a l o f a ll t h e e xis t in g c o a tin g m a t e r ia l a n d recoating the en tire su rface. C om p let e r em ov a l an d r eco a tin g is a v iab le op tio n for at m os p h er ic an d im m er sio n se rv ice exp osu res.
51. Material Selection Factors.— T h e r e a r e nu m erou s factors to be considered w hen se lectin g a co a tin g to m eet s p ecific co n d itio n s. The m ost basic factor is the env ironm en t the coa tin g w ill be su b ject ed to (e.g ., atm os p h er ic, bu rial, or im m ersion su rface exposu re). (See ch a p te r I, su b se ctio n 6, “Se r v ice E xp os u r es .”) Coatings sh ou ld be selected for their intend ed u se (i.e., a co a tin g for m u lat ed for at m os p h er ic se r v ic e e x p o s u re is n o t s u itab le fo r imm ersion). The follow ing are som e other factors to be taken into consid eration w hen se lect in g a co a tin g m a te r ial: (a) Coating Prop erties.— • • •
52
A b ra sio n or er os ion re sist an ce Ad hesion of pr imer A p p ea ra n ce
• • • • •
C olo r a n d g lo ss r ete n tio n . R e coa t w ind ow C u r e o r d r y tim e Flexibility M ild ew or fu n g u s r es ista n ce
(b) Su itability to Sub strate Type.— •
Fe rrous (s te el or iron)
•
N onferrou s (alum inu m , brass, bron ze, o r co p p e r )
•
C o n c r et e o r m a s on r y
•
O l d c o at in g s
•
W ood
(c) Environ me ntal.— •
Tem p eratu re an d hu m idity extrem es a n d v a ria tio n s
•
C av ita tio n .
•
C h em ical co n ta ct
•
Tr a ffic, foo t o r v eh icle
52. Scheduling.— A c ce ss ib le st r u c tu r e s a r e r e la t iv e ly e a s y to s ch e d u le fo r in s p e ct io n a n d m a in te n an ce co atin g w o r k. H o w e ve r, m a n y R e cla m a tion s tru c tu re s s uc h a s inte rior of tu rb ines, p u m p u n its, p en stocks, d raft tu bes, d ischarge lines, and other interior w ater be a ring s ur fa c es a re diffic ult to a cc es s w ith ou t a s ch e d u l e d o u t a g e a n d m a n y a r e a s ca n n o t b e d ew atered in excess of 5 years. Therefore, p lanned or u np lanned ou tages shou ld be tak en a d v a n t a g e o f fo r e it h e r in s p e c tio n o r co a t in g s w ork. In s ch e d u l in g a p la n n e d o u t a g e to p e r fo r m m a in te n a n ce co a tin g w or k , th e r ev en u e lo ss in e le ct r icit y o r w a t er d e liv e r y n e e d s t o b e a cco u n te d for sin ce r ev en u e lo ss w ill like ly b e co m e a sig n i fica n t fa ct o r .
Chapter XI Galvanizing Ga l v a n i z in g is th e ap p licatio n o f zin c o n to a st ee l su r face . Zin c is a n od ic to st ee l (i.e., zin c w ill sa cr i fice its elf to p ro tect steel fro m c o r r o sio n ) . Reclam atio n s p ecifies n u m erou s st eel m eta lw o r k ite m s t o b e g a lv a n iz ed . M etalw ork item s m ay ran ge from sm all item s s u c h , a s b o lt s a n d n u t s , t o la r g e it e m s , s u c h a s gates. The follow ing are reason s to coat over g a lv a n izin g : (1) to for m a b a r r ier coa tin g in bu rial or im m ersion serv ice exp osu res b ecau se the z inc w ill be rap idly con su m ed ; (2) to rep air da m aged areas; and (3) to im p rove
aesthetics (color ap p earan ce). Coating ov er galvan ized su rfaces pr esents u niqu e p roblem s th a t a r e ch a r a cte r ist ic of z in c an d th e co a tin g m aterial selected .
53. Galvanizing Methods.— T h e r e a r e s e v e r a l m ethod s to use w hen ap p lying zinc. Table 3 p rovid e s the m os t com m on m e thod s for g a lv a n izin g an d in clu d es m a n u fact u r in g p r oc es se s, sp ecifica tio n r efe r en ces , zin c coa tin g th ickn es se s, an d ty p ical a p p licatio n s for ea ch m e th od :
Table 3.—Galvanizing methods Method
Process
Specifications
Thickness
Typical application
Electrogalvanizing
Electrolysis
ASTM A 591
Up to 0.14 mil
Interior service exposure: appliance panels, studs, and acoustical ceiling members
Zinc plating
Electrolysis
ASTM B 633
0.2 to 1.0 mil
Interior or exterior service exposure: fasteners and hardware items
Mechanical plating
Peening
ASTM B 695
0.2 to 4.0 mil
Interior or exterior service exposure: fasteners and hardware items
Continuous galvanizing
Hot-dip
ASTM A 653
Up to 4.0 mil
Interior or exterior service exposure: roofing, gutters, culverts, automobile bodies
Hot-dip galvanizing
Hot-dip
ASTM A 123 ASTM A 153
1.4 to 5.0 mil
Interior or exterior service exposure: nearly all shapes and sizes, ranging from nails, bolts, and nuts to large structural items
Thermal Spraying
Hot zinc spray
AWS C2.2
3.3 to 8.3 mil
Interior or exterior service exposure: items that cannot be galvanized by other methods because of their size and shape or because galvanizing must be performed onsite.
Zinc-rich painting
Brush, roller, airless, or conventional spray
Varies with owner's or manufacturer’s specifications
0.6 to 5.0 mil per coat
Interior or exterior service exposure: Items that cannot be galvanized by other methods because of their size and shape or because galvanizing must be performed onsite. Aesthetics (color).
53
Guide to Protective Coatings: Inspection and Maintenance M ost Reclam ation galvan ized m etalw ork item s th a t r eq u ir e p a in tin g ar e b y th e h ot -d ip p r o c e ss . T h is m e t h o d r e q u i re s t h e m e t a lw o r k ite m s t o b e im m er se d in a b a th of m olt en zin c th a t cla d s t h e m et alw or k su r face in a n ea r ly p u r e z in c la y e r .
a n d s eco n d p h a s e r e a ct io n s m a y co n t in u e fo r 1 to 2 y ea r s a fte r th e g a lv a n ize d m a n u fact u r in g p r o ce s s is fin i sh e d , d e p e n d in g o n t h e lo ca l en viro n m en t. Zinc carbon ate (third p h ase r e a ct io n ) is a d e n s e , in s o lu b le m a t e r ia l t h a t fo r m s th e p r o t e ct iv e la y e r . T h e fin a l g a lv a n i z ed s u r fa ce is a d u ll m a t te g r a y .
54. Zinc Corrosion and Service Life.— Z in c, b y i t se lf, d oes n o t co rro d e lik e s teel. C o rros ion of zinc is achieved by exp osing zinc to oxygen a n d m o ist u re. Th e res u lt is a w h ite co rro s ion b y p r o d u c t . Ba r e g a lv a n i z ed m e t alw o r k im m ersed in seaw ater m ay last for 6 m on ths b e fo r e b e in g c o n s u m e d . Ba r e g a lv a n i z in g m a y la st 5 t o 10 y ears in fres h w ater, d ep en d ing on t h e w a t e r ch e m is tr y . H o w e v e r , b a r e g alv an izin g in an at m os p h er ic ser v ice expo su re w ill form a p rotective layer betw een 1 an d 2 y ea r s a fte r th e in itia l g a lv a n izin g p rocess, and this protective layer im p ed es fu r t h e r c o r ro s io n . Th e s erv ice life o f atm osp her ic galvan ized m etalw ork h as been kn ow n to exceed 50 yea rs.
Zinc oxide, zinc hy d roxid e, an d zinc carb on ate p r o d u cts d o n o t fo rm u n ifo rm l y o ve r th e g a lv a n ize d su r face or to a u n ifor m d ep th . A ll th r ee p r od u cts ar e a w h itis h colo r an d n ea r ly im p os sib le to v isu ally d istin g u ish fro m ea ch ot h er . W ith ou t k n ow in g w h ich zin c com p ou nd is p resent, coating ov er galvan ized su rfa ces b eco m es p ro b lem at ic.
56. Contaminants.— C on ta m ina n ts on galvan ized su rfaces are zinc ash r esid u es d e p o site d d u r in g th e ga lv a n iz in g p r oce ss a n d n a t u r a l occu r r i n g w h i te o xid e st a in t h a t fo r m s d u ring s tora ge . The follow ing tw o s e ctions p rov id e a m ore d etailed d escription of zinc ash an d stora ge sta in con tam inan ts.
55. Zinc Chemical Reactions.— Z i n c is a n active m etal and w ill react w ith oth er elem en ts to for m ox id es an d com p ou n d s. Th e fo llow in g zinc com p ou nd s are form ed on th e galvan ized su rface: •
Z in c ox id e is for m ed ab ou t 24 t o 48 h o u r s aft e r t h e g a lv a n i z in g p r o ce ss b y the r eaction of zinc w ith oxyge n in the a ir .
•
Z in c h y d r oxid e is fo rm e d b y th e r e a c tio n o f th e zin c w ith m o is tu r e from r a i n , d ew , o r h ig h co n d en s atio n .
•
Z in c ca rb on a te is fo rm e d b y th e r ea ctio n of z in c ox id e a n d zin c h y d ro x id e w ith carb o n d io x id e from fr e e flo w in g a ir .
Z in c ox id e (fir st p h a se r ea ctio n ) an d zin c h y d r o xid e (s eco n d a r y p h a s e r e a ct io n ) a r e p r o d u c t s t h a t ar e w a t e r so lu b l e an d n o t v e r y d en se. These p rod u cts adh ere v ery loosely to t h e su b s t r a te su r f a ce . P a in t d o e s n o t a d h e r e w e ll to zin c o xid e a n d z in c h y d r oxid e , a n d p a in tin g ov er th es e m ate r ials w ill p r ob a b ly resu lt in p rem atu re coatin g failu re. The first
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(a) Zin c Ash .— In th e ga lvan izing p rocess, p a rtic le s of oxid iz e d z inc floa t on the s u rface of th e m olt en b a th . W h en th e m et a lw or k is rem oved from the bath , resid u e of oxid ized z in c p a r ticle s ca n r em a in on th e m eta lw or k . A thin layer of resid u e can form on th e sur face, a n d th is r esid u e is r efer r ed to as “ z in c a sh .” (b) W et Sto rage Stain.— N ew ly galvan ized it e m s a r e s to r e d a n d s h ip p e d . If t h e st o r ag e area o r sh ipp ing con tainer p rev en ts the cir cu lat ion of ca r b on d iox id e in fre e flo w in g air cond ition s, a w hite ru st w ill form on the ga lvan ized su rface. This is a na tu ral p rocess t h a t is o ft e n r efe r r ed t o as “ w h it e s to r a g e sta in .” W h ite s to ra g e s ta in re su lts fr om a la ck o f ca r b o n d io x id e t o co n v e r t z in c o xid e a n d zinc hy d roxid e to the stable zinc carb on ate com p ou nd . If left u nchecked and sufficient m o is tu r e i s p r e s e n t , a ll t h e z in c m a y b e co n s u m e d (r a r e o ccu r r e n c e), o r t h e z in c m a y b e co n s u m e d in p a t ch y a r e a s , o r t h e r e su lt m a y be r ed u ced zinc th ickn ess. T o p r e v e n t w h i te st o r ag e st a in , m a n u fa ct u r e r s m ay p erform a p osttreatm ent p rocess. The
Galvanizing follow ing are th e m ost com m on p osttreatm ent m e t h o d s a n d t h e ir e ffe ct s o n p a in t in g : Apply a coating of oil to form a barrier from mo isture.— Pain ts w ill not a d h ere to oils, a n d a p p ly in g o il w ill r e su l t in a d h e s io n fa ilu r e if the oil is not rem oved . T o ch e c k fo r th e p res en ce o f o il, p erfo rm a w a te r b ea d te st . Pla ce a d r op of w a te r on th e su rface. If the w ater b ead s, it ind icates the p r es en ce o f oil. Quen ching (coo ling in a water bath).— W a t e r m a y co n tain g r eas e an d o ils th at floa t on the w ater su rface and contam inate th e g a lv a n ize d su r face , re su ltin g in coa tin g a d h e si o n failu re if th e g reas e an d o il are not rem oved . Chrom ate q uenching .— Typ ically, pa ints w ill not ad her e to galvanized sur faces treated b y th is m et h od . Ch r om a te q u en ch in g is b ein g d isco n tin u e d b eca u se of h u m a n sa fe ty an d en viro n m en tal concern s. Pho sphate q uen ching .— A d h e sio n of p a in t is im p r o v e d b y th is m eth o d . Ther e is no easy field test to d eterm ine th e ty p e of q u en ch tr ea tm en t t h a t w a s u se d , if a n y . The m ost reliable m etho d is to contact the g a l v a n i z in g s h o p . (c) Depo sited C ontam inan ts.— Dep osited co n t a m in a n t s a r e fo r e ig n s u b s t a n ce s th a t accu m u late on th e ga lvan ized su rface. The m ost com m on con tam inants are d irt, grease , o il, a n d s o lu b le s a lt s . C h l o r id e s a lt s a r e aggr essively d estru ctive to galvan ized m et a lw or k . For p r ot ect ion ag a in st ch lor id e co n t a m i n a t io n , g a lv a n i z ed it e m s s h o u l d b e p r o t e ct e d b y co n tain ers d u rin g tran s p o rt or storage.
fo r m a t io n o f r ea ct iv e z in c o xid e a n d zin c hy d ro xid e com p ou n d s. The chem ical reaction m ay con tinu e for 1 to 2 years, d ep end ing on local w eather co n d it io n s a n d m e t alw o r k g e om e t ry . • Weath ered galva nized m etalw ork.— T h e s u r fa ce h a s co m p le t ed ch e m ica l co n v er sio n fro m zin c ox id e a n d zin c h y d r o x id e co m p o u n d s to n o n r ea ct iv e zinc carbon ate. (a) Newly Ga lvanized Metalw ork.— Z in c is st ill r e a ct iv e o n n e w ly g a lv a n i z e d m e t a lw o r k , a n d se v er a l con ta m in a n ts m a y ex ist , su ch as oil co a tin g or p os tt r ea tm en t a p p lied at th e p oin t o f g a lv a n i z in g . Ea ch s p e cific co n t a m in a n t m a y re qu ire a s pe c ia liz e d s urfa ce pr e p a ra tion m et h od . Th e fo llow in g ste p s a re su rfa ce p r ep a r a tio n m et h od s fo r r em ov a l of s p ecific conta m inan ts: Rem ova l of white sto rage stain (w hite ru st), if prese nt.— A p p ly a 1- t o 2-p er cen t a m m on ia solution by b ru sh or sp ray . For severe w hite st or a g e s ta in , ap p ly 1 p a r t a cet ic or citr ic acid to 25 p arts of w ater. Thorou gh ly rinse th e area w h e r e th e s o lu t i on w a s ap p lie d w it h w a r m p o t a b le w a t er a n d a llo w t h e a r ea t o a ir d r y . Rem ova l of dirt, grease, an d oil.—So lv en t cleaning in accord an ce with SSPC-SP1. W aterb a s e d e m u ls ifie r s a n d a l k a lin e c le a n e r s h a v e b ee n sh ow n to w or k b es t. En su r e t h a t a lk a lin e clea n er s h a v e a p H of le ss th a n 12 b eca u se zin c w ill d issolve in h ighly a lkalin e solu tions. A p p l y cle a n in g s o lu t i on s b y d i p p in g , sp r a y in g , or b r u sh in g w ith so ft b r ist le b r u sh es. D ip p i n g a n d sp r a yin g w o r ks b est w h e n th e cleaning solu tion is at abou t 140 to 185 d egrees F. Thor ou gh ly rinse the a rea w he re th e solven t w as ap p lied w ith h ot p otable w ater a n d a llo w t h e a r ea t o a ir d r y .
s u r fa ce p r e p a r a t io n o f g a lv a n i z ed m e t alw o r k b efo re p ain tin g d e p en d s on w h e t h er th e m etalw ork is new ly galvan ized or w eathered :
Rem ova l of zinc ash.— A p p ly a 1- to 2-p er ce n t a m m on ia so lu tion b y b r u sh or sp r a y . Th or ou g h ly r in se th e a r ea w h er e t h e a m m on ia solu tion w as ap p lied w ith w arm p otable w ater a n d a llo w t h e a r ea t o a ir d r y .
• Newly galvanized m etalw ork.— Th e su r face is u n d er g oin g th e a ctiv e
Repair of physical defects (high spots and dro plets).— H ig h sp o ts o ccu r w h e n exce ss z in c
57. Surface Preparation.— T h e m eth o d of
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Guide to Protective Coatings: Inspection and Maintenance r u n s d ow n th e e d g es of m et alw or k as it is rem ov ed from th e m olten ta n k. The excess z in c fo r m s p r o tr u sio n s o r ir r eg u la r ed g es. H igh sp ots shou ld be g rou nd off w ith a p ow er t o ol. D r o p l e ts fo r m a t m e t a lw o r k e d g e s w h e r e zinc dr ains w hen the m etalw ork is rem oved fr o m t h e m o lten b ath . D ro p lets can b e gr ou nd d ow n or kn ocked off by p ow er tools. W hen u sing p ow er tools, d o n ot grin d off the z inc to less than th e req u ired th ickn ess. If the z inc on m etalw ork ha s been rem ove d to bare m etal or thinn ed below the sp ecified t h i ck n e ss d u rin g s h ip p in g , co n s tru ctio n , ha nd ling , or installation, the d am aged g a lv a n ize d ar ea s ca n b e r ep a ir ed b y coa tin g w it h a z in c -r ich p r im e r . Removal of zinc oxide and zinc hydroxide com pound s.— Th e r ea ctiv e z in c ox id e a n d zin c hy d roxide com p ou nd s m ay n ot hav e been co m p let ely r em ov ed d u r in g th e in itia l clea n in g p r o c e ss, a nd th ere is n o s im p le field d etection m ethod . To avoid p rem atu re coating failu re, the coating ind u stry recom m en d s one of the fin a l s u r fa ce p r e p a r a t io n m e t h o d s b e e m p lo y e d t o r e m o v e r e a c tiv e z in c o xid e a n d zinc hy d roxid e com p ou nd s; ho w ever , the coating m an u factu rer sho u ld be consu lted b e fo r e a p p ly in g th e p rim er b ecau s e so m e of the m etho d s m ay n ot be com p atible w ith the z in c -r ich p r im e r : Pho sphate treatm ent.— A p p ly a p ho sp ha te co n ta in in g so lu tio n to for m a n on r ea ctiv e z in c p ho sp ha te layer on the su rface and inh ibit the for m atio n of z in c ox id es . Th e t r ea tm en t w ill slig h t l y e t ch th e s u rface, p ro d u cin g an anc hor p r ofile for th e co a tin g p r im er . A p p licat ion is by im m ersion , spr ay , or soft br istle bru sh . The s o lu t io n i s le ft o n fo r a b o u t 3 to 6 m in u t e s a n d r in se d off w ith p ot a b le w a te r . Co lor a tio n is retu rn ed to the galvan ized su rface after w a s h in g s o th a t a n y m is se d a r e a s w i ll b e v isib le a n d can b e r et re at ed . A llow th e s u rfa ce t o air d r y b e fo r e co a t in g . Fo r n e w co n s t ru c t io n m e t alw o r k it e m s t h a t a r e s p e c ifie d t o b e co a t e d , p h o s p h a t e q u e n ch i n g a t the ga lvanizing p lant w ill prod u ce high er qu ality an d at less cost than ap p lication in the field .
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Zinc-rich p rim er sh ou ld n ot be ap p lied to p ho sp ha te treated su rfaces. The p ho sp ha te w ill fo rm a n in su la te d b ar rie r b etw e en th e zin c p a in t p a r ticle s a n d th e zin c g a lv a n iz ed m eta l. To b e e ffectiv e, z in c-rich p rim er s r eq u ire d ire ct co n ta ct b et w ee n th e z in c p a r ticle s in th e p a in t a n d th e zin c m eta l o n th e g a lv a n iz ed su r fa ce . Wash p rime rs.— W a sh p r im e r s a re co atin g m a te r ials for m u lat ed to n eu tr a lize su r face zin c oxides an d zinc hy d roxid es an d to etch th e ga lva niz e d s u rfa ce , p rod u c ing a n a nc hor p rofile for th e coating p rim er. Typ ically, the m a n u fa ct u r e r r e co m m e n d s a sin g l e th i n co a t be ap p lied by b ru sh or sp ray at abo u t 0.3 to 0.5 mils. At th is thickn ess, the galvan ized su rface sho u ld sh ad ow or reta in a n ear m atte g ra y ap p ea ra n ce. If th e g alv an ize d su rfa ce becom es hid d en, the w ash p rim er w as ap p lied too thic kly, a nd it m a y d e la m ina te be c a us e of th e w a sh p r im e r ’s p o or co h esiv e str en g th . A c o m m o n w a s h p r im e r is p o l y v in y l b u t y r a l (SSPC Pa int Sp ecification N o. 27). O th er w ash p r im er for m u lat ion s a r e co m m er cially available. Acrylic passivatio n.— A p p licat ion of a n acid ic acrylic solu tion w ill passivate or neu tralize th e r e a ct iv e z in c o xid e s a n d z i n c h y d r o x id e s a n d rou ghe n the s ur fa c e, p rod u c ing a n a nc hor p r ofile for th e co a tin g p r im er . Th e s olu tio n is a p p lied at ab ou t 0.04 m il (1 m icr on ). Th is m e t h o d i s co n s id e r e d a p p lica b le o n ly fo r v e r y th in la y er s o f z in c o xid es a n d zin c h y d r oxid es. T h e s olu t io n m u s t b e d r y b e fo r e a p p ly in g a n y co a tin g m a te r ial. Sweep blastin g.— This is a light blast clea n in g m et h od to r em ov e t h e r ea ctiv e z in c o x id e s a n d z i n c h y d r o x id e s a n d t o p r o d u ce a n a n ch or p r ofile for th e co a tin g p r im er . Soft a b r a s iv e s sh o u ld b e u s e d t o r e d u ce s ig n i fica n t z in c m et a l los s a n d sh ou ld h a v e a M oh s’ scale h a r d n e s s o f 5 o r le s s a n d a p a r t i cle s iz e b e t w e e n 8 t o 20 m ils . T y p ica l a b r a siv e s ar e alu m inu m or m ag n esiu m silicate, corn cobs, w a ln u t sh e l l, lim e s to n e , a n d s o m e m in e r a l san d s.
Galvanizing Th e b las t n oz z le s h ou ld b e h eld at a r ela tiv ely low ang le to rem ove th e reactive zinc oxid es a n d zin c h y d r ox id es . H old in g th e b las t n oz z le p er p en d icu lar to th e s u r face can q u ick ly rem ove sou nd zinc m etal. Op tim al am bient cond ition s for sw eep blasting are 70 d egr ees F an d 50 p ercent or less relative hu m idity. After sw ee p b las tin g , coa t t h e s u r face w ith in 24 h ou rs. (b) W eath ered Galvanized Metalw ork.— Fu lly w e a t h e r e d g alv an izin g w ith an o u td o o r ex p os u r e o f b et w ee n 1 an d 2 y ea r s s h ou ld h a v e c o m p le t ely c on v e r t e d t h e z in c o xid e a n d z in c h y d r ox id e co m p ou n d s t o fo r m a s ta b le (n on r ea ctiv e) p r ot ect iv e la y er of z in c car b on at e. Th e m os t co m m on su rfa ce p r e p a r a t i on m e t h o d is w a t e r p o w e r w a s h in g a t a p ressu re of abou t 1,450 psi to rem ove d irt, g r e a se , a n d o il. H ig h e r p r e s s u r e s s h o u l d b e a v o i d e d t o red u ce th e risk o f rem o v in g s ou nd zinc. Sw eep blasting is ano ther m ethod u sed , often u sed after w ater p ow er w ash ing to p r o m o t e a d h e sio n o f t h e p r im e r . Aged or weathered galvanized me talwork.— O l d , a g e d g a l v a n i zin g t h a t h a s b ee n in se r v ice fo r se v er a l y ea r s a n d is sho w ing ev iden ce of d eterioration p resen ts a d d it io n a l p r o b l em s a n d r e q u i r e s r e m e d ia l su r f a ce p r ep aratio n m eth o d s d ifferen t fr om those ap p rop riate for n ew ly galvan ized m e t alw o r k . De t e r io r a t ed areas m ay s h o w a red d is h -brow n st a in . Th i s co lo r s tain m ay b e m is tak en for co r ro sio n o f t h e s te el b a se m e t al. Ju s t a b ov e t h e in t e r fa ce b e tw e e n t h e s te e l b a s e m e t a l a n d th e z in c th a t w a s a p p lied d u r in g th e h ot d ip g a lv a n izin g p r oc es s, a zin c-iro n allo y lay er is fo r m e d . Th e z in c -ir o n a llo y la y e r m a y b e co r r o d in g r a t h e r t h a n t h e s te e l b a s e m e t a l, a n d be bleed ing thr ou gh the m ore p u re zinc above, r e su l t in g i n th e red d is h -b ro w n s tain . Z inc -iron a lloy is b r ow n ish , an d st ee l cor r os ion is red d ish. It is difficu lt to visu ally d istin gu ish t h e d i ffe r e n ce b e tw e e n th e t w o m e t als b y co lo r . A m a g n e t ic o r e le ct r o n ic D F T g a u g e c an b e u sed to d eterm ine if the steel base m etal or the
z in c-iro n allo y is co r r od in g . Since zin c is n on m a g n et ic, m ea su r in g ov er zin c w ill p r od u ce a th ick n es s r ea d in g . A r ea d in g show ing thickness ind icates galvanized m a te ria l is pre s e nt (i.e ., brow nis h c olor) (ho t d ip ga lva niz ing is a pp lie d a t a thic kne s s of a bou t 2 to 5 m ils ). R e a dings tha t s how no th ickn ess ind icate ferro u s ru st (i.e., red d ish co lor in d icat es zin c h a s b ee n con su m ed ). Th is is im p o r t a n t b e ca u s e t h e ar e a s t h a t ar e b r ow n ish m a y st ill h a v e s u fficien t g a lv a n izin g m a t er ia l le ft in ta ct, a n d th is w i ll a ffe ct th e su rface p rep ara tion r equ irem en ts. The su rface p rep aration of old , aged ga lvan izing r equ ires the follow ing ste p s: 1. W ater p ow er w ash the en tire sur face to re m ove d irt, oil, a nd gre a s e a t a bout 1,450 p si. 2. A b r a siv ely b las t (N A C E 3/ SSPC -SP6) or p ow er to ol (SSP C -SP3 o r SSPC -SP11) c le a n the ru s te d re d d is h a re a s (little or n o g a l v a n i zin g i n t a ct ) t o b a r e s t ee l a n d feathe r th e ed ges. 3. H a n d (SSP C - SP 2) o r p o w e r t o ol cle a n (SSP C - SP 3) t h e b r o w n i sh - co lo r e d a r e a s (g a lv a n i z in g i n t act ), e n s u r in g n o m o r e g a lv a n izin g is r em ov ed th a n is n e ce ss a r y . 4. Sw eep blast the en tire galvan ized su rface to pr om ote th e ad he sion of the p rim er coat.
58. Coatings.— N u m e r o u s c oa t in g m a t e r ia ls ca n b e a p p lied ov er g a lv a n izin g ; ho w ev er , it is b es t t o e n su r e t h a t t h e m a te r ial s ele cte d is com p atible w ith zinc. The selection d ep end s n ot on ly on com p a tib ility b u t a lso , in cer ta in cas es , on ch em ical tr ea tm en ts, su rfa ce p r ep a r a tio n , an d se r v ice e xp os u r e. C on su lt th e co a tin g m a n u fact u r er or th e s p ecific p rod u ct da ta shee ts for com p atibility w ith sp ecific ch em ical tr ea tm en ts a n d su rfa ce p r ep a r a tion m eth od s . (a) Coating Se lection .— T h e fo llo w in g c o at in g s a r e su i t ab le to o v e r co a t g a lv a n i z in g u n d e r
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Guide to Protective Coatings: Inspection and Maintenance at m os p h er ic, bu ria l, an d im m er sio n se rv ice cond ition s:
•
Bu r i a l o r im m e r sio n s e rv ice e xp o s u r e
" Co al tar ep oxy •
A t m o s p h e r ic s er v ice e xp o s u r e
" Ep oxy " A cr y lic or w a te r -b or n e a cr y lic " M o istu r e cu r ed u r eth a n e " Acrylic latex " Z i n c-r ich e p o x y fo r d a m a g e d a r e a s " W aterborn e latex " Z in c-r ich m o istu r e cu r ed u r eth a n e " Z in c-r ich ae r os ol s p r a y for r ep a ir in g d am aged areas of bare galvan ized su rfaces
" E p o x y p r i m e r w it h U V - r es is t an t a lip h a t ic u r e t h a n e t o p c o a t
" M oistu re-cu red u rethan e p rim er w ith U V-r esista n t a lip h a tic u r eth a n e topcoat
" Zinc-rich ep oxy or m oistu re-cu red u r e t h a n e p r im e r w it h U V - r es is t an t com p atible top coat for d am aged areas
58
fo r d a m a g e d a r e a s Do n ot u se oil-ba sed or a lkyd coating s u n less the y a re s p e cific a lly formu la te d for g a lv a n iz in g . Z in c is an alk a lin e m eta l. M oisture w ill eventu ally p erm eate th rou gh the coating film . The zinc and bind ers in oil-based or a lkyd c oa tings re a c t in th e pr e s e nc e of a lk a lin ity an d m ois tu r e t o fo r m a m et a llic so a p . Th is p r oce ss is calle d sa p on ifica tion . C a s e h i st o r ie s s h o w t h a t oil-b a s ed a n d a lk y d co a t in g s t h a t a r e ad h e r in g w e ll w ill r e q u i re a b o u t 6 m o n t h s t o 1 y e a r a ft e r a p p lica t io n i n a n ou td oo r en v ir on m en t t o b eg in to fail.
Chapter XII Coating Failures Coatings fail for m an y reason s. These failu res c a n b e r e la t ed to m aterial s electio n , form u lation, ad hesion, substrate typ e, a p p lic a tio n , stru ctu re d es ig n , o r ex terio r for ces . Th es e r ela te d failu re ty p es m ay act ind ep en d en tly of each oth er or in concert w ith each oth er. The read er is strong ly u rged to p u r ch a se on e o f th e p h ot og r a p h ic coa tin g fa ilu r e b o o k s lis ted in ap p en d ix B.
59. Material Selection.— To p r ote ct th e su bstr ate, coatings a re r equ ired to resist d e t er io r a t io n f r o m a t m o s p h e r ic, b u r ia l, a n d im m e r sio n s erv ice ex p o s u re. N o o n e ty p e of coating has ev er been d eveloped to p rotected a ll su b st r a te ty p es in all ser v ice ex p o su r es. R a t h e r , m a n u factu rers fo rm u late co atin g s for s p e c ific s e r v ice e xp o s u r e s . C o a t in g m a t e r ia l se lectio n is g en er ally b as ed on se rv ice expo su re su itability, past history p erform an ce, recom m en d ation s from oth er facility ow n ers, an d accelera ted p erform an ce tests. The follow ing are som e exam p les of im p rop er m a t e r ia l se lectio n : •
•
•
Se lectio n o f a p ain t fo r th e w ro n g s e r v ice e xp o s u r e . Fo r e xa m p le , if a n a t m o s p h eric co atin g is sp ecified for im m e r sio n s e rv ice e xp o s u r e , fa ilu r e w ill occu r in a r ela tiv ely sh or t t im e p er io d . Se lectio n o f a p ain t b as ed s o lely on co st s. N o t a ll p a in ts ar e eq u a l. A m a n u factu rer m ay p ro d u ce s o m e excellent p rod u cts but o ther p aints fr o m th e s am e m an u factu rer m ay not p e r f or m w e ll. A s a r u l e-o f-t h u m b , w h at y o u p ay fo r is n o rm ally w h a t you get, and this, in gen eral, ap p lies to p aint m ater ials. Se le ct io n o f a p a in t b a s e d s o le ly o n a n u n s u b sta n tia te d o p in io n . A p e rso n
w it h lim it e d k n o w le d g e o f in d u s t r ia l co a tin g s ca n se lect th e w r on g or p oo r ly p er for m in g m a te r ials , re su ltin g in p r em a tu r e fa ilu r e. •
Se le ction of a pa int s ys tem tha t is no t c omp a tible w ith a n othe r p a int. For exam p le, a coating p rim er m a n u f actu r ed b y on e co atin g co m p a n y s h o u ld n o t b e t o p c o at e d w it h a m a t e r ia l m a n u fa ct u r e d b y a d i ffe r e n t co m p a n y , e ve n if the tw o c oa ting m a te ria ls a re of th e sam e gen eric typ e, such as a p olya m id e e poxy. Inc om p a tibility of solven ts betw een tw o sim ilar p aints is a com m on cau se for p rem atu re failure.
60. Formulation.— Fo r m u l a tio n fa ilu r e s a r e failu r es th a t a r e in h er en t w ith in th e co a tin g m a t er ia l itse lf. Th e co m p o n e n ts o f a co atin g co n sis t o f r esin s, s olv en ts , an d p ig m en ts , an d th ey ar e m ixe d in v a r io u s p r op or tion s. Im p rop er com p on en t m ixtu re d u ring the m a n u fa ctu r in g p r oce ss ca n lea d to fa ilu r e. Form u lation failur es are su bd ivided into th e follo w in g or g a n ic an d in or g a n ic coa tin g cla sses: (a) Fo rmulatio n - O rgan ic Co atings.— O r g a n ic co a tin g s ca n fail b eca u se of ch a n g es in form u lation, raw m aterials, imp rop er p rop ortioning, insu fficient m illing , and other m an u factur ing p rocesses, . Table 4 p rov id es a d escription of form u lation for or ga n ic failur es, the cau se of failu re, and the r em ed y for th e failu res. (b) Fo rmulatio n - Ino rgan ic Zinc.— In or g a n ic co a t in g s s u f fe r fr o m in h e r e n t p r o b l e m s t h a t resu lt in failu res cau sed p rincipally by silicate v eh icles an d m et a llic zin c th a t a r e u se d in th eir c omp os ition. Ta ble 5 p rovid e s a de s c rip tion of th e t y p es an d cau se s o f in or g a n ic zin c coa tin g failu res an d th e rem ed ies for th e failu res.
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Guide to Protective Coatings: Inspection and Maintenance Table 4.—Formulation-related failures for organic coatings (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
Remedy
ALLIGATORING - Very large macrocracking, generally crosshatched pattern.
Internal stress where surface shrinks more rapidly than the body of the coating. Hard topcoat applied over soft undercoat.
Remove failed coating. Apply thin coats and thoroughly dry before applying additional coats. Never apply hard topcoat (epoxy) over soft coats (asphalt).
CHALKING - Surface is soft, powdery, and easily removed by wiping.
Surface disintegration caused by UV sunrays on an organic resin binder; formulated with improper pigmentation.
Select coatings formulated with UVresistant resins (acrylics) and light stable, high hiding pigments.
CHECKING - Surface phenomena with uneven, small, noncontinuous fissures in coating that do not penetrate to the substrate.
Surface stresses resulting from shrinkage caused by weathering and continued coating polymerization and oxidation.
Select a coating formulated with weather-resistant resins, inert reinforcing pigments, and light stable pigments.
CRACKING - Small breaks in coating to substrate. May be linear, cross-hatched, or curved. Cracks may or may not be continuous.
Stress set up in coating because of continued polymerization and oxidation; improper pigmentation or improper coating system.
Select coating formulated from nonreactive, weather-resistant resins; reinforcing pigments; and nonreactive colored pigments. Primer must be compatible with intermediate and finish coats.
DISCOLORATION - Yellowing, graying, or darkening of coating.
Resin or pigment color change caused by weather or chemical reaction.
Select coating formulated with both color stable resins and pigments.
EROSION - Similar to chalking. Surface removed on high spots and brush marks to base or primer coating.
Chalking mechanism, coating surface removed by weathering and abrasion.
Select a tough, chalk-resistant coating with good flow out characteristics that will form a smooth film.
MICROORGANISMS - Blotchy brown or black spots on coating surface causing poor, dirty appearance with softening or slimy feel.
The biodegradation of the coating by bacteria or fungi. Bacteria or fungi use coating ingredients for nourishment.
Use oil coatings containing permanent fungicide or bactericide. Nonoil coatings should use modifiers that will not biodegrade.
MUD CRACKING - Large cracking. Coating may curl at cracks and lose adhesion.
Rapid drying of high filled coatings, especially waterbased materials (water emulsion paints).
Select coatings with strong adhesion. Apply coatings under proper drying conditions and avoid sags or areas of excess thickness during application.
WRINKLING - Furrows and ridges in coating surface. May be linear or random pattern. Wrinkle may be fine or quite large.
Surface reaction where surface of coating expands more rapidly during drying than does the body of the film.
Select coating with even, thorough drying characteristics. Apply evenly and avoid excessive thickness.
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Coating Failures Table 5.—Formulation-related failures for inorganic zinc coatings (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
CHECKING - Usually fine, visible, or microscopic checks. Does not penetrate to the substrate.
The zinc pigment to binder ratio is high, causing rapid drying and resulting in surface cracking.
Formulation should include reinforcing pigments. Apply coating as thin as recommended. Apply second coat only if necessary. Apply under favorable conditions.
CHEMICAL - Pinpoint rusting progressing from spotty to continuous area.
Acid or alkali reaction on both silicate binder and metallic zinc.
Apply resistant topcoats over inorganic zinc coatings.
MUD CRACKING - Fine to fairly large segments, about 1/4-inch across, flaking from the coating surface.
Application too heavy or drying too rapidly.
Apply coating at no more than recommended thickness and apply under favorable drying conditions.
PINPOINT RUSTING - Pinpoint spots of corrosion progressing from a few spots per square foot to almost continuous rusting.
Uneven coating thickness. Thinly coated areas show failure first. This is a normal failure pattern for inorganic zinc coatings.
Apply a maintenance coat at first sign of pinpoint failure.
61. Adhesion.— A d h e s io n fa ilu r e s a r e nu m erou s and can be catastroph ic. Failures are cau sed for a nu m ber o f reasons. On e of the m os t co m m on r ea so n s fo r ad h es ion failu r e is p a in tin g ov er a co n ta m in a te d su b st r a te . C o n ta m in a te d su r fa ce s p r ev en t a d h esio n . Solub le salts left on th e su rface pro m ote o sm o t ic b lis terin g w h ere m o is tu re o r g ase ou s v a p or is tr an sm i tte d th r ou g h th e se m ip e r m e ab le co atin g m aterial, an d g as e s or liqu ids can form betw een the coating an d the su b st r a t e. T ab le 6 p ro v id es a d es crip tio n of t h e t y p e s a n d ca u s e s o f a d h e s io n f a ilu r e s a n d th e rem ed ies for th e failu res.
Remedy
m os t com m on s u bs tra te s a re s tee l, c a st iron, a lu m in u m , zin c, co p p er , co n cr ete , an d w oo d . These sub strates all have d ifferen t ch a r a cter ist ics , su ch as d en sit y , p or osit y , an d chem ical reactivity. Steel is ver y d en se (related to su rface sm ooth n ess), n on p oro u s, an d less chem ically reactive th an other s u b s t r a t e m a t e r ia ls . O n t h e o t h e r h a n d , concrete is not a h igh d ensity (non u niform ed s u r fa ce ) m a t er ia l; it is p o r o u s a n d v e r y chem ically reactive. This sim p lified com p arison illustrates the d ifferen ces betw een s ub s tra te typ e s . Ta ble 7 p rovid e s a de s c rip t ion of the typ es and causes of su bstrate failu res an d th e rem ed ies for th e failu res.
62. Substrate.— Th e t y p e o f su b str at e s u rfa ce can be a factor related to coating failu res. The
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Guide to Protective Coatings: Inspection and Maintenance Table 6.—Adhesion-related failures (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
Remedy
BLISTERING - Small to large (1/32 to 1 inch plus) hemispherical bubbles in the coating that contain gases or liquids. Bubbles may range from 1 per square foot to several hundred per square foot.
Blisters may be due to poor surface preparation, internal soluble materials (salts), or poor wetting of substrate. Osmosis causes absorption of gases into substrate or solvent entrapment (also referred to as “solvent blistering”).
Select a coating with very strong adhesion strength and low moisture vapor transfer rate. Ensure clean substrate with proper surface preparation and reduced soluble salt levels to suit service exposure.
FLAKING or SCALING - Small to large (1/16 to 1 inch plus) pieces of coating, curling at edges. Easily removed from surface, leaving substrate exposed.
Normally, coating is brittle, with internal shrinkage characteristics and marginal adhesion strength. Oil type coatings may scale or flake from galvanized surface (never apply an alkyd to a galvanized surface).
Select a coating with very strong adhesion strength and low moisture vapor transfer rate. Ensure clean substrate with proper surface preparation and reduced soluble salt levels to suit service exposure. For galvanized surfaces, use a primer compatible with zinc.
INTERCOAT DELAMINATION Coatings that do not adhere to the previous coat. Failure is between the primer and the intermediate coat or between the intermediate coat and the top coat. The substrate is not normally exposed.
Coating material is not compatible with undercoat; undercoat surface may be contaminated with dust, dirt, overspray, or other contaminates; or undercoat may have cured beyond maximum recoat time.
Select a coating with good compatibility and adhesion between coats. Ensure that the undercoat surface is clean before applying the next coat. For epoxies, do not expose to moisture (water and humidity) or excessive sunlight before applying the next coat.
PEELING - Coating may be smooth and lying on the surface or hanging in shreds. Little or no adhesion is evident.
Adhesion is less than the tensile strength of the coating. Coating peelings can easily be pulled from the surface down to bare substrate.
Select a coating with very strong adhesion strength and low moisture vapor transfer rate. Ensure that the substrate is clean, the surface has been cleaned properly, and salt has been reduced to levels suited to the service exposure.
UNDERCUTTING - Corrosion byproducts from the substrate build up under the coating and will break the coating at edges or pinholes. The corrosion progresses under the coating.
Poor adhesion because of improper surface preparation (dirt, dust, soluble salts, other contaminates); smooth surface (no surface profile); or coating incompatibility with the substrate surface.
Select a coating with very strong adhesion strength. Apply coating over a surface that has been abrasively cleaned or cleaned by water jet blasting. Use of a zinc-rich primer reduces undercutting.
63. Application.— Co ating failur es are m ost c o m m o n l y related to th e m eth o d o f a p p lic a tio n. Th ere are a v ariety o f reas ons for a p p licat ion -re lat ed failu r es th a t h a v e n ot h in g to d o w ith m aterial selection or im p rop er form u lation. These failu res are m ainly cau sed b y h u m a n s. T h er e ar e n u m er o u s e xa m p les,
62
r an g in g fr om f ailu r e to u n d e rsta n d th e co n se q u en ces of im p r op er ly p r ep a r in g su rfaces to im p rop erly ap p lying coating s to ru s hing the job. Ta ble 8 p rovid e s a de s c rip t ion of ap p lication failu res, the cau se of the failur es, an d the rem ed y for the failures
Coating Failures Table 7.—Substrate-related failures (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
Remedy
AGED STEEL - The surface includes blisters, rust, pitting, tubercles, or adhesion loss in areas where the substrate was exposed to a corrosive environment.
Substrate surface retained minute corrosion byproducts or contaminants even if it was abrasively blasted or water jet blasted to a high degree of cleanliness.
Water jet blast surface with water; dilute phosphoric acid; or saltbonding, chemical-removal solution. Apply an anticorrosion primer or barrier coating with high adhesion strength.
AGED CAST IRON - The surface includes blisters, rust, pitting, tubercles, or adhesion loss in areas where the substrate was exposed to a corrosive environment. A silver gray to a dark gray color may indicate graphite corrosion. This kind of corrosion can be easily cut or pierced with a knife.
Cast iron has a rough, more porous, crystalline surface matrix than steel, causing more moisture to be retained.
Water jet blast surface with water or salt-bonding chemical removal solution. Heat surface to hot-totouch to drive off moisture. Brush apply primer while surface is warm to allow a maximum wet-coat penetration. Select compatible intermediate coat and/or topcoat.
GALVANIZED or METALLIC ZINC - White zinc corrosion byproduct developing under or breaking through the coating.
Formation of zinc salts (oxide, sulfide, oxychloride, zinc soaps) under the coating.
Brush or low-pressure water-jet blast zinc surface or treat with commercial zinc treatment solution. Select an inert, nonoil primer with high adhesion strength.
ALUMINUM - White aluminum corrosion by-product is causing pinpoint coating failure, adhesion loss from smooth surface, blistering, or pitting.
Environmental pH outside the range of 5 to 8.5. Lack of accessible oxygen. Lack of adhesion to a very smooth aluminum oxide surface, i.e., lack of sufficient surface profile.
Light dust blast or soft abrasive blast or treat with commercial aluminum treatment solution. Select a compatible primer with high aluminum surface adhesion strength.
COPPER - Blue or gray-green corrosion by-products, adhesion failure blistering, or pitting.
Lack of adhesion to a very smooth copper surface (no surface profile) or the presence of oxides on surface.
Light brush blast, soft abrasive blast, or treat with commercial copper treatment solution. Select a compatible primer with high copper surface adhesion strength.
CONCRETE - Adhesion loss, blistering, or peeling of coating.
Chemically reactive and high moisture content. Formation of calcium salts under the coating. Pinholes, air, and water pockets in concrete surface. Water vapor transmission through concrete.
Abrasive blast or water jet blast (acid etching not recommended) to obtain clean and dry surface. Select a low molecular weight, high penetrating primer with high alkali resistance (coal tar epoxy or modified epoxy).
For graphite corrosion, it is the selective leaching of ferrous ions from some cast irons, normally gray cast iron.
64. Design.— N u m er ou s co a tin g failu r es occur , not b ecau se of m isform u lated m ater ials, d e fic ie n t su r face p rep aratio n , o r ap p lication er r or s b u t b eca u se of t h e in h er en tly d ifficu lt p rob lem s p resen ted by th e d esign of the s tr u ct u r e. M o s t d e s ig n e rs d o n o t h a v e corro sion m echa n ism s an d coating op era tions
in m in d w h en th ey d esig n st r u ctu r es. H o w e v er , w i th th e p ro p er se le ctio n of co atin g m a t er ia ls a n d a p p lica tio n te ch n iq u e s, m a n y d esign inad equ acies can be over com e. Table 9 p rov ides a d escrip tion of d esign failu res, the cau se of the failur es, an d the r em ed y for th e failu res.
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Guide to Protective Coatings: Inspection and Maintenance Table 8.—Application-related failures (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
Remedy
IMPROPER MIXING - Coating is too thin, pigment distribution is nonuniform, or both. Entire or localized areas may have poor adhesion, uneven color, checking, or cracking.
Failure to sufficiently mix material, resulting in improper pigment-tovehicle ratio; settled pigment remains in bottom of container.
Thoroughly mix the liquid material to an even, smooth, homogeneous consistency, with no color variation. During use, continue mixing as necessary. Mechanical mixing is the preferred method.
IMPROPER THINNING - Poor adhesion or pigment flotation, resulting in uneven color. Separation of pigment and vehicle after application, resulting in pinholing or blushing.
Thinner is incompatible with resins or pigments. Improper drying, resulting in surface tension change. Thinner evaporated too rapidly causing moisture to condense on liquid coating. Excessive thinner, resulting in curdling or flocculation of pigment.
Use only the manufacturer’s recommended thinner for selected coating material in the amounts specified. Add thinners slowly and mix thoroughly.
IMPROPER ENVIRONMENTAL CONDITIONS - Blistering and/or poor adhesion caused by damp, humid conditions. Powdery coating where drying occurred too rapidly (overspray). Soft, uncured coating.
Ice, moisture, condensation (above dew point), or standing moisture on surface before application. Lack of proper cure because the temperature and/or humidity were outside restrictive range.
Apply coatings using the manufacturer’s environmental (temperature, humidity, dew point, and surface condition) restrictions or more restrictive requirements.
IMPROPER THICKNESS Where coating is thin, pinpoint corrosion areas result. Where coating is overly thick, checking, cracking, or flaking result.
Improper applicator technique: too close or too far away during spraying; incomplete or excessive spray passes. Difficult areas (restrictive accessibility or space).
Use proper application techniques for even passes and overlaps, follow the manufacturer’s application instructions, and use the equipment recommended by the manufacturer.
AMINE BLUSHING - Oily, ambercolored film on coating surface for aliphatic, amine-cured epoxy materials.
Material applied relatively thickly on cold, damp days or in similar environments where amine rises to surface and reacts with carbon dioxide and moisture in the air.
Wait for proper temperature and humidity before application.
BLUSHING - Milky or whitish appearance of coating film with a dull or flat finish.
Moisture condensation on coating in high humidity because of fast evaporation or unbalanced thinners. Occurs most often on hot, humid days or in similar environments.
Wait for improved humidity, reduce atomizing air pressure to a minimum, or add evaporation retardant to thinner.
BLEEDING - Staining of topcoats.
Soluble resins or pigments in undercoat migrate to topcoat.
Seal undercoat with coating in which bleeding components are insoluble.
CRATERING - Small, uniform indentations in coating film (also referred to as “pitting”).
Air pockets trapped in wet film during spray application.
Abrasive blast, water jet blast, or roughen affected area; ensuring removal of contaminants within craters; and reapply coating.
FISHEYES - Separation or pulling apart of wet film to expose underlying coat or substrate.
Coating applied over dirt, oil, silicone, or incompatible coating material.
Remove all material by abrasive blasting or water jet blasting, ensue substrate is contaminant free, and reapply coatings.
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Coating Failures Table 8.—Application-related failures (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
HOLIDAYS - Bare areas on the substrate that were not coated by the applicator (also referred to as “painter’s holiday”).
Improper and inconsistent application technique, reflecting a lack of care. Most often occurs in areas difficult to coat.
Apply coating in a careful and professional manner, consistent with industry standards.
LIFTING - Wrinkling, swelling, or blistering appearance on the film surface.
Solvents in a coating attack or swell the underlying coating, resulting in film distortion.
Remove all material by abrasive blasting or water jet blasting and reapply coatings.
ORANGE PEEL - Overall appearance is bumpy. Film surface is smooth but irregular. Resembles skin of an orange.
Inherent with sprayed-on materials; caused by improper application techniques: gun too far from surface, solvent evaporation too rapid, spray pressure too low for proper atomization, paint particles falling outside of spray pattern, or material too viscous.
Brush out excess paint before material cures. Correct spray technique. After material has cured, sandpaper surface before applying another topcoat that reacts more slowly.
OVERSPRAY - Very rough coating surface. Surface may be dry, pebbly, or sandy. Some coated areas may have the appearance of dryness or feel dry (also referred to as “dry spray”).
Improper application techniques: gun too far from surface, solvent evaporation too rapid, spray pressure too low, atomizing pressure too high, paint particles falling outside of spray pattern, or material too viscous.
Before the material cures, remove the overspray by dry brushing, followed by solvent wiping. After the material has cured, wire screen and sandpaper the surface before applying another topcoat that reacts more slowly.
PINHOLES - Small, tiny, deep holes (1/32 inch) in coating, normally through to the substrate. Generally, the distribution of holes appears to be random.
Improper application techniques: gun too far from surface, solvent evaporation too rapid, spray pressure too low, atomizing pressure too high, paint particles falling outside of spray pattern, or pigment settlement.
Correct any improper application techniques. If pinholes already exist and the material has not cured, apply additional coat by brushing into holes. If material has cured, but it is still within the recoat window, apply an additional coat. If outside the recoat window, abrade surface and apply additional coat.
RUNS or SAGS - Downward movement of coating material on vertical or curved surfaces in the form of droplets or streams. Runs are the result of excess material continuing to flow after the surrounding surface has set. Sags are the result of differences between application and setting times. Sags have the appearance of a curtain.
Excessive application of coating material, spray gun too close, too much thinner, surface too hard or glossy to hold material, or temperature too cold for proper drying.
Correct any improper application techniques. Apply thinner coats. If material has not cured, brush out excess material. If material has cured and is still within the recoat window, apply an additional coat. If outside the recoat window, abrade surface and apply additional coat.
Note: Orange peeling is not a coating failure, but the appearance may be objectionable.
Remedy
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Guide to Protective Coatings: Inspection and Maintenance Table 8.—Application-related failures (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
Remedy
SPATTER COAT - Areas of thin coating (less than specified coating thickness), normally at end of the spray pass or around complex sections of structure. Under good lighting conditions, coating appears continuous; under poor lighting, coating appears discontinuous. May develop into pinpoint corrosion at a later date.
Improper application techniques, causing a noncontinuous coating over the surface: inconsistent spray passes not overlapping by 50 percent, spray gun flipped at end of spray pass, or spray gun not held perpendicular to the surface.
Correct any improper application techniques. If material has not cured, apply additional coat. If material has cured but it is still within the recoat window, apply an additional coat. If outside the recoat window, abrasive blast or water jet blast all material off and recoat.
Table 9.—Design-related failures (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description BACK-TO-BACK ANGLES and PLATES - Corrosion between back-to-back angles and plates is resulting in undercutting of coating.
Cause Impossible to apply coating in crevice between angles and plates.
Remedy Design: Use T bar or pipe in construction. Precoat: Coat angles and plates before construction assembly. Stopgap measure: Fill crevice with resinous chalking and topcoat with compatible material.
EDGES - Linear corrosion along edge and undercutting coating away from the edge.
Surface tension causing coating to pull away from edges.
Brush or stripe coat surfaces before full coating. Overlap full coating on both sides of edges. Spray directly at edge to build up thickness and reduce surface tension.
INTERIOR CORNERS - A void or blister is developing under coating.
Excessive coating thickness, resulting in coating shrinkage during or after curing.
Apply multiple thin coats and allow coating to thoroughly dry between coats, but within recoat window.
SKIP WELDS - Corrosion in weld gaps and between overlapping metal is causing undercutting of coating.
Impossible to apply coating in crevices in weld gaps and between metal surfaces.
Provide continuous weld in gaps and overlap areas before applying coating in any corrosive environment.
SMALL DISCONTINUOUS AREAS - Corrosion is developing on edges of bolt heads, bolt threads, nuts, washers, rivets, and other small edged or cornered surfaces.
Small surfaces with high ratio of edges and corners to plain, flat area will increase coating surface tension and cause coating to pull away from edges and corner points.
Brush or stripe coat surfaces prior to full coating. Overlap brush or stripe coat with each full coat applied. Applying multiple thin coats is more beneficial than one thick coat.
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Coating Failures Table 9.—Design-related failures (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure description
Cause
Remedy
STORAGE TANK ROOFS (Interior of umbrella type for center post and rafters) Corrosion is developing between roof and rafter and between lapped roof plates.
Impossible to apply coating in crevices between roof and rafter and between lapped roof plates.
Butt weld or double weld roof plates. Precoat rafters and underside of roof.
WELDS - Corrosion along welds, particularly hand welds, is undercutting coating away from weld. Corrosion along weld may be continuous or discontinuous.
Welding flux in undercuts along weld. Rough weld surfaces. Soap remaining after pressure testing of welds. Blue scale (similar to mill scale) remaining on weld surface.
Remove all soap solution and blue scale. Grind rough welds smooth or nearly smooth. For interior of hydraulic structures, such as pipelines, grind welds down to 1/8 inch, minimum. Abrasive blast weld and apply brush or stripe coat 2 to 3 inches on each side of weld, working coating into all rough areas before applying full coating.
65. Exterior Forces.— Th e en v ir on m e n t th e
w a t e r th a t co n t a in s a b r a s iv e m a t e r ia l s u c h a s s a n d p a r t icle s . In t h i s s e ct io n , or d in a r y a tm osp h er ic e xp osu r es a r e n ot con sid er ed . Table 10 prov ides a d escription of failu res related to exterior forces, the cau se of the failures, and the rem ed y for the failures
c o a tin g i s su b ject to can b e a p rim ary cau s e of failu r e. C or r os iv e e n v ir on m en ts n or m a lly e n co u n t e re d o n R e cla m a t io n p r o je ct s a r e fr e sh w a t e r en v iro n m en ts th at co n tain v arious co n c en t r a t io n s o f d is so lv e d s a lt s a n d flo w in g
Table 10.—Failures related to exterior forces (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure Description
Cause
Remedy
ABRASION or EROSION Thinning or wearing away of coating is resulting in a bare substrate subject to corrosion.
Wear caused by wheeled traffic, impact, wind, or liquid-borne abrasives.
Select coating with strong adhesive properties and specific abrasion and erosion resistance. Thoroughly prepare surface (nearwhite blast minimum) and apply new coating.
CAVITATION - Loss of coating and metal material. Appears as tiny craters overlain by multiple craters in metal surface, accompanied by significant metal loss.
Drop in water vapor pressure, forming air bubbles that repeatedly collapse at high pressure.
Select coating with strong adhesive properties and high cavitation resistance.
CHEMICAL - Dissolution of coating; undercutting or underfilm corrosion.
Selection of unsuitable coating material. Improper coating application.
The prime requirement is to select a coating for the specific chemical service exposure.
67
Guide to Protective Coatings: Inspection and Maintenance Table 10.—Failures related to exterior forces (modified from SSPC, Good Painting Practice, volume 1, third edition, 1997) Failure Description
Cause
Remedy
FAYING SURFACES - Coating failure and corrosion in joint area.
Concentration (or crevice) corrosion caused by oxygen differences between closely spaced or joined coated surfaces, subject to friction-producing movement (e.g., steel plates and high strength bolts).
Precoat metal surfaces before assembly with inorganic zinc coating or a suitable coating with a high coefficient of friction.
GRAFFITI - Painted words or graphics over coated surface.
Vandals painting coated surfaces, especially with spray cans.
Select the manufacturer's graffiti remover and antigraffiti coating
68
Bibliography
Bechtel Pow er Corp oration, Steel Stru ctures P a in tin g C o u n cil, C oat in g an d Lin in g In spect ion M an u al, P ittsb u r gh , P en n sy lv a n ia, 1991. Bookcock, Simo n K., R.E.F. W eaver, B. A p p lem a n , an d G .C . Soltz , Effect s on S u rface Con tam in ant s on C oatin g Life. Bechtel Pow er Corp oration, Steel Stru ctu res P aintin g C ou n cil, Pittsbu rg h , P en n sy lv a n ia, 1991. D ep a r tm en t o f th e N a v y , Paint Failures Cau ses an d R em edies, N a v y C iv il Engineering Laboratory , Port H u enem e, C a lifor n ia, 1982. Ele ctr ica l P o w er Re se a r ch In st itu te , In c., Ste el P en st oc k C oa tin g an d Lin in g Reh a b ilit a tio n : A H y dropower Techn ology R oun du p R eport, v olu m e 3, TR -113584, P lea sa n t H ill, Ca lifor n ia, 2000. Fit z im o n s, Br en d a n , Protective Coatin g In spect ion M an u al, Rob in so n Irw in Te ch n ical Su p p or t Lt d ., En g lan d , 1997. Fit z im o n s, Br en d a n , V isu al Com parison M anu al: A pplication an d Coatin g D efects. Ro b in so n Ir w in Te ch n ica l Su p p o r t L td ., En g lan d , 1998. Gen eric Coatin g T y pes: A n In trodu ct ion to In du strial M aint enan ce Coatin g M aterials, Sm it h , Llo y d M ., ed ., T ech n o lo g y P u b lish in g C om p a n y, P ittsb u r gh , P en n sy lv a n ia, 1996. M u n g er , C h a r les G ., Corrosion Prev en tion by P rotectiv e Coatin g, N atio n al A s s o cia tion of Cor rosion Eng ineer s, H ou ston , Texas, 1984. N A C E In te r n a tio n a l, N A CE Corrosion En gin eer' s R eferen ce Book, s eco n d ed ition, R.S. Tr ese d er , R. Ba b o ia n , an d C .G. M u n g er , ed s., H ou st on , Tex a s, 1991.
N a tion a l A ss ocia tion of C or r osio n En g in eer s, Corrosion Basics: A n In trodu ct ion , H o u s to n , Te xa s, 1984. The Society of Pro tective Co ating s, Good Pain tin g Pract ices, v olu m e 1, th ir d ed itio n , John D . Ke a ne , D e a n Be rge r, H a rold H o w er , Ber n an d R. A p p lem a n , Josep h Bro n o, K itt i C on d iff, M a r k O 'D on n ell, Ja n e t Re x , A i m e e Be g g s , V ilm a M a c u r a , Te r r y Sow er s, a n d M on ica M a d a u s, e d s., P itt sb u r g h , Pe n n sy lv a n ia, 1993. The Society of Protective Coatings, Steel Str u ctu r es P a in tin g C ou n cil, S y st em s an d S pecificat ion s, volum e 2, s e ve nth e d ition , Ber n a r d R. A p p lem a n , Ja n et R ex, a n d T er r y So w e r s, e d s . P it ts b u r g h , P en n sy lv a n ia, 1995. Th e Socie ty of P r ote ctiv e C oa tin g s, T he In spection of Coatin gs an d Lin in gs: A H andbook of Basic Practice for In spectors, O w n ers, an d S pecifiers, Be r n a r d R . A p p lem an , Rich ard W . Drisko, Ju d ith K. N eu gebau r, Simo n K. Bookcock, Russel D a v i so n , L aw r e n ce J. G r a b ia k , C IH , C SP , Jan et R ex, a n d Te r r y Sow er s, e d s., P itt sb u r g h , Pe n n sy lv a n ia, 1997. Th e Socie ty of P r ote ctiv e C oa tin g s, C-1: Fun dament als of Protective Coatings for In du st rial S tru ct u res, v er sio n 10, P itt sb u r g h , Pe n n sy lv a n ia, 1999. Th e Socie ty of P r ote ctiv e C oa tin g s, C-3: S u perv ision /Com pet en t Person T rain in g for D eleadin g of In du st rial S tru ct u res, tw o v o lu m e s, v e r sio n V 7-T , P it ts b u r g h , P en n sy lv a n ia, 1999. Th e Socie ty of P r ote ctiv e C oa tin g s, C-2: S pecifyin g and M anagin g Prot ective Coatin g Projects, tw o v olu m es, v er sio n 7, P itt sb u r g h , Pe n n sy lv a n ia, 2000.
69
Guide to Protective Coatings Th e Socie ty of P r o te ctiv e C o a tin g s, S S PC -V IS 2: S tandard M ethod of Evalu atin g D egree of R u st in g on Pain ted S teel S u rfaces, P itt sb u r g h , Pe n n sy lv a n ia, 2000.
Prepared by W aterjettin g, P ittsb u r gh , P en n sy lv a n ia, 2001.
Th e Socie ty of P r o te ctiv e C o a tin g s, S u rface Preparation S pecifications, P ittsb u r gh , P en n sy lv a n ia, 2000.
Th e Socie ty of P r ote ctiv e C oa tin g s, S S PC-V IS 5/ N A CE V IS 9: Gu ide and R eferen ce Photographs for S teel Su rfaces Prepared by W et A brasive Blast C leanin g, P itt sb u r g h , Pe n n sy lv a n ia, 2001.
The Society of Pro tective Co ating s, S S PC-V IS 4/ N A CE V IS 7: Gu ide and R eferen ce Phot ographs for S teel S u rfaces
Th e Socie ty of P r ote ctiv e C oa tin g s, S S PC-S P 15: Com m ercial G rade Pow er T ool Cleanin g, P itt sb u r g h , Pe n n sy lv a n ia, 2002.
70
Appendix A Organizational Sources for Standards and References A m erican Society of Testing an d M ater ials (A STM) 1916 Race Street P h ilad elp h ia P A 19103 Te lep h on e: (610) 832-9500 Fa x: (610) 832-9555 W e b s it e A d d r e ss : w w w .a s tm .o r g N A CE In ter n ation al (N A CE) P O Box 218340 H ou st on TX 77218 Te lep h on e: (218) 228-6223 Fa x: (281) 228-6329 W e b s it e A d d r e ss : w w w .n a c e.o r g Socie ty fo r P r o te ctiv e C o a tin g s (SSP C ) 40 24 th Str eet, 6 th F lo o r P itt sb u r g h P A 15222 Te lep h on e: (412) 281-2331 ext 16 Fa x: (412) 281-992 W e b s it e A d d r e ss : w w w .s sp c .o r g Bu r e a u o f R eclam atio n G u id e Sp e cifica tio n s W eb site A d d re ss: h tt p :/ / in tr a.u sb r.g ov / g u id es p ecs
A-1
Appendix B Reading Sources Goo d Painting Pra ctice, Steel Stru ctur es Painting M an u al, Volum e 1, Third Ed ition , 1993. (The four th ed itio n is d u e in 2003.) Sys te m s a n d Sp ecifica tio n s, Ste el Str u ctu r es P a in tin g M a n u a l, Vo lu m e 2, Eig h th Ed itio n , 2000. Coating an d Lining Insp ection M an u al, Bechtel Corp oration, 1983, exclusively d istributed by Steel Str u ctu r es P a in tin g C ou n cil (SSPC ), A u g u st 1991, SSPC P u b licat ion N o. 91-12. Th e In sp ectio n of C o a tin g s a n d Lin in g s, A H a n d b ook of Bas ic P r a ctice fo r In sp ector s, O w n er s, a n d Sp ecifie r s, SSPC P u b licat ion N o. 91-12, Fir st Ed itio n , 1997. Corr osion P reven tion b y Protective Co atings, by C ha rles G. Mu ng er, Pu blished by N AC E In te r n a tio n a l, Firs t Ed itio n , 1984. P a in tin g : N ew C on st r u ctio n an d M a in te n a n ce, U .S. Ar m y C or p s o f En g in ee r s, M a n u a l N o. E M 1110-23400, A p r il 30, 1995. FH W A Field M an u al for Bridg e Paint Inspection, U.S. Dep artm ent of Transp ortation, Feder al H ig h w a y A d m in ist r a tio n (FH W A ), FH W A Brid g e C oa tin g s Te ch n olo g y Te a m , O cto b er 1997. Steel Penstock Co ating a nd Linin g Reh abilitation, A H yd rop ow er Techn ology Rou nd u p Rep ort, Vo lu m e 3, Te ch n ical R ep or t TR -113584-V3, A u g u st 2000. Av a i la b le fro m E lectric P o w er R es earch Ins titute (EPR I), 3412 H illvie w A v e nu e , Pa lo A lto C A 94304; t ele p h o n e: (650) 855-2000; C u stom er Se r v ice: (800) 313-3774; W eb sit e A d d r ess: w w w .e p ri.co m Vis u a l C om p a r iso n M a n u a l, A p p licat ion an d C oa tin g s D efe cts , Bren d a n Fitz im on s, Ro b in so n Irw in Te ch n ical Su p p or t Lt d ., En g lan d 1997-1998, (SSP C P u b licat ion N o. 00-8)
B-1
Appendix C Inspection Checklist G D eliv er ed m a te r ials G A p p r o v e d m a t er ia ls , r e co r d b a t ch n u m b e r s G Sto r ed p r op er ly G Con tainers secu red G Shelf life not exceeded G A b r a s i v e m a t e r ia l G C om p lies w ith SSPC -A B1, Cla ss A , Ty p e I o r II G Con tam inan ts G C h eck for p r es en ce o f oil, A STM D 4940 G C h eck for ch lor id e io n , if su sp ect ed w ith C h lor *Rid A te st k it G Re ta in sa m p le G A ir co m p r e sso r e qu ip m e n t G Com p ressed air lines G C h eck for oil a n d w a te r con ta m in a n ts , A STM D 4285 G Bla s t n o z z le p r e s su r e G C h e c k p r e s s u r e a t b la s t n o z z le w it h h y p o d e r m ic n e e d l e g a u g e G Su r f a ce p r ep aratio n G D o n o t p r o ce e d w it h s u r f a ce p r e p a r a t io n i f t h e s u b s t r a te s u r fa ce t em p e r a t u r e is le s s t h a n 5 d eg r ee s F a b ov e t h e d ew p oin t
G D e t er m in e t h e r u s t g r a d e b y o n e o f t h e fo llo w in g p r io r t o cle a n in g : G SSPC -VIS 1, for ab r a siv e b las t cle a n in g G SSPC -VIS 3, for h a n d an d p ow er to ol cle a n in g G SSPC -VIS 4(I), for w a te r jet tin g G Ch eck for chlorid e ion con tam inant in w ash w ater or w ater u sed in w ater jetting , if su sp ected G U se C h lor *Rid W te st k it G P r ep a r a tio n co m p lie s w ith sp ecifica tion m eth od (i.e., N A C E N o. 2/ SSP C -SP 10, N A C E N o . 3/ SSP C -SP 6, etc.)
G C h eck for ch lor id e io n con ta m in a n t a fte r clea n in g w ith C h lor *Rid te st k it G D e t er m in e d e g r e e o f s u r fa ce cle a n lin e s s b y o n e o f t h e fo llo w in g a ft e r cle a n in g : G SSPC -VIS 1, for ab r a siv e b las t cle a n in g G SSPC -VIS 3, for h a n d an d p ow er to ol cle a n in g G N A C E N o . 7/ SSP C -VIS 4(I), fo r w a t er je ttin g
C-1
G Su r face p r ofile G D et er m in e s u r face p r ofile b y N A C E RP 0287 G E n v i r on m en tal co n d itio n s G A m b ie n t (a ir ) t em p e r a t u r e G Su b s t r a te su r f a ce te m p e r a t u r e G Relative h u m idity G D ew p o in t G W in d v elo city , if ap p licab le G C o a t i n g ap p licatio n G C o atin g m aterial co mp lies w ith s p e cific a tions G M ixed in acco rd an ce w ith m an u fa c tu re r’s ins tru c tions G Typ e of ap p lication m ethod u sed G Ensu re strip e coats are ap p lied before overall ap p lication p roceeds G T e m p eratu re an d h u m id ity res tric tions G A ir and su bstrate tem p eratu res are 50 d egrees F or g reater or com p lies w ith the m a n u f actu r er ’s in str u ctio n s
G Su r face s a r e a m in im u m of 5 d eg r ee s F a b ov e d ew p oin t G R elativ e h u m id ity w ith in m anu fa c tu re r’s ins tru c tions G Su rfa ces fre e o f m ois tu re , fro st, a n d ice G C u r in g G C o a t ed it e m s a r e n o t m o v e d o r a llo w e d f o ot tr a ffic b e fo r e d r y G C o m p lies w ith m an u factu rer’s ins tru c tions for te m p e ra ture a n d hu m id ity d u ring c uring p er iod G Po st a pp licatio n in s p ectio n G D r y film t h ick n e s s b y SSP C -P A 2 G H olid a y te st in g b y N A C E RP 0188
C-2
Appendix D Reference Standards Cited in Guide American Society for Testing and Materials (ASTM) ASTM A 123
Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Productions
ASTM A 153
Zinc (Hot-Dip) Coatings on Iron and Steel Hardware
ASTM A 591
Steel Sheet, Electrolytic Zinc-Cated, Light Coating Weight [Mass] Applications
ASTM A 653
Steel Sheet Zinc-Coated (Galvanized or Zinc-Iron Alloy-Coated (Galvanized) by the HotDip Method
ASTM B 633
Electrodeposited Coatings of Zinc on Iron and Steel
ASTM B 695
Coatings of Zinc Mechanically Deposited on Iron and Steel
ASTM D 3359
Measuring Adhesion by Tape Test
ASTM D 4138
Field Measurement of Dry Film Thickness of Protective Coating Systems by Destructive Means
ASTM D 4285
Indicating Oil and Water in Compressed Air
ASTM D 4414
Measurement of Wet Film Thickness by Notch Gages
ASTM D 4417
Field Measurement of Surface Profile of Blast Cleaned Steel
ASTM D 4541
Pull-Off Strength of Coatings Using Portable Adhesion Testers
ASTM D 4940
Conductimetric Analysis of Water Soluble Ionic Contamination of Blasting Abrasives
ASTM D 5064
Conducting a Patch Test to Assess Coating Compatibility
ASTM D 5162
Discontinuity (Holidays) Testing of Nonconductive Protective Coating on Metallic Substrates
ASTM E 337
Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
ASTM E 832
Laboratory Filter Papers
American Welding Society (AWS) AWS C2.2
Recommended Practices for Metallizing with Aluminum and Zinc for Protection of Iron and Steel
D-1
NACE International (NACE)/Society of Protective Coatings (SSPC) NACE RP 0188
Discontinuity (Holiday) Testing of New Protective Coatings on Conductive Substrates
NACE RP 0287
Field Measurement of Surface Profile of Abrasive Blast Cleaned Steel Surfaces Using a Replica Tape
SSPC-AB1
Mineral and Slag Abrasives
SSPC-PA2
Measurement of Dry Paint Thickness with Magnetic Gages
SSPC-SP1
Solvent Cleaning
SSPC-SP2
Hand Tool Cleaning
SSPC-SP3
Power Tool Cleaning
SSPC-SP8
Pickling
SSPC-SP15
Commercial Grade Power Tool Cleaning
SSPC-SP11
Power Tool Cleaning to Bare Metal
NACE No. 1/ SSPC-SP5
White Metal Blast Cleaning
NACE No. 2/ SSPC-SP10
Near-White Metal Blast Cleaning
NACE No. 3/ SSPC- SP6
Commercial Blast Cleaning
NACE No. 4/ SSPC-SP7
Brush-Off Blast Cleaning
NACE No.5/ SSPC-SP-12
Surface Preparation and Cleaning by High- and Ultrahigh-Pressure Water Jetting Prior to Coating
NACE No. 8/ SSPC-SP-14
Industrial Blast Cleaning
SSPC-VIS 1
Abrasive Blast Cleaned Steel (Standard Reference Photographs)
SSPC-VIS 2
Evaluating Degree of Rusting on Painted Steel Surfaces
SSPC-VIS 3
Power- and Hand-Tool Cleaned Steel (Standard Reference Photographs)
NACE No. 7/ SSPC-VIS 4
Guide and Visual Reference Photographs for Steel Cleaned by Water Jetting
NACE-VIS 9/ SSPC-VIS 5
Guide and Reference Photographs for Steel Surfaces Prepared by Wet Abrasive Blast Cleaning
D-2
Appendix E Inspection Equipment In s p e ctio n G au g e s , Ins tru m e n ts, an d Ki ts: •
A d h es ion te st er (Elco m et er ), d es tr u ctiv e t es tin g (op tio n a l)
•
Blast n oz z le a n a ly z er g a u g e (o p tio n a l)
•
C a lib r a te d sh im s
•
Con d u ctivity m eter
•
D r y film t h ick n e s s g a u g e
•
P u ll-off
•
Fix ed o r co n s t an t p r e s su r e p r o b e
•
En v ir on m en ta l m et er for am b ien t a n d su r face te m p er a tu r e, h u m id ity , an d d ew p oin t
•
H olid a y d et ect or (op tio n a l): •
L ow v o lt a g e
•
H ig h v o l ta g e
•
M icr o m e t er a n d r e p l ica t a p e
•
N oz z le o r ifice g a u g e (o p tio n a l)
•
P it g a u g e (o p tio n a l)
•
P r es su r e n ee d le g a u g e (o p tio n a l)
•
Sling p sychrom eter
•
Sw ab che cks for lead an d chrom ate
•
Te st k its , ch lor id e io n sp ecific (C h lor *Rid In te r n a tio n a l)
•
Th er m om et er w ith m a g n et ic b a ck in g
•
To ok e g a u g e, d es tr u ctiv e d r y film th ick n es s in st r u m en t (o p tio n a l)
•
W e t film t h ick n e s s g a u g e
In s p e c ti o n T o o l s : •
Fla s h lig h t
•
1 t o 1-1/ 2 in c h w id e st iff p u t ty k n i fe w it h s h a r p e n e d e d g e
•
Kn ife
•
Latex gloves
•
Plastic booties
•
M agn et
E-1
Appendix F Example of Inspection Daily Check Sheet 1 of 2
COATING DAILY INSPECTION REPORT Project:
Date:
Feature:
Report By:
Contract No:
Paint Contractor:
SPECIFICATIONS
Tabulation No: ______
Coating Category: ________ Coat No.
Item to be Coated: _____________________________
Total DFT (min.): ______ mils
Material Manufacturer
Tab Surface Prep. Method: _________
Product Name
DFT Range
Primer: Intermediate: Topcoat: Reading Time:
WEATHER
1. Substrate Temperature (degrees F): 2. Ambient (Dry Bulb) Temp. (degrees F): 3. Wet Bulb Temperature (degrees F): 4. Relative Humidity (percentage): 5. Dew Point Temperature (degrees F): 6. Item (1) minus (2) (in degrees F): 7. Wind (mph) and Direction: Comments: Surface Preparation Method Used:
SURFACE PREPARATION
Abrasives:
Manufacturer: ______________
Contaminants (ASTM D 4940): Chloride Specific Ion: Compressor Air:
Product Name: _____________
Class A, Type _____
Fines __ yes / __ no; Oil __ yes / __ no; pH ____; Conductivity_______
Test Method Used __________________________; Results _____________ Type: _____________
Surface Profile (NACE RP 0287):
Cleanliness:
SSPC-SP _____ / NACE No. ______
Passes ASTM D 4285: ___ yes / ___ no
No. Measurements Taken ______; Averaged Measured ______ mils
Chloride Specific Ion:
Visual Standards (SSPC/NACE):
______ CFM
Test Method Used _____________ _; Results _____________
VIS 1 __ yes / __ no; VIS 2 __ yes / __ no; VIS 4 (I) __ yes / __ no F-1
2 of 2
COATING DAILY INSPECTION REPORT APPLICATION AND MATERIALS Manufacturer
Product Name
Batch Number
Gal
Color
Thinner Product
Gal/Oz %
Environmental Control: Heaters ___ yes / ___ no; Dehumidification ___ yes / ___ no, Unit Size _________ Material Mixing: Power Mixing Time _____ minutes; Induction Time ___ yes / ___ no, _____ minutes Stripe Coats Applied: ___ yes / ___ no;
Method: ___ Bush/Roller ___ Spray
Application Method: ___ Brush; ___ Roller; ___ Airless; ___ Conventional; ___ Plural; ___ Electrostatic Applied Within Recoat Window: Primer __ yes /__ no; Intermediate __ yes /__ no; Topcoat __ yes /__ no Wet Film Thickness (WFT): Primer ______ mils; Intermediate ______ mils; Topcoat ______ mils Comments: TESTING OF HARDENED COATING Dry Film Thickness (DFT) by SSPC-SP PA2: Area Inspected: ___ less than 300 ft2; ___ less than 1,000 ft2; ___ equal to or greater than 1,000 ft2 Number of 5 Spot Measurement Groups Taken Within Above Inspected Area: _____ at _____ 100 ft2 areas Average of 5 Spot Measurement Groups _______ mils; Conform to Specifications ___yes /___no Discontinuity (Holiday) Testing by NACE RP 0188 Tester Used:
_____ Low Voltage (Sponge)
Set at _______ volts; Comments:
F-2
_____ High Voltage
Number of Defects Found _______; Defects Repaired ___ yes / ___ no
Appendix G Procedure for Detecting Moisture and Oil in Compressed Air (ASTM D 4285) A . Pu rp o s e Th is t es t d et ect s t h e p r es en ce o f m ois tu r e a n d oil co n ta m in a n ts in com p r es se d air for ab r a siv e blasting , air blast cleaning, and coating ap p lication o p erations. The contam inants are d etected v is u a lly . B . Eq u i p m e n t W h ite ab so r b en t m a te r ial, filte r p a p er , blo tt er p ap er , or clot h w ith a r ig id b a ck in g . C . Pro ce d u re 1. A llow th e air com p ressor to rea ch op era ting cond ition s. 2. Sh u t o ff th e ab ras iv e flo w . 3. P la ce t h e a b so r b e n t m a t e r ia l w it h in 2 4 in c h e s o f t h e d is ch a r g e - p o in t -ce n t e r e d a i r st r e a m a n d d ow n strea m from th e in-lin e oil and m oistu re sep ara tors. 4. Allow air to flow for 1 m inu te. 5. Vis u a lly ch eck ab so r b en t m a te r ial fo r th e p r es en ce o f m ois tu r e o r oil. A ny observ ed contam inan ts on th e cloth or in th e air flow w ill requ ire corre ctive action. Tests sh o u ld b e p er fo r m ed at t h e b eg in n in g of th e sh ift or after th e air co m p r ess or h a s b een sh u t o ff. Te st in g is r eco m m en d ev er y 4 h ou r s d u r in g b las tin g op er a tio n s o r m or e fr eq u en tly if h u m id ity is h ig h .
G-1
Appendix H Procedure for Detecting Chlorides and Soluble Salts in Abrasives by Conductivity Method A . P u rp o s e T o d e t ect an d d eterm in e th e lev el o f s olu ble s a lts in a br a s ive s to pre v e nt s ub s tra te d e te riora tion an d sub sequ ent coating failu re. B.
C o n d u cti v i ty M e t h o d 1. Eq u ip m e n t a . Electron ic cond u ctivity m eter 2. P r o ce d u r e a . Ca libr ate th e cond u ctivity m eter a ccord ing to th e m an u factur er’s instru ction s. b . P la ce e q u a l v o lu m e s of a b r a s iv e m a t e r ia l a n d d is t ille d o r d e -io n i z ed w a t e r in a g l a ss a n d st ir for 1 m in u te . Let st a n d for 8 m in u te s a n d st ir ag a in for 1 m in u te . A llow th e a b r a siv e m aterial to settle. c. In se r t t h e co n d u ctiv ity m et er p r ob e in th e w a te r w ith ou t co n ta ctin g ab r a siv e m a te r ial. d . A llo w th e co n d u ctiv ity m eter to sta b iliz e in accor d a n ce w ith th e m a n u fa ctu r er ’s instru ction s. e. Re a d an d r eco r d th e d ir ect r ea d in g in m icr osie m en s.
C . C h l o ri d e -S p e c if i c Io n M e th o d 1. Pu rp ose To d eterm ine th e concentr ation of chlorides in a bra sive m aterials and p rev en t su bstrate contam ination a nd sub sequ ent coating failu re. 2. Eq u ip m e n t C H LO R*TEST A , Ch lor id e Io n Te st Fo r A b r a siv es tit r a tio n k it
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3. P r o ce d u r e a . O v e r fill t h e s m a l l co n t a in e r w it h a b r a s iv e b la s t m a t e r ia l a n d le v e l-o ff w it h t h e m e t a l snap p er inclu d ed w ith th e kit or w ith a straigh t ed ge. b . Re m ov e t h e lid fro m th e C H LO R*EXTRA C T so lu tio n con ta in er an d p ou r th e le v ele d -off b last ab ras iv e m aterial in to the s olution. c. R ep lace th e lid o f th e CH L O R*EXTRA C T solu tion c onta ine r a nd vigorous ly s ha ke for 2 m in u t e s. A l lo w t h e a b r a s iv e m a t e r ia l t o se t tle fo r a b o u t 5 m i n u t e s b e fo r e p r o c e ed in g . C le a r solu tion sh ou ld be v isible abou t a ½ inch from the top sur face. d . H o ld th e titratio n tu b e alo n g t h e m id d le . D o n ot ha n d le or touc h the n a rrow e nd s be for e or after snap p ing th em off. H an d ling of the titration tu be n arr ow end s can conta m inate th e solution w ith bod ily p ersp iration , i.e., salts, an d affect the resu lts. Sna p off both end s of the titr a tio n tu b e an d h o ld th e tu b e in th e so lu tion w ith th e b lu e ar r ow h ea d p oin tin g u p . D o not insert the titration tu be into the ab rasive m aterial because th is m ay p lug th e tub e. e. A llow th e t itr a tio n tu b e t o r em a in in th e e xt r a cte d so lu tio n u n til t h e s olu tio n h a s w ick ed -u p to th e t op of t h e co tt on w ick et . Satu r a tio n of t h e w ick et is co m p let e w h en th e co tt on tip ch a n g e s t o a n a m b e r co lo r . f.
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Im m ed iately after th e cotton tip ha s chan ged to an am ber color, rem ove the titration tu be fro m th e tes t s leev e an d read the c hloride le ve l a t the inte rfa ce of the p ink-w hite color ch a n g e. W h ite in d icat es th e p r es en ce o f ch lor id e. If n o co lor ch a n g e o ccu r s (r em a in s a ll p ink ), th e chlor id e leve l is be low th e th resh old d etection lim it of the titration kit. The chlorid e concentration level is read d irectly from the titration tu be in m icrogra m s per s q u a r e ce n t im e t er o r p p m .
Appendix I Procedures for Detecting Chloride Ion in Water A . P u rp o s e T o d e t erm in e th e co n cen tratio n o f chlorid e ions in w a te r us e d w ith w a te r je tting b la s t cle a ning or for w ater evalu ation to p reven t sub strate contam ination a nd sub sequ ent coating failu re. B.
Eq u i p m e n t C H LO R*TEST W , Ch lor id e Io n Te st Fo r W a te r / Liq u id s t itr a tio n k it
C. Pro ce d u re 1. Rem ove d rop p er assem bly cap from bottle. 2. U se the d rop p er assem bly in th e bottle to tr an sfer th e w at er to b e t es te d . A d d ab ou t a ½ in ch of wa ter to the bottle. 3. H o ld th e titratio n tu b e alo n g th e m id d le . D o n ot ha n d le or touc h the n a rrow e nd s be fore or after snap p ing th em off. H an d ling of the titration tu be n arr ow end s can conta m inate th e solution w ith bod ily p ersp iration (i.e.), salts, an d affect the resu lts. Sna p off both end s of the t it r a tio n t u b e a n d h o ld t h e tu b e i n t h e so lu t i on w it h t h e b lu e a r r o w h e a d p o i n t in g u p . 4. A llow the titration tu be to rem ain in th e extracted solution u ntil the solution ha s w icked -up to t h e t o p o f co t to n w ick e t . Sa t u r a t io n o f th e w ick e t is co m p le t e w h e n t h e c o t to n t ip ch a n g e s to a n a m b e r co lo r . 5. Im m ed iately after th e co tto n tip ha s c ha ng e d to a n a m be r c olor, re m ove the titra tion tu be from th e te st sle ev e an d r ea d th e ch lo r id e lev el a t t h e in te r fa ce of th e p in k -w h ite co lo r ch a n g e. W hite ind icates the p resen ce of chloride. If no color cha ng e occu rs (rem ains all p ink), the ch lor id e le v el is b elo w th e t h r es h old d et ect ion lim it o f th e t itr a tio n k it. Th e ch lor id e concentration level is read d irectly from the titration tu be in m icrogra m s per squ are centimeter or p pm .
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Appendix J Procedures for Determining Blast Cleaning Air Pressure A . P u rp o s e T o m e a su r e t h e b la s t h o s e air p r e s su r e f or a ss es sin g a b r a s iv e b la s t cle a n in g e fficie n cy . B.
Eq u i p m e n t H yp od erm ic need le p ressur e gau ge, 0 to 120 p ou nd s per squ are inch (psi) or m ore.
C. Pro ce d u re 1. Blast clean ing e qu ipm en t is to be op era tiona l at the tim e of testing. If m ore th an on e blast h ose is to be u sed , ope rate all blast h oses. 2. In se r t h y p od er m ic n ee d le p r es su r e g a u g e in to th e in te r ior of t h e b las t h os e im m ed iat ely in front of the b last nozzle an d slan t the n eed le at a 45 deg ree an gle so that it is p ointed in the d irection th e abrasives are flow ing to m inim ize need le clogging and d am age. 3. Re a d th e b las t cle a n in g air p r es su r e d ir ect ly fro m th e d ial g a u g e. N or m a l b las t p r es su r e is b et w ee n 90 an d 100 p si. 4. Pr essu re r ead ings sh ou ld be ta ken p eriod ically or w h en blast clean ing e fficiency d ecreases. N O TE: 1. U se th is t es t m et h od on ly for ab r a siv e b las t h os es . D o n ot u se th is m et h od on coa tin g ap p lication h oses. 2. T h e r e is n o cu r r e n t s ta n d a r d r e fe r e n ce t o d e t e r m i n e b la s t p r e s su r e ; A S TM D 4 264 w a s w ith d r a w n .
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Appendix K Determination of Environmental Factors E n v i r o n m en tal facto rs are d eterm in ed b y va r iou s ins tru m e nts , a nd s om e ins tru m e nts ca n p e rform m u ltiple fu nctions. Electron ic and d igital instrum ents are becom ing increasing ly m ore accu rate, fas te r , m or e a ffor d a b le, a n d acc ep ta b le. Th e in st r u m en ts ar e n ot d et a iled b elo w b eca u se of w id e va riation am on g instru m en t typ es an d becau se of the va riation in the w ay instru m en ts are u sed . Bu t, a s w it h a n y in s tru m en t, alw ay s fo llo w the m a nu fa c tu re r’s ins tru c tions . The follow ing s e c tions d e scr ib e th e in s t r u m e n t a n d t h e p r o ce d u r e s t o b e u s e d t o d e t er m in e e a ch e n v i r o n m e n t a l fa ct o r : A . A m b i e n t Te m p e ratu re b y T h e rm o m e te r 1. D e s cr ip t i on o f t h e P r oce d u r e a . D e t er m in i n g t h e am b ie n t te m p e r a t u r e b y a s in g l e d ir e ct r ea d in g w it h a t h e rm o m e t er . 2. Eq u ip m e n t a . A t h e r m o m e t er o r th e d r y b u l b th e r m o m e t er o f a p s y ch r o m e t er . 3. P r o ce d u r e a . A m b ien t t em p er a tu r e s h ou ld b e t a k en n ea r th e s u r face to b e co a te d . Loca te all th er m om et er s a n d in st r u m en ts w h er e t h ey ar e n ot su b ject to d ir ect su n lig h t, w in d , constru ction lighting, heating or ven tilation d u cts, and w her e they ar e not su bject to other cond ition s th at w ou ld affect tru e tem p era tu re r ead ings. b . L et te m p e r a t u r e e q u i p m e n t st a b iliz e fo r 1 t o 2 m in u t e s if it w a s b r o u g h t fr o m a p l a ce w h e r e th e t em p er a tu r e w a s d iffer en t fr om th e a r ea w h er e t h e e q u ip m en t w ill be u se d (e.g ., an air co n d itio n ed or h ea te d r oo m or n ex t t o s om eo n e's b od y ). c. A ll instru m en ts are d irect read . For electron ic instru m en ts, follow instru ction s an d en su re th at th e co rrect m o d e is b ein g u s e d a n d the re a d ing is on the d e s ire d s ca le, d e gre e s F or Celsiu s. B.
S u b s trate S u rf ace Te m p e ratu re 1. De s crip tio n a . Determ ining the su rface tem p eratu re of the sub strate to be coated 2. Eq u ip m e n t a . Dial th erm om eter w ith a m ag n etic base
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3. P r o ce d u r e a . P lace th e d ial th erm o m eter o n the s te e l s ubs tra te a nd a llow the te m p e ra ture to s ta biliz e for ab ou t 2 to 3 m inu tes. C. Re lati v e H u m id ity an d D e w Po in t (A S TM E 337) 1. De s crip tio n a . D eter m inin g r elative h u m id ity an d d ew p oin t to a scerta in if eva p or ation w ill occu r. The su bstrate su rface is to be at least 5 d egrees F abo ve th e d ew p oint. 2. Eq u ip m e n t a . Psy chr om eter, either slin g or batt ery , and p sych rom etric table an d char ts. b . Ele ctr on ic or d ig ita l m et er (p r ov id es d ir ect r ea d in g s). 3. Proced u re for Psychrom eter a . Th e w ick o f a w et b u lb p sy ch ro m et er (cott on so ck ) sh ou ld b e r ela tiv ely clea n . Dir ty w icks need to be cleaned or rep laced . b . Sa t u r a t e t h e w i ck o n t h e w e t b u l b , b u t k e e p t h e d r y b u lb t h e r m o m e t er d r y . c. W hirl (sling typ e) or op erate fan (battery typ e) un til the th erm om eters stabilize, abou t 20 to 30 second s, and note th e tem p eratu re. d . R ep e a t s te p s 2 a n d 3 w it h o u t r e -w e t tin g t h e w ick u n t il t w o o r m o r e w e t b u l b r ea d in g s a r e equ al to the low est temp eratu re obtained . e. Record th e d ry (air) an d w et bu lb tem p era tu res. f.
Th e relativ e h u m id ity is d eter m ine d from the inte rse ct of the d ry a n d w e t bulb re a d ings on p sychro m etric tables or char ts. Psychr om etric tables and charts n orm ally ar e inclu d ed w ith the in stru m en t.
4. D ew P oin t a . U sing th e p sych rom etric tables: (1) D eterm in e th e atm o s p h eric (ba rom e tric ) p re s s ure for your ge ogr a p hica l loc a tion from U .S. De p a r tm en t o f C om m er ce o r U .S. W ea th er Bu r ea u ta b les . Th e a v er a g e b a r om et r ic p r es su r e a t s ea lev el is ab ou t 30 in ch es of m er cu r y , an d it w ill av er a g e le ss th a n 30 inche s at h ighe r eleva tions.
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(2) D et er m in e t h e d iffer en ce b et w ee n th e d r y an d w et b u lb te m p er a tu r es . Th e w et b u lb tem p eratu re is alw ays less than the d ry b u lb. The d ifference is com m on ly called the “ d ep r ess io n of th e w et b u lb .” (3) Fr om th e t a b les , loca te y ou r g eo g r a p h ic at m os p h er ic p r es su r e (lo ca te d in ta b le h ea d er ), d r y b u lb t e m p e r a t u r e (r o w h e a d e r ), a n d d e p r e s s io n o f w e t b u lb (co lu m n h e a d e r ) a n d d eterm ine the corresp ond ing d ew p oint value. Dew p oint is given in d egrees Fah ren h eit or Ce lsiu s. D . Wind 1. De s crip tio n a . Deter m ining w he n th e w ind velocity can cau se in d ry sp ray , over sp ray , or d am age to n e a r b y e q u ip m e n t , m e t alw o r k , o r p r o p e r ty . 2. Eq u ip m e n t a . Ro ta tin g v a n e a n em om et er s, d ir ect d ial, o r ele ctr on ic (d ig ita l) 3. P r o ce d u r e a . P la ce or h o ld th e in st r u m en t in th e d ir ectio n of th e w in d an d r ea d th e w in d (a ir ) v elo cit y . D ig ital an em o m eters m ay req u ire holding d ow n a s w itch or bu tton for a fixe d p e riod of tim e to d eterm ine th e av era ge a ir velocity. Follow th e m an u factur er’s instru ction s.
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Appendix L Procedures for Detecting Chloride Salts on Prepared or Existing Surfaces A . P u rp o s e T o d e t ect ch lo rid e io n s an d th eir co n c e ntra tion le ve l on p re p a re d s urfa ce s or e xis ting s u rfa ce s for p recoating evalu ation to p reven t sub strate contam ination a nd sub sequ ent coating failu re. B.
Eq u i p m e n t C H LO R*TEST t itr a tio n k it
C. Pro ce d u re 1.
T e st a sp o t w h e r e t h e s u r f a ce is r e la t iv e ly s m o o t h . D o n o t p ick ir r e g u l a r s u r fa ce s su ch a s corrosion p its and w eld sp atter, and d o no t p ick areas betw een d ep ressed and raised su rfaces becau se these su rfaces m ay allow the solu tion to leak ou t.
2.
Pou r the en tire contents from the solution bottle into th e test sleeve.
3.
P e a l o ff t h e b lu e b a ck in g f r o m t h e a d h e s iv e s t r ip o n t h e o p e n e n d o f t h e t es t s le e v e a n d d is ca r d t h e b a ck in g . Re m o v e a ir fr o m t h e t es t s le e v e b y s q u e e z in g b e t w e e n fin g e r s a n d thu m b. Do n ot sp ill any o f the solution. If solution is lost, d iscard the test sleeve an d the rem aining solution a nd bega n w ith a n ew kit.
4.
A p p ly th e a d h es iv e s tr ip of t h e t es t s lee v e t o t h e t es t s u r face an d firm ly p r es s t h e a d h es iv e strip to en su re a p rop er seal. For ap p lying the a d he sive strip to h orizon tal surfaces, allow the solution to fill the closed end of the test sleeve a nd squ eeze th e test sleeve in th e m idd le w ith ind ex an d m id d le finge rs to p rev en t solu tion loss.
5.
M a ss a g e t h e s olu tio n ag a in st th e t es t s u r face for 2 m in u te s. A ll th e s olu tio n sh ou ld b e ex p os ed to th e t es t s u r face d u r in g m a ss a g in g to ex tr a ct a n y ch lor id e s a lts . Th e fo llow in g p r oc ed u r es ar e r eco m m en d ed for th e v a r iou s t es t s u r face p os itio n s, so th a t t h e s olu tio n w ill flow tow ard s th e test su rface w ithou t solu tion loss. a.
H orizon tal and ver tical - Lift the closed end of the test sleeve u p , allow ing th e solution to flow tow ard s the test surface.
b.
O v e r h e a d - L ift t h e clo s e d e n d o f t h e t es t s le e v e u p , a llo w in g t h e s o lu t io n t o flo w t o w a r d s the m idd le of the test sleeve. The n sq u eeze th e em p ty p ortion o f the test sleeve w ith the in d ex an d m id d le fin g ers an d s lid e the finge rs a long the te s t sle e ve , forc ing th e s olu tion to the test surface.
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If th e s olu tio n is le a k in g ou t fr om th e t es t s lee v e, d isca r d th e t es t s lee v e a n d th e r em a in in g solution an d begin w ith a n ew kit. 6.
A fter m assag ing th e solu tion for 2 m inu tes, rem ov e th e test sleeve a n d solu tion from th e test su r face . To r em ov e t h e t es t s lee v e a n d r et a in th e s olu tio n fro m th e t es t s u r face , th e fo llow in g p roced u res ar e recom m en d ed for th e va riou s test su rface p osition s: a.
Vertical and over he ad - Low er th e test sleeve, allow ing th e solution to flow tow ard the closed end of the test sleeve.
b.
H orizontal - W ith th e test sleeve laying flat, squ eeze the solution tow ard s the closed end of t h e t es t s lee v e. Th en , p in ch off a n d lift u p th e t es t s lee v e n ea r th e t es t s u r face , allo w in g the solution to flow tow ard s the closed end of the test sleeve.
7.
P u n ch ou t t h e p er for a te d h ole on th e lid of t h e o r ig in a l b ox con ta in er lid , clos e t h e b ox lid , an d insert the test sleeve w ith th e solu tion into th e hole.
8.
H o ld th e titratio n tu b e alo n g th e m id d le . D o n ot ha n d le or touc h the n a rrow e nd s be fore or after snap p ing th em off. H an d ling the titration tu be n arr ow end s can conta m inate th e solution w ith bod ily p ersp iration (i.e.), salts, an d affect the resu lts. Sna p off both end s of the t it r a tio n t u b e a n d h o ld t h e tu b e i n t h e so lu t i on w it h t h e b lu e a r r o w h e a d p o i n t in g u p .
9.
A llow th e t itr a tio n tu b e t o r em a in in th e e xt r a cte d so lu tio n u n til t h e s olu tio n h a s w ick ed -u p to the top of cotton w icket. Satu ration of the w icket is com p lete w hen the cotton tip chan ges t o an a m b e r co lo r .
10. Im m ed iately after th e cotton tip ha s chan ged to an am ber color, rem ove the titration tu be fr o m th e te st sle ev e an d r ea d th e ch lo r id e lev el a t t h e in te r fa ce of th e p in k -w h ite co lo r ch a n g e. W hite ind icates the p resen ce of chloride. If no color cha ng e occu rs (rem ains all p ink), the ch lor id e le v el is b elo w th e t h r es h old d et ect ion lim it o f th e t itr a tio n k it. Th e ch lor id e co n c en t r a t io n le v e l is r ea d d ir e ct ly fr o m t h e tit r a tio n t u b e in m icr o g r a m s p e r sq u a r e ce n t im e t er o r p p m . 11. Af ter co m p letin g th e test, clean the te s t su rfa ce (s ub s tra te) w ith a c e tone or a lcohol to re mov e all ad hesive strip resid u e. N OT E : T h e p r es en ce o f s o m e s alt io ns a n d c erta in p H ra ng e s ca n a d ve rs e ly a ffe ct the a bove chlorid e test resu lts in th e follow ing w ay s:
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•
The p resence of brom ide, iod ide, or cyan ide ions can yield a high er concentration level than the actua l chloride ions extracted from the test surface.
•
The p resen ce of sulp h id e ions can tu rn th e cotton w ick in th e titration tu be a br ow n ish co lor r a th er th a n w h ite an d can y ield a h ig h er con cen tr a tio n lev el t h a n th e a ctu a l ch lor id e ions extracted from the test surface.
•
p H v a l u e s o f le s s t h a n 3 .5 a n d h i g h e r t h a n 1 1 ca n y i e ld a h i g h e r co n c e n t r a tio n l ev e l t h a n the actua l chloride ions extracted from the test surface.
Appendix M Determining Surface Profile of Blast-Cleaned Steel Using Replica Tape (NACE RP0287 or ASTM D 4417, Method C) A . D e s cri p ti o n To d eterm ine the an chor p attern d ep th of abrasive blasted sur faces by u se of a sp ring m icrom eter an d rep lica im p ression tap e. B.
Eq u i p m e n t 1.
Sp ring m icrom eter
2.
Rep lica im p ression tap e, coar se or e xtra coar se
C. Pro ce d u re 1.
M easu rem en ts are to be ta ken on a sm ooth , flat or cu rv ed p late that is free of su rface dirt, d u s t, an d ab ras iv e p articles th at w ill d is tort res ults . A n a c cu ra te profile ca nn ot be m a d e on p itted or p artially coated are as.
2.
Select the corr ect rep lica tap e ran ge for th e sp ecified p rofile dep th a.
0 to 2 m ils, u se coarse
b.
1.5 to 4.5 m ils, u se extra coarse
T h e r ep l ica t ap e h a s a t h ick n e s s o f 2 m ils b u t w ill v a r y s lig h t ly . 3.
P r ep a r e th e sp r in g m icr o m ete r b y cle a n in g th e an v ils, se tt in g th e g a u g e to zer o, an d ca lib r a tin g w ith a sh im b etw een 1 a n d 4 m ils. Th e sp r in g m icr om ete r sh ou ld b e p r ecis e to 0.3 m il.
4.
Re m ov e a sin g le p iece of r ep lica im p r es sio n ta p e fr om con ta in er an d p u ll off t h e a d h es iv e ba cking . The r elease p ap er (n on ad h esive p iece) w ith th e circle can be d iscard ed . The m ea su r in g p a p er st r ip h a s a 0.4 in ch sq u a r e w h ite p las tic film at th e ce n te r of t h e a d h es iv e b a ck .
5.
Before ap p lying the film to th e blasted sur face, the th ickn ess of the film m u st be sub tracted from the final read ing. Su btra ction of the film thickness can be accom p lished by o ne of the follow ing m eth od s:
M-1
a.
M eas u re th e rep lica tap e w ith the s p ring m ic rome te r a t the rou nd c utou t portion o p p o s it e t h e 0.4 in c h s q u a r e w h it e p l a st ic film a n d s u b t r a ct th e r e p l ica film t h ick n e s s b y on e th e follow ing m eth od s: (1) Su b t r a ct th e t h ick n e s s fr o m t h e fin a l r e a d i n g . (2) T u r n t h e d ia l in d ica t o r a r m o n t h e sp r i n g m icr o m e t er co u n t e r clo ck w is e fr o m z e r o the m easu red rep lica film thickn ess (e.g., for a m easu red 2.2 mils film thickn ess, set th e d ial in d icat or ar m at 7.8). Th is m et h od com p en sa te s fo r th e r ep lica film t h ick n e s s a n d p r o v i d e s a d i r ect r ea d in g .
b.
N om in a l th ick n es s o f th e r ep lica t a p e is 2 m ils. In st ea d of m ea su r in g th e r ep lica t a p e, it is a ccep ta b le p r a ctice to u se th e 2 m il n om in a l th ick n es s a n d su b tr a ct t h e r ep lica film t h ick n e s s b y o n e t h e fo llo w in g : (1) Su b t r a ct th e t h ick n e s s fr o m t h e fin a l r e a d i n g . (2) Set the d ial ind icator a rm at 8.0 (tu rn ing it cou nter clockw ise from zero) on the s p r in g m icr o m e t er t o p r o v i d e a d ir e ct r ea d in g .
6.
Ap p ly the film to the blasted su rface. The ad hesive backing w ill hold th e film in p lace.
7.
W ith a rou nd ed tool (a bar p lastic sw izzle stick has b een foun d to w ork w ell), ru b ov er th e rou nd cutou t p ortion o f the rep lica tap e w ith m od erate p ressu re. The circu lar area of the r ep lica ta p e w ill b eco m e d a r k er or g r a y ish , in d ica tin g th e b la st ed p r ofile h a s b een r ep lica te d . Ensu re the en tire circular area h as u niform ly da rken ed .
8.
Rem ove the r ep lica tap e an d p lace it betw een the a nv ils of the sp ring m icrom eter (w ith cir cu la r a r e a ce n t e r e d b e t w e e n t h e a n v i ls ). G e n t ly r e le a s e t h e t r ig g e r o f t h e m icr o m e t er a n d t a k e r ea d in g . D e p e n d in g o n t h e g a u g e s e t tin g , eit h e r z e r o o r th e m e a s u r e d r e p l ica t a p e t h ick n e s s, e n s u r e o r ig in a l r e p l ica t ap e t h i ck n e s s is su b t r a ct e d fr o m r e a d i n g .
9.
T h r e e r ea d in g s s h o u ld t a k e n in o n e lo ca t io n w it h in a b o u t 3 in c h e s o f e a ch o t h e r a n d a v e r a g ed . L oca t io n r e a d i n g s (t h r e e a v e r a g ed r e a d i n g s) s h o u l d b e t a k en o n e v e r y 100 s q u a r e feet of sur face, or p ortion thereof, to establish consistency of the p rofile.
10. Retain r ep licated tap e sam p les for futu re reference.
M-2
Appendix N Procedures for Measuring Wet Film Thickness (ASTM D 4414) A . P u rp o s e To d eterm ine th e w et coating th ickn ess bein g ap p lied an d to estim ate th e d ry film th ickn ess. B.
Eq u i p m e n t A n o t ch g au g e is a rectan g u lar o r s qu a re -s ha p e d p la te . Ea ch e d ge ha s tw o ou te r proje ctions of eq u al h eig h t. Betw ee n th e o u te r p ro ject ion s is a se rie s o f gr ad u at ed n ot ch es m ar k ed in m ils. Each e d g e o f t h e n o t ch g a u g e is ca lib r a t e d f o r a sp e cific m il t h ick n e s s r a n g e . T y p i ca l n o t ch g a u g e m a te r ials ar e a lu m in u m , p las tic, p olis h ed st ee l, an d st a in les s s te el. N O TE: Th e p lastic gau ge s ar e d isp osa ble an d ar e int en d ed for a lim ited n u m be r o f read ing s. The alum inu m and p lastic gaug es w ill wear d ow n an d becom e ina ccu rate w ith extend ed u se.
C. Pro ce d u re 1.
If p ossible, test a flat area . For cur ved su rfaces, test along th e longitu d inal axis, no t the c urv ed ax is . T est s mo o th areas tha t a re fre e from s urfa ce irre gu la ritie s su c h a s se a m s or w eld s.
2.
Select the m il th ickn ess ran ge a long th e ed ge o f the g au ge for th e an ticipa ted film th ickn ess.
3.
Test imm ed iately after the coating is ap p lied .
4.
Firm ly p ress the g au ge into th e w et coating , ho ldin g th e gau ge p erp en d icu lar to the su bstrate w it h t h e tw o e q u a l o u t e r p r o je ct io n s r es tin g o n t h e s u b s t r at e . D o n o t tilt o r s cr a p e t h e g a u g e t h r o u g h t h e w e t co a t in g .
5.
Rem ove the g au ge from the w et coating an d no te the sh ortest coated step betw een the notches. The w et film thickn ess lies betw een th is valve an d the ad jacent u ncoated step.
6.
Clean the g au ge before tak ing th e next m easu rem en t.
N-1
Appendix O Wet Film Thickness Formulas and Example Calculations A . D e s cri p ti o n D eter m inin g th e w et film th ickne ss (W FT) to a chiev e a d esired d ry film th ickne ss (DFT) B.
Fo rm u las
W it hou t T hin n in g t he C oatin g M aterial
N ote:
P e r ce n t o f s o lid s b y v o lu m e is ex p r e s se d i n d e cim a l fo r m .
Exam p le: The d esired DFT is 8 m ils. The coa ting m ater ial conta ins 83 per cent solid s by vo lu m e. Dete rm ine t h e W FT to ach ieve a n 8-m il DFT.
W it h T hin n in g t he C oatin g M aterial
N ote:
T h e p e r ce n t o f s o lid s a n d t h i n n e r s ad d e d b y v o l u m e is ex p r e s se d i n d e cim a l fo r m .
Exam p le: Th e sp ecifie d D FT is 6 m ils. Th e su r fa ce ar ea s r eq u ir es 5 g a llo n s o f th in n ed p a in t. Th e co a tin g m a te r ial co n ta in s 86 p er cen t s olid s, b y v olu m e. Th e m a n u fact u r er 's in s t r u c t io n s s ta t e 1½ p i n t s o f t h in n e r is a d d e d t o e ach g a l lo n o f co a t in g m a t e r ia l (16 p ints = 1 gallon ). De ter m ine t h e W FT to ach ieve a 6-m il DFT.
O-1
Appendix P Procedures for Dry Film Thickness Gauges (SSPC-PA2) and Example I.
P u rp o s e D e t er m in i n g t h e th i ck n e s s o f a h a r d e n e d c o a tin g .
II. Eq u i p m e n t The n on d estru ctive gau ges d escribed in SSPS-PA 2 are gr ou p ed into tw o ge n era l categ ories: Typ e I, m agn etic pu ll off gau ge. Typ e II, fixed p rob e or con stan t p ressu re p rob e ga u ges. III. T y p e I, M a g n e ti c P u l lo f f G au g e A. De scr i p tio n Typ e I, m agn etic p u ll off gau ges, com m on ly referred to as “ba na na ” gau ges, m easu re th e co a t in g t h i ck n e s s o f a n o n - m a g n e t ic co a t in g o v e r a f er r o u s m e t a l s u b s t r a t e. T h e g a u g e h a s a n exp osed m agn et attached to a sp ring . The am ou nt o f tension ap p lied on the sp ring to lift the m agn et from the coated su rface is d irectly pr op ortiona l to the d istan ce of the m agn et from the ferrou s surface. B. C a l ib r a t io n 1.
U se n on m ag n etic, stan d ard calibr ated shim s, com m on ly chro m e. Plastic and m ylar sh im s are n o t a cce p t a b l e fo r ca lib r a t in g p u ll o ff g a u g e s b e ca u s e p l as t ic o r m y la r is n o n a d h e r e n t a n d m a y ca u s e t h e m a g n e t w it h in t h e g a u g e t o lift p r e m a t u r e ly .
2.
Select a shim that w ill be in th e ran ge of the expected d ry film th ickn ess to be m easu red .
3.
Place the shim on the p rep ared su bstrate o r an y clean bar e steel an d p lace the g au ge on the sh im .
4.
Ro ta te th e d ial fo r w a r d u n til t h e m a g n et con ta cts th e s h im .
5.
Ro ta te th e d ia l b a ck w a r d slo w ly an d ev en ly u n til th e m a g n et b r ea k s con ta ct an d lift s u p . A click in g s o u n d m a y b e h e a rd .
6.
If th e rea d ing d oes n ot ag ree w ith th e sh im th ickn ess, ch eck th e m ag n et for clean lin ess.
7.
If th e read in g is still n o t in ag re e m e nt w ith the s him thickne s s , the ga u ge is out of ca libra ti on a n d sh o u ld b e r e-ca lib r a ted b y th e m a n u fa ctu r er or r ep la ced . F ollow th e m a n u fa ctu r er ’s in st r u ctio n s fo r ad ju st m en t o r r etu r n th e g a u g e to th e m a n u fa ctu r er fo r fa ctor y ad ju st m en t. D o n ot ad ju st th e g a u g e y ou r se lf. P-1
8.
The gau ge is to calibr ated before u se, du ring u se, and after u se to v erify accur acy of rea d ings.
C . P r o ce d u r e 1.
E n s u r e t h e m a g n e t is cle a n .
2.
H old th e ca lib r a te d g au g e fir m ly to th e co a te d st ee l su r face an d r ot a te th e d ial fo r w a r d u n til the m agn et contacts the coated su rface.
3.
Ro ta te th e d ia l b a ck w a r d slo w ly an d ev en ly u n til th e m a g n et b r ea k s con ta ct an d lift s u p . A clicking sou n d m ay be h ear d . The follow ing m ay influ en ce read ings:
4.
a.
Vibrations m ay p rem atu rely brea k th e m agn etic contact.
b.
Soft or tacky coatings m ay inh ibit the lifting of the m agn et.
R ea d t h e co a t in g t h i ck n e s s o n t h e d i a l t h a t a lig n s w it h t h e m a r k e d lin e o n t h e g a u g e a n d r e co r d t h e r e a d i n g .
IV . Ty p e II, Fixe d Prob e o r Co n s tan t Pres s u re Prob e G au g e s A . De sc r ip tio n The ty p e II, fixed or con stan t p ressu re p rob e gau ge, m easu res th e m agn etic flu x associated w ith n on -m ag n etic coating s ap p lied to ferro u s su bstr ates. For reliable read ings, th e ga u ges m u st r e m a in i n d ir e ct co n t a ct w it h t h e co a t e d s u r f a ce u n t il a r e a d i n g i s o b t a in e d . T h e se g a u g e s a r e n orm ally faster an d m ore accur ate th an th e m ag n etic p u ll off gau ges. B.
C.
P-2
C a l ib r a tio n 1.
U se n on m ag n etic or p lastic calibr ated shim stan d ard s.
2.
Select a shim that w ill be in th e expected ran ge of the d ry film th ickn ess to be m easu red .
3.
Place the shim on the p rep ared su bstrate o r an y clean bar e steel an d p lace the g au ge on the sh im .
4.
P la ce th e g a u g e fir m ly a g a in s t th e s h im a n d o b t ain a r e a d i n g .
5.
If the r ead ing d oes n ot agr ee w ith the sh im thickness, ad ju st the g au ge in accord an ce w ith the m an u factur er’s instru ction s. A d ju stm en t is nor m ally cond u cted by p ressing key s to ad ju st u p w ard or d ow nw ard u ntil the gau ge rea d ing an d the sh im thickness ar e in agr eem en t.
P r o ce d u r e 1.
E n s u r e t h e p r o b e i s cle a n .
2.
Set gau ge to rea d in d esired scale, either m ils or m icrom eters.
3.
H old th e calibrated gau ge firm ly to the coated steel sur face.
4.
R e ad th e co atin g th ick n es s o n th e d igita l d is pla y. Som e ga u ge s w ill s tore se ve ra l re a dings for d ow n load ing in to p rinte r an d m ay be cap ab le of avera ging rea d ings.
Exam p l e : Sp ecifica tio n s r eq u ir e t h e u p st r ea m face of a r a d ial g a te b e co a te d . Th e g a te h a s t h e d im en sio n s o f 26 feet in h eigh t alon g th e ra d ius cu rv atu re a n d is 10 feet in w id th . The coating tabu lation sp ecifies 2 c o a ts o f e p ox y at 8 m ils p er co at an d 1 topc oa t of p olyu re tha n e a t 3 m ils for 19-m il D FT, m inim u m , for the total system . Step 1: Det erm ine th e n u m ber of sp ot m easu rem en ts req u ired on an are a ba sis. Su rface area of stru cture: 26 feet x 10 feet = 260 squ are feet Su rfa ce a re a is less th an 300 sq u ar e fe et ; th er efo re , 5 sp ot m ea su re m en ts a re re q u ire d in ea ch of t w o 100 s q u ar e fe et ar ea s (t ot a l of 30 in d iv id u a l g a u g e r ea d in g s). Ste p 2: Th e D FT in st r u m en t is calib r a te d w ith a 20-m il sh im . Ste p 3: An im a g in a r y lin e is d r a w n h or izo n ta lly acr os s t h e g a te at th e m id ele v a tio n , effect iv ely d ivid ing the g ate into equ al low er an d u p p er areas. Five spot m easu rem ents are ran d om ly taken in each area, consisting of thr ee ind ivid u al gau ge read ings w ithin a 1.5-inch-diam eter circle p er sp ot m easu rem en t. Th e follow ing a re th e resu lts:
Lower Gate Area Gauge reading
Spot measurement (DFT in mils) A
B
C
D
E
1
18.2
20.6
21.0
16.7
26.4
2
18.6
19.1
21.8
17.1
29.8
3
17.8
20.4
20.8
16.8
29.0
Average
18.2
20.0
21.2
16.9
28.4
Upper Gate Area Gauge reading
Spot measurement (DFT in mils) A
B
C
D
E
1
22.6
20.4
18.6
19.5
29.3
2
22.1
21.7
18.3
19.9
31.0
3
21.9
21.3
19.4
19.2
30.4
Average
22.2
21.1
18.8
19.5
30.2
P-3
Ste p 4: D ete r m in e m in im u m an d m a xim u m acce p ta n ce th ick n ess cr iter ia . a. The sp ecified coating thickn ess is 19 mils. The allow able criteria are: M in im u m - 90 p er cen t o f sp ecifie d th ick n es s (0.9 x 19 m ils) = 17.1 m ils M a xim u m - 150 p er cen t o f sp ecifie d th ick n es s (1.5 x 19 m ils) = 28.5 m ils b. The follow ing evalu ates the resu lts for thickness accep tance: (1 ) A v erag e s p o t m eas u rem e nts tha t a re be tw e e n the m inim u m s pe c ifie d thickne s s of 17.1 m ils a n d th e m a xim u m sp ecifie d th ick n es s o f 28.5 m ils (a a ) Sp o t m ea su r em en ts A , B, C, a n d E o n th e lo w er g a te ar ea (18.2, 20.0, 21.2, a n d 28.4, resp ectively) are accep table. (b b ) Sp o t m ea su r em en ts A , B, C, a n d D on th e u p p er g a te ar ea (22.2, 21.1, 18.8, a n d 19.5, resp ectively) are accep table. (2) Aver age sp ot m easu rem en ts that a re less than the 90 per cent m inim u m of the sp ecifie d th ick n es s o f 17.1 m ils a t s p ot m ea su r em en t D on th e lo w er g a te ar ea (16.9) ar e not acceptable. (3) Av erage sp ot m easu rem ents tha t are greater th an the 150 percent m axim u m specified th ick n es s o f 28 .5 m ils at sp o t m e a s ure m e nt E on the u p p e r ga te a re a (30.2) a re not accep table. Step 5: From the abo ve eva luation, the follow ing can be conclud ed : On e averag e sing le sp ot m easu rem ent (D) on the low er gate area w as less than th e 90 p ercent m inim u m , and one av erage single spot m easu rem ent (E) on th e u p p er gate area w as greater tha n th e 150 per cent m axim u m . Therefore, the coating th ickn ess d oes n ot conform to the m inim u m and m axim u m thickn ess requ irem ents an d is not acceptable. H o w ev er , ad d itio n a l g a u g e r ea d in g s a r e allo w ed to b e ta k en to v er ify p r ev io u s r esu lts. Sev eral facto rs co u ld h av e affecte d th e ga u ge re a d ings . Poss ible fa c tors inc lu d e ca libra tio n, d irty su rface, soft or tacky coating su rface, p roxim ity to ed ges o r oth er steel m asses, cur va tu re of steel, tilting of p rob e, p ossible oth er n earb y m agn etic sou rces, tem p eratu re ext r em es, a n d v ib r a tio n s.
P-4
Appendix Q Procedures for Discontinuity (Holiday) Testing (NACE RP 0188) I.
P u rp o s e To locate p inh oles an d oth er d efects in h ard en ed coating u sing low or h igh v oltage in stru m en ts.
II. U s i n g a Lo w V o l t ag e In s t ru m e n t f o r C o ati n g T h i ck n e s s e s o f 2 0 M i l s a n d Le s s A . De sc r ip tio n A l o w v o ltag e, n o rm ally b etw een 5 and 90 volts D C , ba ttery p ow e re d d e vice w ith a w e t s pong e electric p rob e is d rag ged across the coated su rface to locate d iscon tinu ities (p inh oles) in the coating film . Shou ld d iscontinu ities be encou ntered , an electric curren t w ill flow to the steel su b st r a te . Th is p r oc es s w ill clos e a n ele ctr ical cir cu it w ith in th e in st r u m en t a n d se t o ff an au d ib le o r v is u a l a la r m . B.
Eq u ip m e n t 1.
C.
T h e fo llo w in g ar e tw o g en eral type s of low volta ge holid a y te s te rs . Ea ch u s e s a w e t s pong e p rob e, bu t th ey a re b ased on d ifferen t electrical pr inciples. a.
Electrom agn etic-sensitive or a solid state electronic relay circu it tha t, w he n d iscon tinu ity is d et ect ed , clos es th e cir cu it a n d p r od u ces an au d ib le o r v isu a l ala r m . Ge n er a lly , th is instrum ent can b e field ad ju sted .
b.
A n ele ctr on ic re lax at ion os cillato r cir cu it m ea su re s th e d ro p in ele ctr ical r es ista n ce betw een th e coating and the steel sub strate and p rod u ces an a u d ible alarm w hen d iscontinu ity is detected. Genera lly, this instru m ent typ e canno t be field ad ju sted .
P r o ce d u r e 1.
En su r e th e co a tin g is s u fficie n tly d r y (se e ch a p te r VIII, su b se ctio n 36, “ D r y in g , Re co a tin g , an d C u r in g ” ) b e fo r e te st in g .
2.
Tes t th e in str u m en t's p ow er su p p ly b at te rie s for su fficien t p ow er w ith th e b at te ry ch eck sw itch . If th e ba tteries ar e low , rep lace or rech arg e th e ba tteries.
3.
Test th e in str u m en t fo r op er a tion a l u se an d ca lib r a te it in accor d a n ce w ith th e m a n u fa ctu r er ’s instructions or N AC E RP0188, sections 3.3 and 3.4, before its initial use.
4.
Attach th e electrical grou nd (neg ative) w ire from the instru m ent to the steel su bstrate.
5.
W et the sp ong e p robe w ith p otable w ater
Q-1
N ote: a.
A l ow -s u d s in g w e t tin g a g e n t s u ch a s th a t u s e d i n p h o t og r a p h ic d e v e lo p m e n t ca n b e ad d ed to th e p otab le w ater at a r atio of ½ fluid ou n ce to 1 gallon of w ater to increa se s en s it iv it y .
b.
The u se of d etergen t w etting solu tions is not p erm itted because a bu bble m ay form over a d efect, rend ering it un d etectable.
6.
T u rn th e in s tru m en t s w itch to the “ on ” p os ition.
7.
Th e s p on g e is to b e m ov ed ov er th e co a tin g su r face at ab ou t 1 fo ot p er se co n d , u sin g a d ou b le p ass over each ar ea an d ap p lying su fficient p ressu re to kee p the su rface w et.
8.
T h e sp o n g e sh o u ld b e k e p t sa t u r a t ed , b u t n o t d r ip p in g w e t , w h i le m o v i n g o v e r th e co a t in g .
9.
W h en a d isco n tin u ity is d et ect ed , th e s p on g e is t o b e t u rn ed on ed g e t o d et er m in e t h e e xa ct s p o t o f t h e d e fe ct , a n d t h e s p o t is to b e m a r k e d fo r r e p a i r . U s e a g r e a se le s s m a r k e r t h a t ca n b e ea sily clea n ed off.
10. If w etting solu tions are u sed , the solu tions m u st be com p letely rinsed off before ap p lying the r e p a ir co a t in g . III. Usi n g Hig h V o ltag e I n s tru m en t fo r C oating T hic kne s s of G re ate r T han 20 M ils A . De sc r ip tio n A h ig h -v olt a g e d ev ice, n or m a lly in ex ces s o f 800 v olt s D C , w ith w et sp on g e e lect r ic p r ob e is p a ss ed ov er th e co a te d su r face to loca te d isco n tin u itie s (p in h ole s) in th e co a tin g film . Sho u ld d iscon tinu ities be en cou nter ed , the electric dev ice w ill sp ark thr ou gh the a ir gap at the d isco n tin u ity an d p r od u ce a n au d ib le o r v isu a l ala r m . A g en er a l ru le-o f-th u m b for d et er m in in g the r equ ired voltage is 100 to 125 volts p er m il; ho w ever , it is best to consu lt the m an u factu rer to p r e v e n t d a m a g in g t h e co a t in g . B.
Eq u ip m e n t 1.
2.
Q-2
The follow ing a re tw o ge n era l typ es of high vo ltage h olid ay testers: a.
Pu lse typ e—d isch arg es a cyclin g, high -voltage p u lse
b.
D i re ct cu r r e n t — d is ch a r g e s co n t in u o u s v o lt a g e
The follow ing a re g en era l typ es of electrod es an d p rob es: a.
H alf- or full-circle sp ring electrod es used for p ipes
b.
Ph osp hor bron ze bru sh p robes
c.
Con d u ctive ru bber strip p robes
C.
P r o ce d u r e 1.
En su r e t h e co a tin g is su fficien tly d r y b efo r e t es tin g . (See ch a p te r VIII, su b se ctio n 36, “D r y in g , Re co a tin g , an d C u r in g .”)
2.
If m oisture is p resen t on the coated su rface, d ry th e su rface before testing b ecau se m oisture w ill in d icate inv alid d iscon tinu ities.
3.
Test th e in str u m en t fo r op er a tion a l u se an d ca lib r a te it in accor d a n ce w ith th e m a n u fa ctu r er ’s instructions or N AC E RP 0188, sections 4.5 and 4.6, before its initial use.
4.
A d ju st th e instru m en t to th e p rop er v oltage sett ing for th e coating th ickn ess.
5.
Attach th e electrical grou nd (neg ative) w ire from instrum ent to the steel su bstrate.
6.
T u rn th e in s tru m en t s w itch to the on p os ition.
7.
To u ch th e p r o b e to a b a r e co n d u ctiv e (st eel) su b st r a te to v er ify th a t it is p r op er ly g r ou n d ed . Electric spa rks shou ld be seen , or an alarm sign al shou ld be activated .
8.
Using a sing le p ass, m ove th e p robe ov er the coated sur face at a rate of abou t 1 foot p er se co n d .
9.
W he n a d iscon tinu ity is d etected, m ark the sp ot for rep air. Use a grea seless m ark er th at be ea sily clea n ed off.
Q-3
Appendix R Procedure for Mechanical (Pulloff) Adhesion Testing (ASTM D 4541; Annex A2) A . P u rp o s e To d eterm ine the ad hesive strength betw een a fu lly cur ed coating and the su bstrate. B.
D e s cri p ti o n Th e a d h es ion te st er m ech a n ically m ea su r es th e r ela tiv e s tr en g th of a d h es ion b et w ee n a co a tin g a n d th e s u b st r a te or b et w ee n coa tin g lay er s. A n alu m in u m p u ll off s tu b (d olly ) is a d h es iv ely b on d ed to th e co a tin g an d allo w ed to cu r e. A p u llin g for ce o n th e b on d ed d olly is co n tin u ou sly in cr ea se d u n til th e d o lly d eta ch es o r a sp ecific fo r ce is a ch iev ed .
C. Eq u i p m e n t Th ere ar e sev era l d ifferen t typ es of p u lloff ad h esion tester s. The ty p e II tester , cited in A STM D 4541, ann ex A.2, is the Elcom eter M od el 106. This mod el is the m ost com m only u sed . Elcom eter M od el 106 is available in six scale ran ges. The scale m ost com m only u sed is 0 to 1,000 pou nd s per sq u a r e in ch (p si), a n d it is d iscu ss ed b elo w . A st a n d a r d 3/ 4-in ch -d iam et er alu m in u m d olly is u se d w ith th e E lcom et er M od el 106. D . Pro ce d u re 1.
Se le ct t h e sp o t w h e r e t h e d o lly w ill b e b o n d e d t o th e c o a tin g . Th e s e le ct e d a r e a m u s t b e la r g e enou gh to accom m od ate the feet of the instru m ent. Dollies shou ld be located at least 2 inches from an y su rface obstru ction s an d ha ve at least 1 foot of vertical clearan ce to accom m od ate in s e r tin g t h e in s t r u m e n t in t h e d o lly .
2.
U se a s u ita b le s olv en t w ip e t o r em ov e s u r face con ta m in a n ts su ch as d ir t, d u st , gr ea se , an d oil from the test spot. Wip e all m oistu re from sur face and then solven t w ipe.
3.
Th e m a n u fact u r er r eco m m en d s t es tin g on ly on flat su r face s; h ow ev er , cu r v ed su r face s o f 24in c h r a d iu s a n d g r e a t er ca n b e t e st e d . Fo r cu r v e d s u r f a ce s w i t h a r a d i u s o f le s s t h a n 24 inch es, the d olly n eed s to b e gr ou n d d ow n to m atch th e existing m etalw or k r ad iu s. The follow ing m atches the d olly typ e w ith th e sur face: •
Flat sur faces - Use stand ard d ollies
•
C u r v ed su r fa ce s - U se d o llie s w ith a r a d iu s t h a t m a tch es t h e su r fa ce r a d iu s t o b e te st ed . Th e m a n u fact u r er w ill fab r icat e d ollie s fo r a s p ecifie d r a d iu s a n d th e fo llow in g cu rv atu res:
R-1
" " 4.
C o n c a v e - o u t e r r a d i u s (e xa m p l e : p i p e e xt e rio r ) C o n v e x - in n e r r a d iu s (e xa m p l e : p i p e in t e r io r )
To p r om ot e a d h es ion of t h e d olly to th e fo llow in g su r face s, r ou g h en th e t es t s p ot ar ea u sin g : • •
Ligh t sand p ap er on glossy su rfaces Co arse r san d p ap er on u n ev en su rfaces
5.
W ipe clean an y gr it and rep eated ly solven t w ipe on the test sp ot.
6.
So lv e n t c le a n a n d r o u g h e n t h e d o lly s u r f a ce u s i n g 40-60 g r it sa n d p a p e r o n t h e d o lly ’s fla t su r face (ta p er ed en d ).
7.
M ix th e a d h es iv e a cco r d in g to th e in st r u ctio n s. Th e a d h es iv e is n or m a lly an ep ox y . A p p ly a thin, smo oth layer of ad hesive to the p rep ared test dolly su rface.
8.
P la ce th e d o lly on th e p r ep a r ed te st sp ot a n d p r ess fir m ly to sq u eez e ou t e xcess ep oxy . D o n o t t w i st th e d o lly .
9.
R em o v e a n y e xce ss ep o x y a r o u n d t h e p e r ip h e r y o f t h e d o l ly w it h o u t d is tu r b i n g t h e d o l ly .
10. A llow th e e p ox y to fu lly cu r e. D ep en d in g on th e t em p er a tu r e, cu r in g tim e m a y ta k e u p to 24 h ou rs. Follow th e ad h esive m an u factur er’s instru ction s. 11. Fo r v er tica l, ov er h ea d , or ot h er su r face s, se cu r e t h e d olly b y ta p in g or u sin g th e m a g n et ic clam p th a t is su p p lied w ith th e t es te r k it. En su r e t h a t t h e m a g n et ic clam p d isc k ee p er is rem oved before use. N o te: D o llies ap p lied w ith in s uffic ie nt a d he s ive or not pe rp e nd ic ula rly p os itione d a re no t accep tab le and w ill pr ov id e err on eou s resu lts. A fter the ep oxy h as cur ed , m ake a circu lar cut th rou gh the coating to the su bstrate a rou nd the d olly w ith the cu tting tool tha t is p rov ided w ith the tester kit. The cu tting tool fits over the d o lly . K its are p ro v id ed w ith a s m a ll d ia m e te r ba r to a ss is t in th is ope ra tion. 12. If testing a flexible coating or su bstrate, p lace the su p p ort ring over the test d olly. Set the d rag in d icato r (s teel p in p ro jecting th rou gh a s lit on the s ha ft a t the s ca le ra ng e ) to z e ro. 13. Slip th e te st er su p p o r t r in g (cla w at t h e b ott om ce n te r of th e te st er ) in th e g r oov e of th e d olly . Ensu re th at th e tester is perp en d icu lar an d tha t the 3 feet of the tester b ear eq u ally on the coated su rface. N ote: Sho u ld th e tester be tilted , on e of the feet not be secu re, or the b earing of the in s t r u m e n t b e u n e q u a l , a s h e a r in g f o r ce m a y b e im p a r t e d t o t h e co a t in g , r es u l tin g i n a n e r r o n e ou s r e a d i n g . 14. Slow ly an d con tin u ou sly r ot a te th e t es te r h a n d w h ee l in a clo ck w ise d ir ect ion u n til t h e d olly is p u lled free or a sp ecified m axim u m tension is achieved .
R-2
15. R e ad th e h ig h es t v alu e attain ed a t the bottom of the d ra g ind ic a tor in ps i. If the d olly d id not p u ll fre e, r ep or t t h e r es u lt a s g r ea te r th a n th e m a xim u m cap a city of t h e in st r u m en t (i.e., 1,000 p si fo r th e E lcom et er M od el 106). 16. Alw ays reset the d rag ind icator to zero after testing. Failu re to reset w ill resu lt in a d istorted o r p e r m a n e n t ly d a m a g e d h e l ica l s p r in g . 17. Repor t one or a com bination of the follow ing typ es of failu re: •
A d h e siv e
" " •
C o h es iv e
" •
F a ilu r e b e tw e e n t h e s u b s t r a te a n d t h e fir s t (p r im e ) co a t Failur e betw een an y tw o coats
Failure or a b reak w ithin an y on e coating layer
G lu e
"
A d h es iv e fa ilu r e o f th e a d h es iv e g lu e b et w ee n th e d olly an d th e co a tin g (coa tin g r e m a i n s in t a ct a n d g l u e r e m a i n s on e it h e r th e co a t in g o r d o lly )
"
C o h e s iv e fa ilu r e o f t h e a d h e s iv e g lu e ( g lu e r e m a in s o n t h e co a t in g a n d d o lly )
R-3
Appendix S Procedure for Hydraulic Adhesion Testing (ASTM D 4541; Annex A3) A . P u rp o s e To d eterm ine the ad hesive strength betw een a fu lly cur ed coating and the su bstrate. B.
D e s cri p ti o n The ad hesion tester u ses a hyd rau lic system to m easu re the relative streng th of ad hesion betw een a co a t in g a n d t h e su b s t r a te o r b et w e e n c o at in g l ay e r s. A u n i fo r m t en s ile lo a d i s a p p lie d t h r o u g h a ho le in th e center of a p u ll stu b u sing a h yd rau lic piston a nd p in. An alum inu m p u ll off stu b (dolly) is ad hesively bond ed to the coating and allow ed to cure. A p u lling force on th e bon d ed d o lly is co n tin u o u sly in cr ea se d u n til th e d olly d eta ch es o r a sp ecific fo r ce is a ch iev ed . Rep rod u cible resu lts are ach ieved becau se the ap p lied tensile load is consistent.
C. Eq u i p m e n t The self-align ing ty p e III tester cited in A STM D 4541, ann ex A 3, is the H ate M ark VII. Testers ar e a v a ila b le in th e fo llo w in g th r ee r a n g es: (1) 0 t o 1,500 p si, (2) 0 to 2,250 p si, a n d (3) 0 t o 3,000 p si. D . Pro ce d u re 1.
Se le ct t h e sp o t w h e r e t h e d o lly w ill b e b o n d e d t o th e c o a tin g . Th e s e le ct e d a r e a m u s t b e la r g e enou gh to accom m od ate the feet of the instru m ent. Dollies shou ld be located at least 2 inches from an y su rface obstru ction s an d p rov ided at least 1 foot of ver tical clearan ce to a cco m m o d a t e in s e r tin g t h e in s t r u m e n t in t h e d o lly .
2.
U sin g a s u ita b le s olv en t w ip e, r em ov e s u r face con ta m in a n ts su ch as d ir t, d u st , gr ea se , an d oil from the test spot. Wipe all mo istu re from sur face and then solven t w ipe.
3.
T h e m an u factu rer reco m m en d s te sting on ly on fla t s urfa ce s ; how e ve r, c urve d s urfa ce s of 24-in c h r a d iu s a n d g r e a t er ca n b e t e st e d . Fo r cu r v e d s u r f a ce s w i t h a r a d i u s o f le s s t h a n 24 inch es, the d olly n eed s to b e gr ou n d d ow n to m atch th e existing m etalw or k r ad iu s. The follow ing m atches the d olly typ e w ith th e sur face: •
Flat sur faces - Use stand ard d ollies
•
C u r v ed su r fa ce s - U se d o llie s w ith a r a d iu s t h a t m a tch es t h e su r fa ce r a d iu s t o b e te st ed . Th e m a n u fact u r er w ill fab r icat e d ollie s fo r a s p ecifie d r a d iu s a n d th e fo llow in g cu rv atu res:
" "
C o n c a v e - o u t e r r a d i u s (e xa m p l e : p i p e e xt e rio r ) C o n v e x - in n e r r a d iu s (e xa m p l e : p i p e in t e r io r )
S-1
4.
C l ean th e b o n d in g s u rface o f the loa d fixture , the Te flon p lu g, a nd the c oa ting a r e a to be tested w ith solven t.
5.
Ligh tly sand the test ar ea to achieve a n ev en , sm ooth su rface and w ipe clean. Rep eat th e solven t w ipe.
6.
Insert the teflon p lug into th e load ing fixtur e u ntil the p lug tip p rotru d es from the su rface.
7.
A p p ly a thin coat of ad he sive ep oxy to th e bon d ing su rface of the fixtu re, taking care n ot to g e t e p o x y o n t h e p lu g .
8.
Pr es s th e lo ad in g fix tu re o n to th e coa ting a n d w ip e the e xce s s a d he s ive e poxy from a rou nd the p eriph ery of the fixtur e.
9.
Rem ove the teflon p lug an d allow the a d he sive ep oxy to cu re in accord an ce w ith the m an u factur er’s instru ction s.
10. Con nect the tester to the load fixtur e. 11. E n s u r e th e g au g e is s et at zero . 12. In c reas e th e p res s u re s lo w ly b y tu rning th e ha n d le cloc kw is e un til the fixture p u lls fre e or u ntil a sp ecified p ressur e is achieved . 13. D i r ect ly r e a d t h e g a u g e v a l u e a t t a in e d in p s i. If t h e d o lly d id n o t p u ll fr e e , r e p o r t t h e r e s u lt a s grea ter th an the m axim u m capa city of the instru m en t. 14.
Repor t one or a com bination of the follow ing typ es of failu re: •
A d h e siv e
" " •
C o h es iv e
" •
S-2
F a ilu r e b e tw e e n t h e s u b s t r a te a n d t h e fir s t (p r im e ) co a t Failur e betw een an y tw o coats
Failure or a b reak w ithin an y on e coating layer
G lu e
"
A d h es iv e fa ilu r e o f th e a d h es iv e g lu e b et w ee n th e d olly an d th e co a tin g (coa tin g r e m a i n s in t a ct a n d g l u e r e m a i n s on e it h e r th e co a t in g o r d o lly )
"
C o h e s iv e fa ilu r e o f t h e a d h e s iv e g lu e ( g lu e r e m a in s o n t h e co a t in g a n d d o lly )
Appendix T Procedure for Measuring Dry Film Thickness by Destructive Means With Tooke Gauge (ASTM D 4138) A . P u rp o s e To d eterm ine the d ry film th ickn ess and the n u m ber of ind ivid u al coats of a coating system B.
D e s cri p ti o n Th e To ok e g au g e is u se d to cu t th ro u g h th e h ar d en ed coa tin g to th e s u b str at e. O n e s id e o f th e cu t is m ad e at a specific ang le thro u gh the coating . A m icroscope w ith a g rad u ated (reticle) scale, at ta ch ed to th e g au g e, is u se d to m ea su re th e e xp os ed coa tin g p er p en d icu lar to th e s p ecific cu t a n g l e to d e t er m in e t h e d r y film t h ick n e s s . T h e n u m b e r o f a p p lie d co a t s a n d t h e in d iv i d u a l t h i ck n es s es can als o b e d eterm in ed , p rovid e d tha t c oa ting la ye rs ca n be id e ntifie d by c olor d iffer en ce o r b y a d ist in ctiv e lin e. Th is m et h od is co n sid er ed d es tr u ctiv e b eca u se th e cu t m a d e in th e co a tin g is a n in te n tio n al d efe ct, u n les s r ep a ir ed . Th e T oo k e g a u g e is m os t o fte n u se d in ev alu ation of coatin g failu res.
C. Eq u i p m e n t A To ok e g a u g e, e ith er alu m in u m or p las tic b od y , w ith an illu m in a te d 50X m icr os co p e a n d r et icle (calibrated ) scale. It includ es three cutting tips an d a m arker p en. D . Pro ce d u re 1.
Select an ar ea of th e co a tin g to te st an d d r a w ab ou t a 1-in ch st r a ig h t lin e w ith th e m a r k er p en . Th e m a r k se r v es a s a r efer en ce lin e.
2.
Sele ct t h e p r op er cu tt in g tip for th e e xist in g coa tin g th ick n es s t o b e m ea su r ed . Th e fo llow in g are th e th ree ty p es of cuttin g tip s an d th eir associated th ickn ess ran ges: • • •
3.
10X tip: 0 to 3 m ils coating th ickn ess 2X tip: 3 to 20 m ils coating th ickn ess 1X tip: 20 to 50 m ils coating th ickn ess
A fter selecting the p rop er cu tting tip, p lace the cu tting tip a nd tw o gu ide stu d s against th e coa tin g su rfa ce, w ith th e cu tt in g tip ju st a b ov e t h e m ar k ed lin e. A lign th e fo re ar m to cu t across (p erp end icu lar to) the m arked line. Draw the forearm straigh t back w ith su fficient p r es su r e t o cu t co n tin u ou sly th r ou g h th e co a tin g in to th e s u b st r a te . M a in ta in th e t h r ee p oin t surface co n tact (cu tter an d 2 g u id e s tud s ) to e ns ur e a s tra ight a n d ve rtic a l c ut. The le ngth of cut into the su bstrate need s to extend slightly beyon d the m arked line.
T-1
4.
View th e cu t th ro u g h th e lig h ted 50X m ic rosc ope a nd foc us on the c oa ting on e ithe r s id e o f th e e xp os ed su b st r a te . Focu s a n d alig n th e r et icle s ca le p er p en d icu lar to th e cu t. Th e co a tin g on on e s id e o f th e cu t w ill be sm oo th er th a n on th e o p p os ite sid e o f th e cu t. If th e cu tt in g tip w as correctly p osition ed , the sm ooth er sid e w ill be on th e left. Alw ays m easu re on the sm oother sid e.
5.
L in e u p th e reticle s cale acro ss the cu t on the s m oothe r s id e a nd c ount the n u m be r of d iv is io n s fo r e ach c o at in g l ay e r in t h e t o ta l s y st e m . Be g in a t t h e ex p o s ed s u b s t ra t e a n d w o r k tow ard s the m arker line.
6.
Th e co a tin g th ick n ess is d ete r m in ed b y th e n u m b er of co u n te d d iv ision s o n th e r eticle sca le. Th e fo llow in g p r ov id es th e t h ick n es s fo r ea ch d iv isio n for ea ch cu tt in g tip :
7.
T-2
Cutting tip
1 - Division represented on reticle scale
10X
0.1 mil
2X
0.5 mil
1X
1.0 mil
H elp ful h ints: •
W he re th e p rim er is an inor gan ic zinc or galva nized zinc, it is d ifficult to d istingu ish the zinc from the su bstrate. To d ifferen tiate betw een steel su bstrate and zinc, u se a 5 p ercent solu tion o f copp er su lfate and d istilled w ater. The steel sub strate w ill tu rn a copp er co lo r , a n d t h e z in c w i ll t u r n b l a ck .
•
Fo r d a r k - co lo r e d c oa t in g s , u s e a liq u i d e r a s e r w h i te -o u t in s t ea d o f t h e fe lt tip m a r k e r .
•
The th ickn ess of coating chips can be m easu red by v iew ing th e cross section of the co a tin g ch ip th r o u g h th e To ok e g a u g e. (Ea ch d iv ision is e q u a l to 1 m il.)
Appendix U Procedures for SSPC-VIS 2 (2000 Revision) A . P u rp o s e To ev alu ate th e am ou n t an d d istribu tion o f ru st on coated su rfaces. B.
D e s cri p ti o n T h i s a p p en d ix p ro v id e a s tan d ard m e thod of e va lua ting a nd qu a lifying the d e gre e of ru s t on p ainted ferrou s (steel or iron ) su rfaces u sing p ictorial im ages (color an d black and w hite p h otog rap h s) w ith a g iven ru st p ercen tag e an d d istribu tion. The r esu lts are rep orte d in a r u st g r a d e s ca le fr om 10 (lea st r u st ed ) to 0 (m os t r u st ed ), an d r u st d ist r ib u tio n is n ot ed b y S (sp ot r u st ), G (g en er a l ru st ), an d P (p in p oin t r u st ).
C. Pro ce d u re 1.
Select an ar ea or ar ea s fo r ev a lu a tion . A r ea siz e m a y r a n g e fr om v er y sm a ll to v er y la r g e, b u t sh ou ld b e r ep re se n ta tiv e o f th e s tr u ctu re ty p e b ein g ev alu at ed . For com p lex s tr u ctu re s, su ch as I-beam s or chan nels, the en tire stru cture can be ev aluated , or the ev aluation can b e limited to certain p ortion s of the str u ctu re su ch as flang e top s, I-bea m w eb, or ed ges.
2.
D e t er m in e t h e r u s t d is tr ib u t i on a n d t h e p e r ce n t a g e o f r u s t b y th e fo llo w in g . a.
Ch oose th e ru st d istribu tion (sp ot, gen era l, or p inp oint) for th e selected are a th at m ost clo s e ly m a t ch e s t h e co r r e s p o n d in g c o lo r o r b la ck a n d w h i te p h o t o g r a p h .
b.
Select the p ercentag e of ru st for th e eva luated area th at m ost closely m atches th e co r r e sp o n d in g p h o t o g r a p h . R u s t s ta in i n g o r d i r t w it h t h e a p p e a r a n ce o f r u s t is n o t t o b e in c lu d e d . Ru s t u n d e r th e co a t in g a n d b r o k e n b lis te r s w it h a p p a r e n t r u s t a r e to b e inclu d ed . N on bro ken blisters are to b e d efine d by th e follow ing an d inclu d ed in the p ercentag e of ru st: (1) Ru st filled b lister (de term ined by o p en ing b lister) is to be incorp orated in the p ercentag e of ru st. (2) Flu id filled b lister (de term ined by o p en ing b lister) is not to b e incorp orated in the p e r c en t a g e of r u s t , b u t it is to b e r eco r d e d s ep a r a t e ly .
c.
3.
Select o n e co rresp o n d in g c olor p hotogra p h th a t be s t re p re s e nts both the ru s t dis tribut i on a n d t h e p e r c e n t a g e o f r u s t fo r t h e e v a lu a t e d a r e a .
De term ine th e ru st gr ad e accord ing to table 1 of the stan d ard . For exam p le, th e ru st d is t r ib u t io n a r e a w a s d e t e r m in e d t o b e “s p o t ,” a n d t h e p e r c e n t a g e o f r u s t w a s “ g r e a te r t h a n 0.3 p er ce n t t o 1 p er ce n t;” th er efo r e, th e r u st g r a d e is “ 6-S.”
U-1
Appendix V Procedure to Determine the Presence of Soluble Lead and Insoluble Lead Chromate in Coatings A . P u rp o s e T o d e t e r m i n e w h e t h e r t h e co a t in g c o n t a in s le a d . B.
D e s cri p ti o n T h e p r e s en ce o f lead an d lead ch ro m a te pigm e nte d c oa tings c a n be d e te rm ine d by a c olor ind icator u sing rea gen ts to sw ab ov er exp osed coating layers. The sw ab test w ill verify on ly the p resen ce of lead an d chro m ate an d w ill not p rov id e qu an titative resu lts. The sw ab test m ay also d etect the p resence of lead chrom ate.
C. Eq u i p m e n t Le a d C h eck Sw a b s m a n u fact u r ed b y H y b r iv et Sys te m s, In c., PO Box 1210 Fr a m in g h a m , M a ss a ch u se tt s 01701; tele p h on e: 800-262-5323. D . Proce d u re fo r D e tecti n g W ater S o lu b le Lead Pi g m e n ts (Le ad O xid e o r Lead Carbo n ate) 1.
C l ea n a n d r e m o v e a ll d u s t a n d d ir t fr o m t h e t es t a r e a .
2.
Cu t abou t a 1/ 4 inch n otch throu gh all coating layers and expose th e sub strate.
3.
Activate the sw ab by crush ing the g lass am p u les m arked “A ” an d “B” on the sw ab tu be.
4.
W ith th e p o ro u s fib er facin g d ow n, sha k e a nd ge ntly s que e z e the s w a b tu be u ntil a ye llow liq u id is v isib le o n th e s w a b tip .
5.
Ru b th e yellow ish sw ab tip in th e exp osed coating n otch for 30 second s.
6.
Results a.
If the sw ab tip or th e test sur face tu rn s p ink or red , lead is p resen t.
b.
If th e s w ab tip o r th e tes t s urfa ce d oe s not turn p ink or re d , le a d is not p re s e nt or is below the d etection ran ge of the ind icator r eagen t.
c.
Lea d ch ro m at e is n ea rly in so lu b le in w at er an d w ill no t im m ed iat ely tu rn colo r. P lace th e s w ab in a p las tic b a g an d r e-e xa m in e t h e s w a b an d th e t es t a r ea in ab ou t 18 h ou r s. If the sw ab tip or th e test area tu rn ed p ink or red , chrom ate is pre sent.
V-1
7.
N eg a tiv e t es t r es u lts sh ou ld b e co n firm ed b y u sin g th e “ Te st C on firm a tio n C a r d ” th a t is includ ed w ith th e kit. Th e card h as ind ivid u al circles on o n e face, an d each circle con tains a s m a ll a m o u n t o f le a d . a.
W ith th e u sed sw ab, squeeze a d rop onto r eagen t w ithin th e test circle.
b.
If p in k or r ed ap p ea r s o n th e cir cle, t h e n eg a tiv e t es t r es u lt is v a lid .
c.
If p ink o r re d d oes n ot ap p ear on th e circle, th e n ega tive test re su lt is inv alid, an d a rete st is r e q u i r ed u s in g a n e w s w a b a n d t e st a r e a .
8.
Th e s w ab ’s r ea g en ts h a v e a 2-m in u te life fr om th e t im e t h e g las s a m p u les ar e b r ok en , an d all testing shou ld be com p leted w ithin th e tim e limit. The sw ab is to be u sed for on e test area o n ly .
9.
R ed b le e d i n g v e r s u s p in k - o r r ed -co lo r e d s w a b •
•
V-2
A re d “b lee d in g ” m ay occu r fo r co at in g s w ith re d p igm en ts (t h e co lor re d ), w h ich includ es red lead p rim ers, w h en testing . This red bleed ing can m ask th e p ink o r re d test resu lts an d can be m isinter p reted . The m an u factu rer r ecom m en d s that o ne of the follow ing m etho d s be u sed to d eterm ine if red p igm en ts, no t lead , are b leedin g from the co a t in g :
"
Cru sh th e colorless solu tion in glass am p u le “B” on ly and squ eeze a d rop on to the s w a b t ip . Sw a b t h e t e st a r e a . If r e d a p p e a r s , it in d ica t e s b le e d i n g i s o ccu r r in g a n d the p resence of lead canno t be confirm ed .
"
Ta k e a cot to n tip d ip p ed in v in eg a r an d sw a b th e t es t a r ea . If re d ap p ea r s, it in d ica t es b le e d i n g is o ccu r r i n g .
If the coating is bleed ing red an d lead is su sp ected bu t cann ot be con firm ed , the m a n u fa ct u r e r r e co m m e n d s o n e o f t h e fo llo w in g m e t h o d s to co n f ir m t h e p r e s e n c e o f le a d :
"
U s e th e s o lu tio n s fro m a m p u le s “ A ” a nd “ B” a nd s que e z e a c oup le of d rop s onto a ne w test area. Do n ot sw ab. The friction of sw abb ing m ay ind u ce bleed ing. If the solution tu rn s p ink or red , lead is p resen t.
"
U se a sod ium su lfid e solu tion su p p lied sep ara tely by th e m an u factur er a t a n ew test area. If the test ar ea tu rn s black, lead is p resen t.
Appendix W Procedure to Determine the Presence of Chromate in Coatings A . P u rp o s e To d eterm ine w heth er the coating contains chr om ate. B.
D e s cri p ti o n Th e p r es en ce o f ch r om a te p ig m en te d coa tin g s ca n b e d et er m in ed b y a co lor in d icat or u sin g r e a g e n ts to s w ab o v er ex p o s ed co ating la ye rs . The s w a b te s t w ill ve rify only the p re s e nc e of ch r o m a te an d w ill n o t p r o v id e q u a n tita tiv e r esu lts.
C. Eq u i p m e n t C h r om a te C h eck Sw a b s m a n u fact u r ed b y H y b r iv et Sys te m s, In c., PO Box 1210 Fr a m in g h a m , M a ss a ch u se tt s 01701; te lep h on e: 800-262-5323. D . Proce d u re fo r D e tecti n g W ater S o lu b le Lead Prim e n ts (l ead o r le ad carb o n ate) 1.
C l ea n a n d r e m o v e a ll d u s t a n d d ir t fr o m t e st a r e a .
2.
Cu t abou t a 1/ 4 inch n otch throu gh all coating layers and expose th e sub strate.
3.
Activate the sw ab by crush ing the g lass am p u les m arked “A ” an d “B” on the sw ab tu be.
4.
W it h t h e p o r o u s fib e r fa cin g d o w n , sh a k e a n d g e n t ly s q u e e z e t h e sw a b t u b e u n t il a cle a r liq u id is v isib le o n th e s w a b tip .
5.
Ru b th e clear solu tion o n th e tip in th e exp osed coating n otch for 30 second s.
6.
Results
7.
a.
If the sw ab tip or th e test sur face tu rn s p ink or p u rp le, chrom ate is pre sent.
b.
If th e s w ab tip o r th e d etection te s t su rfa ce d oe s not turn p ink or p u rp le , c hrom a te is not p resen t or is below the r an ge of the ind icator r eagen t.
N eg a tiv e t es t r es u lts sh ou ld b e co n firm ed b y u sin g th e “ Te st C on firm a tio n C a r d ” th a t is includ ed w ith th e kit. Th e card h as ind ivid u al circles on o n e face, an d each circle con tains a sm all am ou nt of chr om ate. a.
W ith th e u sed sw ab, rub reagen t w ithin th e test circle.
b.
If p in k or p u r p le a p p ea r s o n th e cir cle, t h e n eg a tiv e t es t r es u lt is v a lid .
W -1
c.
8.
W -2
If p in k o r p u r p le d o e s n o t a p p e a r o n t h e cir cle , t h e n e g a t iv e t e st r e su lt is in v a l id a n d a r e t es t is r e q u i r ed u s in g a n e w s w a b a n d t e st a r e a .
Th e s w ab ’s r ea g en ts h a v e a 1-m in u te life fr om th e t im e t h e g las s a m p u les ar e b r ok en , an d all testing shou ld be com p leted w ithin th e tim e limit. The sw ab is to be u sed for on e test area o n ly .
Appendix X Determination of Toxic Metals in Hardened Paint A . O b j e cti v e s 1.
Id en tify ty p e of toxic m etals tha t m ay be in th e p aint o n existin g infra stru ctu res.
2.
Deter m ine concen tration o f toxic m etal in th e p aint.
3.
The resu lts of the an alysis of the existing p aint are requ ired b efore the p aint can be rem oved fo r : • • • • •
B.
P r ed es ig n sp ecifica tio n d a ta g a th er in g P r e m a i n t en a n c e w o r k W o rk er p ro tectio n Protection o f the en vironm ent P ro p er d isp o sa l o f th e old p a in t
S am p l i n g 1. 2. 3. 4.
T a k e p a i n t sa m p l e in a b o u t a 2- t o 3-in c h s q u a r e M ak e su re th e sam p le in clu d es th e p rim er (p rim er con tains m ost toxic m etals) Sam p le in a t least thr ee locations to v erify resu lts Place th e s am p les in s ep arate b a gs a nd la be l e a ch ba g for ide ntific a tion
5.
A su itable tool for sam p ling is a shar p ened
½- to 1-inch w ood
chisel
C. Labo rato ry Te s tin g 1.
T h e p r im a r y m e t als to t es t fo r : • • • • •
2.
C o b a lt , a s so cia t ed w it h b lu e i sh a n d g r e en i sh c o lo r s C a d m iu m , a s so cia t ed w it h s a fe t y co lo r s C h r o m iu m , a s so cia t e d w it h le a d c h r o m a t e , z in c ch r o m a t e , a n d s a fe t y co lo r s le a d L e ad Z i n c (d e fin e d a s a to x ic m e t a l o n l y in t h e St a t e o f C a lifo r n i a )
T h e se co n d a r y m e t als to t es t fo r : • • • • • •
A r se n ic Ba r iu m Ber y lliu m Sele n iu m Silver Va n a d iu m
X-1
3.
Requ est resu lts in p ercen t, by w eigh t of m etal, an d to at least th ree sign ifican t d igits.
4.
T y p ical tes t m eth o d s are EP A 6010B, EPA 7420 (le a d s pe c ific ), O SH A 125G m e ta l s ca n, IC P , or p or ta b le XRF in st r u m en t fo r lea d on ly (re q u ir es cer tifie d op er a to r ).
D . Co s ts A bou t $20 to $25 for ea ch m etal tested —re d u ced cost for sev era l m etals. E.
T e s t Lab o rato ri e s •
Bu r ea u of R ecla m a tio n , Eco log ical R es ea r ch an d In v es tig a tio n (D -8220); con ta ct: C h r is H old r en ; tele p h on e: (303) 445-2178
•
Accred ited Laboratories 1. 2.
A ss oc iat ion : Am er ican In d u st r ial H y g ien e A ss oc iat ion (A IH A ) A ccred itation P rog ram s: • •
3.
X-2
E n v ir o n m e n t a l L ea d L ab o r a to r y A ccr e d i ta t io n P r o g r a m ( EL LA P ) N a t io n a l L ea d L ab o r a to r y A ccr e d i ta t io n P r o g r a m ( N L LA P )
W ebsite A d d ress: w w w .aiha .org (accr ed ite d lab or a to r ies ar e lis te d b y city an d Sta te in table form at)
Mission Statements The mission of the Department of the Interior is to protect and provide access to our Nation’s natural and cultural heritage and honor our trust responsibilities to tribes.
The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally sound manner in the interest of the American Public.
