Corrosion theory
1. What What kind kind of proce process ss is corr corrosi osion? on? Corrosion is an electrochemical process which results from an anodic reaction and at least one cathodic reaction. 2. What factors factors influenc influencee the rate of corrosio corrosion? n? Factors that influence the rate of corrosion as follows. A) Vari Variat atio ion n in in oxy oxye en n con conte tent nt on the the ste steel el surf surfac ace!w e!wet et"d "dry ry)) #) $.% & !A'o(e * *& is is cr critical) C) +res +resen ence ce of impu impuri riti ties es in the the air air !acid !acid,, alk alkal alis is,, sal saltt etc etc.) .) -) %ih %iher er no' no'il ilit ity y meta metals ls in in cont contac actt wit with h the the stee steel. l.! !il illl scal scale) e) /. What particular particular pro'lem related related to splash 0one? 1.$apid chane in xyen content. 2.oisture in the atmosphere is critical ie a'o(e*& /Wa(e mpact and 3rosion. 4.5rowth of arine life. 6.%ea(ily laden salt atmosphere. .echanical and #oat damae. 7.Access to the Workin area. 4. What is mill mill scale and why why it is particular particular pro'lem pro'lem when attemptin attemptin to protect steel? steel? ill scale is an oxide of iron produced when the steel is manufactured. t is a result of the white hot steel into contact with air and formin oxide composed f three layers, Fe nearest steel, Fe/ 4 then Fe2/ on the outside. ill scale thickness ranes from 26 microns to 1** microns. t is essential for mill scale to 'e remo(ed from steel surface durin 'last cleanin for the followin two reasons. ill scale is more no'le than steel and when parts of the mill scale 'reak away the exposed area of steel ie anode will sacrifice themsel(es to preser(e the more no'le surroundin mill mill scale ie cathode. f painted o(er the mill scale which is loosely adherin and flaky will lea(e the steel, 'rinin the paint away from the su'strate thus causin the early 'reakdown of the system due to lack of adhesion. 6. What is is cathodic cathodic dis'andment dis'andment and under under what circums circumstance tancess does it occur? occur? f the impressed current exceeds the corrosion current hydroen as 'u''les are e(ol(ed form the metal su'strate ie the interface 'etween material and coatin. 8his is sinificant pro'lem when coatin defects are present due to strippin action caused 'y the hydroen 'u''les, the coatin dis'ondment is known as cathodic dis'ondment. Surface preparation 1) What is the num'er of the 9wedish standard standard contained within #9 7*7: and list the rust and 'lastin rades toether with their 'rief tittles? 8he 9wedish pictorial standard *6;6:;** is contained within #9 7*7: +reparation of steel su'strates prior to the application of paint and related products. 8he 9wedish standard i(es (isual information on the followin. 1
$ust 5rades< ; which depict the condition of steel 'efore preparation. A = Co(ered in mill scale with little or no rust. # = A mixture of mill scale and rust. C>ill scales one, rusted with sliht surface sur face pittin. ->ha(in rusted and pitted #last Cleanin 5rades 9a1; @iht 'last cleanin 9a2; 8horouh #last cleanin 9a2 Very 8horouh #last cleanin 9a/ = #last cleanin to (isually clean steel 5rades of wire 'rushin 9t 2; 8horouh hand and power tool cleanin !manual) 9t/ ; Very thorouh hand and power tool cleanin !ech.) 2) @ist 'last 'last clean clean surface. surface. 5i(e 5i(e a comparison comparison of 'lasti 'lastin n rades rades to 99+C,#9 99+C,#9 7*7:, 7*7:, #9 42/2 and BAC3. 9a1 @iht #last cleanin< When (iewed without manification the surface shall 'e free from (isi'le oil, rease, dirt and from poorly from poorly adherin mill scale. 9a2 8horouh 'last cleanin< When (iewed without manification the surface shall 'e free from (isi'le oil, rease, dirt and from most of mill scale, rust .paint coatin and forein matter. Any residual contamination shall 'e firmly adherin. 9a2 1"2 Very 8horouh 'last cleanin< cleanin< When (iewed without without manification the surface shall 'e free from (isi'le oil, rease, dirt ,mill scale, rust .paint coatin and forein matter. Any remainin traces of contamination shall show only as liht stain in the form of stripes or spots. 9a2 8horouh 'last cleanin< When (iewed without manification the surface shall 'e free from (isi'le oil, rease, dirt, mill scale rust .paint coatin and forein matter. t shall ha(e a uniform metallic colour. 99+C White metal;9+ 6 Bear white metal 9+ 1* Commercial finish @iht 'last and 'rush off
#97*7: 99 *6 6: ** 9a / 9a 2 1"2 9a 2 9a 1
#9 42/2
BAC3
1 st uality 2 nd uality / rd uality B"A
5rade 1 5rade 2 5rade / 5rade 4
/) What factor influence influence how clean and rouh the surface 'ecomes after 'last cleanin? 8he cleanliness of the steel surface and its amplitude are o(erned 'y the a'rasi(e characteristics and human features as follows. A'rasi(e; 9i0e, 9hape, -ensity, %ardness %uman factor;9peed, Anle, -istance, 8ime 2
$ust 5rades< ; which depict the condition of steel 'efore preparation. A = Co(ered in mill scale with little or no rust. # = A mixture of mill scale and rust. C>ill scales one, rusted with sliht surface sur face pittin. ->ha(in rusted and pitted #last Cleanin 5rades 9a1; @iht 'last cleanin 9a2; 8horouh #last cleanin 9a2 Very 8horouh #last cleanin 9a/ = #last cleanin to (isually clean steel 5rades of wire 'rushin 9t 2; 8horouh hand and power tool cleanin !manual) 9t/ ; Very thorouh hand and power tool cleanin !ech.) 2) @ist 'last 'last clean clean surface. surface. 5i(e 5i(e a comparison comparison of 'lasti 'lastin n rades rades to 99+C,#9 99+C,#9 7*7:, 7*7:, #9 42/2 and BAC3. 9a1 @iht #last cleanin< When (iewed without manification the surface shall 'e free from (isi'le oil, rease, dirt and from poorly from poorly adherin mill scale. 9a2 8horouh 'last cleanin< When (iewed without manification the surface shall 'e free from (isi'le oil, rease, dirt and from most of mill scale, rust .paint coatin and forein matter. Any residual contamination shall 'e firmly adherin. 9a2 1"2 Very 8horouh 'last cleanin< cleanin< When (iewed without without manification the surface shall 'e free from (isi'le oil, rease, dirt ,mill scale, rust .paint coatin and forein matter. Any remainin traces of contamination shall show only as liht stain in the form of stripes or spots. 9a2 8horouh 'last cleanin< When (iewed without manification the surface shall 'e free from (isi'le oil, rease, dirt, mill scale rust .paint coatin and forein matter. t shall ha(e a uniform metallic colour. 99+C White metal;9+ 6 Bear white metal 9+ 1* Commercial finish @iht 'last and 'rush off
#97*7: 99 *6 6: ** 9a / 9a 2 1"2 9a 2 9a 1
#9 42/2
BAC3
1 st uality 2 nd uality / rd uality B"A
5rade 1 5rade 2 5rade / 5rade 4
/) What factor influence influence how clean and rouh the surface 'ecomes after 'last cleanin? 8he cleanliness of the steel surface and its amplitude are o(erned 'y the a'rasi(e characteristics and human features as follows. A'rasi(e; 9i0e, 9hape, -ensity, %ardness %uman factor;9peed, Anle, -istance, 8ime 2
4) 5i(e the essential reuirements for a'rasi(e 'lastin? 8he euipment reuired includin safety features as follows. Compressor pro(idin air supply 1** psi a. +ressur +ressurise ised d pot conta containi inin n a'rasi a'rasi(es (es '. @iuid separator is moisture filter c. Car'on imprenated imprenated hoses and external external coupli couplins ns d. -ead manDs handle handle for direct operator operator control control e. #las #lasti tin n no00 no00le le f. +ersonnel +ersonnel protecti( protecti(ee euipments;A euipments;Air ir fed helmet, helmet, ear defender, defender, 'oots, 'oots, lo(es, lo(es, leather apron. 6) 9ome metals are hard to prepare and paint? Bame three and how you miht prepare them? Bew 5al(anisin< sweep 'lastin, %and a'rades, etch primer. Aluminium< 9weep 'last %and a'rade = For thin aue aluminium an etch primer is used prior to intermediate and finish coats. Bot to 'e 'last cleaned. Chlorinated hydrocar'on shall not 'e used. 3tch primer;poly(inyl 'utyl. 9tainless steel 9weep 'last = 'last = nly aluminium used as 'lastin 'lastin medium. ) What is the roue peak? What pro'lem can it cause? $oue peaks are peaks which stand out a'o(e the reuired profile and should 'e a(oided if applyin thin coatins as they may lead to spot or flash rustin. 7) %ow do you measure surface profile? 3xplain. 8he surface profile may 'e measured 'y a num'er of methods includin the use of a surface profile needle aue. surface replica tape !testex tape) or a surface comparator. 9urface replica tape< 8estex tape or press o film are the commonly used surface replica tape. t is used to conEunction with a dial micrometer, has the ad(antae of pro(idin a permanent record. 8he procedure for carryin out this test is as follows. follows. a) ero the the micrometer micrometer ensurin ensurin the the flat contact contact points points are clean clean ') $emo(e paper 'ackin and stick testex tape to the the surface to 'e measured. c) $u' the testex testex paste paste in to the trouhs trouhs usin usin 'lunt instrum instrument ent until until peaks can 'e seen seen 'uttin up to the transparent plastic. plastic. d) $emo(e $emo(e the testex tape tape from the surface surface and measure the o(erall o(erall thickness thickness with with dial micrometer. e) -educt 6* microns microns from the the readin o'tain o'tain the amplitude amplitude.8he .8he plastic plastic layer layer to which the testex paste is attached is 6* micron thick. G) @ist all safety euipment and clothin reuired for open site 'lastin. a) Hse of car'on imprenated hoses to reduce the chance of static shock. ') Hse of dead manDs handle for direct operator control. c) Ieep the hoses straiht as possi'le to pre(ent kinks which may lead to a 'low out. /
d) Water and oil traps. e) %yperdermic needle aue to control the no00le pressure. f) perator should wear the protecti(e clothin includin air fed helmet, leather apron, 'oots, lo(es, ear defender. ) Warnin sins at the area, 'arrier tape. h) Ieep the compressor pressure 'elow 1** psi.
Paints and Paints application
1) a) ') c) d) 2)
what are the important properties of paint? A'ility to preser(e the surface from corrosionJ other type of deterioration. 9how some sacrificin effect. -ecorati(e purpose. pacity, tintin power, resistance to acid alcoholic and liht. 5i(e the three 'asic inredients within sol(ent carryin paint and list the Eo' each has to do? A traditional sol(ent carryin paint consists of three 'asic inredients these are. #inder #inds the particles toether and holds them in suspension 5i(es the paint its finish akes the coatin adhere in to the surface 5i(es flexi'ility to the paint film. Con(erts the coatin to a solid dry film. 5i(es resistance to water, chemical, and a'rasion. +iment< 5i(es colour to the paint. 5i(es opacity to the paint. 5i(es resistance to acids, alkalis and liht. 9ol(ent< Forms the e(aporati(e part of the dryin process. 8hins the paint so it can 'e applied easily. Washes out the 'rushes and euipment. Acts as a dereasin aent if appro(ed. /) Bame fi(e 'inder"sol(ent com'inations? #inder sol(ent stronest 3poxy acetone Chlorinated $u''er Kylene Alkyd resin White spirit weakest 3mulsion +aint water
%ih power
@ow power
4) Bame opaue piments and i(e their respecti(e colour? Car'on #lack Compound of calcium $ed, yellow Compound of co'alt #lue Compound of chromium 5reen yellow, orane Compound of iron #rown red yellow 4
8itanium dioxide
White
4A)$ust inhi'iti(e piments< anti corrosi(e inc chromate>Lellow inc $ed lead J ron xide;$ed, Coal tar>#lack, Calcium plum'ate>White 4#) metallic piments = inc, Aluminium 6) Bame the +aints J i(e their dryin and curin methods. 3mulsion coalescence Alkyd 9ol(ent e(aporation followed 'y oxidation Chlorinated ru''er 9ol(ent e(aporation 8wo pack epoxy 9ol(ent e(aporation followed 'y chemical curin Fusion 'onded epoxy %eat cured ) 9tate what condition paint must stored? n a dry locka'le well (entilated 'uildin away from any source of heat. aterial should 'e stored at least 6 -e C #elow the flash point and current leislation and manufacturerDs instruction should 'e followed. 7) Bame fi(e methods of applyin paints and compare the ad(antaes and limitations of each other. #rush application Ad(antaes < 3ffecti(e for applyin primer as it works paint well in to a su'strate, which i(es optimum co(erae and mixes in any dust particles ,thus achie(in optimum adhesion. -o not produce o(erspray @ess en(ironment ha0ard @ess wastae and less spottin. @imitations< 9low production ay not ha(e uniform thickness %ih uality 'rushes uite expensi(e. $oller application< Ad(antaes Muicker than 'rush for lare flat surfaces. With extension poles easy to access at ele(ated locations. @imitations< Bon uniform paint thickness. +aint does not work in to a surface. 9ome specifications not permittin roller applications. C) Con(entional 9pray< Ad(antaes 5ood finish 9uita'le for applyin thin material @ess operatin pressure = more safe @ess o(er spray, uicker than #rush @imitations< @ess production. 5ra(ity fed uns to 'e operated at upriht position only. %ih (iscous paint application not possi'le. 6
Airless spray< Ad(antaes< %iher production %ihly (iscous paints easily applied. ore porta'le. Hniform coatin can 'e achie(ed .%ih -F8 @imitations ore wastae and o(erspray %iher euipment and maintenance cost %ih risk of safety due to hih pressure operations. e) 3lectrostatic spray Ad(antaes ore uniform thickness can 'e achie(ed, 5ood finish @ess o(erspray @imitations %ih euipment cost. G) 5i(e types of anticorrosi(e primer. inc chromate inc phosphate $ed lead Calcium plum'ate $ed oxide Coal tar :) 9tate the ad(antaes of airless spray o(er con(entional spray. %ih rate of production Hniform film thickness can 'e achie(ed. @ess fo and re'ound 9i0e and anle of the tip can 'e controlled 'y the uantity of flow and pattern. %ih (iscous paint can 'e easily applied. 1*) What paints ha(e to 'e considered when 'rush paintins? +rimers ha(e to 'e considered when 'rush paintin 'ecause 'rushin works a paint into a su'strate;surface which i(es optimum co(erae and mixes in any dust particles thus achie(in optimum adhesion. 11) What method of paint application is performed for primer and why? +rimers ha(e to 'e considered when 'rush paintin 'ecause 'rushin works a paint into a su'strate;surface which i(es optimum co(erae and mixes in any dust particles thus achie(in optimum adhesion. 12) -efine the tie coat and i(e an example. A coat of paint which can tie two normally incompati'le systems toether. !Where adhesion pro'lem sol(ent strippin or 'leedin miht occur.) 3. Aluminium leafin primer for the application of Alkyd o(er #itumen due to 'leedin. 1/) -escri'e 'arrier paint system and sacrificial paint coatins<; #arrier paint system <; 8he su'strate is isolated from the en(iron mental which causes corrosion 'y usin a coatin of low permea'ility. 8his may 'e achie(ed 'y applyin a thick coat of paint ha(in low permea'ility.
3.. epoxy, polyurethane. 9acrificial coatins< 9acrificial coatins contain piments which cathodically protect the iron or steel su'strate to which the paint is adhered. 8hese piment particles e(entually corrode there'y sacrificin themsel(es to corrosion. n order to ha(e these properties the sacrificial piment must 'e ino'le to the material to 'e coated. inc and aluminium are the most common types of piments employed. 17) -escri'e what ualities a laminar piments i(es and name four piments. @aminar piments are small flakes which ha(e leafin effect when a paint dri(es, this means the flakes of piment o(erlap each other like tree lea(es on the round. 8he result in an excellent coatin to resist the passae of water. With impro(ed tensile strenth. ..., mica, lass flakes and aluminium flakes are examples of laminar piments. 1G) -efine the term pot life, nduction period, 9helf life. +ot life<; 8he pot life is the maximum period of time after mixin in which the paint must 'e used. 8his can (ary few minutes and depends on 8emperature.. nduction period< ; nduction period is the minimum period of time durin which mixed compounds are left to stand 'efore use. 8his is allowin for certain chemical reaction to take place and or the time allowed for air 'u''les to escape. nduction periods are typically up to /* minutes. 9helf life<; 8he maximum period of time a paint in ood condition in its container 'efore openin and recommended 'y the paint manufacturer. Paint and Film testing
1) What does a fineness of rind aue measure? 8he fineness of rind aue measure the deree of dispersion of a paint. Also known as hemen rind aue. 2) What does a crypto meter measures and two examples of crypto meter. A crypto meter measures the opacity or the hidin power of the paint posses. + Fund crypto meter, %idin power charts. /) What determines the deree of loss of paint may posses? 8he deree of loss determined 'y a) deree of piment dispersion. ') 9i0e of piment particles 7
c) 8he piment (olume concentration d) #inder type. 4) What is a flash point? -escri'e the procedure for determination of flash point. Flash point is the minimum temperature at which the (apour of liuid will inite if an external source of inition was introduced. Flash point determination of paints or sol(ents may 'e carried out in accordance with #9 /:** part A: usin a closed cup of A'el type. +rocedure<; Fix the A'el cup containin the su'stance for the assessment into a water 'ath. Acti(ate the source of inition e(ery de C rise in temperature. Apply a heat source to the water 'ath and monitor the air"(apour temperature in the A'el cup. A flash point temperature is identified when a 'lue flame flashes o(er the su'stance 'ein assessed. 6) What is density and how do you asses it? 5i(e to reasons for its use. -ensity is weiht per unit (olume of su'stance posses. -ensity N mass"(olume m " cc +rocedure for measurin density usin a 1** cc density cup. Weih the cup to the nearest deci ram usin a la'oratory 'alance with a 1*** m capacity and a sensiti(ity of O";; *.1 m $emo(e the co(er and fill with paint to within 2.6 mm of 'rim Carefully replace the co(er so that air any excess paint is expelled throuh the (ent Wipe off any surplus paint from the co(er then re weiht. -etermine the weiht of the paint 'y su'tract on. -i(ide the weiht 'y 1** if the density in "cc is reuired. Hses<; a) this procedure can 'e used to determine the uantity of any added thinner. ')to determine whether a two pack paints ha(e 'een mixed in the correct .
preparations.
) What is (iscosity and what euipment is used to measure (iscosity of a free flowin paint and thixotropic paint? G
Viscosity is a measure of a fluidDs resistance to flow. 9 unit B.s"s. m C.5.9 unitN poise easure 'y usin Viscometers
Viscosity of free flowin paints can 'e measured usin a flow cup, there are many types includin Ford cup, redwood and ohn flow cup. +rocedure for measurin (iscosity usin a ford cups no 4. a) #rin temperature of the paint within 2*O"; *.6 de C ') @e(el the apparatus ,then with the end of one finer o(er the orifice of the cup, rapidly fill it with paint. c) Allow a moment for air 'u''les to rise then draw a flat ede across the top of the paint le(el with the edes. d) $emo(e the finer from the orifice and start the stop watch simultaneously with the commencement of the paint stream. 8he watch is stopped when the first distincti(e 'reak in the paint stream occurs. e) 8he time in seconds taken as the (iscosity. For the thixotropic paints the (iscosity can 'e measured 'y a rotation (iscometer or another type of (iscometer paints. !Ier' =stormer (iscometer cone and plate (iscometer and roto thinner) 7) What is specific ra(ity and how is testin for s.. carried out? $elati(e density or specific ra(ity is the density of any su'stance compared to the density of water. 9pecific ra(ity N -ensity of the su'stance"density of water. G) Bame the three adhesion tests and descri'e how one of them is carried out? Adhesion is the force that resists the separation of two surfaces in contacts. a) Cross cut test ') Cross hatch c) -olly test.! pull off adhesion test) +rocedure for pull of adhesi(e test a) Clean and derease the surface to 'e tested. ') $ouhen the surface fine"medium rain emery sheet. c) ix reular araldite and stick dolly dolly to the surface and lea(e for 24 hours at 26 de C d) Cut paint around the dolly down to the su'strate usin a special cutter. :
e) Attach pull off instrument and apply pullin the force. f) 8est results reuire careful interpretations. 9ome normal (alues o'tained for accepta'le Adhesion are as follows. 16** psi ; epoxy 'ased systems /*** psi
; alkyd 'ased systems 12*** psi
; 0inc etch primer.
:) Bame four artificial weatherin de(ice and what are these desined to stimulate? Artificial weatherin de(ices are desined to create accelerated weatherin to speed up the duration of different test to speed up the duration test to 'e carried out to determine the coatin systemDs 'eha(iour at specific condition. a) tropical 'ox<; to simulate hih humidity en(ironment. ') 9alt spray test<; 9timulate a marine en(ironment. c) Water soak test<; to access paint systems resistance to water a'sorption. d) Cold check test<; test for low temperature contraction crackin. e) 8emperatures cyclin <; to access film flexi'ility at alternate hot and cold temperatures. 1*)
9tate two dryin and curin tests and how they are operated?
#allotini test< ; 8iny lass 'alls known as 'allotini are allowed to fall in to a freshly painted test panel. 8he test panel mo(es slowly 'eneath the fallin 'alotini o(er pre set period of time. the time of the test is (aria'le and the speed can 'e adEusted so that the panel /** mm lon can take 'etween 1 to 24 hours to test, where the 'alotini fails to stick to the painted panel dryin has occurred. 9tyllus test <; 8he stylus test employs a series of trailin needles which pass o(er the wet painted panel ,'ecause the needles are set at different tensions at can 'e esta'lished when the paint is tack dry hard dry and fully cured. 11)
What is w.f.t? %ow does you measure it? What are the ad(antaes of usin it?
Wet film thickness is the thickness measured immediately after a coatin has 'een applied. 8he wet film thickness may 'e found 'y usin a com' aue or an eccentric wheel. +rocedure for measurin w.f.t usin a com' aue. a) immediately after the application of paint the com' aue should 'e firmly place don the surface in such a way the teeth are normal the plane of the surface. ') 8he aue should then remo(e and the teeth examined in order to determine the shortest one to touch the wet film. 8he film thickness should 'e recorded as as lyin 'etween the last touchin tooth and first non touchin tooth. 1*
c) At least two further readins should 'e taken in different places in a similar manner in order to o'tain representati(e results o(er the painted one.
Ad(antaes<; ;
if the w.f.t. is known any de(iation from specified thickness rane can 'e immediately rectified.
;
f the w.f.t is known the approximate -F8 can 'e calculated if the (olume of solids are known -F8N WF8 . V9" 1**
12) What is -F8? 9tate the principle of 'ein a'le to use a 'anana aue for measurin -F8? 9tate cali'ration procedure for 'anana aue? 8he 'anana aue only used for measurin the thickness of non ferromanetic coatin applied o(er a ferromanetic su'strate. Cali'ration procedures <; a) Choose a manetically insulated shim of known thickness, close to the thickness of the paint you expect to find. ') +lace the shim on the same su'strate surface finish as the surface finish on which the paint to 'e measured ids attached. e.. if the paint is on a 'lasted surface ,cali'rate the aue on a uncoated 'lasted surface. c) +lace the manet on the shim and press firmly on the instrument, wind the scale wheel forward !away from you) until the manet is definitely attached to the shim"su'strate. d) 5radually wind the wheel 'ackwards slowly until the manet detaches itself. At this point mo(e the cursor on the instrument to the thickness of the shims shown on the scale wheel. With some instrument the scale itself must 'e mo(ed to line up with the fixed cursor. 8he instrument is now cali'rated and may 'e used to measure the d.f.t of any non manetic film to within a claimed accuracy of O";; 6& in some cases. 1/)
-escri'e a destructi(e test for determinin the -.F.8 of the paint?
+aint nspectorDs aue<; +aint nspectorDs aue in one such type of destructi(e test aue. A small PVQ shaped Cut in to the coatin at a fixed anle o(erned 'y a cutter 'uilt in the aue. 8he width of the channel is then measured on a raticule scale 'y means off microscope which is 'uilt in with the instrument. 14)
%ow do you calculate -F8, WF8, V9&?
-F8 N V9 & . WF8 " 1** 11
WF8 N -F8 .1** " V9 & V9& N -F8 .1** " V9 &
16)
-escri'e the cathodic dis'ondment test <;
f the impressed current exceeds the corrosion current hydroen as 'u''les are e(ol(ed from the metal su'strate i.e. at the interface 'etween the material and coatin. 8his is sinificant pro'lem when curin defects are present due to as trippin action caused 'y the hydroen 'u''les, the coatin dis'ondment known as cathodic dis'ondment. 8he test incorporates a coated test panel with hole drilled in to the coatin. 8his simulates a paint film defect. 9urroundin the hole a plastic tu'e is lued down and filled with sodium chloride solution to act as an electrolyte. Wires from 'attery are attached to the panel and to a metal rod set in to the liuid of plastic tu'e. a current is then impressed to make the panel cathodic. 8he coatin is assessed after a period of timin e.. a few weeks for the amount for strippin which has occurred from the 'oundary of the hole. Weather condition
1) Bame three en(ironmental conditions when would you stop paintin? 2) When shall coatin not 'e applied? 3n(ironmental conditions rain, snow, hih wind t is not permissi'le to apply paint when the followin conditions apply<; ;
durin snow rain or hih wind
;
When the air or metal temperatures is down to within / de c of the dew point temperature.
;
When the air and metal temperatures are 'elow 6 de C
;
When the relati(e humidity is a'o(e :* &
/) Why the en(ironmental test is carried out durin a paintin proEect? 3n(ironmental tests are carried out durin a proEect in order to (erify the weather conditions are accepta'le to the specifications to carried out the paintin inspection. 4)9tate the condition at which #5as allow paintin to take place? r what are the accepta'le application condition for 'lastin and paintin? Hnder #5as specification the accepta'le application condition for 'lastin andpaintin are; when there is no rain, snow or hea(y wind the air and metal temperature is at least / de C a'o(e the dew point temperature. $elati(e humidity less than :* &. 8he 8emperature for application are within the manufactures i(en limit 12
4) 3xplain $%, -+, Am'ient temperature and 9teel temperature ; $.%. <; $elati(e humidity is the amount of water (apour in the air expressed in a percentae. -ew point< ; -ew point is the temperature at which condensation would form on a surface. Am'ient temperature <; t is the surroundin air temperature also referred as dry 'ul' temperature. 9teel temperature<; it is the temperature of the su'strate prior to paintin. !anetic steel thermometer, diital thermometer) 6) 3xplain how en(ironmental test are carried out? What euipment is used to find $% and -+? 3xplain its use. 3n(ironmental conditions like $% and dew point are measured usin a hyrometer of which there are many types. 8he whirlin hyrometer or psychrometer consists of two mercury thermometers set side 'y side in a frame in a frame in which is pro(ided with a handle and spindle so that the frame and thermometer can 'e rotated uickly a'out hori0ontal axis. 8he 'ul' of one thermometer is called wet 'ul' thermometer, is co(ered with a closely fitted cylindrical cotton wick. 8he end of which dips into the distilled water or clean rain water contained small cylinder attached to the end of the frame. 8he frame is rotated 'y hand for /* to 4* seconds as fast as possi'le so that the 'ul's pass throuh air at least 4 miles per sec. 8his causes the water to e(aporate from the wet 'ul'. the wet 'ul' cools down to a constant wet 'ul' temperature due to the e(aporation rate of water from the wet wick. Always read the wet 'ul' temperature 'efore dry 'ul' temperature immediately after rotation. $epeat the operation until consecuti(e readins of each 'ul' temperature aree to within *.2 de C. f it is 1** & $% the wet 'ul' will 'e the same temperature as dry 'ul', 'ecause no e(aporation can occur. i.e. the air is saturated .f the wet 'ul' and dry 'ul' temperatures are the same the current temperature is the dew point. 8he $% and dew point can not 'e read directly from the apparatus, hyrometric ta'les or special slide rules must 'e used. Inspection standards and Specifications
1) What does #9 2*16 lossary of paint terms refer to and i(e three examples. Faults which occur with paints are descri'ed in #9 2*16 = lossary of paint terms. 8hese faults are due to three main causes. 1) Fault in the can !anufacturin faults) 2) +ro'lem which occur due to poor preparations /) +ro'lem which occur due to incorrect or poor application or interference 'y weather. 1/
#leedin< 8he action of a material in penetratin and discolourin a coatin a coatin applied on top of it. #listerin< 8he formation of dome shaped 'listers in a paint film. 8hey can 'e 'listers which are usually caused 'y the expansion and contraction of the paint film aainst the su'strate or osmotic 'listers which can 'e caused 'y water " sol(ent entrapment or hyroscopic salts left on a 'last cleaned surface. Chalkin< 8he 'reakin down of a paint film 'ecome chalkin or powdery usually due to disinteration of the 'inder caused 'y attack from H. V. liht or se(ere weather condition. 2) What does #94G** and how it is used in construction industry. #9 4G** +aint colours for 'uildin purpose specifies 1** colours which ha(e 'een selected from the frame works of the 2/7 colours contained in #9 6262. 3ach colour in #9 4G** is identified 'y three chief ualities as follows. %ue<; 8he first part sinifies hue or colour and consists of an e(en num'er of two numerals and 12 main hues are used and num'ered. *2; red purple o4 reds * yellow red *G yellow red 1* yellows 12 yellow reen 14 reen 1 reen 'lue 1G 'lue 2* +urple 'lue 22 Violets 24 +urples 5reyness< 8he second part sinifies reyness i.e. the apparent amount of difference in reyness 'etween one colour with another. Fi(e rades are used each detained 'y a letter. A = aximum reyness # ; 16 to 2: 14
C; /1 to 4* - = inimum reyness 3 = +ure = Bo reyness. Weiht< 9aturation Colour of similar hue and reyness may differ in colour 'rihtness or intensity of colour. 8his uality termed as saturation, may 'e defined as the intensity of any particular hue when compared with a neutral rey of similar lihtness of the spectrum colours 'ein the most intense or of hihest saturation. 8he weiht is i(en in pairs of num'ers from *1;6. 5roups of colours within each of the fi(e reyness ranes are raduated hih to low (alue. 3ach of these raduations is num'ered, A 5reyness = *1 ; 1/ # reyness = 16 ; 2: C reyness = /1 ; 4* - reyness = 4/ ; 46 3 reyness = 4: = 6 #9 4G** can 'e used Can 'e used to identify existin colours when maintenance paintin and is a method 'y which all manufacturers can make exactly the same colour. /) %ow do #as define the followin? a) Bew al(anisin ; A al(anised steel surface up on which cohesi(e oxide layer has not yet formed. !#riht, shiny =less than three months 'efore) ') Weather 5al(anisin< ; A al(anised steel surface up on which a cohesi(e oxide layer has formed 'y natural weatherin.!dull and lack of sheen) c) @on term protection< ; the estimated period for the corrosion protection is typically 1* years. -) edium term protection ; 8ypically 6 years. 3) 9hort term protection< ; 8ypically 2 to / years. 4) What is the procedure for remo(in oil, rease from a su'strate after preparation has taken place?
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f oil or rease found on a surface after it has 'een prepared that area must 'e swa''ed with an appro(ed sol(ent followed 'y a 2 & deterent wash washin with clean water throuh dryin and re 'lastin. 6) What is procedure for remo(in oil, rease from a surface 'efore preparation commences? 9mall areas of oil and rease shall 'e remo(ed with an appro(ed sol(ent where as lare areas can 'e i(en to low pressure deterent washin which must 'e followed 'y rinsin with clean water and thorouh dryin. ) What is the procedure for remo(e alae and mould rowth from pipe works? Alae and mould rowth shall 'e treated with a 'ioloical aent and left for 24 hours at least in order that 'iocide can kill the spores. t shall than 'e remo(ed 'y scru''in with stiff 'ristle 'rushes and clean water wash. ) What distance must 'e left at areas to 'e welded whan paintin? For 0ink rich paint 76 mm shall 'e left from the end preparation. 7) %ow much new paint o(erlap reuired o(er old repairs? inimum 1** mm. G) what must one pneumatically and electrically operated power tool euipment 'e ? All euipments whether pneumatically or electrically operated shall ' e earthed. All euipments shall 'e non spark and flame proof. :) What type of sheetin may or may not 'e used for protection aainst spillae and spottin? 9heetin of non flamma'le nature must 'e employed to protect areas aainst spillae and spittin. 8arpaulins must not 'e used. 1*) What areas of work does +A 1* not co(er? +A 1* not co(ers paintin work of the followin. a) #elow round !'uried) ') ffshore installation c) nternal coatin of piers d) 9to(e enamel coatin. 11) What is #9 7*7: ? +reparation of steel su'strates 'efore application of paints and related products. 12) What is #9 /:** And #9 4G**? 1
#9 /:** ethod f tests for paints. #9 4G** 9pecification for paint colours for 'uildin purposes. 14) What is #9 64:/? Code of practice for protecti(e coatin of iron and steel structure 1/) What is #9 676*? 14) As inspector what do you consider as your main responsi'ilities? a) 8o asses the condition of su'strate prior to treatment ') 8o inspect surface preparation in accordance with #9 7*::< measure and record amplitude once in daily. c) 8o ensure material used on site are to clients specification. d) $elati(e humidity, dew point, air temperature, metal temperature to 'e checked and recorded at least four times daily. e) Wet and dry film thickness to 'e checked and recorded freuent inter(als. f) 8o witness and and inspect application of each coat and inspect completed paint system in accordance with the clients specification and ood paint inspection practice. ) 8o su'mit daily and weekly reports recodin all the rele(ant information as reuired 'y the client. Copies to 'e retained 'y inspector. 16) @ist contractor malpractices. a) Hsin unualified personnel. ') Hsin unsafe plant and scaffoldin. c) Hsin euipment in poor condition, d) Carryin out further work 'efore inspection has taken place. e) Attemptin to skip a coat. f) Apply the coatin system in wron seuence. ) +aintin or preparin a surface durin 'ad weather condition< rain, snow mist wind etc. h) Hsin incorrect paint. i) Hsin a paint which out of expiry date E) Applyin too much sol(ent to the paint. k) n correct storae of paint. 17
l) Applyin low thickness coatin. m) Attemptin re use expenda'le a'rasi(es. n) nsufficient 'lastin or paintin a difficult access area. o) Cleanin surfaces with cottons. or ras. p) Bot o'ser(in induction and pot life timins. ) Hse of incorrect paint type or mixin different manufacturers product. r) nsufficient attention paid for house keepin. Paint Faults
Alliaterin< ; A drastic type of cra0in producin a pattern resem'lin the the hide of a crocodile or alliator. #leedin; the action of a material in penetratin and discolourin a coatin applied on top of it. #ittiness ; 8he process of particles of Eell, flocculated material or forein matter in a coatin material or proEectin from the surface of a film. #loomin< ; A deposit resem'les the 'loom on a rape that some times forms on the loss film of a coatin causin loss of loss and dullin of colour. #listerin; Formation of dome shaped 'listers or proEection in paints in the dry film of a coatin material 'y local loss of adhesion and liftin of the film from the underlyin surface. #lushin; ilky shady appearance inWhite. Chalkin< ; 8he 'reakin down of a paint film to 'ecome chalky or powdery usually due to the disinteration of the 'inder medium caused 'y attack from H.V. liht or se(ere weather condition. Checkin< ; crackin that comprises fine cracks which do not penetrate the top coat and are distri'uted o(er the surface i(in the sem'lance of a small pattern. Cissin; a failure of the paint to form a continuous film usually due to oil, rease 'ein present on the surface. Co'we''in;8he formation of a fine filament of partly dried +aint durin the sprayapplication of a fast dryin +aint. Craterin; 8he formation of small 'owl shaped depression in the film of a coatin material. Cra0in; Crackin that resem'les checkin 'ut the cracks are deeper and 'roader.
1G
Crackin<; 5enerally the splittin of a dry paint or (arnish film usually as a result of aein. -ry spray< ; 8he production of a rouh or slihtly 'itty film form sprayed coatin material where the particles are insuffiently fluid flow toether to form a uniform coatin. Flakin< ; liftin of the coatin material from the su'strate in the form of flakes or scales. Flocculation<; 8he separatin out of a paint constituents in the tin and their refusal to 'e stirred 'ack toether aain. 5rinnin<; 9howin throuh of the su'strate dud to the in adeuate hidin power of the coatin material. %olidays<; issed or poorly coated areas on a painted surface. @iftin <; softenin ,swellin or separation from the su'stance of a dry coat as the result of the application of a su'seuent coat. rane peel ; 8he uniform pock marked appearance in particular of a sprayed film resem'les the peel of an orane due to the failure of the film to flow out to surface. smotic 'listers< ; formation of dome shaped 'listers which can 'e caused 'y water entrapment, sol(ent entrapment or hyroscopic salts left on a 'last cleaned surface. +in holin< ; 8he formation of minute holes down throuh a paint coatin caused 'y escapin air 'u''les. $opiness <; ! #rush marks) +ronounced 'rush marks that ha(e not flowed out 'ecause of poor properties of the coatin material. $esidual tack< ; 8he deree of stickness remains in a film of a coatin material which does not reach the true tack free stae. 9aponification<; 8he formation of a soap 'y the reaction 'etween a fatty acid ester and an alkali. Wrinklin<;8he de(elopment of wrinkles in a film of a coatin material durin dryin mainly due to the initial formation of a surface skin. BGAS PA 10
1) What is #as +A :? $efers to paint properties and performance reuirements. 2) What is #5A9 +A 1*? $efers to the technical specification for new and maintenance paintin at works and site for a'o(e round pipe line and plant installations. /) What are the definitions for the followin from +A 1*? 1:
A) Compliant coatin< ; A coatin which complies with the 3n(ironmental protection act . ') @on term protection = 8ypically 1* years edium term protection = typically 6 years 9hort time protection = typically 2;/ years d) Fully weathered 5al(anisin<; A al(anised steel surface upon which a cohesi(e oxide layer has formed 'y natural weatherin. e) -ew point< ; the temperature at which condensation would form on asu'strate. f) $elati(e humidity<; the amount of water (apour in the air expressed as a percentae. ) nduction period < 8he lenth of time a paint is reuired to stand after mixin and 'efore application. 8his time allows air 'u''les to escape and or chemical reaction to take place and is specified 'y the paint manufacturer. h) +ot life; 8he lenth of time ! followin induction) that a point remains in an apply a'le condition accordin to the manufacturers instruction. i) 9helf life<;@enth of time a paint can 'e stored,'efore it can 'e used. E) 8 wash; An etch primer for 0inc metal surfaces #lue in colour it turns 'lack upon dryin if it has 'een applied successfully. k) 9heetin for protection<; 9heetin of a non flamma'le nature must 'e employed to protect areas not 'ein prepared or painted from contamination. l) askin outs<; the contractor must mask out items to 'e protected durin preparation and paintin in order to pre(ent malfunction of the plant. 9uch areas typically or fire protection euipment, weld end preparation, atmosphere sensin head ,(ent on control euipment, flame trap, lu'ricatin points name plate etc.8he contractor is responsi'le for remo(in all maskin material. 4) What are the Condition for final surface preparation<; When conditions in the workin area are such that metal surfaces are moist, damp or wet, final preparation shall not 'e carried out. ;
Any surface preparation procedure or method of cleanin shall not 'e allowed to contaminate wet paint film.
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3uipment used shall 'e of non sparkin type.
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3lectrically operated tools are not permitted.
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+ower tools operated 'y compressed air shall ha(e oil trap (apour trap fitted to the compressed air lines. 2*
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All contaminants shall 'e remo(ed 'y means of an appro(ed sol(ent.
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Allae and mould rowth when in e(idence shall 'e treated with 'iocide aent and left for at least 24 hours in order that the 'iocide can kill the spores. t shall then remo(ed 'y scru''in with stiff 'ristles 'rushes and clean water or 'y use of hih pressure water wash.
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All surfaces shall normally 'e dry 'efore paintin commences.
6) Condition for application of paint as per +A 1* <; +aint shall normally applied when a) the $% & is less than :*& ') the air and metal temperature is at least / de C a'o(e the -+ c) Am'ient and su'strate temperature should not 'e 'elow the set out 'y the paint manufacturer for particular paint. d) +aint shall not normally apply when conditions in the workin 0one are such that the workin surface 'ecomes moist or dump durin the paintin operations. e) +aintin euipments shall 'e used in accordance with the paint manufacturerDs recommendations. f) All paint shall 'e applied in order to produce a firmly adherin continuous film, free from misses, runs tears, sa etc. ) 9tripe coatin shall 'e carried out to welds edes etc in order to achie(e a full paint film thickness as specified. h) All painted areas must 'e thorouhly dry 'efore 'ein o(er coated and any contamination of the paint film should 'e remo(ed 'efore further coats are applied. i) Final coatin shall 'e free from sinificant (isi'le imperfection. Health and safety
1) What document state health and safety at work? %.A.9.W.A. < ; ha0ardous and safety at work act1:74. 2) What year was the health and safety act passed? 8he control of su'stances ha0ardous to health reulations 1:GG come in to force 1 st cto'er 1:G:!C9%% reulations). 4) %ow lon would 'e records of examinations monitorin test for fi(e years and /* years for identifia'le employees. 6) 3+A = en(ironmental protection act waste material disposal. 21
) What is VC? Volatile oranic compound. 7) %ow would structures coated 'y lead 'ased paints 'e 'last cleaned? Wet 'last system or enclosed reco(ery 'last system shall 'e used for remo(in lead 'ased paints. G) Bame some hea(y metals used in coatin and paintin? Work permit is an clearance to carryout an work in a safer manner .as per contract specification. Bame and descri'e three tests for locatin solu'le iron salts and mill scale on a 'lasted 9u'strate. Solule iron salts < 8he potassium ferricyanide test may 'e used to detect the presence of colourless solu'le iron salts which may 'e present in the pits after 'last cleanin. f thee salts present they will accelerate corrosion causin rust spot which may in turn 'reak the 'ond of any applied coatins leadin to failure of the coatin system. 9pray the fine mist of distilled water on to a small area of the surplus usin a scent spray type of 'ottle.
Wait a moment for any water droplets to e(aporate and then apply a potassium ferricyanide test paper 'y pressin down for 2 to 6 seconds. $emo(e the test paper and check to see if any salts ha(e 'een drawn 'y capillary action. they show as +ersian 'lue spots. Solule chlorides 8he sil(er nitrate test may 'e used to detect the presence of solu'le chlorides. Preparations make 2& solution !'y weiht) of sil(er nitrate in distilled water.
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Cut strips of filter paper and store in a sealed plastic 'a.
+rocedures a) wet filter paper strip with sil(er nitrate solution. ') +ress the test paper on to the steel surface and lea(e in contact for 2* seconds. c) $emo(e the filter paper and wash thorouhly in distilled water . d) Any sil(er chloride formed remains on the paper when the paper is immersed in to photoraphic de(eloper, the chlorides shows up as 'rown 'lack areas. !ill scale" 8o test the presence of mill scale particles left 'ehind after 'lastin to
#9 7*7: rades 9a / the copper sulphate test is used. 22
+rocedure< A fine mist of slihtly acidic copper sulphate solution is sprayed on to a localised area of approximately 1** mm in diameter. 8he steel turns a 'riht copper colour and any mill scale particles show as 'lack spots. Bame fi(e items that can 'e included in paints to impro(e its performance or suita'ility for a certain use. a) -rier or catalyst -riers added to accelerate the dryin process. -rier consists of compound of metal e.. Bapthenats of co'alt, 0irconium ananese. ') +lastici0ers< a plastici0er is a paint reduces the 'rittleness of the dried film 'y allowin the molecules of the paint to mo(e more easily. 8here 'y makin it more plastic. c) 9ta'ilisers %olds modern synthetic film formers intact and helps to pre(ent flocculation occurrin in tin. d) 3xtenders< 3xtenders are cheap mineral powders which can 'e added to paint in order to make it flow easily, increase opacity and reduces cost. e) Anti skinnin aent< anti skinnin aents pre(ent or slow down the formation of a skin on the surface of a paint in its container 'y retardin or eliminatin polymer rowth due to oxidation. f) 8hixotropic aent thixotropic added to paint i(e a elly like structure which i(e the paint hih 'uild and anti sa properties. dentify six paints 'y their 'inder name. Alkyd, Cellulose, Chlorinated ru''er, emulsion, epoxy, poly urethane, (inyl What is the difference 'etween thermosettin and thermoplastic? +aints which melt when heat is applied are known as thermoplastic coatins. Coatins which do not melt after the application of heat are known as thermo set coatins.What is impressed current and what pro'lem can arise from its incorrect use? mpressed current is a type of cathodic protection system.e.. used for lare areas of pipes. f the impressed current exceeds the corrosion current hydroen 'u''les are e(ol(ed from the metal su'strate i.e. at the interface 'etween the material and the coatin. 8his is a sinificant pro'lem when curin defects are present due to strippin action caused 'y the hydroen 'u''les leads to coatin dis'ondment is known as cathodic dis'ondment. Bame the two types of paint mill and i(e two examples of each?
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1) -irect chare mill< which take and mix all the raw inredients toether .e.. #all mill, Attritor mill, %ih speed dispersers 2) +re mix mills 8ake the inredients which ha(e 'een pre mixed to a rouh consistency and refine this mixture to hih uality paint. 3.. #ead mill !pear or sand mill), Colloid mill, 8ipple roll mill, sinle roll mill. What is the title of #9 /:**? 8he #ritish standard for dealin with testin is BS #$00 method of test for paints% 8his document is di(ided into eiht separate parts each one dealin with a separate aspects of testin procedures. 8hey are 5roup A = test on @iuid paint !excludin chemical test) 5roup # = test in(ol(in chemical examinations of liuid paints and dried paint films. 5roup C = 8ests associated with paint film formulation. 5roup - = optical tests on paints 5roup 3 = echanical tests on paints 5roup F = -ura'ility tests on paint films 5roup 5 = 3n(ironmental tests on paint films. 5roup % ; -efects Bon destructi(e -.F.8. aue ;; 3lectronic aue, #anana aue -estructi(e -.F.8 5aue = +aint nspectors aue. what two coats of paints are applied at works? At works the followin two coats of paints are applied a) %ih solids sol(ent 'ased 3poxy primer 76 icrons minimum. #) 3poxy .. 76 icrons minimum. what is the maximum allowed time for primin to take place followin preparation and 'y what method is primer applied? 8he maximum allowed time for primin to take place after preparation in all cases is 4 hrs. 8he 'rush is (ery effecti(e for applyin primer as it works paint well into a su'strate and produces an excellent finish. What do #5as class as a hot duty ser(ice? etal surfaces that will reach a temperature in excess of :: -e C when in ser(ice is classed as hot duty ser(ice. Fire or Flame shall not e used to cleanout paint &ettles
Bame a 'lack piment in common use apart from coal tar. Car'on 'lack. 24
$e(ersi'le head = Hsed to clean out any 'lockaes in the orifice of the no00le. Fluid 8ip = @ined with tunsten car'ide .the orifice si0e o(erns throuhput of the paint and the orifice anle o(erns the si0e of spray pattern. 1) +A;:< +aint type appro(ed for particular Eo' Appro(ed paint manufacturer !ser(ice and price) 8est to 'e done 'y manufacturer. /) 53 " 9$ "21 #last cleanin operation. @on term protection< +aint system to last without recoat. White rust = Weathered al(anisin more than / months old. anufacturerDs temperature limit for application. ;Whirlin hyrometer and dew point calculator. Check on hyrometer ;
more freely
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cali'ration sticker
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Water in column.
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Wick is clean
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#reakae on thermometer.
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Check close to work area
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8ake 2 set of readin at least
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8ake mornin 'efore work commence
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Facin the wind direction.
f profile is more than reuired amplitude For small area =A'rade with emery @are area a) $e'last usin smaller si0e a'rasi(es. ') reduce the no00le pressure c) keep distance 'etween surface and no00le. d) 8ime =#last more uickly !less time) e) Hse straiht 'ore no00le. 26
9+A 1 ;Complaint sol(ent 'ased system n the finish coat usually used to pre(ent chalkin if epoxy is used. Hrethane. 9+A Bew al(anisin full system minimum 12* microns and must include an coat. For 99 full system minimum 12* microns!-o not reuire ) ;Polyurethane ad'antages +olyurethane finish coats are often used to replace epoxy finish coats. 8hey ha(e the followin ualities. ;
%ih loss
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$etain the loss
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%old the colour
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A'rasion resistant
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3asily cleaned
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5ood resistance to H.V.liht.
Ad'antages of epo(y
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ore flexi'le
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Hsed on damp surfaces
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#uild thickness
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Chemically cured and hard
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echanical resistance.
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3poxy not cured 'y oxidisin. Cured 'y chemical reaction 'etween two components.
9plash 0one< oxyen on water is 1"6 & of air and corrosion protection 'y sacrificial anode only.!Bo paintin is done) 8emperature of water, saltiness of water. ;9urface preparation depends 8ype of paint @enth of protection 2
Muality of finish +ressure washin 1** psi maximum S)eep lasting 8o remo(e any forein material.
+ressure drop 'etween compressor and no00le Compressor leaky 8oo lon hose @eakae in couplin, Iink in hose ;#9 72: %ot dip al(anisin. ;9ix opaue piments with respecti(e colours. Calcium plum'ate = white Coal tar; 'lack $ed iron oxide =red $ed lead =red ink chromate =yellow ink phosphate ; white. #leedin< 8o pre(ent 'leedin a tie coat should 'e applied. Alkyd and #itumen< tie coat should 'e Aluminium leafin primer. ;sol'ent stripping depend on sol(ent power of paint applied o(er. Chlorinated ru''er and alkyd>aluminium leafin primer. -ry 'lister = -ue to localised adhesion. When applyin care should 'e taken to a(oid addin more sol(ent. i.e. wft may 'e wron. 8 wash; 8o pro(ide a key for new al(anised surface. +aintin application #rush or spray appropriate 4 hour.!except 9+4 immediately) %.A.9.W.A. ; %ealth and safety at work act 1:74 8his act deals with the duties of the employer and the employee in the work place.
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8he main duty of the employer is to pro(ide a safe workin en(ironment. 8he main duties of the employee are to keep themsel(es and others safe at all times 'y their action at work. 8hey also ha(e a leal duty to report accidents, incidents or spillaes. C..9.%.%.<; Control of su'stances ha0ardous to health 1:GG. 8his acts deals with the use, handlin, transport storae packain and la'ellin of many ha0ardous materials. n our industries it deals mostly with sol(ents sand and dust. What additional information you should need when maintenance paintin a pipeline without remo(in the existin coatin" 8he followin additional information to 'e recorded is. ;
Bature of the existin system must 'e esta'lished to decide the type of preparation to 'e commenced.
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Amount of surface contamination.
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3xtent of corrosion.
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3xtent of paint 'reaks down.
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Compati'ility of the existin system with the new system. if not compati'le select the appropriate tie coat.
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n ser(ice en(ironmental condition.
Holiday and pinhole detector
%oliday misses d or poorly coated areas +inhole< inute defects caused 'y escapin air 'u''les when the paint dries. 6 (olts per micron; +rocedureearth the su'strate a) +ass a metal 'rush!holidays) or wet spone!pin hole) o(er the painted surface at a pre set (oltae :typically 6 (olts"micron and at a controlled speed. ') When a defect is found an audio or (isual warnin will 'e i(en. c) 8hese areas must 'e marked repaired and retested. #9 /:** Applied (oltae should 'e less than the di electric strenth of the coatin material. ;ordent solution, t wash, wash primer N etch primer Aluminium etch primer = poly (inyl 'utyl %ow corrosion occur? 2G
a) Baturally occurrin ')3lectro chemical process c) 8hrouh electrolyte. #leedin< -iscoloration of newly applied coatin o(er existin coatin #loomin A loss of loss and milky type appearance due to a wet paint film comin into contact with cold or damp air. @iftin Applyin a coat of paint 'efore the pre(ious coatin was fully dried causin patches of the underneath coatin to 'e lifted off in to the newly applied coatin. 9ol(ent strippin< applyin a coat of paint with a (ery stron sol(ent causin patches of the underneath coatin to 'e stripped off. xidation t is a chemical reaction 'etween the 'inder and oxyen to 'rin a'out the dryin of a one pack paint. Chemical curin< t is a chemical reaction 'etween an epoxy 'inder and a catalyst to 'rin a'out the curin of two pack paint. (erspray @ost of paint on to other surfaces or in to the atmosphere when sprayin. #9 4G** it is a rane of 1** standardised colours taken from the frame work of 2/7 colours of #9 6262. Hses 8he ways in all manufacture make paint in same colour. 5al(anic series @ist of metal compounds in their order of no'ility in sea water at am'ient temperatures. 5old
Bo'le ! sta'le )
9il(er Copper ill scale ron Aluminium inc
ino'le ! un sta'le)
We can use al(anic series to 'rin a'out cathodic protection of steel in two ways. #i metallic corrosion, sacrificial coatin. Flash point = indication of fire risk chlorinated ru''er 1/ to 21 thou N24** psi %.#.epoxy
17 to 2/ thouN /*** psi 2:
inc rich primer
17 to 2/ thou N 2G** psi
1: thou N 26** psi. anufacturerDs data sheet +roduct description $ecommended use 8echnical information Application data Condition durin application -ryin and curin time $ecommended paintin system 9torae and packin %ealth and safety 1) %ow is 9weep #last performed? After a'rasi(e 'lastin, cut off the flow of a'rasi(e. nly pure air will flow throuh the no00le at the same speed. +roEect it on the 'lasted surface so that any a'rasi(e i.e. rit particles. -ust etc will 'e 'lown off 'y the air from the 'lasted 9urface. 3nsure that no dust particles are present. 9imple test; stick clear cello tape on the 'lasted surfaceJ pull it out and check for any dust particle is present. 4. Hse of Wet Com' 5aue. WF8 C# 5AH53. t is pushed firmly into the wet paint so that the outer most teeth make contact with the su'strate. %eld at riht anles to the surface. 5aue is remo(ed and the teeth are examined. WF8 lies 'etween the last tooth i.e. Coated and the first tooth that is Hncoated. idpoint 'etween this is WF8.
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8heory Muestion 1. 3tch +rimers J their uses? 2. Function Juse of 9ol(ents ? /.-ifferent 8ypes of 9urface +reparation ? 4. Critical. +iment. Volume .Concentration !C.+.V.C) 6. +reparation f 8wo +ack +aints for Hse .9ealers for %ih 8emperatures 9urfaces ?. 7. +urposes of #.9.4G** ? G. Mualities of +olyurethane Finish Coats ? :. Ad(antaes J -isad(antaes of 3poxy +aint 9ystem ? 1*.-etail operation of Airless J Con(entional 9pray 9ystem? 11. Action taken when coatins are applied out of 9euence ? 12.$isk Assessment when cleanin J+aintin ? 1/. +ro'lems when -ensity and Viscosity of a paint are not correct ? 14.Visual inspection steps reuired for 'last clean surfacesJ-ry paint films ? 16. Con(entional J Airless 9pray 9ystem ? 1. 9euence of e(ents leadin to Clients nspection ? 17 .Hse of 3lectrostatic spray system ? 1G. Functions of +rimers, idcoats, and Finish Coats ? 1:. Client" Contractor $elationship ? 2*. +urpose of Workin to uality +lan ? 21. Factors which cause +oor Adhesion of +aint 9ystem? 22. $ust inhi'iti(e properties of +aint system? 2/. $ecordin of nformation followin +roEect Completion? 24. 3xplain #arrier J9acrificial Coatins? 26. 3n(ironmental 8estin< +aint Film +ermea'ility +aint Film Flexi'ility . %umid 3n(ironment , arine Condition 2. +aint Faults< #loomin #leedin Chalkin Cissin Crackin 5rinnin Flocculation (erspray smotic #listerin. #ased on +ractical. 1. Checks J Hse of Whirlin %yrometer? 2. Calculation of -ew point J$elati(e %umidity ?. /. 3n(ironmental limits for +aintin Application? 4. dentification of A'rasi(es? 6. dentification of $ust rades J#last cleanin rades? . Cali'ration of -ial micrometer? 7. 9election of a W.F.8. Com' 5aueJ $eadin of it? G. @imits for 8estex 8ape? :. $eduction of #last cleaned 9urface? 1*. +rinciple in which #anana aue works? 9tate the Cali'ration +rocedure? /1
1What is Corrosion"? What factors influence corrosion? 2. What is ill scale? Why should it 'e remo(ed? /. @ist the items that are needed for open site 'lastin? 4. What factors determines the cleanliness of the steel surface? 6. What are the $ust rades #last cleanin rades? . What is +aint? What does it contains? 9tate the functions of .it? 7. Bame four rust nhi'iti(e +rimers? G. What do you understand 'y C.+.V.C ? :. 9tate different methods of dryin J curin i(e 3xamples of each? 1*. What is a 8ie;coat? What are laminar piments, state their use? 11. What is #.9.2*16? 3xplain #listerin, Chalkin, Cisssin, Flocculation, 5rinnin. %olidays. 12. What is pacity? %ow do you measure it? 1/. -efine Viscosity? 9tate a method to determine it? 14. What is -ensity? What is the use -ensity cup? 16. %ow do you select a wet com' aue, for what it is used? 1. 9tate the cali'ration procedure for a #anana 5aue? 3xplain the principle of it? 17. What is a -olly test " 1G. 9tate under what conditions +aintin can proceed? 1:. What are the main $esponsi'ilities J -uties of +aintin nspector? 2*. @ist Contractors alpractices? 21. 9tate the (arious methods of +aint Application? #riefly explain it? 22. What is a work permit? What do you understand 'y C9%%, %A9WA? 2/. Write the Formulae in which you use in +aintin Works? 24. What information is needed 'efore you undertake a maintenance Contract prior to Coatin? 26. What is not co(ered in #5+A1*? What is #5+A: " 2. -efine -ewpoint, $elati(e %umidity, nduction +eriod, +otlife, Flash point ? 27. What are the areas that need to 'e masked? 2G. What 9afety precaution to 'e followed in a #lastin J+aintin Work? 2:. %ow will you treat the surface affected 'y Alae ould 5rowth? /*. What action will you do to rectify surfaces contaminated with oil? /1. What are the essentials thins to consider on aintenance +aintin Ro'? /2. What is the use of 99*6 6:** J #9 4G**, #9/:**, #964:/, #926:, #92G42.#97*7: //. -escri'e the operations in(ol(ed in 9.+.A. 1 /4. Why sealer is to 'e used? 3xplain a paintin system for hih temperature ser(ices? /6. 9tate the system for ferrous surfaces which are -amp? 2) 3xplain a'out scaffoldin safety? /) What are the main features to maintain ood relationship 'etween contractor and client? 4) What are the seuences of acti(ities you will follow for final client inspection? 6) 3xplain the ad(antaes of urethane paints? ) 3xplain the ad(antaes of epoxy paints? 7) %ow will you reduce the risk at site? /2
