Question & Answers for Coating Exams Q A
What What kind kind of of pro proce cess ss is corr corros osio ion? n? Corr Corrosi osion on is an elect electro roche chemic mical al proce process ss..
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Define Define corros corrosion? ion? Why do uncoa uncoated ted steel steel stru structu ctures res corrode corrode?? Corros Corrosion ion is an electr electroche ochemica micall process process.. In practi practical cal terms terms;; iron iron ore is is an oxide oxide of iron iron in chem chemical ical balance with atmosphere, atmosphere, following conversion conversion with iron ore to iron, the chemical balance changes and the resulting iron become active but it always have the tendency to revert to its original state when it contact with the natural environment.
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What What fac facto tors rs infl influe uence nce the the rate rate of of corr corros osion ion?? Vari Variat ation ion in oxyge oxygen n content content on the the materi material al surfac surface. e. materials being in contact with iron, acids, and alkalis.
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What What is a mill mill scale, scale, and why why is it a partic particula ularr problem problem with with attem attempting pting to to protect protect steel steel?? When When ferrous ferrous metal metal is forge forged d into flat flat plates, plates, beams beams and girde girders. rs. It is worke worked d at tempera temperatur turee often exceeding 1000˚C while the metal is in this white hot state it is in contact with the cool air and rapidly oxidizes, the results in the formation of a thin flaky layer called mill scale. Mill scale must be removed from the surface of the steel before painting painting take place mill scale is noble to steel there for in close contact with each other steel will corrode.
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What What part particu icula larr probl problem emss rela relate te to the the spla splash sh zone zone?? The area area of the the materi materials, als, which which are are neither neither in water water nor nor in air due due to waves waves,, high tide tide and low low tide etc are cold cold splash zone. zone. There is variation variation in oxygen oxygen level on the surface surface of the material, material, due to medium change. Corrosion rate can be accelerated due to this reason.
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What What is the number number of the the Swedish Swedish standa standard rd containe contained d within within BS 7079 7079 and list list the rust rust and blasti blasting ng grades together with their brief titles? The Swedis Swedish h pictorial pictorial standa standard rd 05-59-0 05-59-00 0 is contained contained with with B.S. 7079 Prepar Preparatio ation n of Steel Substr Substrate atess Prior to the application of paint and related products.
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Chlo Chlori ride dess and sulfid sulfides es,, higher higher nobil nobilit ity y
The Swedish standard gives visual information on the following: Rust Grades:- which depict the condition of steel before preparation. A. Covered Covered in millscal millscalee with little or no rust. B. A mixtur mixturee of mill millsca scale le and rust. rust. C. Millscale Millscale gone, gone, rusted rusted with with slight slight surface surface pitting. pitting. D. Heavil Heavily y rusted rusted and pitted. pitted. Blast Cleaning Grades: SA 1 – Light blast cleaning SA 2 – Thorough Blast cleaning SA 2 ½ - Very thorough blast cleaning SA 3 – Blat cleaning to visually clean steel Grades of Wire brushing: ST 2 – Thorough hand & power tool cleaning (manual) ST 3 – Very thorough hand & power tool cleaning (mechanical)
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List List blast blast cleani cleaning ng surfa surface. ce. Give a compari comparism sm of blasting blasting grades grades to to SSPC, SSPC, BS 7079, 7079, BS BS 4232 4232 and NACE? SA. SA. 1 – Lig Light ht Blast last cle cleanin aning g When viewed without magnification, the surface shall be free from visible oil, grease, dirt and from poorly adhering adhering millsca millscale. le. SA 2 – Thorough Blast cleaning When viewed without magnification, the surface shall be free from oil, grease, dirt and from most of the millscale, millscale, rust, paint coating and foreign foreign matter. Any residual residual contamination contamination shall be firmly adhering. SA 2 ½ - Very thorough blast cleaning. When viewed without magnification, the surface shall be free from visible oil, grease, dirt and from millscale, millscale, rust, paint coatings coatings and foreign matters. matters. Any remaining remaining traces of contamination contamination shall show only as light stains in the form of spots and strips. SA 3 – Blast cleaning to visually clean steel. When viewed without magnification, the surface shall be free from visible oil, grease, dirt and shall be free from millscale, millscale, rust, paint coatings coatings and foreign foreign matter. matter. It shall have a uniform uniform metallic metallic colour. Comparison of Blasting Grades SSPC White metal (SP 5) Near white white metal metal (SP 10) 10) Commercial finish Light blast & Brush off
BS – 7079 SA 3 SA 2 ½ SA 2 SA 1
BS - 4232 Ist Qlty 2nd qlty 3rd qlty N/A
NACE Grade 1 Grade 2 Grade 3 Grade 4
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What What factor factor influe influence nce how clea clean n and how rough rough the surf surface ace becom becomes es after after blast blast cleanin cleaning? g? The cleanl cleanlines inesss of the steel steel surface surface and and its amplit amplitude ude are govern governed ed by the abrasiv abrasivee character characterist istics ics and human factors as follows: ABRASIVE HUMAN FACTORS Size Speed Shape Angle Density Distance Hardness Time
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Give Give the the essent essential ial require requirement mentss for for abrasiv abrasivee blas blastin ting? g? The equipme equipment nt requ required ired includin including g safet safety y featur features es as as foll follows ows:: Compressor – providing air supply – 100 psi Pressurised pot – containing abrasive Liquid separator i.e. moisture filter Carbon impregnated hoses & external coupling Deadmans handle for direct operator control Blasting nozzle (ventori shaped) Personnel equipment – Airfilled helmet, ear defender, boots, gloves & leather apron.
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Some Some metals metals are are hard to to prepare prepare and and paint? paint? Name Name three three and how how you migh mightt prepare prepare them? them? New New Galv Galvan aniz izin ing: g: Sw Swee eep p blas blasti ting ng,, hand hand abra abrade de,, etch etch prim primer er-- wher wheree abov abovee two two opti option onss are are impractical. Aluminum: Sweep blast, Hand abrade – for thin guage aluminum an etch primer is used prior to intermediate and finish finish coats. Not to be blast cleaned. Chlorinated hydrocarbon solvent shall not be used. Etch primer – Polyvinyl butyl. Stainless steel: Sweep blast – only aluminum used as blasting medium
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What What is is roug rough h peak? peak? What What pro probl blem em can can it it caus cause? e? Roug Rougee Peak Peakss are are peak peaks, s, which which stand stand out out abov abovee the the requ requir ired ed profi profile le and shou should ld be avoi avoide ded d if applying thin coating as they may lead to spot or flash rusting.
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How How do you mea measur suree surfac surfacee profi profile le?? Expla Explain in the the metho method? d? The surfa surface ce profile profile may may be measure measured d by a number number of methods methods inclu including ding the the use of a surfac surfacee profile profile needle guage, surface replica tape (Testex tape) or a surface comparator. Surface Replica Tape: Testex tape or Press-O-Film is the commonly used surface replica tape. It is used in conjuction with a dial micrometer, micrometer, has the advantage of providing a permanent record. record. The procedure procedure for carrying out this text is as follows. Zero the micrometer ensuring the flat, contact points are clean. Remove paper backing and stick testex tape to the surface to be measured. 3. Rub the Testex Testex paste in to the thorough thorough using using a blunt blunt instrume instrument nt until peaks can be seen butting up up to the transpar transparent ent plastic. plastic. 4. Remov Removee the the teste testex x tape tape from from the surface surface and meas measur uree the overall overall thickne thickness ss with with dial dial micrometer 5. Deduct Deduct 50 mic from from the readin reading g to obtain obtain the amplitu amplitude. de. The plasti plasticc layer to which which the testex paste is attached is 50 mic thick.
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List List all Safety Safety Equi Equipme pment nt and clothin clothing g requir required ed for for open open site site blasti blasting? ng? Use of of Carbon Carbon impre impregnat gnated ed hosed hosed to reduc reducee the chance chance of of static static shock. shock. (Rei (Reinfor nforced ced)) Use of Deadmans handle for direct operator control Keep hoses straight as possible to prevent kinks, which may lead to a blow out. Use of external coupling. Liquid separator. Hypodermic needle guage – to control the nozzle pressure. Operator should wear protective clothing, including air fed helmet, boots, gloves, ear defender and leather apron. Warning signs at the area, barrier tape Keep the compressor pressure below 100 PSI
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Give Give the three three basic basic ingred ingredient ientss within within a solvent solvent carry carrying ing paint paint and and list the the job each each has to do? do? A traditi traditional onal solve solvent nt carrying carrying paint paint consi consists sts of three three basic basic ingre ingredient dients, s, these these are Binder- It binds the particles together and holds them in suspension, gives the paint its finish, makes the coating adhere to the surface, gives flexibility to the paint film, converts the coating to a solid dry film, give resistance to water, chemical and abrasion. Pigment Pigment – Gives colour to the paint, gives opacity to the paint, gives resistance resistance to acids, alkalis and light. Solvent – Forms the evaporative part of the drying process, thins the paint so it can be applied easily, washes out brushes and equipments, acts as a degreasing agent if approved.
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Name Name four four Bind Binder erss / Solve Solvent nt comb combina inati tion? on? Binder Solvent Strongest Epoxy Acetone high power Chlor. Rubber Xylene Alkyd Resin White spirit Weakest Emulsion paint Water low power
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Name Name six six opaque opaque pigm pigment ent and give their their respe respecti ctive ve colo colour? ur? Carbon – Black Compound of calcium – red, yellow Compound of cobalt – blue Compound of chromium – green, yellow, orange Compound of Iron – brown, red, yellow Titanium dioxide – white Rust inhibitive pigment (anti corrosive) Zinc chromate – Yellow Zinc phosphate – White Red lead – Red Coal Tar – Black Calcium plumbate – White Red Iron Oxide – Red Metallic Pigment May be used to anti corrosive properties or to give metallic finish. Cathodic Protection Zinc and Aluminum
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Name Name 5 paint paintss and and give give thei theirr dryi drying ng and and curing curing metho methods ds?? Emusio usion n – Coal oalesence nce Alkayd – Solvent evaporation followed by oxidation. Chlorinated Rubber – Solvent evaporation only. 2 pack Epoxy – Solvent evaporation followed by chemical curing Fusion bonded epoxy – Heat cured.
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Stat Statee at what what condi conditi tion on pai paint nt mus mustt be stor stored ed?? In a dry, dry, lockab lockable, le, well well ventil ventilated ated buil building ding away away from from any sourc sourcee of heat. heat. Materia Materiall should should be store stored d atleast 5 C below the flashpoint and current legislation and manufactures instruction should be followed.
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Name Name 5 methods methods of apply applying ing paints paints and and compare compare the the advantag advantages es and limit limitati ation on of each each method? method? Brush ap application: Advantages: Effective for applying primer as it works paint well into a substrate, which gives optimum coverage and mixes in any dust particles. Thus achieving optimum adhesion. Do not produce overspray, less environmental hazard, less wastage and less spotting. Limitation: Slow production, may not have uniform thickness, high quality brushes quite expensive.
Roller application: Advantage: Quicker than brush for large flat surfaces, with extension poles easy to access at elevated locations. Limitation: Non-uniform Non-uniform paint thickness thickness,, paint does not worked worked in to a surface, surface, some specs specs not permitting permitting roller roller applications. Conventional Spray: Advantage: Suitable for applying thin material, good finish, less operating pressure – move safe, less equipment and maintenance cost, less over spray, quicker than brush. Limitation: Less production, gravity fed guns to be operated at upright positions only, high viscous paint application not possible. Airless Spray: Advantage: Higher production (more quality production), highly viscous paint easily applied, more portable, uniform coating can be achieved, High DFT. Limitation: More wastage & over spray, higher equipment & maintenance cost, high risk of safety due to high pressure pressure operations. operations. Electro static spray: Advantage: More uniform thickness can be achieved, good finish, less over spray. Limitation: High equipment cost. Q A
Give Give 6 typ typee of anti antico corr rros osiv ivee prim primer er?? Zinc chromat omatee – Yellow Zinc phosphate – White Red Lead – Red Calcium Plumpate – White Red oxide – Red Coal Tar – Black
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State State the the advanta advantages ges of airless airless spray spray over over conve conventio ntional nal spray. spray. High High rate of produc productio tion, n, Uniform Uniform film film thick thicknes nesss can be achiev achieved, ed, less less fog & rebou rebound, nd, size size and angle angle of the tip can be easily control the quantity of flow and pattern, high viscous paint can be easily applied.
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Which Which paints paints have to be conside considered red when when brush brush painting painting?? Or Or What method of paint application is performed for primer and why? Primer Primerss have to be consid considere ered d when brush brush painti painting ng because because bushing bushing works works as as paint in in to a substrat substratee surface, which gives optimum coverage and mixes in any dust particles, thus achieving optimum adhesion.
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Defi De fine ne the the tie tie coa coatt and and giv givee an an exa examp mple le
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A coat coat of paint paint,, which which can tie two normal normally ly incomp incompat atibl iblee syst system emss toge togethe ther, r, (where (where adhesi adhesion on problem, problem, solvent stripping stripping or bleeding bleeding might might occur). occur). Example: Aluminum leafing primer for the application of alkyd over bitumen due to bleeding.
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Descri Describe be barri barrier er paint paint system system and sacrifi sacrificial cial paint paint coat coating? ing? Barr arrier ier Pai Paint nt Syst ystem: The substrate is isolated from the environment, which causes corrosion by using a coating of low permeability. permeability. This may be achieved achieved by applying a thick coat of paint having having low permeability. permeability. Eg. Epoxy, polyurethane Sacrificial Coatings: Sacrificial Sacrificial coating contain pigments, pigments, which cathodically cathodically protect the iron or steel substrate substrate to which the paint is adhered, these pigment particles eventually corrode thereby sacrificing themselves to corrosion. In order to have these these properly, the sacrificial pigment must be ignoble to the material to be coated. coated. Zinc and aluminum aluminum are the the most common common type type of pigments pigments employed employed..
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Descri Describe, be, what is Laminar Laminar Pigmen Pigmentt and and name name 4 pigme pigments nts?? Pigm Pigment entss having having a leafi leafing ng effect effect like fallen fallen leaves leaves overla overlappi pping ng each other other resul results ts in exce excell llent ent resistance to the passage of water, also create a very strong coating. MIO, mica, glass flakes and aluminum flakes are eg of laminar pigments.
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Define Define the term term Pot Pot Life, Life, shelf shelf life, life, induc inductio tion n perio period? d? Pot Life: The pot life is the maximum period of time after mixing in which the paint must be used, this can vary few minutes to few hours. Shelf life: The max. period of time a paint in good condition in its container before opening in its container before opening opening and recommended recommended by the the paint manufact manufacturer. urer. Induction Period: It is the min. period of time during which the mixed components are left to stand before use. This is to allow for the certain chemical reaction to take place and for the time allowed for air bubbles to escape. Induction periods are typically up to 30 minutes.
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What What does does a finen finenes esss of of gri grind nd gaug gaugee mea measu sure re?? The finen fineness ess of grind grind gauge gauge meas measure uress the degr degree ee of disp dispers ersion ion of of paint. paint. Also Also known known as Hegm Hegman an grind gauge.
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What What does does a cryptom cryptomete eterr measur measuree and and two two exampl examplee of crypt cryptome ometer ter?? A cryptom cryptomete eterr measur measures es the the opacity opacity or or hiding hiding powe powerr of paint paint poss possess esses. es. Pfund cryptometer Hiding power charts.
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What What deter determin mines es the the degre degreee of gloss gloss of of a paint paint may may poss posses? es? The The deg degre reee of of glo gloss ss dete determ rmin ined ed by Degree of pigment dispersion Size of pigment particles The pigment volume concentration Binder type – measured by gloss meter.
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What What is a flash flash point? point? Desc Describe ribe the the procedur proceduree for deter determin mining ing of flas flash h point. point. Flas Flash h point point is the minim minimum um tempe tempera ratu ture re at which which the the vapour vapour of a liqui liquid d will igni ignite te if an exte externa rnall source of ignition was introduced. Flash point determination determination of paints or solvents solvents may be carried out in accordance with BS 3900 part A9 using a closed cup of abel type Procedure: Fix the Abel cup containing the substance for the assessment into a water bath. Activate the source of ignition every ½ 0 C rise in temperature. Apply a heat source to the water bath and monitor the air/vapour temperature in the Abel Cup. The flash flash point point tempera temperature ture is identif identified ied when when a blue blue flame flame flashe flashess over the substanc substancee being being assessed.
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What What is densi density ty and and how do you you assess assess it? it? Give Give two two reas reason on for its use? use? Densit Density y is weight weight per per unit volume volume of a substa substance nce possess possess.. Density = mass / volume unit = gm/cc By using laboratory balance weigh the the cup to the nearest decigram with sensitivity of + 0.19 Remove the cover and fill with paint to within 2.5 mm of the brim. Carefully replace the cover so that air and any excess paint is expelled through the vent. Wipe off any surplus paint from the cover then reweigh. Determine the weight of the paint by subtraction. Divide the weight by 100 if the density in g/cc is required. Purpose: To determine whether two pack paints have been mixed in the correct proportions. This procedure can be used to determine the quantity of any added thinner.
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What What is Viscos Viscosity ity and and what equipm equipment ent is used used to meas measure ure visco viscosit sity y of the free free flowing flowing paint paint and and thixotropic paint? Visc Viscosi osity ty is a measu measure re of a fluid’ fluid’ss resis resista tance nce to flow flow.. Visc Viscos osit ity y of free flow flowing ing paint paintss can be measured by using a flow cup, there are many types including Ford cup, red wood and Zohn flow cups. Procedure for measuring viscosity using a Ford cup No. 4. Bring temperature of paint to within 20 + 0.50 Level the apparatus, then with the end of one finger over the orifice of the cup rapidly fill it with paint. Allow a moment for air bubbles to rise, then draw a flat edge across the top of the cup to wipe off the paint level with the edges. Remove the finger from the orifice and start the Stop watch simultaneously with the commencement of the paint stream. The watch is stopped when the first distinctive break in the paint stream occurs. The time in seconds is taken as the Viscosity. For thixotropic paints, the viscosity can be measured by a rotation. Viscometer or another type of Viscome Viscometer ter,, which which works works the paints. paints. (Kerb(Kerb-sto storme rmerr viscome viscometer ter,, cone and plate plate viscom viscomete eterr and rotathinner)
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What What is speci specific fic gravit gravity y and how is testin testing g for speci specific fic grav gravity ity carri carried ed out? out? Relative Relative density density or specific specific gravity gravity is is the density of any substance substance compared compared to the the density density of of water. water. Specific gravity = density of given substance Density of water
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Name Name 3 adhes adhesion ion tests tests and and descr describe ibe how how one of them them is is carri carried ed out? out? Adhesio Adhesion n is the the force force that resist resistss the separa separatio tion n of two two surface surfacess in contac contact. t. 1. Cross cut test. 2. Cross hatch. 3. Dolly test (pull of adhesion test) Procedures for pull of adhesion test: Clean and degrease the surface to be tested. Roughen the surface with fine/medium gr. Emery cloth. Mix regular araldite and stick dolly to the surface, leave for 24 hrs at 25 0 C Cut paint around the dolly down to the substrate using a special cutter. Attach pull off instrument and apply pulling force. Test result requires careful interpretation; interpretation; some normal values obtained for acceptable acceptable adhesion are as follows. 1500 psi – epoxy based systems 3000 psi – alkyl based systems 12000 psi – Zinc etch primer
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Name Name 4 artifi artificial cial weath weatheri ering ng device device and and what what are these these desi designe gned d to stimul stimulate ate?? Arti Artific ficia iall we weat ather hering ing device devicess are are desi designe gned d to create create accele accelerat rated ed we weat athe heri ring ng to speed speed up to the duration of different test to be carried out to determine the coating systems behaviour at specific condition. Tropical box – to simulate high humidity environment Salt spray box – simulates a marine environment Water soak test – to asses paint systems resistance to water absorption. Cold check test – test for low temperature contraction cracking. Temp. Cycling – to assess film flexibility at alternate hot & cold temperature.
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Stat Statee 2 drying drying cur curing ing tes tests ts and and how how they they are are oper operat ated ed?? Ballotini te test: Tiny glass balls balls known as ballotini, ballotini, are allowed to fall on to a freshly painted best panel. panel. The test panel moves slowly beneath the falling ballotini ballotini over a preset period of time; the time of the test is variable and the speed can be adjusted so that a panel 300 mm long can take between 1 to 24 hour to test, where the ballotini fails to stick, to the painted panel drying has occurred. Stylus test: The stylus test employes a series of trailing needles which pass over the wet painted panel, because the needles are set at different tensions it can be established when the paint is in tack dry, hard dry and fully cured.
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What What is WFT? WFT? How How does does you you measur measuree it? What What are are the the advanta advantages ges of of using using it? it? Wet film film thick thickness ness is is the thickn thickness ess meas measured ured imme immediat diately ely after after a coati coating ng has been been applied. applied. The wet wet film thickness may be found by using a comb gauge or an eccentric wheel.
Procedure for measuring WFT using a comb gauge: Immediately after the application of paint the comb gauge should be firmly placed on to the surface in such a way the teeth are normal to the plane of the surface. The gauge should then be removed removed and the teeth examined in order to determine the shortest one to
touch the wet film. The film should should be recorded as lying between the last touching tooth tooth and first non-touching tooth. Atleast two further readings should be taken in different places, in a similar manner, in order to obtain representative results over the painted area. Advantages: If the WFT is known, any deviation from the specified thickness range can be immediately rectified. If the WFT is known, the approximate DFT can be calculated if the volume of solid is known. DFT = WFT x VS / 100. Q A
What What is DFT? DFT? Stat Statee the the prin princi cipl plee of being being able able to use a bana banana na gauge gauge for taki taking ng DFT? DFT? State State calibration procedure for a banana gauge? DFT is the dry film thickness of the coated surface and is measured in microns. The banana gauge is only used for measuring the thickness of non-ferromagnetic coating applied over a ferromagnetic substrate. Calibration Procedures: Choose a magnetically insulated shim of known thickness, close to the thickness of the paint you expect to find. Place the shim on the same substrate surface finish as the surface finish on which the paint to be measured is attached. For eg, if the paint is on a basted surface, calibrate the gauge on a uncoated blasted blasted surface. surface. Place the magnet on the shim and press firmly on the instrument, wind the scale wheel forward (away from yourself) until the magnet is definitely attached to the shim/substrate. Gradually Gradually wind the wheel wheel backwards backwards slowly slowly until the the magnet detaches detaches itself. itself. At this point, point, move the curser on the instrument instrument to the thickness thickness of the shim as shown on the scale wheel. With some some instrument the scale itself may be moved to line up with fixed cursor. The instrument is now calibrated and may be used to measure the DFT of any non magnetic film to within a claimed accuracy of + 5% in some cases.
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Descri Describe be a destru destructiv ctivee test test for for dete determi rmining ning the DFT of paint paint?? Pain Paintt Insp Inspec ecto tors rs Gaug Gaugee (PIG (PIG)) Paint inspector guage is one such type of destructive test gauge. A small V shaped channel is cut into the coating at a fixed angle governed by a cutter built into the gauge. The width of the channel is then measured on a gratitude scale by means of a microscope which is again built in to the instrument.
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How How do do you you calc calcul ulat atee DFT DFT,, WFT WFT & VS% VS% DFT = VS% x WFT / 100 WFT = DFT x 100 / VS% VS% = DFT x 100 / WFT
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Descri Desc ribe be the the cat cathod hodic ic disbon disbondm dmen entt tes test: t: If the impre impresse ssed d current current exceeds exceeds the corro corrosio sion n current, current, hydro hydrogen gen gas bubble bubbless are evolved evolved from from the metal substrate substrate ie at the interface between the material material and coating. This is a significant significant problem when curing defects are present due to a stripping action caused by the hydrogen bubbles, the coating disbondment is known as cathodic disbondment.
The test incorporates a coated test panel with hole drilled into the coating; this simulates a paint film defect. Surrounding the hole a plastic tube is glued down and filled with sodium chloride solution to act as an electrolyte. electrolyte. Wires from from a battery are attached attached to the panel and to a metal rod set into the liquid of plastic tube; a current is then impressed to make the panel cathodic. The coating is assessed after a period of time. (eg) a few weeks, for the amount of stripping which has occurred from the boundary of the hole. Q A
Name Name 3 envir environm onmen enta tall condi conditi tions ons when when would would you stop stop paint painting ing?? Or When When shall shall coating coating not be applied. 3 Envir Environm onmen enta tall condi conditi tions ons:: Rain Rain,, Snow Snow & high high wind wind.. It is not permissible to apply paint when the following condition apply: During rain, snow or high wind. When the air or metal temperature is down to within 30C of the dew point temperature. When the relative humidity is above 90%.
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Why are the the enviro environme nmental ntal test test carr carried ied out out during during a painti painting ng project project?? In order order to verify verify the weathe weatherr conditio conditions ns are accept acceptable able to the the specific specificatio ation n to carry out out the painting painting operation.
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Expla Explain in RH, RH, DP, DP, Ambi Ambient ent tem temp p and ste steel el temp temper eratu ature re?? RH:: Relative RH Relative humid humidity ity is the the amount amount of wate waterr vapour vapour in the air air express expressed ed in a percenta percentage. ge. DP: Dew point is the temperature at which condensation would form on a surface. Ambient Temp: it is the surrounding air temperature also referred as dry bulb temperature. Steel Steel Temperat Temperature: ure: it is the temperat temperature ure of the substra substrate te prior to paintin painting. g. (Magnet (Magnetic ic steel steel thermometer, digital thermometer).
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Expla Explain in how how envir environm onmen enta tall test test are carr carrie ied d out? out? What What equip equipme ment nt is used used to find find RH and and DP? Explain its use? Environ Environment mental al conditi conditions ons like like RH and dew dew point are are measure measured d using a hygrome hygrometer ter of which which there there are many types. The whirling hygrometer consists of two two mercury thermometer set side by side in a frame which is provided with a handle and spindle so that the frame and thermometer can rotated quickly about a horizontal axis. axis. The bulb of one thermometer thermometer is called Wet bulb thermometer. thermometer. It is covered with a closely fitted cylindrical cotton wick, the end of which dips into distilled water or clean rain water contained in a small cylinder attached to the end of the frame. The frame is rotated by hand for 30 to 40 seconds as fast as possible so that the bulbs pass through air at least 4 m/s. This causes the water to evaporate from the wet bulb. The wet bulb cools down to a constant wet bulb temperature temperature due to the evaporation evaporation rate of water from the wet wick. Always Always read the wet bulb temperature before dry bulb temperature temperature immediately immediately after the rotation. Repeat the operation until consecutive readings of each bulb temperature agree to with 0.20C. If it is 100% RH, the wet bulb will be same temperature, because no evaporation can occur, i.e. the air is saturated. saturated. If wet bulb and dry bulb temperature temperature are the same the current current temperature temperature is the dew point. The R.H and dew point point can not be read directly directly from the the apparatus, apparatus, hygrometer hygrometer tables or special slide rules must be used.
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What does BS 2015 - GLOSSARY OF PAINT TERMS refers to and give three examples? Faults, Faults, which which occur occur with with paint paints, s, are are describ described ed in BS BS 2015 – GLOS GLOSSAR SARY Y OF PAINT PAINT TERM TERMS. S. These faults are due to three main caused. 1. Fault Fault “in the the can”. can”. (Manuf (Manufact acturi uring ng fault faults) s) 2. Problem Problem,, which which occur occur due due to poor prepara preparation tion..
3. Problem, Problem, which occur occur due incorrec incorrectt or poor application application or interfer interference ence by weather. weather. Examples: Bleeding: The action of a material in penetrating and discolouring a coating applied on top of it. Blistering: Blistering: The formation of dome shaped blister in a paint film. They can be dry blisters blisters which are usually caused by the expansion and contraction of the paint film against the substrate or Osmetric blister blister which can be caused by water/solvent water/solvent entrapment entrapment or hygroscopic salts let on a blast cleaned surface. Chalk Chalking ing:: The brea breaki king ng down down of a paint paint film film to becom becomee chalk chalky y or powde powdery ry usual usually ly due to disintegration of the binder caused by attack from UV light or severe weather condition. Q A
What What is BS 4800 4800,, and how it is is used used in in const construc ruction tion industr industry? y? BS 4800 4800 Paint colou colours rs for for building building purpo purpose se specif specifies ies 100 100 colours colours which which have been been selecte selected d from the the frame work of the 237 colours contained in BS 5252. Each colour in BS 4800 is identified by three as follows: HUE: The first part signifies HUE or colour and consists of an even number of two numerals and 12 main hues are used and numbered 02 – Red Purple 14 – Greens 04 – Reds 16 – Green Blues 06 – Yellow Reds 18 – Blues 08 – Yellow Reds 20 – Purple Blues 10 – Yellows 22 – Violets 12 – Yellow Greens 24 – Purples GREYNESS: The second part signifies greyness, i.e. the apparent amount of difference in greyness between one colour with another. Five grades are used, each defined by by a letter. A B C D E
- Max. Greyness - Min. greyness - Pure – No greyness
WEIGHT: (Saturation) Colours Colours of similar similar hue and greyness greyness may differ differ in colour brightness brightness or intensity intensity of colour. colour. This quality termed as saturation, may be defined as the intensity of any particular hue when compared with a neutral grey of similar lightless of the spectrum colours being the most intense or of highest saturation. * The weight is given given in pairs of numbers from from 01 to 56. Groups of colours colours within within each of the five greyness ranges are graduated high to low value. Each of these graduation is numbered; A Greyness – 01 to 13 B Greyness Greyness – 15 to 29 C Greyness Greyness – 31 to 40 D Greyness – 43 to 45
E Greyness – 49 to 56 BS 4800 – can be used to identify existing colours when maintenance painting and is a method by which all manufactures can make exactly the same colours. Q A
How How do do Bga Bgass def defin inee the the foll follow owin ing? g? New galvanizing: A galvanized steed surface upon which cohesive oxide layer has not yet formed. (bright & shiny, less than 3 months old) Weather Galvanizing: A galvanized steel surface upon which a Cohesive oxide layer has formed by natural weathering (dull & lacking in shine) Long Term Protection: The estimated period for the corrosion protection is typically 10 years. Medium Term Protection: Typically 5 years. Short Term Protection: Typically 2 – 3 years.
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What What is the procedu procedure re for remov removing ing oil, oil, grease grease form a subst substrate rate after after prepar preparati ation on has taken taken place? place? If oil oil or grease grease is found found on on a surface surface after after it has has been been prepare prepared d that area area must must be swabbe swabbed d with an approved solvent followed followed by a 2% detergent detergent wash, washing with clean water, water, thorough thorough drying and reblasting.
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What What is proced procedure ure for remo removing ving oil, oil, grease grease from from a surface surface befor beforee preparat preparation ion comme commences nces?? Small Small areas areas of oil and and grease grease shall shall be remove removed d with an appro approved ved solve solvent, nt, where where as large large areas areas can can be given to low pressure detergent washing, which must be followed by rinsing with clean water and thorough drying.
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What What is the the procedu procedure re for for remov removing ing algae algae & mould mould growt growth h from from pipe pipe work? work? Algae Algae and mould mould grown grown shal shalll be treated treated with with a biocid biocidal al agent agent and left left for 24 24 hour atle atleast ast in orde order r that biocide can kill the spores. It shall then be removed removed by scrubbing with stiff bristle bristle brushes and clean water or by use of high-pressure water wash.
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What What dista distance nce must must be left left at areas areas to be weld welded ed when when painti painting? ng? For Zinc rich rich paint paint 75mm 75mm shall shall be be left left from from the end prep prepara aration tion..
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How How much much new pai paint nt ove overl rlap ap requi require red d over over old old repai repair? r? Minimum 100 mm.
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What What must must pneumat pneumatical ically ly and elect electrica rically lly opera operated ted power power tool tool equipm equipment ent be? be? All equi equipmen pmentt whethe whetherr electri electricall cally y or pneumat pneumatical ically ly operate operated d shall shall be earthed earthed.. All equip equipment mentss shall shall be non-spark non-spark and flame flame proof. proof.
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What What type of sheeti sheeting ng may may or may may not be used used for for protec protection tion agai against nst spill spillage age & spott spotting? ing? Sheeting Sheeting of a non-fl non-flamm ammabl ablee nature nature must be empl employed oyed to prote protect ct areas areas against against spilla spillage ge & spottin spotting. g. Tarpaulins must not be used.
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What What area areass of of wor work, k, do do PA PA 10 10 not not cov cover er?? PA 10 10 not not cove covers rs paint painting ing work work of of the the fol follo lowi wing ng:: Below ground (buried), offshore installations, internal coating of pipes & store enamel coating.
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What is BS 7079?
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Prepara Preparatio tion n of steel steel substrat substrates es before before applica applicatio tion n of paints paints and rela related ted product products. s.
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What is BS 39 3900 & BS 48 4800? BS 3900 3900 – Met Metho hod d of of tes testt for for pain paints ts BS 4800 – Specification for paint colours for building purposes.
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What is BS 54 5493 & 5750 BS 5493 5493 – Code Code of pract practice ice for for protec protective tive coati coating ng of iron iron and and steel steel stru structur cture. e. BS 5750 –
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As an an Inspect Inspector or what what do you consid consider er as your main main responsi responsibili bilitie ties? s? To assess assess the conditi condition on of subst substrate rate prior prior to to treat treatment ment.. To inspect surface preparation in accordance with BS 7079; measure and record amplitude once daily. To ensure material used on site are to client specifications. Relative Humidity, dew point, air temperature and steel temperature to be checked and recorded at least four times daily. Wet and dry film thickness to be checked and recorded at frequent intervals. To witness and inspect application of each coat and inspect competed paint system in accordance with the client’s specifications. To submit daily and weekly reports, recording all the relevant information as required by client. Copies to be retained by the inspector.
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Paint Faults? Bleeding: Discolouration of newly painted surface due to inter penetration of substances by natural movements Rust Blooming: First stage of corrosion process Blistering: Formation of done shaped blisters or projection in paints in the dry film of a coating material by local loss of adhesion and lifting of the film from the underlying surface. Chalking: The formation of friable (easily give away) powdery coating, on the painted surface caused by disintegration of the binder medium due to ultra violet or moister. Cheeking: Cracking that compress fine cracks which do not penetrate the topcoat and are distributed over the surface giving the resemblance of a small pattern. Cissing: Due to contamination, the wet paint try to slope backwards from small areas of the surface leaving no coating. Cratering: The formation of small bowl shaped depression in the film of a coating material. Crazing: Cracking that resembles checking but the cracks are deeper and broader.
Cracking: Generally the splitting of a dry paint or varnish film usually as a result of ageing. Dry Spray: The production of a rough or slightly bitty film from sprayed coating material where the particle are insufficiently fluid to flow together to form a uniform coating. Flaking: Lifting of the coating material from the substrate in the form of flakes or scales. Flocculation: The development of loosely coherent solid aggregates in a pigment – vehicle dispersion. Which will not mix back even after re-stirring. Grinning: The showing through of the substrate due to the inadequate opacity (hiding power) of a paint film which has applied to it. Holidays: Missed or poorly coated areas on a painted surface. Chemical Curing: A part from the oxidation, oxidation, paint are cured cured due to the presents of a catalyst in the paint when when they mix together. Lifting: Failure caused by the swelling of a dry film of paint or varnish when another coat is applied over it. It may due to stronger solvent, when new coat is applied over the old one. Orange Peel: The uniform pock marked appearance in particular of a sprayed film resembles the peel of an orange due to the failure of the film to flow out to a level surface. Osmotic blister: Formation of dome shaped blister, which can be caused by water entrapment solvent entrapment, or hygroscopic salts left on a blast-cleaned surface. Pin holing: The formation of minute holes down through a paint coating caused by escaping air bubbles. Ropiness: (Brush Marks) A finish in which the brush marks have not flowed out, or due to continuing to brush the paint after the film has begun to set. Saporification: The formation of soap by the reaction between a fatty acid ester and an alkali. Wrinkling: The development of wrinkles in a film – a coating material during drying mainly due to the initial formation of a surface skin. Compliant Coating: A coating which complies with the environmental protection act of 1990.
Fully Weathered Galvanising: A galvanized steel surface upon which a cohesive oxide layer has formed by natural weathering. Dew Point: The temperature at which condensation would form on a substrate. Relative Humidity : The amount of water vapour in the air expressed as a percentage. Induction period : The length of time a paint is required to stand after mixing and before application. This time allows air bubbles to escape and chemical reaction to take place and is specified by the paint manufacturer. Pot life: The length of time that a paint remains in a applicable condition according to the manufacturers instruction. T wash: An etch primer primer for zinc metal surface surfaces. s. Blue in colour colour it turns turns black upon drying drying if it has been applied successfully. Sheeting for protection: Sheeting of a non-flammable nature must be employed to protect areas not being prepared or painted from contamination. Masking out: Cover out items which is not to be prepared and painted. Oxidation: After the painting, when the surface is coming in to contact with the oxygen the binder polymerized and form a strong layer. A.G.I.: Above ground installations.
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What is Bgas PA PA-9 Refers Refers to paint paint propert properties ies and perform performance ance require requirement ments. s.
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What is Bgas PA PA10 Refers Refers to the the technica technicall specifica specificatio tion n for New and and Mainten Maintenance ance Painti Painting ng at works works and site site for above above ground pipeline and plant installations.
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Condi Conditi tions ons for final final surf surfac acee prep prepar arat ation ion.. When When condit conditio ions ns in the worki working ng area area are are such that that metal metal surf surfac aces es are mois moist, t, damp damp or we wet, t, final final preparation preparation shall shall not be carried carried out. out. Any surface preparation, procedure or method of cleaning shall not be allowed to contaminate wet paint film. film. Equipment used shall be of non-sparking type. Electrically operated tools are not permitted.
Power tools operated by compressed air shall have oil and vapour trap fitted to the compressed air lines. All contaminants shall be removed by means of an approved solvent. Algae and mould growth when in evidence shall be treated with a biocidal agent and left for atleast 24 hrs in order that the biocide can kill the spores. spores. It shall then be removed removed by scrubbing with with stiff bristle bristle brushes and clean clean water or by use of a high pressure pressure water water wash. wash. All surfaces shall normally be dry before painting commences. Q A
What What docum document ent state state healt health h & safe safety ty at at wor work? k? Healt He alth h and Safe Safety ty at at Wor Work k act act 1974 1974 – (H.A (H.A.S .S.W .W.A .A))
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What What yea yearr was was the the Hea Healt lth h & Safe Safety ty Act Act pas passe sed? d? The contr control ol of subst substance ancess hazardou hazardouss to health health regu regulati lations ons 1988 1988 came came into forc forcee on 1st October, 1989. (COSHH regulation).
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How How long long woul would d recor records ds of per perso sonne nnell expos exposed ed be kep kept? t? Employe Employers rs must must keep records records of exami examinati nation/ on/ monit monitori oring ng test for for 5 years; years; 30 yrs for identi identifiab fiable le employees.
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EPA & VOC Environ Environment mental al Protect Protection ion Act & Volat Volatile ile Organic Organic Compou Compound nd
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What What is the differe difference nce betwe between en thermo thermoset setting ting & therm thermo o plasti plastic. c. Paint Paint which which melt melt when when heat heat is applied applied are are known known as as thermo thermoplas plastic tic coati coatings. ngs. Coating which do not melt after the application of heat is known as thermo set coating.
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What What is impres impressed sed curr current ent and and what what problem problem can can arise arise from from its its incorr incorrect ect use? use? Impres Impressed sed curre current nt is a type type of Catho Cathodic dic protec protectio tion n system system e.g. e.g. Used Used for large large areas areas of pipes. pipes. If the the impressed current exceeds the corrosion & current, hydrogen gas bubbles are evolved from the metal substrate substrate i.e. at the interface between between the material and the coating. This is a significant significant problem when curing defects are present due to a stripping action caused by the hydrogen bubbles leads coating disbondment is known as cathodic disbondment.
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What What do B.Ga B.Gass clas classs as as a hot duty duty serv service ice?? Metal Metal sur surfa face cess that that will will reac reach h a temper temperatu ature re in exc exces esss of 990C when in service is classed as hot duty service.
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Adva Advanta ntage ge & Disa Disadva dvant ntage age of Polyu Polyure retha thane ne Polyu Polyure rethe thene ne fini finish sh coats coats are ofte often n used used to repla replace ce epoxy epoxy fini finish sh coats. coats. They have have the the follo followi wing ng qualities: High Gloss, Retain the gloss, Hold the colour, Abrasion resistance, Easily cleaned, Good resistance to UV Light, chemical and weather resistant, Cures down to 00C. Disadvantages: Two Component May cause skin problem
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Adva Advant ntag agee & Disad isadva vant ntag agee of of Epo Epoxy xy Advantage More Flexible Used on Damp surfaces Chemically cured and hard Mechanical resistance
Disadvantage It is difficult to over coat Poor UV resistant, chalk in sunlight Temp Dependent. Epoxy is not cured by oxidizing. Cured by chemical reaction between two components. Q A
What additional additional informat information ion you should when maintenance maintenance painting painting a pipeline pipeline without without removing removing the existing coating? The follow following ing additio additional nal inform informatio ation n to to be recorde recorded d are: are: Nature of of the existing existing system system must must be establis established hed to decide decide the type type of preparatio preparation n to be carried carried out. out. Amount of surface contamination. Extent of paint breaks down. Extent of corrosion Compatibility Compatibility of the existing existing system with the new system. system. If not compatible compatible select the appropriate appropriate Tie-coat. In service environmental condition.
