COATING QA

Question & Answers for Coating Exams Q A

What kind of process is corrosion? Corrosion is an electrochemical process.

Q A

Define corrosion? Why do uncoated steel structures corrode? Corrosion is an electrochemical process. In practical terms; iron ore is an oxide of iron in chemical balance with atmosphere, following 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.

Q A

What factors influence the rate of corrosion? Variation in oxygen content on the material surface. Chlorides and sulfides, higher nobility materials being in contact with iron, acids, and alkalis.

Q A

What is a mill scale, and why is it a particular problem with attempting to protect steel? When ferrous metal is forged into flat plates, beams and girders. It is worked at temperature 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 take place; mill scale is noble to steel therefore in close contact with each other steel will corrode.

Q A

What particular problems relate to the splash zone? The area of the materials, which are neither in water nor in air due to waves, high tide and low tide etc are splash zone. There is variation in oxygen level on the surface of the material, due to medium change. Corrosion rate can be accelerated due to this reason.

Q

What is the number of the Swedish standard contained within BS 7079 and list the rust and blasting grades together with their brief titles? The Swedish pictorial standard 05-59-00 is contained with B.S. 7079 Preparation of Steel Substrates Prior to the application of paint and related products.

A

The Swedish standard gives visual information on the following: Rust Grades: - which depict the condition of steel before preparation. A. Covered in mill scale with little or no rust. B. A mixture of mill scale and rust. C. Mill scale gone, rusted with slight surface pitting. D. Heavily rusted and 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)

Q A

List blast cleaning surface. Give a comparison of blasting grades to SSPC, BS 7079, BS 4232 and NACE? SA. 1 – Light Blast cleaning When viewed without magnification, the surface shall be free from visible oil, grease, dirt and from poorly adhering millscale. SA 2 – Thorough Blast cleaning When viewed without magnification, the surface shall be free from oil, grease, dirt and from most of the millscale, rust, paint coating and foreign matter. Any residual 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, rust, paint coatings and foreign matters. Any remaining traces of 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, rust, paint coatings and foreign matter. It shall have a uniform metallic colour. Comparison of Blasting Grades SSPC White metal (SP 5) Near white metal (SP 10) Commercial finish Light blast & Brush off

BS – 7079 SA 3 SA 2 ½ SA 2 SA 1

BS - 4232 Ist Quality 2nd Quality 3rd Quality N/A

NACE Grade 1 Grade 2 Grade 3 Grade 4

Q A

What factor influence how clean and how rough the surface becomes after blast cleaning? The cleanliness of the steel surface and its amplitude are governed by the abrasive characteristics and human factors as follows: ABRASIVE HUMAN FACTORS Size Speed Shape Angle Density Distance Hardness Time

Q A

Give the essential requirements for abrasive blasting? The equipment required including safety features as follows: Compressor – providing air supply – 100 psi Pressurized pot – containing abrasive Liquid separator i.e. moisture filter Carbon impregnated hoses & external coupling Deadmans handle for direct operator control Blasting nozzle (venturi shaped) Personnel equipment – Air filled helmet, ear defender, boots, gloves & leather apron.

Q A

Some metals are hard to prepare and paint? Name three and how you might prepare them? New Galvanizing: Sweep blasting, hand abrade, etch primer- where above two options are impractical. Aluminum: Sweep blast, Hand abrade – for thin guage aluminum, an etch primer is used prior to intermediate and 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

Q A

What is rough peak? What problem can it cause? Rouge Peaks are peaks, which stand out above the required profile and should be avoided if applying thin coating as they may lead to spot or flash rusting.

Q A

How do you measure surface profile? Explain the method? The surface profile may be measured by a number of methods including the use of a surface 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, has the advantage of providing a permanent record. The 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 paste in to the thorough using a blunt instrument until peaks can be seen butting up to the transparent plastic. 4. Remove the testex tape from the surface and measure the overall thickness with dial micrometer 5. Deduct 50 microns from the reading to obtain the amplitude. The plastic layer to which the testex paste is attached is 50 microns thick.

Q A

List all Safety Equipment and clothing required for open site blasting? Use of Carbon impregnated hosed to reduce the chance of static shock. (Reinforced) 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

Q A

Give the three basic ingredients within a solvent carrying paint and list the job each has to do? A traditional solvent carrying paint consists of three basic ingredients, 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 – Gives colour to the paint, gives opacity to the paint, gives 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.

Q A

Name four Binders / Solvent combination? Binder Solvent Strongest Epoxy Acetone high power Chlor. Rubber Xylene Alkyd Resin White spirit Weakest Emulsion paint Water low power

Q A

Name six opaque pigments and give their respective colour? 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

Q A

Name 5 paints and give their drying and curing methods? Emulsion – Coalescence Alkyds – Solvent evaporation followed by oxidation. Chlorinated Rubber – Solvent evaporation only. 2 pack Epoxy – Solvent evaporation followed by chemical curing Fusion bonded epoxy – Heat cured.

Q A

State at what condition paint must be stored? In a dry, lockable, well ventilated building away from any source of heat. Material should be stored at least 5 C below the flashpoint and current legislation and manufactures instruction should be followed.

Q A

Name 5 methods of applying paints and compare the advantages and limitation of each method? Brush 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 paint thickness, paint does not worked in to a surface, some specs not permitting 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 operations. Electro static spray: Advantage: More uniform thickness can be achieved, good finish, less over spray. Limitation: High equipment cost. Q A

Give 6 type of anticorrosive primer? Zinc chromate – Yellow Zinc phosphate – White Red Lead – Red Calcium Plumbate – White Red oxide – Red Coal Tar – Black

Q A

State the advantages of airless spray over conventional spray. High rate of production, Uniform film thickness can be achieved, less fog & rebound, size and angle of the tip can be easily control the quantity of flow and pattern, high viscous paint can be easily applied.

Q

Which paints have to be considered when brush painting? Or What method of paint application is performed for primer and why? Primers have to be considered when brush painting because bushing works as paint in to a substrate surface, which gives optimum coverage and mixes in any dust particles, thus achieving optimum adhesion.

A

Q A

Define the tie coat and give an example A coat of paint, which can tie two normally incompatible systems together, (where adhesion problem, solvent stripping or bleeding might occur). Example: Aluminum leafing primer for the application of alkyd over bitumen due to bleeding.

Q A

Describe barrier paint system and sacrificial paint coating? Barrier Paint System: The substrate is isolated from the environment, which causes corrosion by using a coating of low permeability. This may be achieved by applying a thick coat of paint having low permeability. Eg. Epoxy, polyurethane Sacrificial Coatings: Sacrificial coating contain pigments, which cathodically protect the iron or steel substrate to which the paint is adhered, these pigment particles eventually corrode thereby sacrificing themselves to corrosion. In order to have these properly, the sacrificial pigment must be ignoble to the material to be coated. Zinc and aluminum are the most common type of pigments employed.

Q A

Describe, what is Laminar Pigment and name 4 pigments? Pigments having a leafing effect like fallen leaves overlapping each other results in excellent resistance to the passage of water also create a very strong coating. MIO, mica, glass flakes and aluminum flakes are eg of laminar pigments.

Q A

Define the term Pot Life, shelf life, and induction period? 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 paint in good condition in its container before opening in its container before opening and recommended by the paint manufacturer. 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.

Q A

What does a fineness of grind gauge measure? The fineness of grind gauge measures the degree of dispersion of paint. Also known as Hegman grind gauge.

Q A

What does a crypto meter measure and two example of crypto meter? A crypto meter measures the opacity or hiding power of paint possesses. Pfund crypto meter Hiding power charts.

Q A

What determines the degree of gloss of a paint may posses? The degree of gloss determined by Degree of pigment dispersion Size of pigment particles The pigment volume concentration Binder type – measured by gloss meter.

Q A

What is a flash point? Describe the procedure for determining of flash point. Flash point is the minimum temperature at which the vapour of a liquid will ignite if an external source of ignition was introduced. Flash point determination of paints or 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 point temperature is identified when a blue flame flashes over the substance being assessed.

Q A

What is density and how do you assess it? Give two reason for its use? Density is weight per unit volume of a substance possess. Density = mass / volume unit = gm/cc By using laboratory balance weigh 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 are 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.

Q A

What is Viscosity and what equipment is used to measure viscosity of the free flowing paint and thixotropic paint? Viscosity is a measure of a fluid’s resistance to flow. Viscosity of free flowing paints can be measured by using a flow cup, there are many types including Ford cup, red wood and Zahn 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, and 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 Viscometer, which works the paints. (Kerb-stormer viscometer, cone and plate viscometer and rotathinner)

Q A

What is specific gravity and how is testing for specific gravity carried out? Relative density or specific gravity is the density of any substance compared to the density of water. Specific gravity = density of given substance Density of water

Q A

Name 3 adhesion tests and describe how one of them is carried out? Adhesion is the force that resists the separation of two surfaces in contact. 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 250 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; some normal values obtained for acceptable adhesion are as follows. 1500 psi – epoxy based systems 3000 psi – alkyl based systems 12000 psi – Zinc etch primer

Q A

Name 4 artificial weathering devices and what are these designed to stimulate? Artificial weathering devices are designed to create accelerated weathering to 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.

Q A

State 2 drying curing tests and how they are operated? Ballotini test: Tiny glass balls known as ballotini are allowed to fall on to a freshly painted best panel. The test panel moves slowly beneath the falling 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 employs 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.

Q A

What is WFT? How do you measure it? What are the advantages of using it? Wet film thickness is the thickness measured immediately after a coating has been applied. The 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 and the teeth examined in order to determine the shortest one to touch the wet film. The film should be recorded as lying between the last touching 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 is DFT? State the principle of being able to use a banana gauge for taking DFT? 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 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 wind the wheel backwards slowly until the magnet detaches itself. At this point, move the curser on the instrument to the thickness of the shim as shown on the scale wheel. With 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.

Q A

Describe a destructive test for determining the DFT of paint? Paint Inspectors Gauge (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.

Q A

How do you calculate DFT, WFT & VS% DFT = VS% x WFT / 100 WFT = DFT x 100 / VS% VS% = DFT x 100 / WFT

Q A

Describe the cathodic disbondment test: If the impressed current exceeds the corrosion current, hydrogen gas bubbles are evolved from the

metal substrate i.e. at the interface between the material and coating. This is a 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. Wires from a battery are 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 3 environmental conditions when would you stop painting? Or When shall coating not be applied. 3 Environmental conditions: Rain, Snow & high 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%.

Q A

Why are the environmental test carried out during a painting project? In order to verify the weather conditions are acceptable to the specification to carry out the painting operation.

Q A

Explain RH, DP, Ambient temp and steel temperature? RH: Relative humidity is the amount of water vapour in the air expressed as a percentage. 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 Temperature: it is the temperature of the substrate prior to painting. (Magnetic steel thermometer, digital thermometer).

Q

Explain how environmental test are carried out? What equipment is used to find RH and DP? Explain its use? Environmental conditions like RH and dew point are measured using a hygrometer of which there are many types. The whirling hygrometer consists of 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. The bulb of one thermometer is called Wet bulb 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 due to the evaporation rate of water from the wet wick. Always read the wet bulb temperature before dry bulb temperature 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. If wet bulb and dry bulb temperature are the same the current temperature is the dew point. The R.H and dew point can not be read directly from the apparatus, hygrometer tables or special slide rules must be used.

A

Q A

What does BS 2015 - GLOSSARY OF PAINT TERMS refers to and give three examples? Faults, which occur with paints, are described in BS 2015 – GLOSSARY OF PAINT TERMS.

These faults are due to three main caused. 1. Fault “in the can”. (Manufacturing faults) 2. Problem, which occur due to poor preparation. 3. Problem, which occur due incorrect or poor application or interference by weather. Examples: Bleeding: The action of a material in penetrating and discoloring a coating applied on top of it. Blistering: The formation of dome shaped blister in a paint film. They can be dry blisters which are usually caused by the expansion and contraction of the paint film against the substrate or Osmotic blister which can be caused by water/solvent entrapment or hygroscopic salts let on a blast cleaned surface. Chalking: The breaking down of a paint film to become chalky or powdery usually due to disintegration of the binder caused by attack from UV light or severe weather condition. Q A

What is BS 4800, and how it is used in construction industry? BS 4800 Paint colours for building purpose specify 100 colours which have been selected from 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 other colors. Five grades are used, each defined by a letter. A - Max. Greyness B C D - Min. greyness E - Pure – No greyness WEIGHT: (Saturation) Colours of similar hue and greyness may differ in colour brightness or intensity of 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 in pairs of numbers from 01 to 56. Groups of colours 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 – 15 C Greyness – 31 D Greyness – 43 E Greyness – 49

to 29 to 40 to 45 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 doBGAS define the following? 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.

Q A

What is the procedure for removing oil, grease form a substrate after preparation has taken place? If oil or grease is found on a surface after it has been prepared that area must be swabbed with an approved solvent followed by a 2% detergent wash, washing with clean water, thorough drying and reblasting.

Q A

What is procedure for removing oil, grease from a surface before preparation commences? Small areas of oil and grease shall be removed with an approved solvent, where as large areas can be given to low pressure detergent washing, which must be followed by rinsing with clean water and thorough drying.

Q A

What is the procedure for removing algae & mould growth from pipe work? Algae and mould grown shall be treated with a biocidal agent and left for 24 hour at least in order that biocide can kill the spores. It shall then be removed by scrubbing with stiff bristle brushes and clean water or by use of high-pressure water wash.

Q A

What distance must be left at areas to be welded when painting? For Zinc rich paint 75mm shall be left from the end preparation.

Q A

How much new paint overlap required over old repair? Minimum 100 mm.

Q A

What must pneumatically and electrically operated power tool equipment be? All equipment whether electrically or pneumatically operated shall be earthed. All equipments shall be non-spark and flame proof.

Q A

What type of sheeting may or may not be used for protection against spillage & spotting? Sheeting of a non-flammable nature must be employed to protect areas against spillage & spotting. Tarpaulins must not be used.

Q A

What areas of work, does PA 10 not cover? PA 10 not covers painting work of the following:

Below ground (buried) offshore installations, internal coating of pipes & store enamel coating. Q A

What is BS 7079? Preparation of steel substrates before application of paints and related products.

Q A

What are BS 3900 & BS 4800? BS 3900 – Method of test for paints BS 4800 – Specification for paint colours for building purposes.

Q A

What is BS 5493 & 5750 BS 5493 – Code of practice for protective coating of iron and steel structure. BS 5750 –

Q A

As an Inspector what do you consider as your main responsibilities? To assess the condition of substrate prior to treatment. 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.

Q A

Paint Faults? Bleeding: Discoloration 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. Checking: 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 tries 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, paint is cured due to the presents of a catalyst in the paint 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 be 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. Saponification: The formation of soapy layer 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 Galvanizing: 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 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 paints remains in an applicable condition according to the manufacturer’s instruction. T wash: An etch primer for zinc metal surfaces. Blue in color it turns black upon 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 are 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. Q A

What is Bgas PA-9 Refers to paint properties and performance requirements.

Q A

What is Bgas PA10 Refers to the technical specification for New and Maintenance Painting at works and site for above ground pipeline and plant installations.

Q A

Conditions for final surface preparation. When conditions in the working area are such that metal surfaces are moist, damp or wet, final

preparation shall not be carried out. Any surface preparation, procedure or method of cleaning shall not be allowed to contaminate wet paint 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 at least 24 hrs in order that the biocide can kill the spores. It shall then be removed by scrubbing with stiff bristle brushes and clean water or by use of a high pressure water wash. All surfaces shall normally be dry before painting commences. Q A

What document state health & safety at work? Health and Safety at Work act 1974 – (H.A.S.W.A)

Q A

What year was the Health & Safety Act passed? The control of substances hazardous to health regulations 1988 came into force on 1st October, 1989. (COSHH regulation).

Q A

How long records of personnel exposed would be kept? Employers must keep records of examination/ monitoring test for 5 years; 30 yrs for identifiable employees.

Q A

EPA & VOC Environmental Protection Act & Volatile Organic Compound

Q A

What is the difference between thermosetting & thermo plastic. Paint which melt when heat is applied are known as thermoplastic coatings. Coating which do not melt after the application of heat is known as thermo set coating.

Q A

What is impressed current and what problem can arise from its incorrect use? Impressed current is a type of Cathodic protection system e.g. Used for large areas of pipes. If the impressed current exceeds the corrosion & current, hydrogen gas bubbles are evolved from the metal substrate i.e. at the interface between the material and the coating. This is a 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.

Q A

What does B.Gas class as a hot duty service? Metal surfaces that will reach a temperature in excess of 990C when in service is classed as hot duty service.

Q A

Advantage & Disadvantage of Polyurethane Polyurethane finish coats are often used to replace epoxy finish coats. They have the following qualities: High Gloss, Retain the gloss, Hold the colors, Abrasion resistance, Easily cleaned, Good resistance to UV Light, chemical and weather resistant, Cures down to 00C. Disadvantages: Two Component May cause skin problem

Q

Advantage & Disadvantage of Epoxy

A

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 information you should when maintenance painting a pipeline without removing the existing coating? The following additional information to be recorded are: Nature of the existing system must be established to decide the type of preparation to be carried out. Amount of surface contamination. Extent of paint breaks down. Extent of corrosion Compatibility of the existing system with the new system. If not compatible select the appropriate Tie-coat. In service environmental condition.