ENGINEER by Emam Sayed

PAINT & PAINTING INSPECTION

SURFACE PREPRATION

BASIC PAINT TECHNOLOGY

PAINT TESTING

PAINT APPLICATION

COATING FAULTS

INSPECTION

PA- 10 (BRITISH GAS PAINTING SPECIFICATION)

K.A.stephenson

Surface and Surface Preparation Corrosion Corrosion is a chemical change brought by an electrochemical process called electrolysis. Steel is Anodic. Millscale is Cathodic. Anode corrodes faster than cathode. Millscale flakes of from steel, the exposed steel is having contact with atmosphere, which contains moisture and oxygen. The exposed steel, which is anodic will sacrifice to protect the millscale and corrodes. Factors influvence the rate of Corrosion 1. Rapid change in oxygen content 2. Moisture content in the atmosphere is above 60% 3. Acid, Alkaly, Sulphide and Chloride content in the atmosphere Millscale A thin black flaky lair of oxidised iron is called millscale. Steel is anodic to millscale. When millscale flakes of from the steel. the exposed steel scarifces it self to preserve the millscale. Surface Preparation Surface preparation is the most important factor in Painting & Coating. The success and failure of a coating depends on the correct surface preparation. Methods of surface preparation. 1. Degreasing 2. Wire Brushing. Needle Gunning. K.A.stephenson

3. Grinding.4.

5. Abrasive Blast Cleaning 6. Chemical Cleaning Water Blasting. 8. Weathering 9. Flame Cleaning Steam Cleaning

7. 10.

Dry Abrasive Blast Cleaning is the best method of surface preparation for long term protection coating systems. Blasting: The cleaning and roughening of a surface by the use of abrasive, which is projected on to the surface by compressed air. Speed = Approximately 450 m.p.h., Recommended Pressure is 7 bar (100psi) Drop of 1 psi pressure will drop 1.5% efficiency Equipment for Hose pressure checking = Hypodermic Needle Gauge Types of Nozzles: 1. Straight bore nozzle: The velocity of abrasive leaving a straight bore nozzle at 100psi is approximately 220 m.p.h. Straight bore nozzle provide an uneven surface prepration, this type is mainly using for small and repair areas and on softer metals. 2. Venturi nozzle : The velocity of abrasive leaving a venturi nozzle at 100psi is approximately 450 m.p.h.. 12mm nozzle held 450mm from surface will gives approximately 150mm Dia area. Blasting angle 75 to 80 Â° Short Nozzles (under 150mm) for easy clean surface. Long Nozzles (above 150mm) for hard to clean surface. K.A.stephenson

Metallic and Mineral abrasives commonly used are : 1. Steel or Chilled Iron Grit 2. Steel or Chilled Iron Shot 3. Copper Slag 4. Garnet 5. Grit and Shot mixed (70% to 80% Shot, 20% to 30% Grit) Other expendable abrasives are: Sponge, Poly Styrene, Walnut Shells, Ceramic grits and Crushed Glass. The use of Sand is not recommended. C.O.S.H.H. 1988 Regulations do not allow the use of sand containing free Silica in dry blasting operations due to the health hazard of Silicosis. C.O.S.H.H (The Control of Substances Hazardous to Health Regulations 1988.) Came in to force at October 1989 and revised in 1994. As per the regulation duty of:Employer :- 1st duty is to eliminate hazard and if this is not possible he must offer full protection against them. employees for 30 years and casual visitors for 5 years. Employee:- Keep himself and others safe by his actions at all times. He has a statutory duty to report any accidents, incidents or spillage. As far we concerned solvents and sands only covered in COSHH. Lead, Paint and Highly flammable liquids have their own separate legislation. Factors affecting the choice of abrasive are: 1. Specific Gravity 2. Hardness & Toughness 3. Size 4. Shape K.A.stephenson

5. Coast Human factors are: 1. Speed 2. Angle 3. Distance 4. Time Surface Profile: The shape of cross-sectioned blast cleaned surface is known as Surface Profile or Anchor Pattern. The size of the profile as measured from the Peaks to Trough height termed as Amplitude. Peaks are produced above the permitted Amplitude are known as Rogue peaks. Equipmentâ&#x20AC;&#x2122;s for measuring of Surface Profile: 1. Surface Profile Needle Gauge 2. Micrometer with Testex Tape (corn plaster method) 3. Surface Comparator. ( 1. Fine Profile, 2. Medium Profile, 3. Course Profile) Blasting grades The grade of a blast finish relates to the amount of surface contaminant remaining after blasting. BS 7079-(SS-05-59-00) Preparation of steel substrates before application of paints and related products is a pictorial standard which shows the degree of surface cleanliness both before and after blasting. Rust grades: A- Steel surfaces largely covered mill scale but little or no rust. K.A.stephenson

B- Steel surfaces which has a mix of rust and millscale. C- Steel surface on which the millscale has rusted away or from which it can be scraped, but with little pitting visible to the naked eye. D- Steel surface on which heavily rusted and general pitting is visible to the naked eye. Blast cleaning preparation grades: 1. White metal (Visually cleaned steel metal) - Sa 3 -SSPC-SP5 NACE -Grade1 2. Near White metal (Very thoroughly blasting) - Sa 2 1/2 SSPC-SP10 NACE -Grade2 3. Commercial finish (Thorough blasting) - Sa 2 SSPC-SP6 NACE -Grade3 4. Light blast & Brush off (Light blasting) - Sa 1 SSPC-SP7 NACE -Grade4 Safety Use of carbon impregnated hose to reduce the chance of static shock Use of a dead-mans handle to stop the operation immediately. Keep the hoses as straight as possible to prevent kinks which may lead a blowout. Use external couplings if joining hoses together. Internal couplings reduce the bore and the eroding action of the abrasive could lead to a blowout. Operators should wear protective clothing, including an air fed helmet, boots, leather apron and gloves. Wet Blasting K.A.stephenson

Wet blasting methods are good for removing Chlorides from surfaces and are good for the removal of toxic coatings. Ex. Red Lead Paint films. Disadvantages: Availability and drainage of water. The production and disposal of sludge. The extra coast of supplying and mixing of substrate inhibitor. The problems associated with drying large surface areas or the coast of water miscible primers. Different Methods of Wet Blasting are: High pressure pure water blasting: Operates at 35000 psi. (Extremely dangerous) High-pressure water plus abrasive injection: Operates at 20000 psi. also dangerous. Low pressure water plus abrasive injection: Operates at 100 psi. (High coast and low efficiency) Steam blasting, with or without abrasive injection: Operates at 100 psi . This method is good for surfaces contaminated with oil, grease etc.. (High coast low efficiency) Air blasting with water injection: Water with or without an inhibitor is injected in to an air/abrasive stream. Operates at 100 psi. Hand and Power tool cleaning 1. St 2- Manual Cleaning using Scrapers, wire brushes etc.. 2. St 3- Power tool Cleaning-using power tools like power wire brush needle guns etc.. K.A.stephenson

Power wire brushing may occur Burnishing on the surface, which will provide only poor adhesion Needle Gunning: (Jasonâ&#x20AC;&#x2122;s hammer) Needle Gun consists of many air operated reciprocating tungsten needles. Needles have a small cross section, useful for cleaning difficult areas like rivet heads and welds. After cleaning abrade the surface. Flame Cleaning The application of Oxy-acetylene or Oxy-propane flame to the steel surface. Differential expansion between the millscale and the metal, flakes off the rust scales. Rust is also De-hydrated and converted in to dry powder. Chemical Cleaning (pickling) 1. Degreasing 2. Pickling: Immersion in a tank of 5-10% sulphuric acid at 65-70Â°C remove millscale rust etc.. 3. Clean water wash to remove acid 4. Phosphating Tests to detect surface contamination 1. Testing Millscale - Copper sulphate test: Spray a fine mist of copper sulphate solution to the test required surface. The steel turn to a bright copper colour and any millscale particles show as black spots. Remove the copper from the surface by abrading or grinding. K.A.stephenson

2. Testing of Soluble Iron Salts- Potassium Ferrocyanide Test: Spray a thin mist of distilled water to substrate. Wait for the droplets to evaporate. Press the Potassium Ferro-synide paper to the steel surface 2 to 5 seconds remove and examine the PF paper. If soluble iron salts are present a prussian blue spots can find. 3. Testing of soluble Chlorides- Silver Nitrate test: Soak filter paper in the 2% silver nitrate solution . Press the wet filter paper on the surface. After 20 seconds wash it in distilled water. Immerse the washed filter paper in photographic developer for 2 min. Chlorides will show up as brown-black spots. 4. Testing of soluble sulphate- Barium Chloride Test: 6 % Barium chloride and saturated solution of Potassium Permanganate. Soak the filter paper in barium chloride solution, drain and dry the filter paper. Press the filter paper on the surface backed by a peace of wet filter paper soaked in the potassium permanganate solution. Pink spots on the barium chloride treated filter paper show the presence of soluble sulphates. Surface preparation of non-ferrous metals 1. New Galvanised surfaces A galvanised steel surface up on which, a cohesive oxide layer has not yet formed. Bright and Shiny, less than 3 months old. K.A.stephenson

If sweep blast or hand prepration is not possible an etch primer ‘ T-WASH’ shall be used. T-Wash – Blue in colour it turns black up on if it has been applied sucessfully. 2. Weathered Galvanised surfaces Over 3 months old, dull, with cohesive oxide lair. Only stiff bristle brushing for surface prepration. No sweep blast or hand abrading. 3. Aluminium surfaces Thin gage Aluminium should not be blast cleaned. Treat with etch primer (PVB) Chlorinated hydrocarbon solvent shall not be used. 4. Stainless Steel Only Aluminium oxide should be used as the abrasive for sweep blast.

BASIC PAINT TECHNOLOGY Types of Paint

K.A.stephenson

Basically three types of Paints exist 1. Solvent carrying Liquid Paint 2. Solvent free liquid paint 3. Powder paint Paint will consist of three principal components 1.Binder (Film former) 2.Pigment 3.Solvent (Thinner) Binder + Solvent = Vehicle 1. Binder Binder converts the liquid to solid dry film. Binder binds the particles together. It provides finish to the coating. Binder makes the coating adhere to the surface. It gives elasticity to the film. Binder provides resistance to water chemical and abration A Paint type is normally identified by its binder. e.g. Acrylic, Alkyd, Epoxy, Emulsion, Silicone, Chlorinated rubber, Polyurethane etc.. A paint binder forms Polymers when drying takes places. The name Polymer means “Many parts” and is a giant Molecule formed by the linking up of millions of small molecules called Monomers. (Monomer means “Single part”) The process by which the monomer molecules are linked is called Polymerization (During the drying of paint film). Three types of Polymers are: 1. Linear Polymer (single bond) K.A.stephenson

- e.g. Vinyls

2. Branched Polymer - e.g. Chlorinated rubber 3. Complex Polymer (Cross linked) - e.g. Epoxy, Polyurethane etc.. Linear polymers and Branched polymers which have a ability to re-soften (Melt) by applying the solvent or heat. Complex polymers (Cross linked polymer) once fully cured cannot be re-softened. Paint binders may consist of resin, oil or resin and oil. Resin 1.Natural resins : e.g. Shellac, Copals, Demmars etc.. 2.Synthetic resins : e.g. Epoxy, Alkyd, Vinyl etc.. Oil Before synthetic resins un saturated drying oils were used as film formers. Ex. Linseed oil, Tung oil, Soya bean oil etc.. Paints which contains more oil than resin is refered a Long Oil Paints. These paints are slow drying & elastic. Mainly using for decorative purposes. Paints which contain more resin than oil is refered as short oil Paints. These paints are fast drying. Using for structural coating. Semi-drying and non drying oils are used in certain paints. e.g. Alkyd. Pigments

K.A.stephenson

Pigments are solids in powdered form, which provides colour and opacity. Pigments may be organic or inorganic, most pigments used in paints are inorganic. It improve the strength of the paint film. It protect the premeability of the paint film. It provides rust inhibitting properties. It add body (thiken the liquid paint). Also pigments improve adhesion. Also gives resistence to acid alkaly and light. e.g. Carbon-(Black), Cobolt-(Blue), Calcium-(Red,Yellow), Iron oxides-(Brown,Red,Yellow), Titanium dioxide -(White) Zinc Phosphate (White), Zinc Chromate (Yellow) Red lead and red oxide (Red) Coaltar (Black) Calcium Plumbate (White) etc.. These all are Opaque Pigments . An un pigmented paint is known as Varnish. Rust Inhibitive (Anti-corrosive) pigments used in Primers for corrosion prevention. e.g. Zinc chromate, Zinc phosphate, Red lead, Calcium plumbate, Coal tar etc.. Metalic pigments for decoration and protective properties. e.g. Zinc, Aluminium Extender pigments for increasing viscosity, reducing gloss. Using extenders is lower coast. e.g. Kaolin, Chalk, Talc, Slate dust etc.. Laminar Pigments - Pigment particles looks like leaf or hands, when drying takes place pigments overlap and interwave and forms a solid film, which provides excellent coating to resist the passage of water. Ex. MIO, Mica,Glass flakes and Aluminium flakes etc... K.A.stephenson

Pigment Volume Concentration (p.v.c.) Each paint has a optimum ratio between the amount of binder and the amount of pigment it contains. this is known as the Critcal Pigment Volume Concentration (c.p.v.c.) and controls the paints properties. e.g Low pigments and high binder means high gloss paint with poor opacity High pigment and low binder means a flat paint with good opacity Too much pigments will give a porous film due to poor wetting. Too much binder gives a high gloss with low opacity, which has a tendency to chalk and blister. Aggregates: Pigments particles group together in small groups are known as Aggregates. Solvents Solvents reduce the Viscosity until suitable for the intended application. Solvent must be volatile so that it evaporates from a coating of a paint to leave viscous film. e.g. Xylene, White spirit, Turpentine, Acetone, Alchohols, Water etc.. Important properties of a solvent are: 1. Solvent Power - Strong solvents, The molecules of the paint to move more easily. 2. Rate of evaporation - Method of application will affect evaporation if the rate of evaporation is too quick. Problem may arise during application. e.g. Dry spray. K.A.stephenson

3. Flash point - The lowest temp at which the vapor of the flamable material will be ignited if an external source of ignition was introduced Measuring equipment is closed cup of the Abel type 4. Toxicity -(Poison content in the paint) The toxicity of a solvent can be determined from its occupational exposure limit expressed in patrs per million. (p.p.m.) Other Constituents in the Paint a) Plasticizers: are adding flexibility to the paint film. e.g. Castor oil, Coconut oil (Non drying oil). b) Anti settling agents: retrad the formation of sediment in the bottom of paint containers and help maintain the paints uniform consistancy during the paints shelf life. e.g. Bentones and Waxes. c) Driers: (Applicable to oil based paints) added to acelerate the drying process in oil based paints. e.g. Cobalt Napthenate- improves surface drying Calsium Napthenate- improves surface hardness d) Anti-skinning agents: (Applicable to oil based paints) to reduce skin formation in the container. e.g. Thymol, Methy Ethyl Ketoxime. Paint Drying & Curing ( BS 2015) Glossary of paint and related term Drying - The change of a coating material from the liquid to the solid state, due to evaporation of solvent, physio-chemical K.A.stephenson

reactions of the binding medium or a combination of these process. Air drying- Drying process in normal temp. Forced drying - Heat above the ambient temp, but below that used for stoving. Stoving - Heat, using an oven or infrared energy. Various terms exist in relation to the drying of a paint film. 1. Dust dry : Dust no longer adheres to the paint film 2. Surface dry : Dry on the surface but soft and tacky underneath (oil based paints) 3. Touch dry : Slight pressure with fingers does not leave a mark. 4. Tack free : Free fom tack, even under pressure. 5. dry to handle : Can handle with out damage. Drying Mechanisms 1. Solvent Evaporation: When the solvent evaporates the polymer reforms and become hard. Solvent evaporation is Reversible-Non convertible e.g. Acrylic, Chlorinated rubber, Vinyls etc.. 2. Oxidation: Dry first by solvent evaporation then oxidation. The polymer then begin to cross link and form a dry film. Non reversible-Convertible e.g. Alkyds, Oil modified phenolics, Epoxy esters etc.. 3. Chemical Curing: Dry intially by solvent evaporation, if a solvent is present and then by polymerization due to chemical reaction with the curing agent. Non reversible-Convertible e.g. Epoxy, Etch primers, Polyurethane etc.. K.A.stephenson

4. Coalescence: Dry intially by water evaporation. This allows the polymers which have already formed to join together. Reversible-Non convertible e.g. Acrylic Emulsions and Vinyl Emulsions. Convertible Coating â&#x20AC;&#x201C;(Non-Reversible film) A convertible coating is one which chemical changes up on drying. Therefore the dry paint cannot be softened or damaged if its own solvent is applied to it. Non-Convertible Coating â&#x20AC;&#x201C;(Reversible film) A non convertible coating does not change chemically up on drying, but dries by evaporation only and can be damaged or softened if its own solvent is applied to it. Thermosetting and Thermoplastic Thermosetting is where heat is applied to cure and up on drying a chemical change accured. Apply of further heat will not resoften the coating. Thermoplastic is non-convertiible coating. Apply of heat can melt or damage the coating. Two pack paints are used taking in to the consideration the Pot Life and in some cases the Induction Period. Pot Life -After mixing a two pack paint the maximum length of time after induction which the paint can remains in a applicable condition.

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Induction Period - The Minimum period of time during which the mixed components are left to stand before use. This is to allow for certain chemical reactions to take place and /or time allowed for the air bubbles to escape. Induction periods are typically up to 30 minites. There are several other curing mechanisum which only be employed where the curing agent may already present in the paint and activated by external means. a) Heat (low-bake ovans) b) Ultra-violet radiation c) Infra-red radiation d) Electron beam e) Atmospheric moisture Coating Systems Corrosion Protection Methods: The paint system protects the substrate from corrosion by a combination of one or more of the following methods. 1. The barrier principle : Using of a low permeability coating isolating the substrate from Environment. E.g. Polyurethane, epoxy 2. Passivation : Corrosion is retarded or arrested by chemical reaction between Rust inhibitive pigments in the primer and the substrate. E.g.Zinc phosphate 2. Cathodic protection : Coating the substrate with a paint containing metallic pigments K.A.stephenson

Like Zinc or Aluminum, which are ignoble to the substrate. Layers of paint film & its functions 1. Primer : To provide maximum and lasting adhesion to a substrate. To provide a key for the next layer. To retard corrosion by means of an inhibitive pigment. 2. Mid coat : Mid coats to serve as barrier to prevent the passage of water. Primer and finish coats are thin coats, without a mid coat inhibitive pigmnts in the primer would be wash out or diluted which will lead to corrosion. Mid coats will build up the film thickness to provide more even surface by filling in slight surface irregularities 3. Finish coat : Gives a surface its final appearence, colour and gloss etc.. Each coat of paint shall be of a contrasting colour to the previos coat. Zinc Rich Primers:- The zinc acts as a sacrificial anode when in contact with a steel surface at localised areas damage such as scratches. Types of Coating system There are various ways to classify paint systems. K.A.stephenson

A. Function, B.Binder type, Colour

C. Pigment type, D.

Barrier Coat: A low premeability coating which isolate the substrate from the enviornment. Tie Coat: A coat of a paint which acts as a intermediatry between two in-compatible systems. Sacrificial Coatings The pigments scrificed it self and protect the substrate to which the pigents is adhered. e.g. Zinc & Aluminium. Powder Coating: Basically powder coatings are solvent free, they may be thermosetting or thermoplastic. Epoxy powder gives a thermoset coating, which can be used on underground pipe lines. Each thermoset powder contain a base and curing agent, which are activated by means of heat source. Water Borne Coatings: Use water as a solvent in place of the hydrocarbon solvents normally associated with the coatings industry. The binder types which are in comman use , using water as a solvent is: Alkyds, Epoxies, Acrylated rubber, Acrylics, Bitumens, Silicones, Polyurethane, Vinyls etc.. Advantages:K.A.stephenson

1. V.O.C Complaint (Volatile Organic Componds ) No GWP or ODP GWP = Global Warning Potential ODP = Ozone Depletion Potential 2. No Toxic, 3. Non flammable 4. Water is cheap and readly available 5. Odourless, 6. Compatability 7. Low Viscosity Dis Advantages:1. Requires high degree of surface preparation 2. Needs inhibitors and other additives 3. Slow evoporation rate 4. Needs non ferrous application 5. Less durable Moisture tolerant systems The surface that requires coating may be below the dew point temperature. a) Damp surface : Temperature below dew point but no water on surface. b) Moist surface : Moisture on the surface. c) Wet surface : Free water are present on the surface. Paint using are:1) One pack polyurethene, 2) Solvent free two pack epoxy, 3) Moisture tolerant chlorinated rubber Cathodic Protection A coating system is the primery defence against corrosion, but when this caoting system is damaged corrosion may occur. Cathodic protection is a secondary line of defence against corrosion. There are two methods of applying cathodic protection K.A.stephenson

1. Sacrificial anodes (Galvanic anodes) Sacrificial anodes may be used where the current required to achive cathodic protection is small. If steel is to be cathodically protected, magnesium, zinc or aluminium anodes may be used. 2. Impressed Current Impressed current is second line for cathodic protection after sacrificial coating. Voltage from an external power source called a transformer rectifier is impressed on the circuit between the pipline and buried earth connections known as ground beds resulting in a direct current being discharged. If too great current applied to the pipe line Hydrogen Gas forms and pushes off the sacrificial coating, this is known as cathodic disbondement. Paint Colours BS 4800 Paint colours for building purposes. BS 5252 Frame work for colour co-ordinaton for building purpose. BS 4800 is a range of 100 standerdised colours selected from 237 colours found in BS 5252 for the use of construction industry. It is identified in numbers and letters. By making of paint colours this set of numbers and letters conform each manufactorer can guarantee to produce exactly the same colour, in that way the colours become standerdized. Paint Mills In Paint manufactering paint mills are for breakdown or disperse the groups of pigment particls. K.A.stephenson

A) Direct charge dispersing mills: The liquid and solid ingrediants are added directly to the mill which are: 1) Ball Mill : Horizontlly mounted steel cylinder containing steel or procelain balls whichcontinually cascade down on to the ingredients when the cylinder is rotated. 2) Attritor Mill: Basically this is vertical ball mill. The cylinder is stationary and the balls are agitated by rotating shafts. This gives higher degree dispersion in short time. 3). High speed disperser: Vertical shaft at the end of which is a disc shaped serrated edged impetter which rotates in a high speed. 4). Kady & Silverson Mills: Both are high speed mills (20 gls/ day) B) Pre-mix Mills: Pre-mix mills are for high quality requirements (Maximum disperson of the pigment). 1). The Bead Mill or Sand/Pearl Mill: Most modern frequenly used mill for the large scale production. Rotating dicss attached to a shaft help to achive shear as the paint slury is forced through small abrassive particles present in the cylinder between discs. This mill gives high degree dispersion. (1000 gal./day) 2. Colloid Mill: These mills are quite versatile, have a high output and are particularly suited to emulsion K.A.stephenson

Paints. 3. Triple Roll Mill: This mill consist of three parallel rollers , each runs at different speed and rotates different direction. Using for the production of paste meterials such as mastics. this is an expensive technic. 4. Single Roll Mill: (Single roll refiner) Mainly using for refining purpose after milling operations. Small batch production and low efficiancy.

Paint Testing (Quality Control & Performance) BS 3900 - Methods of test for paints Group A - Tests on liquid paints (Excluding chemical tests) B - Test involving chemical examination of liquid paints and dried paint film C - Tests asssosiated with paint film formation D - Optical tests on paints E - Mechanical tests on paint film F - Durability tests on paint film G -Enviornmental tests on paint films (Including tests for resistence, corrosion and chemical) H- Designation of intensity, quality and size of common types of defect, general Principles and rating schemes K.A.stephenson

Different Paint Film Testing 1. Fineness of Grind:- Degree of dispersion of a paint can be assesd with a fineness of grind gauge also known as HEGMAN GRIND GAUGE. A quantity of paint poured in to the groove(s) and a flat edged scraper pulled along the length towards the shallow end. This ensures that the groove is filled and surplus paint is removed. With in three seconds the scale should be observed to assess the point, where within a 3mm band across the grove 5 to 10 pigment particles break the paint surface. 2. Volatile Matter/ Non volatile matter:Procedure 1. Weigh a throughly dry watch glass and stirrer 2. Add approximately 2 grams of paint and reweigh 3. Drive of volatile in an air oven at 105Â° C for 3 hours. 4. Reweigh; determine volatile content and non-volatile content by simple calculation. 3. Flash Point: - BS 3900 Part A 9 FlashPoint is the lowest temp. at which the vapour of the flammable materials will ignite If an external source of ignition was introduced. Abel Cup Test Procedure: 1. Fix the Abel cup containing the substance for assessment in to a water bath. 2. Activate the source if ignition every 1/2Â° C rise in temp. K.A.stephenson

3. Apply a heat source to the water bath and monitor the air/vapour temp. In the Abel cup 4. Flash point temp. is identified when the blue flame flashes over the substance being assessed 4. Viscosity:Viscosity is a measure of fluid resistance to flow A fluid with High viscosity means - Thick fluid A fluid with Low viscosity means - Thin fluid Instruments using for measuring viscosity are known as viscometers. Unit of viscosity are- Poise, Newton, Dyne, Stoke, Centi Poise, Centi Stoke, and Seconds. Viscometers- Rotational Type- BS 3900 A7 1. Kerbs-stormer Viscometer 2. Cone and plate Viscometer 3. The Rota thinner A simple method for measuring the viscosity of free flowing paints is Flow Cup (Ford flow cup No. 4) Thixotropic Paints Rotational type Viscometer. (Kerbsstormer) Flow Cup operating procedure1. Level the apparatus, then with the end of one finger over the orifice of the cup, rapidly fill it with paint. K.A.stephenson

2. 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 edges. 3. Remove the finger from the orifice and start the stopwatch simultaneously with the commencement of the paint stream. The watch is stopped when the first Distinctive break in the paint stream occurs. 4. The time in seconds is taken as the viscosity. 5. Density: Density is weight per unit volume. Formula: - Density = Weight Volume Relative density or Specific Gravity is the density of any substance compared to the density of water. Procedure for measuring density using a 100 cm3 density cup 1. Weigh the cup 2. Remove cover and fill with paint to with in 2.5 m of the brim 3. Carefully replace the cover 4. Wipe off any surplus paint from the cover 5. Reweigh 6. Determine the weight of the paint by subtraction 7. Divide weight by 100 if the density in g/cmď&#x20AC;ł 6. W.F.T.: Wet Film Thickness

K.A.stephenson

WFT is taken immediately after a coating has been applied. Instruments : 1) Comb Gauge 2) Eccentric wheel WFT = 100 x DFT V.S % 7. D.F.T : Dry Film Thickness Four methods of determining the DFT a) Non-destructive test gauges b) Destructive test gauges c) Test panels d) Calculation a) Non-destructive test gauges 1. Eddy current/Electronic gauge 2. Magnetic film thickness gauge (Banana gauge) 3. Pull-off gauge or Tinsley pencil 4. Magnetic horseshoe gauge b) Destructive test gauges: Mainly using for ferromagnetic paint film (MIO) testing. The paint inspectors gauge (P.I.G) c) Test Panels : Metal plates of known thickness may be used to measure DFT indirectly. d) Calculation: DFT = VS% x WFT 100 K.A.stephenson

Weathering and artificial weathering To determine how a coating will behave in natural weather conditions. Painted test plates are weathered for pre-determined time e.g. months or years. The test plates may be exposed to any environment, e.g. Marine or Industrial, to determine the coating systems behaviour in specific conditions Artificial Weathering Devises (Weatherometers): a) Tropical box : High Humidity b) Salt spray box : Marine Environment c) Water soak : Resistance of water absorption d) Temperature cycling : Expansion and contraction testing e) Cold check testing : Low temperature contraction craking Testing of mechanical properties 1. Abrasion resistence: Painted panels are abraded for a specified period of time by some particular instruments using falling sand, revolving rubber wheels, wire wool or by similar mean and then evaluated for the degree of abration. 2. Hardness : Pendulam test - Koeing Albert apparatus 3. Flexibility: Bent test 4. Impact resistence: Falling weight impact test K.A.stephenson

5. Drying or curing test: 1. Ballotini test Tiny glass balls known as ballotini are allowed to fall in to a freshly painted slowly moving test panel. The amount of ballotini sticking to the surface will reduce as the surface dries. The drying time is recorded corresponding to the position where the last glass ball adheres. 2. Stylus test or Beck koller needle test Set-up is similar to the ballotini test. Number of needles of variable weight are allowed to trail across the freshly painted surface. When the paint is wet the needle touch the substrate, as drying occurs the needle score the film and eventually corrosponding to the interface at the position where the scratch is no longer visible. 6. Gold leaf test: Residual touch 7. Mechanical Thump Test: Motor driven mechanical thump test 8. Pencil scratch test: using pencil to test hardnes of paint film 9. Mechanical scratch test: Needle with adjustable load applied to test panel. Minimum load to scratch, recorded. 10. Opacity: Opacity is the hiding power of paint film K.A.stephenson

1.Cryptometers 2. Hiding power charts 11. Degree of gloss: The degree of gloss mainly depand on the degree of dispersion of pigment in the paint film. Also the amount and the type of binder used, other factors are method of application, skilled oprator and absorbency of the surface. Testing equipment :- Gloss meter 12. Adhesion test: a) Vee cut test: With sharp knife cut vee 12mm b) Cross cut test: With sharp knife cut 6 line vertically and horizontly. Cover area with adhesive tape and snatch. c) Dolly Test : Pull of adhesion test d)Hydrolic adhesion test: 13. Cathodic Disbondment test: Weather Conditions The coating specification should always state the weather conditions in which a coating can and cannot be applied. B GAS allowed weather conditions are: For preparation The air or metal temperature must not be below the dew point. K.A.stephenson

For Painting The air or metal temperature must be above 3Â°C of the dew point The R.H.% must be below 90% Follow the manufactors minimum and maximum recomended temperature. Measuring R.H% and dew point - Whirling Hygrometer + DP/RH Calculator Measuring Metal temp. - Magnetic temp. gauge or Electronic temp. gauge Paint Application Methods of application 1. Brush Application a) Cheap to purchase b) Easy to maintain c) Slow job d) Good job in right hands e) Poor access f) Works paint well in to the substrate g) Cannot apply all coating types h h) Sheeting up only is required (No masking required on surrounding) i i) Personal protection is minimum 2. Roller Application K.A.stephenson

a) Cheap to purchase b) Two to three times quicker than brush c) Easy to maintain d) Washing out time is significant. Also washing out uses a lot of solvent e) Access is better (Extension poll) but cutting in needs to be done by brush f) Finish is poor (Orange peel) g) Not so good adhesion to substrate h) Roller spray i) Gives an uneven coating j) Variety of shape roller heads available k) Suitable for large flat areas 3: Spray Application: a) Conventional Spray: 1. Gravity feed 2. Suction feed 3. Pressure feed or remote cup Conventional spray is a) More costly than brush but cheaper than airless spray b) 4 to 5 times faster than brush c) Good job in right hands d) Access is only good in pressure feed only e) Washing out time is significant f) Washing out uses lot of solvent g) Do not apply all coating types h) Only good for some paints e.g. Cellulose i) Masking out time significant j) Personal protection clothing required K.A.stephenson

h) Safety becomes a consideration b) Airless Spray: Airless spray is considered to be the main tool for Industrial Painting. Airless spray is a) Expensive to purchase b) 20 to 30 times quicker than brush c) Large areas can be covered d) Only method for applying high builds materials e) Washing out time is significant and uses a lot of solvent f) Safety is major consideration (Trigger locking, static electricity, personal protecting clothing required) g) Parts are very expensive h) Swivel tip (for blockage) i) Masking is required Comparing the way in which conventional and airless spray work: The conventional spray a mixture of air and paint is fed to the gun at comparatively low pressure (typically 30 to 100 psi) at the gun. This mix is atomised and projected on to the surface with a relatively small fan pattern and relatively low thickness. In airless spray, paint is fed in to a fluid pump. This pump can be adjusted to multiply the 100 psi in let pressure up to 60:1 ratio. Therefore if the ratio adjusted to 35:1, the paint would be pressurised and delivered at 3500 psi. This pressurised paint is then fed to gun by means of high-pressure fluid line. The paint is only atomised when the trigger is pulled and the paint is K.A.stephenson

released in to the air at high pressure because no air is involved in the delivery of the paint, it is called airless. High volume and high thickness of paint are achieved. Electrostatic Spray: Method of painting of ferrous surfaces. Spraying in which electric charge attracts paint to surface. a) Very expensive to purchase b) Specialist application for small and tubular components c) Paint particles are negatively charged d) Substrate positively charged e) Coats all around component f) Gives an even coating g) Very little wastage of material Other coating methods are: Dip coating, Flow coating, Curtain coating, Spin rotating etc. Metal Coatings are: 1) Galvanising, 2) Sherardizing 3) Electro plating 4) Hot metal spraying etc..

Coating Faults Coating Faults BS 2015 1. Bittiness - The presence of particles of gel or foreign matter in the coating material or projecting from the K.A.stephenson

surface of a film. Caused by lack of care and attention to cleanliness in surface preparation, materials and equipment. 2. Bleeding -

This appears as staining or discoloration of an applied paint by a constituent of the surface or the pervious coating. The solvent(s) of the new paint can cause certain organic pigments, coal tar, or bitumen to dissolve. To prevent bleeding the surface can be sealed with an aluminium sealer before application of the new paint.

3. Blistering Formation of blisters in the dry film by local loss of adhesion and (Bubbling)lifting of the film from the underlying surface. Presence of Hygroscopic salts or soluble iron salts in the surface can create blisters. 4. Blooming This is the formation of a surface dust on gloss type paints usually due to the moisture in the atmosphere. Loss of gloss and dulling of colour. 5. Cissing Cissing describes the appearance of a wet paint film, which has (Crawling) either been applied to a grease or oil contaminated substrate, or the application method has been contaminated. It appears as tiny K.A.stephenson

unwetted areas where the paint has contracted away from the contamination. Crawling is an extreme form of cissing and in the retraction of the wet paint from large areas of the surface. Both defects can be considered due to the lack of surface tension 6. Cracking - Crazing, Crocodiling, Mud Cracking etc.. This is where breaks in the paint film occur and extend through to the substrate. It can be the result of inadequate elasticity of the paint system applied on to a substrate, which expands and contracts. Cracking is usually a precursor to flaking. 7.Chalking - The formation of friable, powdery coating on the surface of the paint film. Caused by the degradetive action of the weather and / or Ultra Violet radiation. 8. Cratering in the film.

Formation of small bowl shaped dispersions

9. Curtaining, - A downward movement of a paint film between the times of (Sagging, application and setting, resulting an uneven coating having a thick Runs) lower edge. Because of poor workman ship or excess amount of K.A.stephenson

Thinner in the paint can increase the flow of the paint.

10. Flaking

- Lifting of the coating material from the substrate in the form of flakes or scales. nadequate surface and intercoat preparation, poor application, incorrect choice of primer, paint applied over chalking surface etc.. are the causes for the paint fault.

11. Holidays -

Discontinuity, pinholes etc..

12. Lifting - Failure caused by the swelling of dry film of paint or varnish when another coat is applied over it and usually manifested by a wrinkled appearance. 13. Orange peel - This is a defect with an appearance resembling the skin of an orange and is usually brought about by the rapid evaporation of the solvent before the paint has flowed out. The cause include too great a spraying distance, excessive air pressure, excessive environmental temperature, substrate temperature too high, or combination of these. 14. Wrinkling, during drying, K.A.stephenson

The development of wrinkles in a paint film

(Rivelling) surface slain.

usually due to the initial formation of a

15. Flocculation Manufactering fault of paint, separated materials in the paint difficult to bind together. 16. Grinning The underlying surface showing through due to the inadequate opacity of the paint film applied to it. It can be caused by colour differences between successive coats, uneven application, over thinning of paint, or failure to adequately mix settled pigment in the can prior to application. 17. Dry Spray - This is partly dry paint particles which have failed to coalesce and thus presents a sandpaper effect. It can be caused by too great spraying distance, too wide a spray fan, or excessive air pressure in relation to nozzle size. 18. Efflorescence - Not a paint defect. It is the development of crystalline deposit on the surface of brick, cement, etc., due to water containing soluble salts, coming to the surface, and evaporating so that the salts are deposited. In some cases the deposit may be formed on the top of any paint film present, but usually the paint K.A.stephenson

film is pushed up and broken by efflorescence under the coat. 19. Failure at burnt or backs of weld areas The localised heat of burn and weld areas can severely damage the binder and leave unbonded carbonised residues. These residues have to be removed and the affected areas re-treated, otherwise there will be flaking due to the ingress of moisture under the paint. 20. Failure at weld areas Failure at weld areas can be brought about from a number of reasons. Due to the chemical nature of weld flux, moisture can be absorbed thus creating an Electro-chemical cell leading to corrosion. It is therefore essential that all weld flux (spatter) be removed prior to preparation and painting. 21. Failure at edges and corners Any paint applied to edges and corners of structures will eventually suffer breakdown due to the surface tension of the film drawing it away from the edges. This can cut down the film thickness by factor of three. As a result all edges and corners should be radiused where possible, but an additional coat of paint applied as a â&#x20AC;&#x2DC;stripecoatâ&#x20AC;&#x2122; is suitable alternative. 22. Mould growth Fungi, algae and mould growth. Moisture is the essential prerequisite for their development and K.A.stephenson

growth, consequently they can occur in conditions of high humidity or on surfaces which have high moisture content. Remedial action is ideally a reduction in humidity and moisture content, and the application biocidal agents to kill the growth. 23. Saponification Saponification means the formation of soap, and it occurs when an alkali attacks the oil constituent of oleoresinous paints in the presence of moisture. The paint film loses gloss, colour, and becomes soft and sticky. The defect may be a result of external attack by alkaline substances, such as the cleaning down detergents not being completely washed off. 24. Ropiness A finish in which the brush marks have not flowed out, this being the normal appearance of a paint or varnish having poor levelling properties. A similar appearance may also produced in a paint, which normally has good levelling properties, by continuing to brush the paint after the film has begun to set.

Inspection

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Specification - Specification is the governing document for coating work. It will define what the supplier or the subcontractor is required to do. Inspection duties - It is the duty of a painting inspector to ensure all painting and associated operations are carried out in accordance with the specification(s) for the contract. 1) General duties: a) Learn the specification(s) b) Get to know the plant c) Get to know the personnel d) Ensure all concerned understand the specification. e) Keep the Engineer in formed at all times of any departure from the specification. f) Make written reports at an agreed frequency. g) Conduct and/or attend site meetings. 2) At the beginning of a day: a) Check the environment b) Check the equipment c) Check the materials d) Check the previous days work e) Agree the days work programme with the site contractors senior personnel. 3) During the day a) Check the environment b) Check the equipment c) Check the materials usage K.A.stephenson

d) Check each operators work e) Check the standard 4.) On completion of the work at each stage a) Ensure that system meets the specification by carrying out or witnessing tests. b) Check for any application faults 5). At the end of the day a) Check the days work b) Check the housekeeping c) Complete reports. 6). On completion of the job a) Make the final check on integrity of the work b) Write the summary report. As per painting inspection procedure Painting inspectorâ&#x20AC;&#x2122;s duties are: 1)Access the rust condition of substrate prior to treatment. 2)Access the prepared surface in accordance with SS-0559-00. 3)Measure and record the amplitude 4)Ensure the materials used as per the client specification 5)R.H%, Dew point, Steel and Air temperature to be checked and recorded at frequent intervals 6)Wet & Dry film thickness to be checked and recorded. K.A.stephenson

7) Witness & Inspect each coat of application, and inspect completed paint System in accordance with clients specification 7)To submit daily, weekly and job completion reports, recording all relevant information as required by the client. Copies to be retained by inspector. The Inspector should be aware of the typical contractor malpractices, which are: 1. Use of unskilled operators and unsuitable equipments 2. Painting or preparing surfaces during inclement weather conditions; rain, snow, fog, mist etc.. 3. Painting before inspection of substrate preparation or previous coat. 4. Applying two paint coats to the same area in one day assuming specification does not allow this 5. Missing out a coat. 6. Use of wrong solvent or an excessive amount of solvent 7. Using diesel in the paint (as a thinner or plasticiser) which will prevent proper drying 8. Use of incorrect paint type or mixing different manufactures products 9. Storing paint incorrectly 10. Use of date expired paints 11. Re-using of expendable abrasives 12. Insufficient blasting or painting in difficult access areas, under pipes etc.. 13. Apply low thickness of paint K.A.stephenson

14. Cleaning surfaces with cotton waste or rags. Lint free paper tissues must be used PA 10 - Technical Specification for BRITISH GAS TRANSCO. General Cleanliness: Ensure that adequate protection is given to surrounding areas and adjacent structure to avoid spotting, overspray and other condemnations. Ensure the masking of equipments, atmosphere sensing heads, spray heads vents on control equipments etc.. Metallic Zinc is not allowed to touch with stainless steel. Washing with solvent required. Oil & Vapour traps (filter) fitted to compressed air for power tools. All Algae and mould growth shall be treated with biocidal agent for a minimum 24 hours. It can be removed and clean by water. Surface profile - Not less than 30 m and not grater than 75 m Wet blasting system for lead based paint. Following wet blasting dry blasting to remove subsequent flash rusting. Ferrous impact tools not normally used. Needle gunning- Profile not exceeds 100 m. Remove rogue peaks. Abrasive disk - Special care required, danger of creating Notches All weld flux and spatter shall be removed, Blast cleaning recommended on weld areas. K.A.stephenson

Any oil or grease on the prepared surface - Solvent cleaning followed by 2% detergent solution then with clean water, then abrasive cleaning repeated. Disposable lint - free swabs shall be used; cloth rags shall not be used. SPA - Specific Painting Application SPA 1 New and Maintenance painting for LONG TERM Protection of installations and components Two Main Systems for BGAS 1. Compliant solvent-based Paint system Primer : High build epoxy aluminium primer minimum DFT 75 m 2nd Coat : MIO Minimum DFT 75 m 3rd Coat : High Build epoxy undercoat minimum DFT 75 m Finish Coat : Epoxy or Polyester acrylic finish minimum DFT 40 m Total DFT : 265m 2. Water - borne acrylic system Primer : Minimum DFT 50 m 2nd Coat : MIO Minimum DFT 75 m 3rd Coat : Undercoat minimum DFT 50 m Finish Coat : Minimum DFT 50 m K.A.stephenson

Total DFT

225m

Mask out Degreasing with approved solvent Blast clean SA 2.5 Profile max. 75 m Clean surface immediately prior to painting

At works Primer – High solids Solvent based Epoxy primer DFT 75m Epoxy MIO DFT 75 m

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On Site Compliant Solvent Based System

On Site Water Borne System

Under coat – Water Borne Under coat – High Build U/C 50m Epoxy U/C Finish Coat – Water Borne DFT 75m Finish 50m Finish Coat – Poly Acrylic Total DFT – 250 m Finish DFT 40m Water Borne System on Total DFT – 265 m site Total DFT 225 m SPA 1a -Preparation for Painting of uncoated or unsuitably coated surfaces at works or site 1. All surfaces not to be painted shall be masked 2. Blast clean Bs 7079 Sa 2 1/2, Profile with in the range of 30 m and 75m 3. Clean all surfaces immediately prior to primer application 4. Apply Primer as per the system recommended 5. 2nd coat MIO 6. Before applying 3rd and final coat clean all surfaces (Degreasing, Washing with a 2% Detergent) SPA1b - Preparation of Painted surfaces with Limited damages Surface prep: BS 7079 ST3 Mechanical wire brushing High solid solvent based epoxy primer and epoxy MIO One coat of High Build undercoat and One finish coat. K.A.stephenson

For installations previously painted with drying oil or chlorinated rubber paint systems maintenance painting can generally carried out with any of the following systems. 1. Compliant Solvent Base System Or 2. Water Borne System SPA 2 - New and Maintenance painting for indoor use or SHORT TERM protection. SPA 2 a - New paint for indoor use and for short term protection 1. All surfaces not to be painted shall be masked 2. Washing 3. St 3 Mechanical cleaning 4. Edges of existing sound coating shall be feathered 5. One coat of primer by Brush. The paint shall overlap on to any existing coating by at least 100mm. DFT 45 m 6. One coat of MIO by Brush DFT 45 m 7. If a decorative appearance is required one coat of under coat 45 m and one Coat of finish 25m shall be applied. SPA 2 b - Maintenance painting 1. Spot prime - DFT 45m 2. Spot MIO - DFT 45m 3. Apply Undercoat - DFT 45m 4. Apply Finish coat - DFT 25m K.A.stephenson

Or Spot prime + Spot MIO + One full coat of MIO DFT 50m SPA 3 Painting of metal surfaces for hot duties SPA 3 a - Operating temp. 100° C to 149° C 1. Masking 2. Washing 3. Blast clean 2 1/2 Profile 75m 4. Primer - Heat Resistant Aluminium pigmented epoxy DFT 250m Or Urethane Primer - DFT 100m Heat resistant paints are normally aluminium pigmented no finish coat required. SPA 3 B - Operating temp. 150° C to 340° C 1. Masking 2. Washing 3. Blast clean Sa 3 Profile 75m 4. Optional Systems a) Thermally sprayed Aluminium b) In-organic zinc silicate c) Poly siloxane inorganic coating SPA 3 c - Operating temp. above 340°C 1. Masking 2. Washing 3. Blast clean Sa 3 profile 75 m K.A.stephenson

4. Apply thermally sprayed Aluminium Or a) In-organic zinc silicate b) Apply silicone sealer c) Apply heat to cure sealer Or Polysiloxane in-organic Coating SPA 4 Painting of Damp Ferrous surfaces Moisture tolerant system for Damp surfaces 1. Degreasing with solvent, The surface shall subsequently be washed with a 2% detergent. 2. Blast clean Sa 2 1/2 3. Washing with clean water, droplets and standing water shall be removed from the surface. Cloths and rags shall only be used if they are lint-free. 4. All paints shall be brush applied 5. Apply Moisture tolerant system in accordance with Manufactures Instructions. SPA 6 Painting of Non Ferrous surfaces Corrosion protection required Non Ferrous surfaces are: 1. New galvanised Surfaces 2. Weathered galvanised surfaces 3. Previously painted galvanised surfaces 4. Aluminium surfaces K.A.stephenson

Paint System 1. Water borne acrylic 2. Epoxy high build 3. Alkyd or modified alkyd Total DFT is 120ď m New Galvanising - If sweep blast or hand abrading is not possible (impractical), an Etch Primer (T-Wash) shall be used. Weathered galvanising - Only stiff bristle brushing for surface preparation, no sweep blast or hand abrading Aluminium -Thin gauge Aluminium should not be blast cleaned. Treat with Etch primer. Chlorinated Hydrocarbon solvent shall not be used. The following Non Ferrous materials are painted for Cosmetic Purposes. 1. Stainless Steel Only Aluminium Oxide should be used as the abrasive for sweep blast Paint System - 1.Water borne acrylic, 2. Epoxy High build (Chloride free) 2. Pre-painted Cladding 3. Glass Reinforced Plastics (GRP) 4. Fusion Bonded Epoxy (FBE) 5. Multi Component Liquids (MCL) 6. Concrete Paint System for (2 to 6) 1. Water borne Acrylic 2. Moisture cured Urethane K.A.stephenson

3. Alkyd or Modified Alkyd

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