Coating

Transcript

PAINT & PAINT APPLICATION. Three basic ingredients of a traditional solvent carrying paint. (i) (ii) (iii) Binder or Vehicle. Pigment. Solvent Functions of this ingredient. (i) BINDER 1. Binds the particles together and holds them in suspens suspension. ion. 2. Gives the paint its finish. 3. Gives flexibility to the paint film. 4. Gives resistance to Water, Chemicals & Abrasion. 5. Converts the coating to a solid dry film. 6. Makes the coating adhere to the surface. Functions of this ingredient. (i) BINDER 1. Binds the particles together and holds them in suspens suspension. ion. 2. Gives the paint its finish. 3. Gives flexibility to the paint film. 4. Gives resistance to Water, Chemicals & Abrasion. 5. Converts the coating to a solid dry film. 6. Makes the coating adhere to the surface. (ii) PIGMENT 1. Gives co lour to the paint. 2. Gives opacity to the paint. 3. Gives resistance to Acid, Alkali & Light. (iii) SOLVENT 1. Forms the evaporation part of the drying process. 2. Thins the paint so it can be applied easily. 3. Washes out brushes and equipment. 4. Acts as a degreasing agent if approved. Paint storage: Paints and thinners shall be stored in well-ventilated buildings. away from any sources of heat and taking into account current legislation and manufacturers storage conditions or 5°C below or less than flash point. Paints may be covered with tarpaulins or equivalent at the application site for fourteen days. Each paint container shall be marked in accordance with 09-SAMSS-060 (Aramco standard) Paint shall not be used from a container, which shows signs of leakage. Paints, which have exceeded the shelf life, shall be discarded. SAES: Saudi Aramco Engineering Standards. SAES-H-001: Selection requirements for Industrial coatings. SAES-H-100: Painting requirements for Industrial facilities. SAES-H-101: Approved protective coating systems. APCS-1B : Fire proofing. APCS-26/26T: Operating upto 120 deg.c SAES: Saudi Aramco Engineering Standards. APCS-1C: Primer only to touch-up and repair galvanizing that will not be coated with another system. SSPC PA2: Measurement of dry paint thickness with magnetic gauges. SSPC SP1: Solvent cleaning. Do not use kerosene, diesel, or other detergents that leave an oily film. Paint preparation: Paints, which have gelled, shall not be used. Paint skins shall be cut and removed before application on recently opened and partially used containers. If any skinning is found on previously unopened paint, those cans should be set aside and not used. Paint preparation: Prior to application all paint shall be thoroughly mixed until it is homogeneous. For quantities over five liter, a power stirrer shall be used. If sludge is formed in the bottom of the can then mixing shall be contained until the paint is homogeneous. If the sludge cannot be dispersed, the paint shall not be used. All paints in a coating system shall be supplied by the same manufacturer. Partial mixing and twocomponent and multi-component coating is prohibited. Very Important Rules for the mixing of paint Up to 5lts in size may be mixed by hand. Above 5lts must be mechanically mixed (Stirrers). SOME DEFINITIONS INDUCTION PERIOD It is a length of time a 2-pack paint has to stand after mixing and before application. The time allows air bubbles to escape or chemical reaction to take place, and is stated by the paint manufacturer. POT LIFE It is the length of time following induction period or after induction that a 2-pack paint remains in an applicable condition according to the manufacturer’s instruction. Dew point: The temperature at which condensation would form on a substrate. Relative Humidity( R.H): The amount of water vapor in the air expressed as a percentage and calculates from the wet and dry bulb temperatures. Flash point: The lowest temperature at which a given material will flash, if a flame or spark is present. Shelf life: Maximum interval in which a material may be stored in a usable condition. Batch number: Manufacturer's data number for production date. Masking out: Must be carried out on items to be protected during preparation and painting, items normally masked out are control equipment, fire protection equipment, weld ends, sensing and spraying heads, name plates. Rust blooming: It is caused by moisture or humidity on new blasted steel and shows up before priming. Procedure for removal of soil and grease from a surface before preparation commences. Because of oil & grease paint will not spread properly. White spirit should not be used. Use only approved solvent with safety precaution to be followed. For applying solvent use disposable swab. Do not use cotton rags. After solvent cleaning use a detergent pressure washing followed by clean water, rinsing and then drying it. Solvent like Xylene. Procedure for removal of oil and grease from a surface after preparation. Contaminated area must be swabbed with an approved solvent, followed by a 2% detergent wash, further followed by a washing with clean water, thorough drying and re-blasting. Care must be taken that disposable lint free swab must be used once only. T-Wash It is an etch primer. When applied first it provides a key for new galvanized steel. Blue in colour. Turns black upon drying. *T-wash should not be used in aluminium. Use PVB* Paint application: Not allowed Painting Condition General: Paint shall not be applied if one or more of the following conditions exist. 1. The substrate surface temperature is less than 10 deg.C 2. The substrate surface contains oil, grease, dirt, loose paint, loose rust or other surface contaminants. 3. The substrate surface temperature is less than 3 deg.C above the dew point. Paint application: 1. Adverse weather conditions exist such as but not restricted to the following, a). Winds strong enough to blow sand, salt spray or other foreign matter on to the surface being painted. b). Wind strong enough to cause dry sprayer other wise cause serious variation in the spray pattern when applied by spray gun. Note: Primer, intermediate coat and topcoats shall be of contrasting colors always. If more than one application is required to achieve the specified minimum dry film thicknesses of the primer, intermediate coat or topcoat, these coats shall also be of the same color. Allowable Painting conditions. 1. The air and metal temperature is at least 3ºC above the dew point temperature. 2. The relative humidity is less than 90 % 3. The temperature for application for application is within the manufactures given limit. Very Important. Welds, edges, bolts and rivets shall be given a brush applied stripe coat prior to normal painting. Methods of Paint Application: There are three methods of applying paints as follows. (i). BRUSH 1. 2. 3. 4. 5. 6. 7. Cheap to purchase. Easy to maintain. Slow to use. Cannot apply all coating type. Good for applying primer. Best for strip coat application. Access is poor. (ii). ROLLER 1. 2. 3. 4. 5. 6. 7. Cheaper to purchase. Easy to maintain. 2-3 times quicker than brush. Leaves an uneven coating. Exterior poles make better access. Roller spray is messy. Orange peel & heel marks effects are undeniable. (iii). SPRAY 1. 2. 3. 4. 5. 6. Very expensive. Up to 30 times quicker then brush. Only method for applying high volume and high thickness. High degree of safety required P.P.E is required. Masking out is required. Maximum allowed time for priming to take place following the surface preparation . Maximum four hours following completion of blasting. Distance to be left at areas to be welded when painting. - Seventy five (75 mm). New paint overlapping old on repairs. 100 mm. Distance and angle a spray gun is held from the surface. Distance - 18", 450 - 600mm, at an angle of 90 . Things to avoid to clean out paint kettles or to dispose of rubbish. Fire or Flames should not be used. EIGHT POSSIBLE MALPRACTICES. 1. Using unqualified personnel. 2. Carrying out further work before inspection completed. 3. Attempting to skip a coat. 4. Preparing and painting when weather conditions are unsuitable. 5. Using paint, which is out of date. 6. Using incorrect solvent for degreasing. 7. Not observing induction and pot life times. 8. Incorrect storage of paint. Protective coatings and their drying or curing method. 1. Alkyd - Solvent evaporation followed by oxidation. 2. Chlorinate rubber –  Solvent evaporation only. Non-convertible coating. 3. Two pack epoxy - Solvent evaporation followed by chemical reaction. 4. Fusion bonded epoxy - Heat Non-destructive D.F.T. gauge & Destructive gauge. (i). Non-destructive gauge: Banana gauge or Electronic gauge like Elcometer model No: 345 & 456 (i) Destructive gauge P.I.G. - Paint Inspectors gauge. Paint Defects Bleeding: Is a discoloration of a new paint applied over an old one. Bitumen and paints contain red pigments are particularly problematic. Blooming: It is where a finishing paint assumes a milky type appearance and the loss of gloss due to color or dampened air settling on the paint before it was dry. Blistering: Dome shaped blisters formed due to contraction - dry blisters. Osmotic blisters: It is formed due to entrapped liquid, gas and salts. Chalking: Paint becomes powdery or chalky. Break down of the binder due to ultraviolet light and also due to poor weather condition. Cissing: In-complete paint films due to paint over oil and grease. Grinning: Seeing the underlying surface through the finish coat. Color contrast, lack of opacity. Holidays: Poorly or missed coating. Pin holing: Holes down through the paint caused due to escape of gases. Flocculation: Separating out paint constituents in the tin and the refusal to be stirred back together again. Lifting: Attempting paint over, underneath a coating, which is not fully cured. The evaporating solvent will lift up, picking up. Roopiness: Brush marks in a painted surface. Solvent Stripping: Paint with a powerful solvent will lift the coating underneath due to the power of the solvent. Oxidization: The drying process between certain binders and oxygen e.g. alkyd resin. Chemical Curing: The mixing of two components which produces drying in a two-pack paint.