PAINT BASICS AND CORROSION IN METAL AIA103Basic Composition of Paint Solvents (Liquids) Pigments Additives Resins (Binder) 2 Prime Pigments • Titanium Dioxide (TiO2) •provides excellent hiding power and whiteness •available as a solid (powder) or liquid (slurry) • Zinc Oxide •controls mildew •resists ultra-violet light •resists yellowing Titanium dioxide is the world's primary pigment for providing whiteness, brightness and opacity. 3 Alkyd. Epoxy.Resins • Types: Latex. Polyurethane • Binds or glues ingredients (pigments and additives) of paint together • Resin provides adhesion to the substrate • Resin provides durability & resistance properties: • U-V resistance • Moisture resistance • Chemical resistance • Stain resistance • Fade resistance • Chalk resistance • Block resistance 4 . velvet. etc. • Gloss is measured at 60° for flat to gloss ranges. low sheen. satin. pearl. suede.Gloss/Sheen Levels • Gloss or Sheen of paint refers to reflectivity or how shiny the dry paint film is. 5 . • Sheen is measures at 85° between flat to eggshell • Some paint manufacturers use different terms to define products between flat and semi-gloss: silk. eggshell. • There is lack of standards and confusion in the paint industry related to gloss or sheen levels. low luster. Gloss/Sheen Levels Term Flat Velvet/Low Luster Eggshell Low Sheen Semi-Gloss Gloss Gloss @ 60° 0-5 5-10 10-20 20-30 55-70 75+ Sheen @ 85 0-5 5-15 15-25 6 . linseed. 7 . tung-oil oil commonly used Benefits of alkyds: -Superior brushing characteristics -Abrasion resistance -Excellent flow and leveling -Good adhesion -Used in rust preventative paint Alkyds have limited availability and use in California.Alkyd Resin Technology ALKYD (Oil-Based) • • • A synthetic resin made by reacting alcohols and fatty acids Soya bean. Latex Resin Technology LATEX (water-based) Synthetic polymers Main resins - 100% Acrylic Styrene Acrylic Vinyl-Acrylic Acrylic Copolymer Vinyl Acetate Ethylene 8 . Latex Resin Technology QUALITY Latex paint benefits include: * Ease of application * Yellowing resistance * Chalk resistance * Washability * Good flow & leveling * Excellent adhesion * Improved adhesion * Low odor * Color retention * Gloss retention * Durability * Flexibility * Scrub resistance * Water clean-up 9 . Over that time. Top left: Alkyd paint Top right: Vinyl-Acrylic paint Bottom left: Alkyd paint Bottom right: 100% acrylic paint 10 . while it has chalked and faded. and. it retains its original green color.Acrylic vs. Alkyd Paints These paints have been exposed to the elements for 46 years. The 100% acrylic paint remains in remarkably good shape. the PVA (and the alkyd) paints have disintegrated. The paint film is essentially intact. the paint on the right half. The colors of the paints were identical when applied. an alkyd. and chalked. All have lost gloss. faded. After 15 years of weathering. The acrylic paints. have proven remarkably durable with good color retention.Acrylic vs. the appearance of the alkyds has changed dramatically. in contrast. 11 . Alkyd Paints The paint on the left half of each board is acrylic. 12 .Premature Coating Failure DEFINITION: The deterioration of the coating system. more rapidly than would normally be expected under the service conditions. or corrosion of the coated surface. copper oxide. 13 . In aluminum. Salts in the water will accelerate the process. • These metals will not rust or corrode unless a conductor between the two metals or atoms is present. aluminum oxide and in copper. • Water or oxygen in contact with the metal for a longer period of time is normally the conductor that starts the rusting or corrosion process. The new compound is called oxide. In iron it is called Iron oxide.Corrosion • Simply put. corrosion is created when two dissimilar metals at atomic levels come into contact with each other and create a chemical reaction. • Passivators are a coating applied at time of manufacture to protect the zinc. dew. condensation) contain no dissolved salts or minerals. • Acid or acid rain. will accelerate the deterioration of the zinc finish. 14 . Pure water will react with zinc hydroxide quickly to create white rust.• White Rust Galvanized Metal • Pure water (rain. 5% • Unforeseen Circumstance 10-15% • Improper Specification 25-30% • Improper Prep/Application 45-55% 15 .Causes Of Paint Film Failures (New ) • Faulty Products 2 . THERE ARE TWO (2) MAJOR CAUSES FOR IMPROPER COATING SPECIFICATIONS 16 . Inadequate or incomplete project information 2. Lack of product knowledge 17 .1. PROJECT INFORMATION NEEDED……. 18 . CUSTOMER NEEDS DETERMINE COATING SYSTEM EVALUATE THE ENVIRONMENT DETERMINE SURFACE PREPARATION EVALUATE SERVICE REQUIREMENTS EVALUATE EXISTING SURFACE CONDITIONS 19 . sharp edges) • Removing tightly bound mill scale & rust 20 .What are the Goals of Surface Preparation? To provide a surface suitable for painting by: • Removing contamination • Providing a surface profile • Removing or smoothing irregularities (pits. projections. What Surfaces Require Preparation? • Iron and Steel • Galvanized Metal • Aluminum • Copper • Miscellaneous metals • Pre-Coated Metal Siding • Previously Painted 21 . CORROSION ! HOW MUCH ? 22 . 23 . Results of Pin Hole Rusting of the Primer 24 . What is the Environment? • • • • • Type – P Type – M Type – C or Type – A 25 . Type P: Protected Architectural 26 . Type P: Protected Architectural • • • • Not subject to chemical contaminants Normal humidity range Normal industrial interior Corrosion of steel or galvanized surfaces negligible 27 . Type M: Moderate 28 . Type M: Moderate • Exterior weathering • Normal industrial atmosphere • Moderate concentrations of chemical fumes • Corrosion of steel < 3 mils / year and galvanized substrates negligible • Concentrations of chemical interior – light to moderate fumes without humidity 29 . Type C: Corrosive 30 . mists or dust • Corrosion of steel 3 .Type C: Corrosive • Moderately aggressive chemical fumes.6 mils / year and galvanized substrates < 1 mil per year • Adjacent to Type A: but at least • 30 yards away 31 . Type A: Aggressively Corrosive 32 . mists dusts or contaminates Corrosion of steel > 6 mils / year and galvanized substrates > 1 mil per year Usually confined to an area within 30 yards from corrosion source 33 .Type A: Aggressively Corrosive • • • • Immersion service Excessive exposure to aggressive chemical fumes. Application • Apply the coating system using one manufacturer • Apply according to the manufacturer’s recommendations • Apply to the Dry Film Thickness (DFT) as stated by the manufacturer • Recoat within the window specified by the manufacturer • The finish system shall be a solid uniform finish free of voids and pinholes. 34 . Factors Affecting Coating Performance Protection • Structural Design (We can’t control) • Coating Selection • Surface Preparation 35 . A Poor Design 36 . Other Design Considerations • Surfaces should be smooth (e.g. welds) • Welding preferred to riveting • All surfaces should be well drained • Stiffening members should be on the outside surface of tank or vessel 37 . THANK YOU PROVIDER J476 .