Color Coating Literature’s

The exact composition of a particular paint is often complex and proprietary. In general, however, most paint contains the following:

• Binder The paint binder (or resin) is the solid material that forms the bulk of the paint film. It is generally a tough, amorphous polymeric material that gives the paint most of its thermal, mechanical, and weathering properties.

• Solvents It adjusts the viscosity of the paint to suit the method of application. Turpentine is generally used as a thinner in oil paints. In emulsion paints, water is used as a thinner.

• Pigments Paint pigments are small, hard particles that come in a wide variety of shapes. Their principle functions are to cover the substrate since most binders, by themselves, are more or less translucent. To provide color as required by the appearance of the finished product.

• Additives Additives are modifiers added to paint, usually in small quantities, to achieve special effects. They modify the properties of either the wet film or the dried paint and can affect flexibility, color fastness, gloss, solvent resistance,etc.

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Incorporation of pigments and extenders into the binder resin to obtain a product smooth & homogeneous. Dispersed in a mixture of solvent which remains liquid throughout the formulation of the film. The first step in making paint involves mixing the pigment with resin, solvents and additives to form a paste. Then paste to be routed into a bead mill. A large cylinder that agitates tiny particles making them smaller and dispersing them throughout the mixture. This is done in high speed dispersion tank which is circular. There is a rotating shaft with blades which agitates the mixture and blends the pigments in solvent. Adjustment of viscosity.

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Pre Painting

Coil coating is the most advanced technique for applying organic coating (liquid or film) to sheet metal in a continuous process. Since its inception in the early 60’s the European coil coating industry has produced over 8 billion sq. m., of precoated metals and its products are firmly established in markets such as construction, automotive, domestic appliance, heating and ventilation, packaging, office furniture, shelving, caravans, lighting etc.

Post Painting

Post painting means, painting a metal surface after producing components. Example: Automotive, Appliances using powder coating

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Bare coils of metal are placed on an unwinder or decoiler where the metal is observed for defects. The metal is then cleaned and chemically treated in preparation for painting. Brushes can be used to physically remove contaminants from the sheet, or the metal may be abraded by flap sanders to further enhance the surface. Pretreatments are used to provide the bond between the metal and the coating, in addition to adding any corrosion resistance. The type of chemical treatment varies with the type of metal being used. After drying, the strip enters a coating room for a coat of primer usually on both sides of the sheet. The pickup roll transfers the coating liquid from the pan to the applicator roll. The liquid is then pumped into the pan, and then overflows back to the supply reservoir, where it is remixed and filtered. The paint sheet then enters an oven in which the coating is cured at high temperatures for 15 to 30 seconds. The strip exits the oven and is cooled with air and water. A majority of specifications call for two coats (primer and top coat) on each side of the sheet, requiring a pass through a second coater room and oven. The fully painted sheet then exits the second oven and is cooled before inspection and rewind.

Optimum balance of properties. Guaranteed uniform Surface finish. Enhanced corrosion resistance of substrate. A durable surface which minimizes handling damage. A material which can precisely and consistently meet design specifications in terms of coating thickness, appearance and overall performance. Expenditure on effluent disposal eliminated. Efficient, Energy Saving, Environmental Friendly, Economical. Prepainted metal can be fabricated, formed, drilled, riveted, embossed & bent into required shape and size. Prepainted metal stands against aggressive environmental weathering conditions.

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Pre-painted galvanized steel sheets can be use on roofing , walling , cladding , false ceiling, appliances, rolling shutter doors, fencing, cold boxes, pre-engineering buildings, sign boards, partitions, office furniture, drums, insulations etc.

ASTM A755/A755M – 15

Standard Specification for Steel Sheet, Metallic Coated by the Hot-Dip Process and Prepainted by the Coil-Coating Process for Exterior Exposed Building Products. EN 10169 – Continuously organic coated (coil coated) steel flat products. General information (definitions, materials, tolerances, test methods) JIS 3312 – Pre-painted Hot Dip Zinc coated Steel sheets and coils Pre-painted steel Test standards (EN13523)

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• Formability

• Durability

• Robustness

• Corrosion protection

• Visual appearance

• Cost

• And any special requirements such as chemical resistance

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Lead paint is any paint that relies on lead compounds for its colour. White lead, or lead (II) carbonate (PbCO3), is a typical example, and was once widely used to paint wooden surfaces in homes. Other lead compounds, like vivid yellow lead chromate (PbCrO4), were used as coloured pigments. As well as giving the paint its tint, lead pigments are highly opaque, so that a relatively small amount of the compound can cover a large area. White lead is very insoluble in water, making the paint highly water-resistant with a durable, washable finish. Lead carbonate can also neutralise the acidic decomposition products of some of the oils that make up the paint, so the coating stays tough, yet flexible and crack-resistant, for longer.

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Lead-free Paints :

Some paints are now manufactured without lead. The most widely used lead substitute is titanium dioxide, also used for coloring food. Organic pigments can also be alternatives. For quicker drying and gloss, zirconium can be used. The barium-zinc-sulfur combination replaces white lead. But the substitutes are costlier than lead. Therefore, the manufacturers prefer to use lead in paints. In India, Nerolac has launched its lead-free paints. Now the company does not add any lead or other heavy metals in its manufacturing process (see logo), claims nerolac.com. ICI Dulux, too, does not use lead in its paints. Around the image of a green tree its label states: No added lead, mercury, chromium compounds. Asian Paints and Berger Paints also make similar claim. However, lead contamination, lower than limits set by various organizations, may occur through ingredients.

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