April 4, 2009
Automotive paint is mixture of basic ingredients that include a pigment, a binder and thinner. It’s the composition of each that is the tricky part. The paint itself can be water, acrylic or oil based and the chemical composition, application and properties of each base vary widely. Lets look at the various components of automotive paint.
Most modern automotive paint is water based, using a low solvent urethane does produce a softer and more porous paint. This recipe is mostly for environment regulations and are non-toxic.
Paint thickness – Most modern vehicle painting systems comprise of a primer coat of approximately 2 Mils, a color coating of about 1 to 2 Mils and a final clear coat that is up to 3 or 4 Mils thick. To visualize the thickness a Mil is 0.001 inches thick. A single piece of saran wrap is .75 Mils thick. If you folded saran wrap to make it 9 to 10 sheets thick , that is the thickness of about 7Mils which is the thickness of your primer, color and clear coat all together. I would try it out. put 10 layers together and just see how thick your paint is, it’s not thick at all. The color part is only 2 or 3 layers of saran wrap thick ( as a comparison )
Paint Composition – The paint itself is made up of Color ( pigment ) and is generally titanium oxide. This makes up the primary color of the paint, other secondary colors or pigment additives comprise of various compounds such as calcium, talc, mica, etc. These secondary compounds are added to achieve a desired viscosity, levelling, sheen, appearance or flexible properties. A binder is also required and is used with both the color and clear coat layers. This component gives the paint and clear coating it durability and keeps everything bonded together ( it’s hardness ). A resin is also the term used for the binding portion of the formula.
Below the paint and primer, there is a layer you can apply (not usually done by new car manufacturers ), it is an epoxy coating. This seals the surface and enhances the bonding ability of the primer and paint to the surface of the vehicle. It is often used in high end cars, and restoration projects.
The clear coat is a clear two-part paint. It is a polyurethane or urethane paint that provides a tough, clear and durable protection layer to the software water-based color coatings. Because water-based paints are generally more porous, the clear coat bond exceptional well to them, producing a permanent bond between the layers.
Types of paints.
Lacquer – Nitrocellulose type lacquer paint has rapid drying and low viscosity properties and is applied with a spray gun. When polished, and waxed, it far surpasses in durability and appearance the qualities of the Japanese lacquers. Acrylic type lacquer is a substitute for nitrocellulose lacquer and use an acrylic resin as a base. These lacquers have a characteristic of being brittle, therefore a solvent is added to these formulas to soften the paint. This type was used extensively by GM.
Enamel – synthetic enamels are generally superior in film strength, adhesion, sheen, flexibility and durability over all other paints. It dries by solvent evaporation, like the lacquer paints, but the resin remains soft and sticky as the solvents evaporate. The curing process is then completed by the reaction between the resin and oxygen. The curing process produces a hard finish. This curing process can be accelerated by heat and is why you see a lot of cars being backed in the sun or heat booths to complete a paint job. Acrylic Enamel is similar to synthetic enamel, but is modified with acrylic resin, which is not soft and sticky when the solvent evaporate. It still cures further with oxygen reaction. Polyurethane enamel was developed to withstand the severe stress of high speed airplane surfaces, which are subject to rapid temperature changes and flexing. This paint was much more durable than the acrylic enamels. Acrylic urethane enamels were developed to withstand environmental elements, such as acid rain and ultra violet (UV) radiation, and is the most durable paint to date.
Modern Technology – 2007 +
Nano technology – CeramiClear is the latest development and uses micro sized ceramic particles to provide a durable finish. This coating requires special care and does not react well to traditional detailing and polishing processes. Consult the manufacturer for maintenance and care procedures.