Paint Materials Guide - Color Chemistry

Understanding Paint Top-Coat Materials

Steve Dulcich May 25, 2010 0 Comment(s)
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The drawback to the factory acrylic lacquer was definitely long-term durability, especially in comparison to today's materials. The paint was susceptible to chemical and environmental damage, fade, and loss of gloss over time. Worst of all, the paint became brittle with age and would crack and check, literally self-destructing. Although acrylic lacquers are still available, these paints are all but obsolete in the world of commercial automotive refinishing. About the only application where these products would be considered would be in contemplating an authentic OEM restoration.

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Eventually, by the '80s, General Motors phased out the lacquer paints in favor of an evolution of modern paint materials, beginning with acrylic enamels, and leading to the basecoat/clearcoat material formulations in use today.

Modern Materials
The basis for the modern commercial finishing processes today are acrylic enamels, urethanes, and increasingly, water-borne or water-based products. As noted, acrylic enamels have been utilized by the OEM manufacturers for many decades, and these paints have long been the standard for the refinishing industry as well. The common air-dry enamels are at the bottom rung of the acrylic enamel ladder, typically the material of choice for a low-dollar, blow-over paint shop. Air dry enamels are very slow to cure, are only moderately tough in terms of chemical resistance, polish poorly, and are prone to fade.

As early as the '70s, highly developed catalyzed acrylic enamel formulations began to come on the market, with cross-linked chemistry that offered exceptional gloss, durability, and an excellent ability to be polished. With these very desirable attributes, the catalyzed acrylic enamels became the mainstay of the commercial and custom painting industry. These paints are still readily available, and offer outstanding value and results. For a single-stage paint application (no clear coat) to mimic the OEM lacquer paint, these catalyzed acrylic enamels are a viable alternative.

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The next level in the evolution of paints was the move from acrylic enamels to urethane paints. These formulations essentially took the best attributes of the catalyzed acrylic enamels and went one step further in durability. Most commercially available paint product lines, particularly the higher-end products, are all urethane formulations.

Paint product formulations are continuing to evolve, with many of the changes having to do with reducing toxicity and meeting environmental concerns. With this there is a move towards reducing solvents, particularly those classified as Volatile Organic Chemicals. VOC levels are closely regulated in the commercial refinishing industry in some areas, prompting paint manufacturers to revise formulations to meet the ever-tightening requirements. An evolution resulting from these forces is the expanding use of water-borne or water-based paint products. These products are designed with formulations to allow them to be soluble in water rather than petroleum-based solvents. While early on, these formulations had significant problems, ongoing development has led to much-improved and sometimes superior products that fit under this category. Some localities have mandated these formulations to replace solvent based paints in commercial refinishing.

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Single vs. Two-Stage
With the advent of modern paint systems, so came the prevalent use of clear coats as the final top coat of the paint system. In older refinishing systems, the paint was what you got-and that was it. The color coats of paint carried all of the color, sheen, and gloss of the finish, a system now referred to as a "single-stage" paint system. This is the type of paint finish that was original to all older production cars, including classic Corvettes.


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