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Paint Your Car with...Water?

By Rich Boone, Product Manager and Eastwood Expert

Water-based paints are the future of automotive coatings...the very near future. All automotive paint manufacturers are working on this technology and many have already released water-based products into both the OEM and refinishing markets. The transition from solvent-based paints, such as urethanes, to water-based is not a difficult one. Although there are differences, there are also a number of similarities between water-based and solvent-based paints.

Both technologies are the same in their core composition. Both are composed of a pigment for color and a binder for a film. The pigments used are often identical, giving water-based paints the same light-fastness and color options as a solvent-based paint. The binders, while chemically different, are both forms of an acrylic and each are made specifically for exterior uses, giving water-based paints the durability necessary for an automotive coating. The key element which separates the two is the carrying agent, that is, the mode by which the pigment and binder are transmitted from the gun to the substrate.

Conventional paints use solvent, which rapidly dissipates from the surface for chemically controlled time windows, whereas water-based paints utilize water, which evaporates at a slower rate depending on temperature, humidity and air flow. The cost of the solvent-based paint's quicker cure time is the release of noxious fumes into the air, a major drawback compared to water-based paints. However, as water-based paints continue to evolve, mild co-solvent reducers and additives are being introduced to improve performance and drying times. Though not as severe as solvent-based paints, there is a slight release of a noxious element when such reducers are used with water-based paints. This is why it's important to always use proper respiratory protection when painting with any type of automotive paint.

Water-based and solvent-based paints are typically compatible. Urethane primers, paints and clears work perfectly well with water-based paints. Some water-based systems, such as Auto Air colors, depend on using a urethane primer and clear along with its paint for a complete finish. The key behind the compatibility is that water-based paints are non-reactive and able to accept and bond with any type of solvent, provided the content of the solvent is not too harsh or volatile. Urethane paints and modern lacquers with lower VOC content work well. Some enamels and lacquers use a very harsh solvent, which degrades the composition of water-based paints. It's advisable to test first if you have any doubts about the compatibility of a product.

Water-based primers and paints are not a new technology for automotive coatings. They've been around for over a decade. Their increased exposure and hastened development have been due to efforts to comply with increasingly demanding environmental standards. Water-based topcoat clear technology has not developed to the point where it is a suitable replacement for urethane clears. Fortunately, the two are compatible and, when used properly, a beautiful finish can be achieved while reducing VOC exposure without compromising the quality or integrity of the finish.