History of Automotive Coating

Throughout the 50s and 60s, corrosion was the major cause limiting automobile s life span. Cationic electrodeposition of a protective coating was the major invention in the late 1960s, eliminating corrosion as a major cause of automotive failure [5]. In this process electrically charged paint particles are deposited from aqueous solution onto metallic substrates by application of an electrical field. Today, 99 % of all vehicles manufactured use some type of electrocoat process. 

In the late 80s and early 90s new laws were enacted that governed the content and application of paints. The amounts of volatile organic compounds (VOC) were lowered using water-borne binder systems. Automotive paint systems are now well within VOC limits and comply with EPA standards for emissions. Today approximately 14 million vehicles are coated with water-borne technology each year. Out of the 99 North American assembly plants, 33 plants are using water-borne based coats (6). The main suppliers of OEM coatings are PPG, Dupont, BASF, Nippon and Kansai Paint company. 

Another approach to VOC reduction is the use of powder coatings, however, there is a lot of cost in converting existing spray booths to suit powder application. Hence, a variation on this theme is to use slurries of powder in water as automotive clearcoats. A new dearcoat system has been introduced, that offers zero emissions, is powder dispersed, and is stabihzed in water [7]. This method is used commercially by Daimler-Chrysler in Europe. 

Bayer recently won the Presidential Green Chemistry Challenge Award for its two-component water-home polyurethane system. Generally, isocyanates, one of the raw materials for polyurethanes, are unstable in water. Trying to make water the carrier for isocyanates was no easy task. Bayer modified isocyanate molecules to stabilize them in water, so customers can apply them together with polyols, just prior to painting, to make polyurethane coatings (8). 

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