AUTOMOTIVE PAINTS 1-11 AUTOMOTIVE PAINTS 1. PERFORMANCE OF PAINTS The following kinds of performance are required of automotive paints: (1) RUST PREVENTION Rust preventing performance is crucial to the undercoat (putty, primer-surfacer, etc.) that is applied directly to the steel surface. (2) FILLING RUST PREVENTING II Filling is used to fill dents in the damaged bodywork, sanding scratches and pin holes in the undercoat. (3) SEALING {PREVENTION OF ABSORPTION) Putty and other undercoat materials often have many tiny holes. When the top coat is applied directly over those porous materials, those holes will absorb the wet paint and the top coat will lose its luster.
To protect the top coat from absorption, a paint having a sealing power must be applied before the top coat can be applied. FILLING When the top coat is applied directly over the undercoat containing a partially exposed steel sheet, the new paint in the exposed area tends to run. This also pre- sents a problem in paintwork. Sealing, called the second coat, is also used to ensure even absorption of the new paint in the undercoat. Adjustment of paint absorption is one of the important roles of paint. PREVENTION OF ABSORPTION (4) COSMETIC QUALITY When applied properly, paint gives the col- or, luster and smoothness to the surface.
In addition, all these elements will last over a long period of time. (5) ADHESION The base metal or the undercoat must firmly hold the new coat of paint so that the two coats will never peel away from each other. (6) WORKABILITY Another important requirement for paints is the ease of use. They must be mixed easily, applied easily, must dry quickly and must also be ground and polished easily. COSMETIC QUALITY - 13-