PAINT PRETREATMENTS FOR ALUMINUM

摘要

Chemical conversion coatings are the most widely used prepaint treatment processes for metal substrates. Processes specifically designed for aluminum are of recent origin. These include accelerated chromate phosphates, chromate oxides, anodizing and, very recently,nonchromate formulations. Historically, however, phosphoric acid cleaners, wash primers, and iron and zinc phosphates have all been utilized as paint pretreatments with satisfactory results. Among these.the chromate types provide the most reliable under film corrosion protection and paint adhesion. Anodized coatings, especially unsealed sulfuric and chromic acid types, are also comparable in performance, but fall far short of the productivity and cost effectiveness of the chromate processes.