High-resolution SEM studies of chromate conversion coatings

Scanning electron microscope studies have shown that chromate paint pretreatment of commercial purity Al resulted in the deposition of a film comprising layers of spherical-shaped particles. On alkali-etched substrates, the particle size varied from between 60 to < 10 nm. The larger particles tended to occur either in some of the larger pits on the surface or in the vicinity of intermetallic particles. Uniformly sized 50-60 nm particles were deposited on the surface of a polished substrate. Penetration of organic resins into the particulate surfaces may contribute towards the good paint and lacquer adhesion resulting from the pretreatment process. 18 ref.--AA(UK/US).