Abstract
Reserch on avoidance of hazardous chemical substances in baking enamel coating on aluminum alloy has been continued and weatherability has been estimated by outdoor expsure tests in Okinawa and south of latitude 38 degrees N in Southeast islands. In this paper, the outdoor expusure test results on test pieces that applied chromium VI, chromium III, chromium phospahte, chromium-free chemical conversion and anodic oxidation as the surface preparation and coated with solvent type thermosetting fluorocarbon enamel are reported. Main results are as follows. (1) The coating on anodic oxidized aluminum alloy has most excellent wetherability and chromium VI chemical converted has excellent corrosion prevention effect as wel as the anodic oxidized. (2) It is judged that the coating on chromium III chemical converted has not quite different from chromium VI chemical converted in corrosion inhibition effect. However, the difference is claer in combination of kinds of chemical reagent and paint. (3) The coating on some chromium-free chemical conversion has enough corrosion protection effect. However, many kinds of the chemicals has remakable deterioration and it is difficult to keep stable quality. Therefore, it is necessary to apply carefully the chromium-free chemicals.
