Environmental management for baked enamel coating system onto aluminum alloy building materials

Part19 Analysis of outdoor exposure test specimen for different types of pretreatment

Abstract

Reserach on avoidance of hazardous chemical substances in baking enamel coating on aluminum alloy has been continued. In this paper, analysis results of coating film surface, and backface and cross section of peeled off film that has been outdoor exposed for 84 months at 2 sites in Okinawa mainland are reported. Main results are as follows. (1) Sodium and Chloride on the outdoor exposed specimen surface are largely detected from the specimen that has exposed at Ikeijima where the coating has been deteriorated since early in their exposure test. (2) Existance of aluminum chloride and oxide are estimated in the blistered part based on elements detected from the substrate surface and the peeled off coating backface that has been blistered. (3) It is presumed that chrolide exists on the coating blistering part on the aluminum substrate and aluminum oxide has been produced based on the cross section observation. (4) It is judged that the adherent chloride to the specimen causes to accelerate the deterioration including the coating gloss down, chalking and blistering etc. (5) Elements analysis on the outdoor exposed test pieces is useful for coating durability estimation.