Elimination of Electrocoating on Aluminum Intensive Vehicles

Due to the inherently superior corrosion resistance of aluminum compared to steel and galvanized steel, electrocoating is not an absolute necessity for aluminum intensive vehicles. Therefore the possibility exists to eliminate electrocoating and thereby reduce overall finishing costs for aluminum body structures. Previous work has shown that selected powder primer/surfacers applied to non-chrome pretreated aluminum panels resulted in adhesion, corrosion and appearance characteristics equal to or better than conventionally phosphated, electrocoated and finished material. To demonstrate this concept on a complicated automotive body structure, a corrosion test piece was devised that incorporated the features of a body-in-white. The test piece included both adhesively bonded AA5754 components and AA6111 mill finished sheet. Distribution of the powder coating on these specimens, adhesion, cosmetic and galvanic corrosion performance were evaluated. In addition to the technical feasibility of this finishing treatment, a detailed analysis of the potential cost savings derived from optimized processing of aluminum prior to primer/surfacer application is shown for comparison to conventional processing.