Search Results

Conventional prepainted organic coatings on zinc nickel substrates consist of a dried-in-place chrome bearing pretreatment layer followed by a thin film solvent-based organic topcoat. This system is generally applied in order to provide additional corrosion protection to the brittle zinc nickel layer subsequent to forming. An improved version of this organic/metallic coating system has been developed which consists of applying a one-coat water-based chrome bearing epoxy to zinc nickel material. In addition to the production efficiencies gained by applying a one-coat prepainted system, enhancements are also realized with regard to corrosion resistance and formability characteristics. It has also been found that a novel curing technique can be utilized in order to allow for higher temperature curing of prepainted materials on bake hardenable substrates without adversely affecting mechanical properties.

Poor durability of steel/adhesive bonds in the presence of moisture has inhibited widespread structural use of this joining technology. The durability of metal/adhesive bonds can be influenced by a number of variables. Effects on durability due to substrate, surface preparation, and environmental exposure were examined using single lap-shear adhesive joints. Cold rolled steel, galvanized steel, and Zincro-metal adherends were untreated, alkaline cleaned, lubricated or zinc phosphated prior to bonding. All samples using treated bare steel exhibited higher initial bond strength but poor to fair durability. However, samples prepared from Zincrometal adherends actually retained most of their initial strength even in accelerated environments. The reported results suggest that simply cleaning adherend surfaces prior to adhesive bonding is inadequate to insure long term durability.