Automotive Test Procedures-Corrosion versus Adhesion Properties of Painted Metal Substrates

One measurement of the quality of a phosphated and painted metal substrate is through the use of accelerated test procedures involving corrosive environments. The subsequent test results have been found to have dependance upon the specific test procedure that was utilized. In particular, the effects of the acidulated rinse upon galvanized steel were strongly dependent upon the test procedure involving adhesion measurements after water immersion; whereas, a negligible effect was exhibited via a cyclic scab test procedure. Finally, it was determined that a chemical modification of the phosphate coating composition can alter the effects of the acidulated final rinse upon hot dipped galvanized steel with respect to adhesion performance.