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With ever-increasing emphasis on the environment and the decrease in available landfill locations, the generation and disposal of phosphate sludge has become a challenge in many countries. This study examines key parameters of a trication zinc phosphating process and their effect on sludge generation. Using Design Of Experiment, (DOE), principles, the effects and interactions of the key parameters were identified and used to optimize the process to achieve a 30% reduction in sludge without compromising performance. Included in the results are the derived regression equations for sludge, coating weight, metal loss, p-ratio and APGE cosmetic corrosion.

This is the second paper which describes the activities of the SAE Automotive Corrosion and Prevention (ACAP) Division 3 (Environmental Mechanisms) Cosmetic Corrosion Subcommittee's evaluation of cosmetic corrosion test methods using the American Iron and Steel Institute (AISI) supplied test materials. The results from fourteen corrosion tests are compared with field results obtained after two years of on-vehicle exposure in Montreal and St. John's, Canada. Standard statistical methods for treating such data are used. The accelerated tests that were evaluated include cyclic, environmental, outdoor, as well as proving ground tests. Conclusions are drawn regarding the use of these tests and suggestions are made for further work.

The accelerated corrosion test performance of various automotive sheet steels was used to determine the effectiveness of chromium-containing (Cr+3/Cr+6) and chromium-free post-treatments. Laboratory prepared panels treated with state-of-the-art pre-treatment systems, followed by either a chromium-containing or a chromium-free post-treatment, were painted with cathodic e-coat and topcoat systems being used by different automobile manufacturers. These panels were then tested in a number of accelerated corrosion tests used by the automotive industry. The test results showed that a chelating-polymer, chromium-free post-treatment gives corrosion performance equal to that of a post-treatment containing chromium.