Influence of Climatic Factors in Cyclic Accelerated Corrosion Test Towards the Development of a Reliable and Repeatable Accelerated Corrosion Test for the Automotive Industry

摘要

Two designs of experiments (DOE) made of 9 accelerated tests each were used in order to study the influence of a selection of important climatic parameters such as the concentration of NaCl (1 and 0.5wt%), the drying level (45 and 70% RH), the basic humidity cycle (12 and 24 hours), the frequency of salt spray (2 and 7 times per week) and the temperature (35 and 45°C). The accelerated corrosion tests of a duration of 6 weeks were all performed using automatic chambers. In addition, another parameter related to mud containing chloride salts was also studied in order to simulate the effect of road mud on cosmetic materials. Different automotive materials were selected in order to study the resistance to cosmetic corrosion, perforation corrosion and bi-metallic corrosion. For cosmetic materials, coated panels of cold rolled steel (CRS), zinc coated steel (HDG, 10μm) and aluminium alloys (e.g. AA6016 and AA6063) were chosen. Perforation corrosion was investigated using crevice panels of CRS, zinc coated steel or different grades of aluminium alloys (6000 and 5000 series). From the results, the influence of testing conditions on the cosmetic and perforation corrosion of different automotive materials was obtained. As an example, it was shown that an elevation of the temperature from 35 to 45°C in the cyclic corrosion test increased the scribe creep on painted CRS and aluminium alloys while it has no significant effects on painted HDG panels. The results were also compared to that obtained after two years of exposure at a marine exposure site and on busses driving in area using deicing salt. From the results, it was shown that one of the test performed gives a good correlation to field results. The repeatability of this test was also studied.