Effects of salt deposition and temperature on polarization resistance of steel and the galvanic current of steel-aluminum couples during exposure to cyclic humidity

Use of aluminum alloys for automotive applications is growing steadily. How ever, galvanic corrosion is a major concern with those alloys. Because of t he predominate use of steels in the automotive industry, the majority of ac celerated test procedures commonly accepted by industry are designed for co smetic corrosion and perforation of steels. Adopting such tests for galvani c corrosion of aluminum alloys without a fundamental understanding of the p rocess may produce misleading results. Electrochemical studies were conduct ed to examine the acceleration effects of several parameters on different t ypes of corrosion. Galvanic corrosion of Al 6111 (UNS A96111) and cold-roll ed steel (Al/CRS) couples and general corrosion of CRS substrates were stud ied. Test results showed increases in sodium chloride deposition and temper ature decreased polarization resistance of steel and increased the galvanic corrosion current of the Al/CRS couples.