Abstract
As the use of aluminum for automotive applications continues to grow, there will likely be a continually growing number of applications involving steel-to-aluminum joints. For such an assembly, galvanic corrosion concerns must be addressed. This program has focused specifically on a comparison of the galvanic corrosion behavior of currently used and candidate auto body sheet (ABS) alloys. The objectives for this program were to compare the galvanic corrosion performance of candidate aluminum ABS alloys, coupled to bare and galvanized steel, and to develop an understanding of the electrochemical principles governing galvanic corrosion of ABS coupled to steel. The results indicate that there are many critical experimental parameters that can significantly influence the measured galvanic corrosion severity of a given material. The influence of many of these parameters are discussed in detail. Furthermore, the relative merits of various quantifiers for galvanic corrosion are discussed. Data are presented that indicate that simple approximations such as differences in corrosion potential, or even the traditionally accepted weight loss measurements can provide misleading information. The most informative evaluation criteria are shown to be the alloys’ inherent localized corrosion susceptibility, and the degree to which a galvanic couple to steel enhances this susceptibility. Electrochemical and "coupon exposure" data are utilized to corroborate the conclusions.
