Evaluation of Corrosion Protection Methods for Magnesium Alloys in Automotive Applications

摘要

Magnesium alloys are susceptible to galvanic corrosion. Consequently, it is often necessary to apply coatings to magnesium components for isolation purposes. However, previous publications suggest the effectiveness of commercial coatings can vary widely. Therefore, an extensive corrosion screening study was performed to evaluate pre-treatment and coating systems currently available for use within the automotive industry. This paper focuses on a selection of conversion and anodized coatings. In many instances, these coatings were used in conjunction with either powder coat or an electro-coat to assess the additional protection offered by a supplemental barrier. Scribe test results and corroded area determination after accelerated corrosion testing are presented and used to quantify the pre-treatment performance. These results are supplemented by DC polarization measurements to determine the level of passivation. Finally, SEM micrographs were used to determine coating thickness variability and morphology. The overall performance of each pre-treatment and coating is then assessed with respect to corrosion protection and robustness.