Abstract
The need for employing multi-material-mix in engineering applications is increasing day-by-day. Such situations lead to galvanic corrosion, especially in the case of dissimilar weldments joining magnesium and aluminium alloys. Hence suitable surface treatments are necessary to combat these issues. Conventional, mostly chemical pre-treatments, cannot be applied because of the electrochemical potential differences. This includes both cleaning and conversion coating. Therefore the PEO process should be used to produce an alternative “conversion” coating by combining cleaning and coating for both materials in one treatment bath. Such a pretreatment is required for good adhesion of further paint build-up to mitigate the general and galvanic corrosion problems involved with multi material mix weldments. Thus the development of a surface modification procedure for the treatment of welded joints comprising dissimilar materials viz., magnesium and aluminium alloys, by plasma electrolytic oxidation (PEO) is one alternative. We will present results of our study to develop coatings on friction stir welded joints comprising the aforementioned alloys. Correlations of processing parameters, microstructure and properties are presented and the advantages and disadvantages of such a treatment are discussed.
