Effects of inhibitors on corrosion behaviour of dissimilar aluminium alloy friction stir weldment

Abstract

Dissimilar weldments comprising age hardenable AA7075 and AA6056 aluminium alloys were produced by friction stir welding. Corrosion behaviour of the weld nugget/TMAZ region and parent materials were characterised in chloride solutions. Chromate, molybdate and cerium nitrate additions were made to the chloride solution and their effect on the corrosion behaviour of weldment was assessed. The electrochemical studies on the different regions of the dissimilar friction stir weldment, performed in 3.5% solutions suggest that chromates are better in terms of inhibition efficiency, and a more or less similar beneficial effect on the corrosion resistance was received by all the regions by the addition of chromate inhibitor. From the view point of environmental issues, both molybdate and cerate can be thought of as inhibitor; however, their efficiency levels are definitely below that of chromates in neutral chloride environments.