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/thermomechanically affected zone and parent materials was characterised in chloride solutions. Chromate, molybdate and cerium nitrate were added to the chloride solution and their effect on the corrosion behaviour of the weldment was assessed. Electrochemical studies on different regions of the dissimilar friction stir weldment, performed in inhibited 3·5%NaCl solutions, suggest that chromates are better in terms of inhibition efficiency and inhibit all regions of the weld area to a similar extent. From the viewpoint of environmental issues, both molybdate and cerate may also be thought of as effective inhibitors; however, their efficiencies are definitely below that of chromates in neutral chloride environments.