Corrosion Behaviour of Friction Stir Welded Aluminium Alloys: Unpredictability and Protection

Abstract

The corrosion susceptible regions in friction stir weldments of aluminium alloys are largely unpredictable. Several factors dictate the undesirable susceptibility of an Al alloy friction stir weldment. A change in temper or processing parameters can significantly alter the corrosion behaviour of an Al alloy weldment. Pronounced zonal heterogeneities induced by the welding process causes increased corrosion rate of the susceptible region due to galvanic coupling with the more noble regions. To prevent this, different protection methods and techniques have been employed and are currently being developed. Laser surface melting, post-weld heat treatment, micro-arc oxidation, application of corrosion resistant material, conventional anodizing, and pre-sputter deposition prior to anodizing have all been shown to improve the corrosion resistance of friction stir weldments of different Al alloys.