A study on the effect of plasma electrolytic oxidation on the stress corrosion cracking behaviour of a wrought AZ61 magnesium alloy and its friction stir weldment

Friction stir weldments of a wrought AZ61 magnesium alloy produced in a robotic friction stir welder under optimised welding conditions were characterised for microstructure, mechanical properties, corrosion and stress corrosion cracking (SCC) behaviour. The effect of surface modification in the form of a plasma electrolytic oxidation (PEO) coating on the corrosion behaviour of the weldment was assessed. The weldment exhibited a joint efficiency of 94%, nevertheless, the weld nugget region was found to have a higher susceptibility to SCC than its parent material counterpart. Even though the PEO coating had provided a good resistance to general and pitting corrosion, it could not completely prevent SCC of this weldment in ASTM D1384 solution.