Effect of heat treatment on microstructure and corrosion behavior of Al6061 alloy weldment

In this research, the corrosion behavior and microstructure of Al6061 alloy welded by GTAW (Gas tungsten arc welding) and followed by various heat treatments have been investigated. The microstructure of both weld metal (WM) and base metal (BM) was studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Corrosion behavior was investigated in 3.5 wt.% NaCl aqueous solution. Results indicated that BM consists of Fe-rich coarse intermetallic particles. These particles were found to act as cathodic regions with respect to surrounding matrix. Potentiodynamic polarization curves confirmed that WM is cathode rather than BM in different heat treatment cycles. Moreover, it was found that heat treatment led to displacement of the BM corrosion potential to noble direction. Observations of corroded surfaces confirmed localized corrosion.