Effect of Salt Spray Corrosion Performance on Variable Polarity Plasma Arc Welding of Aerospace Aluminum Alloy

Variable polarity plasma arc welding (VPPAW) can be used for the excellent welding of 5A06 aluminum alloy, which is promising for aerospace applications due to its excellent welding performance and small welding deformation. In this paper, the corrosion behavior of the welding specimens was studied by a metallographic microscope, scanning electron microscope, energy dispersive spectrometer, x-ray diffractometer, and electrochemical workstation. The VPPA welded joint metallographic specimens were subjected to salt spray corrosion tests for 24, 54, 84, 114 and 144 h. The results showed that the heat-affected zone (HAZ) is more sensitive to corrosion than the weld metal (WM) and the base metal (BM), which resulted from the existence and distribution of β(Al3Mg2) and Al6(FeMn) phases in welded joints. The corrosion resistance of VPPA welded joints is WM > BM > HAZ. However, salt spray corrosion increased the corrosion sensitivity of the WM. With the increase of salt spray corrosion time, the WM corrosion tendency raised, and the corrosion resistance of WM became lower than the BM. The corrosion rate curve showed an increasing trend at first and then decreased with the increase of corrosion time, and the corrosion rate reached the highest at 84 h.