Influence of micro-arc oxidation film on corrosion of inhomogeneity of 7A52 aluminum alloy friction stir welding joint

Due to dynamic recrystallization of the 7A52 aluminum alloy friction stir welding joint weld zone. The grain size is relatively small, the organization presents “onion ring” distribution. the thermo mechanically affected zone is distributed along the plastic flow direction, and the grain size of the heat affected zone is obviously grown. The unevenness of the joint structure leads to different corrosion behaviors in different regions. The results show that when there is no micro-arc oxide film, the blunt current of the base material is much smaller than that of the weld nugget area and the heat(thermo mechanically) influence zone, and it is easier to passivate; when the thickness of the micro-arc oxide film is 50 μm, the base material is blunt The current is less than the weld nugget zone and the heat(thermo mechanically) influence zone. The thinner micro-arc oxide film has no obvious effect on the improvement of joint corrosion inhomogeneity; when the thickness of the micro-arc oxide film is 70 μm, the passivation characteristics of different regions of the joint are closing, the micro-arc oxide film helps to reduce the influence on the unevenness corrosion of joint structure in different areas of the joint.