Corrosion behavior of aluminum 6061 alloy joined by friction stir welding and gas tungsten arc welding methods

Wrought aluminum sheets with thickness of 13 mm were square butt-welded by friction stir welding (FSW) and gas tungsten arc welding (GTAW) methods. Corrosion behavior of the welding zone was probed by Tafel polarization curve. Optical metallography (OM) and scanning electron microscopy together with energy dispersive spectroscopy (SEM-EDS) were used to determine morphology and semi-quantitative analysis of the welded zone. FSW resulted in equiaxed grains of about 1–2 μm, while GTAW caused dendritic structure of the welded region. Resistance to corrosion was greater for the FSW grains than the GTAW structure. In both cases, susceptibility to corrosion attack was greater in the welded region than the base metal section. T6 heat treatment resulted in shifting of the corrosion potential towards bigger positive values. This effect was stronger in the welded regions than the base metal section.

► FSW demonstrated higher corrosion resistance than GTAW of 6061 Al alloy.
► FSW and GTAW both demonstrated poorer corrosion behavior than the base metal.
► FSW produced ∼1–2 μm equiaxed grains in joint region and ∼150 μm in base metal.
► GTAW resulted in semi-cast dendritic structure.
► T6 heat treatment improved corrosion resistance of both FSW and GTAW joints.