Microcapillary polarization measurements of friction stir spot welds made in AZ31B magnesium alloy

Microcapillary polarization procedures were optimized to examine the corrosion characteristics of the various microstructural zones developed during friction stir spot welds made in AZ31 magnesium alloy. Tungsten carbide tracing confirmed the location and shape of the stir zone in the weldment. The stir zone was determined to be the noble region while the base metal and the thermo‐mechanically affected zone were found to be active. The thermo‐mechanically affected zone was found to be most susceptible to localized corrosion attack due to its proximity to the noble stir zone, and the subsequent formation of a macrogalvanic cell. Corrosion rates of individual weld regions were measured.