Improved corrosion resistance achieved in a friction stir processed Mg-5Zn-0.3Ca alloy with fragmented precipitates

The microstructure of an as-cast Mg-5Zn-0.3Ca alloy was significantly modified by friction stir processing, which improved the alloy's corrosion resistance. In electrochemical results, the corrosion current density of the FSPed sample at the open circuit potential in 3.5 wt% NaCl aqueous solution decreased to 4.3 mu A/cm2 (about 1/7 that of the as-cast sample). The improved corrosion resistance was attributed to the weakening of galvanic corrosion caused by precipitate fragmentation. In addition, a large number of fine cathodic precipitates tended to accu-mulate on the corroded surface, thereby forming a denser deposition layer and enhancing the shielding effect against corrosion propagation.

Automated summary

Friction stir processing has significantly improved the corrosion resistance of an as-cast Mg-5Zn-0.3Ca alloy by modifying its microstructure, weakening galvanic corrosion, and enhancing the shielding effect against corrosion propagation with the accumulation of cathodic precipitates on the corroded surface.