Enhanced corrosion resistance by engineering basal-oriented grains in Mg-Al-Sn-Ca alloys to retard H/O/Cl adsorption through friction stir processing

The present work demonstrates that friction stir processing/welding (FSP/FSW) significantly enhances the corrosion resistance of twin-roll cast (TRC) Mg-Al-Sn-Ca alloy, reducing the corrosion rate to as low as 0.5 mm/y. This improvement arises from a substantial increase in basal-oriented grain fraction (from 12 to 70%) alongside grain refinement and secondary-phase spheroidization. The enriched basal-oriented grains suppress the adsorption of H, O, and Cl, inhibiting key electrochemical processes such as hydrogen evolution, localized oxidation, and chloride-induced pitting corrosion. Importantly, no galvanic corrosion is observed between TRC base metal and FSP zone, highlighting the dual potential of FSP/FSW for both corrosion-resistant surface engineering and structural joining.