IMPROVING CORROSION PERFORMANCE OF AZ31B Mg ALLOY SHEET BY SURFACE POLISHING

AZ31B Mg alloy sheets in the as-received and polished conditions were compared in terms of their corrosion behavior. It was found that the as-received surface has significantly poorer corrosion performance than the polished surface. It is strongly suggested that a surface cleaning treatment should be conducted for AZ31B parts in production. A preliminary analysis of the improvement by polishing was carried out. Iron contamination of the as-received surface is thought to be responsible for its poor corrosion performance. However, the detailed mechanism of the detrimental effect of the iron-contaminant on corrosion is unclear according to a theoretical analysis of the polarization behavior of steel in the same corrosion environment. It appears that in addition to metallic iron particles, iron oxides and carbonates on the surface could also deteriorate the corrosion performance of the AZ31B sheet.