Exfoliation Corrosion Behavior of Cold-Rolled Mg-14 mass% Li-1 mass% Al Alloy in NaCl Solution

Abstract

Cold-rolled Mg–Li system alloys represent the exfoliation corrosion on the surface of the longitudinal and the transverse sections. In this study, the origination of the exfoliation corrosion of the cold-rolled Mg–Li alloy was clarified. In the initial stage of the corrosion, the oxide film formed immediately on the surface of each section, and then the film destruction with a remarkable bubble generation was observed in a certain spot. There were microcracks on the trace of the film destruction along the grain boundary. The corrosion resistance in the annealed specimen was more than that in the as-rolled specimen because the microstructure of the as-rolled specimen has elongated and thinned grains by severe cold rolling. The exfoliation corrosion was not observed in the annealed specimen, because the annealed specimen has homogeneous equiaxial grains. The successive film destruction in annealed specimen progressed along the grain boundary to random direction. Moreover, the initiation time of the bubble generation was delayed in the annealed specimen.