Effect of combinative addition of strontium and rare earth elements on corrosion resistance of AZ91D magnesium alloy

The influence of strontium(Sr) and rare earth(RE) elements on the corrosion behavior of AZ91D magnesium alloy was investigated by conventional corrosion testing and electrochemical measurements in 3.5% NaCl solution. After comparing the mass loss and hydrogen evolution of the samples, the microstructures of the alloys and the morphologies of their corrosion product films were characterized by electron probe microanalysis-energy dispersive spectrometry(EPMA-EDS) and Auger electron spectroscopy(AES). Compared with individual addition of Sr or RE to AZ91D, the combinative addition of 0.5% Sr and 1% RE to AZ91D successfully decreases the corrosion rate further, which can be attributed to the depression of micro-galvanic couples, as well as the formation of more protective film due to aluminum enrichment. The combinative addition of strontium and rare earth elements to AZ91D magnesium alloy appears to be a promising approach to increase its corrosion resistance.