Understanding on corrosion mechanism of oxidized AZW800 alloy in 3.5 wt% NaCl solution

Magnesium alloys are more widely used at higher temperatures. However, it is not well known whether oxide layer, produced at high temperature, could show corrosion protection. Thus, the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance. The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion, leaving randomly bulky pits. While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion. The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion. While subsequently, aggravated corrosion would occur owing to defects of oxide layer and less protective products film. Besides, present of oxide layer eliminated micro-galvanic couple on alloy surface. The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.