Influence of oxalic acid on the corrosion behavior of AZ91D magnesium alloy in deionized water

Due to its light weight, Mg alloy can be applied to automotive engines and cooling systems to reduce vehicle weight, energy consumption and exhaust pollution. However, ethylene glycol-type coolants can be oxidized into oxalic acid, glyoxylic acid and other substances at high temperature, which can cause the damage of Mg alloy. In this paper, electrochemical methods, hydrogen evolution and surface analysis methods were used to study the influence of oxalic acid on the corrosion behavior of AZ91D magnesium alloy in deionized water. The results indicated that the oxalic acid accelerated the corrosion of Mg alloy, and its corrosion rate increased with the concentration of oxalic acid. However, interestingly, the corrosion rate of Mg alloy in oxalic acid solution slowed as the immersed time lengthened, which could be related to the accumulation of corrosion products and the consumption of hydrogen ions. The main corrosion product of the corrosion of Mg alloy in oxalic acid solution was composed of magnesium oxalate.