Review of the atmospheric corrosion of magnesium alloys

Mg atmospheric corrosion is induced by a thin surface aqueous layer. Controlling factors are microgalvanic acceleration between different phases, protection by a continuous second phase distribution, protection by corrosion products, and degradation of protective layers by aggressive species such as chloride ions. The Mg atmospheric corrosion rate increases with relative humidity (RH) and concentrations of aggressive species. Temperature increases the corrosion rate unless a protective film causes a decrease. O2, SO2 and NO2 accelerate the atmospheric corrosion rate, whereas the corrosion rate is decreased by CO2. The traditional gravimetric method can evaluate effectively the corrosion behavior of Mg alloys.