Influence of temperature on the atmospheric corrosion of the MgAl alloy AM50 produced by semi-solid cast and high pressure die cast technique

Paper i proceeding, 2013

The effect of temperature on the atmospheric corrosion of the MgAl alloy AM50 was investigated in the laboratory. The alloy was investigated in both semi-solid cast and high pressure die cast form. Polished samples were exposed to air containing 400ppm CO2 for up to 4 weeks at 22ºC, 4ºC and -4oC at 95% relative humidity (RH). The rate of corrosion was determined by mass gain and metal loss measurements. The corrosion products were analyzed by SEM/EDX. Analysis by XRD showed that the composition of the crystalline corrosion product depended on the exposure temperature. Both materials exhibited a strong positive correlation between temperature and the rate of NaCl-induced atmospheric corrosion. It is suggested that the temperature dependence of corrosion is related to the dissolution of alumina in the passive film. The semi-solid cast material exhibited lower average corrosion rates at all three temperatures.