Atmospheric corrosion of magnesium alloys:: Influence of temperature, relative humidity, and chloride deposition

Laboratory tests have been performed to determine how climatic parameters, e.g., relative humidity, temperature, and the amount of sodium chloride (NaCl), influence the corrosion rate of magnesium alloys AZ91D (UNS M11916) and AM50 (UNS M10500). The effect of the surface state also has been investigated. The exposures were performed at 75%, 85016, and 95% relative humidity (RH) and at 25degreesC and 35degreesC. The amount of NaCl ranged from 14 mug cm(-2) to 240 mug cm(-2). The corrosion rate of both materials increased as a function of temperature, RH, and amount of NaCl. A strong influence of the surface state, i.e., as-cast or polished, was observed mainly due to the combined effect of an active surface layer and the roughness of as-cast surfaces.