Salt spray corrosion behaviour of new Mg–Al alloys containing Nd or Gd

Abstract

The influence of chloride concentration on the salt spray corrosion behaviour of new AZ91D and AM50 alloys containing rare earth (RE) elements was evaluated. The corrosion rate of both materials increased with increasing chloride concentration, particularly for NaCl concentrations above 2 wt-%. The addition of Nd or Gd reduced the amount of β-Mg₁₇Al₁₂ phase and resulted in the formation of RE containing intermetallics that were less noble than the Al–Mn inclusions but more noble than the β-Mg₁₇Al₁₂ phase. The latter modifications decreased the corrosion rate of the AM50 alloy by up to 90% but did not give a clear benefit to the corrosion resistance of the AZ91D alloy.