Corrosion study of new surface treatment/coating for AZ31B magnesium alloy

Abstract

Different surface preparation processes and post-treatments were applied to ‘electroless’ E-coated AZ31B magnesium alloy. The corrosion performance of the differently treated samples was assessed by means of ASTM B117 salt spray, anodic polarisation curve and electrochemical impedance spectroscopy measurements respectively. The results show that the corrosion resistance of the ‘electroless’ E-coated AZ31B can be ranked in the following order: wet polishing+curing>dry polishing+curing≈wet polishing>dry polishing>commercial benchmark treatment. It suggests that a suitable pre- or post-treatment can significantly further improve the corrosion performance of an ‘electroless’ E-coated Mg alloy. The surfaces of the differently pre- and post-treated AZ31B were examined by SEM. It appears that the different corrosion resistances can be attributed to different microstructures of the surface films on AZ31B.

Keywords:

• Corrosion
• Surface treatment
• Coating
• Mg alloy

The authors would like to thank Ms L. Q. Zheng for her assistance in salt spray tests. The authors would also like to thank Dr J. Herbst for his help in the report editing.