N,N,N′,N′-tetramethylethylenediamine on anticorrosion ability of micro-arc oxide coatings formed on magnesium alloy AZ91D

Abstract

Oxide coatings on AZ91D alloy were prepared using micro-arc oxidation techniques at a low applied voltage in the Si–P electrolyte with the additive, hexamethylenetetramine or tetramethylethylenediamine (TMEDA). The additives in the Si–P electrolyte smoothed the cracks/pores on the oxide coatings. The 0·1M TMEDA in the Si–P electrolyte improved two orders of the magnitude of the anticorrosion ability from bare AZ91D alloy to the anodic coating, which was prepared by the Si–P electrolyte with 0·1M TMEDA. The surface roughness R_a was reduced from 10·2 to 1·1 μm, when the oxide coating was anodised in the low breakdown voltage and low thermal stress in the Si–P electrolyte with 0·1M TMEDA. In this work, the aforementioned additives in the Si–P electrolyte smoothed the surface of the oxide coating and modified the crystalline structure, resulting in a better anticorrosion ability.