Microstructure and properties of microarc oxidation coating formed on aluminum alloy with compound additives nano‐TiO ₂ and nano‐ZnO

Abstract

Abstract In this work, microarc oxidation (MAO) technology was used to form oxide ceramic coating on the surface of aluminum alloy. The combined additives nano‐TiO 2 and nano‐ZnO were added into the silicate electrolyte, and the effect of the compound nano‐additive on microstructure and properties of MAO coating was investigated. The results show that compared with those of the nano‐additive‐free coating formed on aluminum alloy, the thickness, hardness, abrasion resistance and corrosion resistance of the nano‐additive‐containing coating are obviously improved. The surface of coating with nano‐additive becomes smooth, dense, and there are less porosities and microcracks. Moreover, the content of crystal phase α‐Al 2 O 3 and γ‐Al 2 O 3 increases visibly on the nano‐additive‐containing MAO coatings, and new phases Al 3 Ti and Zn 0.6 Ti 0.4 are detected in the coatings, which are mainly contributed to the excellent corrosion resistance and abrasion resistance of the film. When the contents of nano‐TiO 2 and nano‐ZnO are, respectively, 4 and 2 g·L −1 , the film has better comprehensive performance, the thickness and hardness of the film could reach 52 μm and HV 692, respectively.