Formation of uniform passive oxide layers on high Si content Al alloy by plasma electrolytic oxidation

In this research, we demonstrated the successful fabrication of conformal passive oxide layers on a high Si content Al alloy by a plasma electrolytic oxidation (PEO) process. The PEO process of Al-12 wt% Si alloy was performed in an electrolyte containing sodium hexametaphosphate ((NaPO(3))(6)) andammonium metavanadate (NH(4)VO(3)), and the variation of the morphology of the electrochemically generated oxide layer was investigated. When NH(4)VO(3) was added to electrolyte, the oxide layer uniformly covered the entire surface of Al-12 wt% Si alloy, and the synthesized oxide layer was confirmed to be a mixture of Al(2)O(3), V(2)O(3) and V(2)O(5). In addition, the oxide layer exhibited a uniform black color, and this is expected to solve the problem of non-uniform colorizing caused by different oxidation behaviors of Si-rich phases during surface treatment. (C) 2010 Elsevier B.V. All rights reserved.