Incorporation of Carbon Nanotubes Into Oxide Layer on 7075 Al Alloy by Plasma Electrolytic Oxidation

Abstract

A study was made to investigate the influence of carbon nanotubes (CNTs)-incorporated oxide layer on corrosion resistance and microstructure of 7075 Al alloy prepared by plasma electrolytic oxidation (PEO). To protect 7075 Al alloy from corrosion, the present work deals with the electrochemical response of the oxide layer on 7075 Al alloy specimen prepared by PEO method under AC condition in an electrolyte containing CNTs. Because of the strong zeta potential of the functionalized CNTs, the incorporation of CNTs was achieved through the combined effects of electrophoresis and physical mixing in molten oxide. From the results of potentio-dynamic tests in 3.5 wt % NaCl solution, the PEO-treated sample containing CNTs shows better corrosion properties than that without CNTs. This was attributed to the fact that significant decrease of pore density by the incorporation of CNTs into the oxide layer. High corrosion resistance of the PEO-treated 7075 Al alloy was also revealed by impedance tests and analyzed in relation to the equivalent circuit model. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3617754] All rights reserved.