The effect of post-sealing incorporation with different Na2MoO4 concentrations on the corrosion behavior of 6063 aluminum alloy coated via micro-arc oxidation coating

Abstract

In an attempt to investigate the impacts of different Na2MoO4 concentrations on the corrosion behavior of 6063 aluminum alloy coated via micro-arc oxidation (MAO) coating, a series of concentrations of Na2MoO4 solutions were prepared for post-sealing treatment. The coatings with and without Na2MoO4 post-treatment were analyzed by SEM, XRD and EDS. The results indicated that the post-sealing treatment with 0.1 M Na2MoO4 solution could effectively seal the pores and cracks owning to the formation of Al2(MoO4)3 on the surface. Moreover, the EIS results showed that addition of molybdate could significantly enhance the corrosion resistance of the substrate, revealing that |Z|0.01 Hz of MAO + 0.1 M Na2MoO4 sample was 1.47×107 Ω•cm2 which was three orders of magnitude higher than that of the pristine MAO. The polarization test results revealed that a noticeable corrosion rate decrement with incorporating molybdate to the MAO coating was achieved.