Corrosion Resistance and Microhardness of Double Layer Coatings of Aluminium Alloy

Abstract

The anodized aluminium oxide and double layer of anodized aluminium oxide with electroless Ni-P coating on 6061 aluminium alloy substrate were prepared for corrosion resistance and microhardness. The corrosion resistance of the Anodized Aluminium Oxide (AAO) layer and double layer of anodized aluminium oxide with Ni-P coatings were compared by electrochemical impedance spectroscopy studies in 3.5 wt.% NaCl solution.  A comparative study based on corrosion resistance and hardness was achieved. Compared with corrosion studies, it was found that the anodized aluminium oxide coating shows a high resistance of corrosion than the double layer of anodized aluminium oxide with Ni-P coating. Microhardness found anodized aluminium oxide with Ni-P was shows more than anodized aluminium oxide layer due to filled Ni-P into anodized aluminium oxide. The results indicate that the anodized aluminium oxide coating can be a better corrosion protection on aluminium alloys than double layer of anodized anodizing aluminium oxide with electroless Ni-P coatings.