Preparation and Corrosion Resistance Property of Molybdate Conversion Coatings Containing SiO2 Nanoparticles

In this paper, molybdate conversion coatings containing SiO2 nanoparticles were successfully prepared on AZ31 magnesium alloy. The effect of SiO2 nanoparticles on the weight of molybdate conversion coatings was investigated. The surface morphology of molybdate conversion coatings containing SiO2 nanoparticles was examined by scanning electron microscopy (SEM). The polarization curves, electrochemical impedance spectroscopy (EIS) and weight loss measurements were employed to evaluate the corrosion resistance of molybdate conversion coatings containing SiO2 nanoparticles in 3.5 wt% NaCl solution. The results demonstrate that the weight of molybdate conversion coatings reaches a maximum value when the concentration of SiO2 nanoparticles is 4 g L-1. The SiO2 nanoparticles are uniformly distributed in the molybdate conversion coatings. The results of weight loss measurements and electrochemical methods show that the addition of SiO2 nanoparticles in the conversion treatment has significantly improved the corrosion resistance property of molybdate conversion coatings. (C) 2013 The Electrochemical Society. All rights reserved.