Optimization of effective processing parameters of hybrid anti-corrosion Si/Zr sol–gel coatings doped with cerium salt for aluminum alloy 6061

Abstract

In this study, the Taguchi method was used to design of experiment to obtain optimum conditions for hybrid Si–Zr sol–gel coating doped with cerium nitrate. The experimental design consisted of five different parameters at four levels. An orthogonal array of L16 type was utilized. With these experiences it was intended to find the suitable sol–gel deposition conditions for the aluminum alloy 6061. Chemical composition of the hybrid films were studied by attenuated total reflectance-fourier transform infrared spectroscopy. Field emission scanning electron microscopy was used to investigate the structural feature of coatings. Corrosion performance of coatings was evaluated by potentiodynamic polarization test. The response parameter of hybrid coatings was measured in terms of corrosion rate. The optimum processing parameters were predicted on the basis of data analysis and S/N ratio using analysis of variance. The results showed that by using optimal experimental parameters, the corrosion rate of aluminum alloy 6061 was decreased five orders of magnitude in compare to uncoated alloy 6061. This study has been based on design and optimizing effective parameters of hybrid organic-inorganic Si-Zr coatings doped with cerium reagent by Taguchi method. The effect of molar ratio of Si-bearing precursor, Zr content, Ce content, curing temperature and time was evaluated on corrosion rate of substrate. By deposition of the coatings on AA6061 the corrosion rate was decreased up to four orders of magnitude. Preparation of optimum coating led to decreasing in corrosion rate five orders of magnitude.