Corrosion behaviour of electroless Ni–P–TiO 2 nanocomposite coatings using Taguchi

Abstract

This paper reports an experimental study of corrosion characteristics of electroless Ni–P–TiO₂ nanocomposite coatings. Coating process parameters are optimised for maximum corrosion resistance based on L₉ Taguchi orthogonal design with four process parameters, namely, concentration of nickel source solution, concentration of reducing agent, concentration of TiO₂ powder and bath temperature. Corrosion behaviour of the electroless Ni–P–TiO₂ nanocomposite coatings was evaluated in 3·5 wt-%NaCl aqueous solution using polarisation technique. Scanning electron microscopy and energy dispersive X-ray spectroscopy analysis were used for studying surface morphology and chemical composition of the electroless Ni–P–TiO₂ nanocomposite coatings. The results showed that incorporation of TiO₂ in coating causes an increase in corrosion resistance and improves surface morphology. Finally, optimum conditions were achieved as follows: concentration of nickel source solution, 50 g L⁻¹; concentration of reducing agent, 10 g L⁻¹; concentration of TiO₂ powder, 10 g L⁻¹; and bath temperature, 85°C.