Formation of ceramic nanocomposite coatings on aluminium by anodisation using magnesium sulphate with silicate additive

Abstract

Nanostructured composite coatings on aluminium were fabricated by an anodisation technique. In this study, special attention was also given to investigate the effect of current density (CD) on surface morphology, elemental/phase composition and corrosion behaviour. In addition to this, thickness and growth rate were optimised with respect to anodising time and concentration of the electrolyte. Nanocomposite coatings on aluminium substrates with an average crystallite size of 48 nm were obtained by anodising in an aqueous sulphate electrolyte solution after a comprehensive investigation of the anodisation conditions. Energy dispersive spectroscopy analysis confirmed that the aluminium content in the top of the coatings increases as CD is raised up to 0·15 A cm−2. Atomic force microscopic analysis confirmed that the mean distribution, average roughness and root mean square roughness values increase significantly at CD above 0·15 A cm−2. The corrosion behaviour of the fabricated nanocomposite coatings was also evaluated using Tafel polarisation and electrochemical impedance spectroscopy.