Evaluation on physico-chemical and corrosion properties of anodized aluminium surface using sodium oxalate-sodium silicate bath at room temperature

Abstract

This study offers a comprehensive characterization of anodic surface layers formed in sodium oxalate electrolyte and systematically analyses the influence of addition of sodium silicate. X-ray diffraction, scanning electron microscope-EDAX and atomic force microscope studies are used to establish the correlation between electrolyte composition and anodized aluminium (Al). Stable anodic Al layers comprising tailored porosity and surface characteristics are achieved under optimized conditions, which exhibit corrosion current density (Icorr: 1.04 x 10-5 μA cm-2) with high corrosion resistance of 7.03 x 102 Ω cm-2. Effect of anodization variables upon surface morphology, kinetic parameters, microstructural characteristics and thickness of anodized Al is evaluated. Gradient distribution of Si and O also indicates the relative content of silicate as illustrated by EDAX. Interpreted results from electrochemical impedance spectra and Tafel analysis are well-matched with physico-chemical analysis. Stable anodic Al layers comprising tailored morphology with high corrosion resistance are achieved under optimized conditions.