Zinc phosphating is a chemical conversion process that has been widely used in industry for corrosion protection and primer for painting. In this investigation, the effect of activation treatment with nickel acetate on the microstructural evolution and corrosion resistance of the zinc phosphate coating on mild steel was studied. The chemical composition and morphology of the coatings were analyzed via scanning electron microscopy (SEM) and energy‐dispersive spectroscopy (EDS). The corrosion resistance of the coatings was evaluated using polarization curves and electrochemical impedance spectroscopy (EIS) in an aerated 3.5% NaCl solution. Surface morphology observations revealed that the activation treatment increased the population density and refined the grain size of the coating. The electrochemical results showed better barrier protection characteristics and corrosion resistance for activated phosphate coatings compared with inactivated coatings.
Zinc phosphate coating is commonly used for corrosion protection of metallic materials, mainly mild steel. In this study, influence of the pH of phosphating bath on the surface morphology and corrosion resistance of zinc phosphate coatings on mild steel was investigated. The phosphate layers were deposited on steel from phosphating bath at different pH values (1.75 ~ 2.75). The surface morphology and composition of phosphate coatings were investigated via scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The corrosion resistance of the coating was evaluated by polarization curves (anodic and cathodic) in an aerated 3.5% NaCl solution. The results showed that better surface coverage and corrosion resistance for the steel phosphated at pH 2.75.
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