Influence of processing time on the phase, microstructure and electrochemical properties of hopeite coating on stainless steel by chemical conversion method

Abstract

Recently, hopeite coatings on metals, obtained by the zinc phosphate chemical conversion (ZPCC) process, has attracted increasing attention owing to their potential biomedical application. The present study focused on the processing time necessary for the formation of hopeite coatings by the ZPCC method on stainless steel. It was shown that the coatings were composed of hopeite with a minor amount of phosphophyllite. Both the coating mass and bath efficiency reached the highest values after ZPCC treatment at 75 °C for 30 min. Electrochemical analysis revealed that the coating obtained for 30 min presented the best corrosion resistance and thus represented the optimum time. Adhesion tests indicated that the coating was strongly attached on the substrate.