Formation and corrosion resistance of a phosphate chemical conversion coating on medium carbon low alloy steel.

Chemical conversion coatings have attracted much attention in recent years due to their excellent characteristics such as corrosion resistance, wear resistance, adhesion and lubrication. In this study, a phosphate chemical conversion (PCC) coating was fabricated on medium carbon low alloy steel using a facile PCC method with Fe2+ curing process at room temperature. It is shown that the coating was composed of hopeite (Zn3(PO4)2·4H2O) and minor phosphophyllite (Zn2Fe(PO4)2·4H2O) in the form of fine and flaky crystals along the direction inclined or perpendicular to the substrate surface. The adhesive test indicated that the PCC coating was strongly attached on the substrate. Electrochemical analysis revealed that the as-prepared coating imparted better corrosion resistance to the steel substrate. [ABSTRACT FROM AUTHOR]