Investigation on the Mechanism of Forming Rare Earth Conversion Coating on Zinc Plating

A cerium conversion coating was prepared on zinc plating by chemical conversion treatment of specimens in an aqueous solution of the main salt as Ce(NO3)3·6H2O and the oxidant as 30% H2O2.The max pH of interface,Potential-pH plot of Ce-H2O and Potential-pH plot of Zn-H2O were calculated,the result inferred that the cerium conversion coating consisted of zinc oxide,cerium dioxide and hydrated cerium(Ⅲ and Ⅳ) oxide and the chemical composition of the cerium conversion coating was proved by XPS.