Study on corrosion resistance behavior and formation mechanism of Ce conversion coating on manganese

Abstract

Ce conversion coatings have received extensive attention from researchers due to their excellent corrosion resistance and environmental friendliness. Here, Ce conversion coatings on manganese were prepared by treating in the cerium nitrate conversion solution. The influence of treating parameters was studied and optimized. The surface morphology, element composition and chemical state of Ce conversion coatings were studied by means of SEM, EDS, XRD and XPS. Electrochemical methods of polarization curve and electrochemical impedance were used to study the corrosion resistance of conversion coatings. The results showed that the Ce conversion coating contained mainly Mn, O and Ce, and its forms were manganese oxide and cerium oxide. Electrochemical tests showed that Ce conversion coating can not only effectively improve the corrosion resistance of manganese substrate, but also has good acid and alkali resistance. Discussion on the formation mechanism of cerium conversion coating shows that the conversion treatment is beneficial to inhibit the further oxidation of manganese to the higher valence state.