Study of Melioration of Stainless Steel Surface by Phosphatisation with RE Additives and Mechanism

It was done to try to advance properties of stainless steel surface by phosphatization with rare earth (RE) additives. Comparing different additives showed that the order of their contribution to advancement of film corrosion resistance was NO2− > La3+ > MoO42- >> Ce3+ as well as that of its wear resistance was Ce3+ >> MoO42- > NO2− > La3+, therefore, that of phosphating rate is MoO42- > Ce3+ >> NO2− > La3+. Varieties in configuration and composition of the coating induced by REs were analyzed by SEM and EDS. And it was parsed that the IR phenomenon that RE appended made almost the absorption peak for PO43- in 1116 cm-1 a survival, which hints that the rate P/(P+ H) increases along with corrosion resistance in the film. Furthermore, discussion about the mechanism of RE's intensifying the process made it clear that the RE is an excellent catalyst with the power for holding oxygen, which can markedly accelerate phosphate coating growing and develop the abrasive resistance and anticorrosive properties not only because of its effect of nucleation but because of that of cathode-depolarization.