Performance Comparision of Passivation Films on Galvanized Steel Treated with Rare-earth Cerium and Lanthanum Salts

The optimal processing parameters and conditions of passivation films on galvanized steel sheet treated with rare-earth cerium and lanthanum salts were obtained by orthogonal experimental method.The lead acetate test,salt spray test,weight loss test,EIS,SEM and XRD etc.were used to analyze the performance of passivation films.The results showed that the corrosion resistance of lanthanum film was better than that of cerium film,and the former was more close to the conventional chromate conversion coating.The lanthanum film was more dense and thicker,and had higher coverage on the matrix than cerium film.XRD analysis showed that the main filming materials of cerium salt and lanthanum salt was La2O3 and CeO2 respectively.The adhesion of lanthanum film reached 5B and was better than that of cerium film.