X-ray photoelectron spectroscopy (XPS) was used to investigate the content and chemical valence of chromium element,and the content of compounds in chromate passive film formed on commercial tinplate via a cathodic electrolytical treatment.The effect of the content and chemical valence for different surface state was studied by using ultrasonic process.From the results,it was shown that there existed Cr,O and Sn in the passivation film.The chromium element in the film was mainly in the forms of Cr(OH)3,Cr2O3, and Cr in the natural surface.The Cr(Ⅵ) changed to lower value in the process of cathodic electrolytical treatment.A small quantity of Cr(Ⅵ) was found in the defective surface besides Cr(OH)3 and Cr2O3.The content of chromium element in the defective surface was lower than that in the natural surface.When ultrasonic process was added,the content of chromium element in the defective surface was obviously lower than that when no ultrasonic process was added.When ultrasonic process was used,the small quantity of Cr(Ⅵ) originally adsorbed on the defective surface disappeared because of the strong elution produced by ultrasonic.