Abstract:Passivation coatings were prepared on tin-plating steel by an electrochemical method. The corrosion resistance of the coatings was tested by CuSO4 drip experiment, electrochemical impedance spectroscopy, Tafel and SEM. Effects of current density, additives and passivation time on the properties of the passivation coatings were studied. It is concluded that the corrosion resistance of passivation films increases first and then becomes steady with the increasing of passivation time. When the passivation time is 40 s, the corrosion resistance of the coating is the best. The technological parameters of the passivation solution are obtained by experiment as following: sodium molybdate 25 g·L–1, phytic acid 6.5 g·L–1, pH=4.5, time 40 s and Jk=1.5 mA·cm-2. The apparent morphologies of the coating are well-proportioned covered on the surface of tin coatings. The results show that the corrosion potential of the tin layer is increased by 0.108 V, the corrosion current decreased by 2.3577×10-5 A·cm-2, and the drip time increased by 23.3 s. The passivation effect of the coatings prepared by the electrochemical method is nearly to that of chromating, and it increases the corrosion resistance of the tin coating effectively