Characterization and corrosion resistance study of the Fe-Cr films electrodeposited from trivalent chromium sulfate electrolyte

Fe-Cr alloy films were prepared by direct current electrodeposition using trivalent chromium sulfate electrolyte. The reaction process was clarified by cyclic voltammetry and the influence of the deposition voltage on the characteristics of the alloy was investigated by GIXRD, SEM and AFM. The chemical composition of the surface passivation film was analyzed by XPS. The corrosion performance of Fe-Cr alloy films was analyzed by Tafel polarization curves and AC impedance spectra. The results show that the electrodeposition process mainly involves the reduction process of Fe2+ and Cr3+ under glycine complexation, accompanied by hydrogen evolution reaction at high deposition voltage. The deposition voltage has obvious effect on the crystallographic structure, morphology and composition of the alloy films. Compact and uniform amorphous Fe-Cr films can be obtained at a deposition voltage of 1.9 V and the content of Cr reaches 40%. A comparison of the corrosion potential, corrosion current and polarization resistance for the deposits indicates that the Fe-Cr alloy film prepared at deposition voltage 1.9 V have superior corrosion resistance. The main chemical composition of the passivation film is Cr2O3, CrO3, which contribute to its excellent corrosion resistance.