The black chromate conversion coating was prepared on zinc-iron (0.58wt.% ) alloy deposits by immersing in a proprietary chromate bath. A number of surface analytical techniques, such as X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) coupled with microprobe analysis (energy dispersive X-ray analysis: EDXA), atomic absorption spectroscopy, titration and potentiodynamic measurements were used to characterize the chromate conversion coating. X-ray photoelectron spectroscopy measurements confirmed that the major constituents of the chromate conversion coating were Zn, Cr and O, and a small amount of Cu, Ag, S and Fe was also detected. The chromate conversion coating showed a two-layers structure. The outer layer (the major part of the coating) consisted of Cr 2 O 3 , Cr(OH) 3 , Cr(OH)CrO 4 , Zn 2 (OH) 2 CrO 4 and a small amount of absorbed H 2 O. The inner layer was a transition region where the content of metallic zinc increased and that of metallic chromium and oxygen decreased until a constant composition was reached. Fe was incorporated into the chromate conversion coating and located in the inner layer (adjacent to zinc-iron alloy deposit). Chromium chemical analysis showed that the chromium content of the coating which was the sum of Cr(III) + Cr(VI) was 0.0295g/m 2 , and Cr(VI) content of the coatings was 0.02g/m 2 . Potentiodynamic measurement was used to evaluated the corrosion performance of chromated and unchromated zinc-iron alloy samples in 3.5% NaCl solutions. It was found that the corrosion resistance of the zinc-iron (0.58wt.%) alloy deposit was significantly improved after the chromate treatment. SEM observation indicated that the surface morphology was characterized by some 'dried riverbed' microcracks. Based these results, a mechanism for the formation of black chromate conversion was proposed, and synergistic effects between chromate conversion coating and zinc-iron alloy deposit on corrosion resistance of steel was also discussed.