In this report, the mechanism of electrodeposition of Zn–Fe–Co alloy on a steel surface at different deposition time and concentrations of cobalt ions was precisely investigated. To clarify the deposition mechanism, various electrochemical methods were applied. In particular, potentiodynamic polarization was used to ascertain the corrosion behavior of the deposited films. The results indicate that the increase of the sweeping rate and the increase of the Co2+ concentrations in the deposition bath leads to a significant improvement for the steel anti-corrosion takes place. The film contents were carefully analyzed by AAS and EDX. Furthermore, the coated films were also characterized by SEM and XRD to identify the surface morphology and structure, respectively. The alloys electrodeposition, under the used experimental conditions, was an anomalous type. The outcomes indicate the following series of events: Co ions adsorbed on the substrate in the first few seconds; followed by adsorption of Fe ions and then Zn ions onto the freshly adsorbed and deposited Co, means that the normal codeposition. With time progressing, the adsorption of zinc ions suppresses the subsequent accumulation of iron and cobalt, although it does not completely block it.