Zn-Co alloys electrochemically deposited on steel under various deposition conditions were investigated. The influence of deposition current density, temperature and composition of deposition solution on the phase structure and corrosion properties of Zn-Co alloys were studied. It was found that Zn-Co alloy obtained from chloride solution at 5 A dm(-2) showed the best corrosion properties, so this alloy was chosen for further examination. Epoxy coating was electrodeposited on steel and steel modified by Zn-Co alloy using constant voltage method. The effect of Zn-Co alloy on the corrosion behavior of the protective system based on epoxy coating is interpreted in terms of electrochemical and transport properties, as well as of thermal stability.