A vanadium-based conversion coating as chromate replacement for electrogalvanized steel substrates

▶ We develop a new environmentally friendly coating, vanadium conversion coating, for the corrosion protection of eletcrogalvanized steel. ▶ According to the results, the V-treated EG plate shows the best corrosion protection property compared with the untreated and Cr-treated EG plates. And the vanadium coating mainly consists of vanadium and oxygen, which mainly exist as V 2O 5, VO 2, and its hydrates. The vanadium conversion coating as chromate replacement was prepared on electrogalvanized steel (EG) plates previously treated in a solution mainly composed of vanadate. Corrosion behavior of these EG plates in contact with 3.5% NaCl solution was investigated using potentio-dynamic measurement and electrochemical impedance spectroscopy (EIS) measurement. The morphology and composition of the vanadium conversion coating were studied using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) in conjunction with argon-ion sputtering. According to the results, the V-treated EG plate shows the best corrosion protection property compared with the untreated and Cr-treated EG plates. The vanadium-rich coating is composed of the closely packed particles. The coating mainly consists of vanadium and oxygen, which mainly exist as V 2O 5, VO 2, and its hydrates such as V 2O 5· nH 2O, VO(OH) 2.