Understanding of the corrosion protection by V(IV) conversion coatings from a sol-gel perspective
By Gao, Zhiqiang; Zhang, Dawei; Hou, Lifeng; Li, Xiaogang; Wei, Yinghui
Published in Corrosion Science
2019
Abstract
The mechanisms by which V(IV) (tetravalent vanadium) as a film ingredient protects the surface remain dim. This work gives a clear and concise understanding of the corrosion protection of hot-dip galvanized (HDG) steel by vanadyl oxalate (VOC2O4) conversion coatings from a sol-gel perspective, along with data from X-ray photoelectron spectroscopy (XPS) surface characterization, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. An elaborate integration of experimental results and thermodynamic analysis suggests that the protection can be exerted persistently as long as V(IV) is available in sufficient quantities at susceptible sites to maintain hydrolysis, condensation, and polymerization.