The corrosion performance and adhesion properties of the epoxy coating applied on the steel substrates treated by cerium-based conversion coatings

• Cerium-based conversion coating was post-treated by zinc phosphate conversion coating.
• Epoxy coating was applied on the Ce and Ce–Zn surface treated steel substrates.
• Surface morphology and composition of the surface treated samples were studied.
• Anticorrosion and adhesion properties of the epoxy coating were studied.
• Ce–Zn treated sample showed the highest adhesion and anticorrosion properties.

The surface morphology and composition of the cerium-based conversion coatings (Ce) were studied for the St-37 steel substrate which was post-treated in an ambient temperature zinc phosphate chemical treatment bath (Ce–Zn). Then, the epoxy/polyamide coating was applied on the substrates treated with Ce, Zn and Ce–Zn chemical treatments. The surface characterization and electrochemical investigations were made by scanning electron microscope (SEM), energy dispersive X-ray photoelectron spectroscopy (XPS), contact angle measuring device, pull-off test and electrochemical impedance spectroscopy (EIS). Results revealed that the epoxy coating applied on the Ce–Zn treated sample showed the highest adhesion and corrosion protection properties.