Protective properties of epoxy coatings electrodeposited on steel electrochemically modified by Zn-Fe alloys

• Main Authors: Bajat Jelena B., Mišković-Stanković Vesna B., Kačarević-Popović Zorica M.
• Format: Article
• Language: English
• Published: Association of Chemical Engineers of Serbia 2004-01-01
• Series: Hemijska Industrija
• Subjects: electrode position; Zn-Fe alloys; steel; epoxy coatings; corrosion; EIS
• Online Access: http://www.doiserbia.nb.rs/img/doi/0367-598X/2004/0367-598X0410450B.pdf

Epoxy coatings were electrodeposited on steel and steel modified by Zn-Fe alloys using the constant voltage method. Zn-Fe alloys were electrodeposited on steel at different current densities. The effect of the Zn-Fe alloy on the corrosion behavior of the epoxy coating was interpreted in terms of the electrochemical and transport properties. It was shown that the best properties, i.e. the largest values of the pore resistance and the smallest values of the coating capacitance, a longer period of almost constant Rp and Cp values, and the smallest diffusion coefficient of water through the epoxy coating, as well as the smallest amount of water absorbed inside the epoxy coating, were found for epoxy coatings on steel modified by a Zn-Fe alloy deposited at 4 A dm-2. During prolonged exposure to 3% NaCl, this Zn-Fe alloy significantly improves the corrosion stability of the epoxy coating: almost unchanged values of Rp and Rct were observed, due to the formation of a pseudo-passive layer of corrosion products, which is a good barrier to the transport of water, oxygen and electrolyte ions.