The Relationship Between Adhesion and Electrochemical Parameters of Epoxy Resin on Mild Steel

Electrochemical impedance spectroscopy (EIS) has been employed in the investigation of the corrosion characteristics of epoxy polymeric film both coated and attached as a free film without adhesion on mild steel panels during immersion in 3.5 wt% NaCl solution. Meanwhile gravimetric liquid sorption experiments were used to evaluate water uptake inside the coating. The results of impedance spectroscopy indicate that epoxy resin shows greater anticorrosion protection characteristics when applied on mild steel than attached as a free film. Attached Free films present higher value of water uptake compared with coated samples. Adhesion seems to play a major role in the protection of the metals. The first step of electrolyte penetration through the coating is related to water uptake and after that a different process occurs, that could be either the penetration of the water in the bulk of the polymer, or the slow diffusion of ions.