The effect of resin concentration and electrodeposition bath temperature on the corrosion behaviour of polymer-coated steel

Abstract

A.C. impedance measurements carried out on epoxy-resin electrocoated steels have been used to determine the pore resistance, capacitance and relative permittivity of the organic films. The time dependence of these characteristics for the electrodeposited coatings, formed at different resin concentrations in the electrodeposition bath and at different bath temperatures, shows the effect of resin concentration and bath temperature on the protective properties of organic coatings deposited on steel. An increase in the concentration of the resin in the electrodeposition bath increases the pore resistance and decreases the electrical capacitance and relative permittivity of the organic films. Similarly, an increase in the bath temperature above 25 °C increases the pore resistance and decreases the electrical capacitance and relative permittivity. These changes reflect the increases in film thickness obtained at higher resin concentrations or at the higher bath temperatures.