ELECTRODEPOSITION COATING OF EPOXY RESIN ON PHOSPHATED STEEL: OPTIMIZATION OF KEY FACTORS

Abstract

Organic coating using electrodeposition method has attracted substantial attention in the last few years. This method of coating provides many advantages, including surface smoothness, less environmental pollution, and good performance of protection against corrosion. In the current investigation, an electrodeposition method was used to coat a uniform layer of epoxy resin on phosphated stainless steel plate. Epoxy resin was converted to cationic tertiary type amine resin. This cationic epoxy resin, which contains ammonium group in the end of the polymer chain, was synthesized by ring-opening reaction of an epoxy resin with secondary amine in the presence of a proton donor. The so prepared cationic resin was dispersed in water, giving an emulsion containing charged polymer particles. A layer of resin was successfully electrodeposited on the phosphated stainless steel plate and physical properties of the layer were studied. A detailed study aiming to obtain reliable information of coating properties was carried out. The effect of a number of factors, including electrodeposition voltage, electrodeposition time, pH value of the emulsion, solvent content, resin Epoxy Equivalent Weight (E.E.W.) resin concentration, and bath temperature on deposition yield and coating adhesion was studied with a view to optimize these factors. Variables affecting the rupture voltage were also investigated.