Studies on the Adhesion and Corrosion Performance of an Acrylic-Epoxy Hybrid Coating

A hybrid acrylic polyol-epoxy polyol coating cured with aliphatic polyisocyanate has been developed to provide corrosion protection on mild steel panels. Polyisocyanate served as a hardener to initiate crosslinking and as a coupling agent to enhance adhesion of the hybrid polymer resin to the metal surface. The hybrid systems were prepared by blending an acrylic polyol resin (A) with an epoxy polyol resin (E) in various weight ratios and by applying them on pre-treated cold rolled mild steel panels. The dry film thickness was maintained within the range of 40 to 80 mu m. The panels were allowed to cure under ambient air condition for 1 week prior to testing. Corrosion resistance and mechanical properties of the coating were studied and characterized. This paper discusses several specific examples on the use of electrochemical impedence spectroscopy (EIS) in the study of coatings in accelerated exposure and the analysis of EIS data from such studies. It is observed that, of the nine coating formulations, one has been found to perform well as an effective and durable hybrid coating.