Evaluation of Nonchromated Thin Organic Coatings for Corrosion Inhibition of Electrogalvanized Steel

The toxicity of chromium that is used to impart corrosion resistance to galvanized steel created environmental and health-related concerns and generated a great deal of interest in developing chrome-free treatment coatings. In the present work, organic-inorganic composite coatings were used to coat electrogalvanized steel (EG) sheets for corrosion protection without degrading its weldability property. The new coatings composed of specially modified polyurethane dispersion hybridized with silicate and unique inorganic-organic inhibitors were developed during this work. It was found that about $1{\mu}m$ thickness of coating layer is secure enough in corrosion resistance of flat and formed part even after alkaline degreasing. Overall chemical resistances including fingerprint resistance and paint adhesion property were satisfied with the test specification of Sony technical standard of SS-00260-2002. Therefore, it is concluded that the newly developed chrome-free product can replace the conventional chromated product.