Development of Next Generation Chromate-free Coatings by Noble Inorganic Polymer

Abstract

In recent years, domestic production of electrogalvanized steel sheets has decreased due to market erosion by low-priced products and the poor sales performance of Japanese electrical appliance manufacturers. In order to overcome this situation, it was necessary to develop a high/multifunctional chromate-free coating that is capable of reducing manufacturing costs by the mass production effect of high-speed production and aggregation of small quantity varieties, reduction of submaterials and process omission by users. Trends in the expansion of chromate-free products also extend to building material applications, and the use of chromate-free products was recommended in the 2016 Public Work Specifications published by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) in Japan. Based on the results of fundamental research on the corrosion resistance mechanism of a self-assembled monolayer (SAM), the authors conceived a complex of silicate and ultrafine silica that features high adhesion by covalent bonding with zinc and a high barrier property by three-dimensional crosslinking. For electrical appliances, our current development work includes (1) a high functionality chromate-free coating that compatibilizes corrosion resistance and electrical conductivity and (2) a multifunctional chromate-free coating with lubricity and paint adhesion, and for building materials, (3) a low-cost chromate-free coating with weather resistance.