Study on the cross-sectional microstructure of a thin ceramic coating on stainless steel surface fabricated by the application and calcination of an aqueous clay mineral paste

Abstract In this study a technique is described that enables the ceramic coating on stainless steel with good adhesion via a simple application, drying, and calcination process using an aqueous paste based on clay mineral dispersion. On the basis of this technique, the cross-sectional microstructure of the interfacial area between the clay-derived ceramic coating and stainless steel was analyzed in detail, and the mechanism behind the coating of the ceramic layer with good adhesion was investigated. From the results of elemental mapping using transmission electron microscopy, scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, it was discovered that iron from the stainless steel diffuses into the ceramic coat, and the specific passivation film of the stainless steel integrates with the clay mineral-derived ceramic coating during the calcination, revealing that such chemical reactions are effective in promoting strong adhesion between the coat and stainless steel surface. In addition, a unique advantage of using this coating method was discovered in that even if there are small natural scratches on the raw stainless steel, the clay mineral paste can be used to cover these, resulting in a good, flat surface.