ELECTROLYTIC REACTIONS IN VITREOUS ENAMELS AND THEIR RELATION TO THE ADHERENCE OF ENAMELS TO STEEL*

Abstract

ABSTRACT All the metals between iron and copper in the electromotive‐force series of metals are plated out of solution during the firing of sheet‐steel ground coats by the electrolytic action of the hot iron base. Of these plates, cobalt, nickel, and antimony promote adhesion, each of the following factors probably playing a part: (1) The plates of these metals adhere tenaciously to steel while enamel does not. (2) The coefficients of thermal expansion of these metals are intermediate between those of steel and those of commercial ground‐coat and cover‐coat glasses, thus giving a gradation of coefficients found desirable by Danielson and Sweely. (3) The enamel glass is mechanically bonded to the metal plate by dendrites, aided by any jagged projections and holes. (4) These metal plates are insoluble in the molten enamel; thus any structure favorable to adhesion, once formed, remains.