Standardizing Shop Practices Relative to Making and Application of Steel Ground Coat Enamels. I

Abstract

I The effect of manganese dioxide on the physical properties of ground coat enamels is: (1) to give a good gloss; (2) to give a harder enamel; (3) to reduce the coefficient of expansion of the glass in which it is used; (4) when used with cobalt a uniform color desirable in stove work is obtained; (5) no difference in the adhesion of the ground coat between enamels using manganese, cobalt, or combinations of dioxides is apparent; (6) no effect on chipping is apparent; (7) while not absolutely essential in ground coats it is very desirable for use from an economy stand point. II. A theory of ground coat adherence based on the fact that part of the steel is oxidized to iron oxide which is partly absorbed by the fused enamel and into which some of the enamel penetrates is set forth, and an explanation given of various effects obtained. III. Most of the things which should be done to maintain control in making and firing of ground coats for sheet steel are emphasized. IV. The method of control for application of ground coat enamel by weighing the amount of dry enamel on a sheet of metal of known area is described. This is used to maintain a uniform consistency of the enamel. Other essential features which have in the past caused trouble to many enamelers are mentioned.