Effect of Coefficient of Expansion of Ground‐ and Cover‐coat Enamels on Thermal‐shock and Impact Resistance *

Abstract

Four antimony cover-coat enamels, four fluoride cover-coat enamels, gnd four groundcoat enamels were formulated to give varying coefficients of expansion. The calculated values were 250, 275, 300, and 325 X 10-l. The observed c d c i t n t 8 of expansion are included in the paper. The enamels were applied to standard 2-quart mdding pans and were tested for thermal shock and impact resistance using the standard methods of the Enameled Utensil Manufacturers' Council.The results show that thermal-shock resistance is controlled chieflp by the coefficient of expansion of the ground-coat ahdey&coat enamels. The best results were obtained by using a cove-coat enamel with a low coefficient of expansion and a grotmdhoat with a high coefficient of expansion. No conclusive evidence was found to indicate any effect of the coefficient of expansion of the ground-and cover-coat enamels on impqt resistance.The solubility resistance and reflectance curves for the enamels are also incladed.