Porcelain enameled 316L stainless steel with different surface pretreatments was produced by a slurry-fusion technique for evaluation of the enamel/steel adherence using an electrical conductivity meter. From the measured results, it is found that the adherence of the porcelain enamel to the steel depends on the roughness of the enamel-steel interface, which, in turn, is controlled by surface pretreatments of the steel substrates. The difference in the adherence of the enameled steel can be explained from an examination of the microstructure of enamel-steel interfaces by scanning electron microscopy. Good adherence is associated with those specimens that have a long enamel-steel interface contour, i.e., rough interfaces. In addition, X-ray diffraction analysis of the delaminated enamel fragments upon impact deformation reveals that failure of the enamel coatings in an oxidized steel occurred at the oxide-steel interface which is supposed to have strong chemical bonding, and that the oxide scales present before enameling are partially dissolved in the enamel during firing. The difference in the coefficients of thermal expansion among enamel, oxide, and steel is likely to play an important role in determining the failure mode of the enameled stainless steel. In summary, these results suggest that the adherence of the porcelain enamel to the 316L stainless steel is mainly controlled by a mechanism of mechanical interlocking.