Abstract: The present invention provides methods for preparing or repairing a chemically-resistant coating such as a porcelain enamel on a metal substrate. One such method involves forming a ground coat on the substrate, cooling the substrate to substantially near ambient temperature, optionally by applying a heat source to cool the substrate slowly, followed by flame-spray depositing a coating material onto the softened ground coat. Then, the substrate is allowed to cool slowly so the chemically-resistant coating can form with less stress. Optionally, an induction coil is used to heat the substrate, both to form the ground coat and to slow the cooling of the substrate.