Method of applying a metal layer of large adhesive strength on enamels

To achieve a high adhesive strength of a metallization on an enamel, the surface of the enamel is first roughened and simultaneously treated by ultrasound to remove loose particles. Then the layer is conditioned by a wetting agent, activated and the metal layer is deposited chemically. Particularly good results are obtained when the conditioning and activation of the surface are performed at a temperature slightly elevated above room temperature, about 40 DEG C., for about 5 minutes and the roughening is performed chemically by treating with a 2% solution of ammonium hydrogen fluoride. The enamel substrates of our invention are limited to enamels, which are glass-like or partially crystallne salts of polysilicic acid which may incorporate oxides of alkali metals, alkaline-earth metals, aluminum, lead, boron, cobalt, nickel, titanium, zinc or zirconium or inorganic additives such aas sulphites, fluorides or arsenites