Metal vessels, especially those used in chemical plants, may be coated on one or more surfaces with a layer of acid resisting glass. The invention lies in coating the glass with a layer 4 of fluoroplastic so as to improve the chemical resistance of the glass and to prolong the useful life of the metal vessel. The substrate 2 is preferably of carbon steel or cast iron. Two or more layers of glass may be applied, the layer 5 adjacent to substrate 2 being to promote adhesion between substrate 2 and glass layer 6. Layer 6, 7, 8 are of corrosion resistive glass.