Abstract: To provide a cover coating for metal surfaces subject to corrosion by water, typically steel surfaces in salt water, for ships, structural components, and the like, in which cathodic protection by application of a negative voltage to the metal is provided, a two-layer coating is applied in which the base coating applied to the metal comprises a mixture of finely divided zinc and polyisocyanate prepolymers capable of hardening or curing under ambient humidity, with dryers, gelling, and pigment agents, and high boiling point solvents, covered by a cover coating, preferably in two to three layers, of a mixture of tar with polyisocyanates, fillers, dryers, solvents, and micaceous iron ore or hematite powder.