Abstract: Metal substrates in corrosive environments, such as gas and oil pipelines, are normally prone to embrittlement caused by absorption of the hydrogen atoms cathodically evolved during various corrosion processes. This is substantially prevented by providing an active substance in the vicinity of the metal substrate, and in electrical contact therewith, the active substance being a sulphide or mixed sulphide of a metal of Group Vb, VIb or VIIb of the Periodic Table or of a rare earth metal, especially WS.sub.2 and MoS.sub.2. The active substance is preferably applied as or in a coating on the surface of the substrate, with an overcoating of, for example, a thermosetting resin, preferably being employed for mechanical and environmental protection.

Abstract: Metal substrates in corrosive environments such as gas and oil pipelines, are normally prone to embrittlement caused by absorption of the hydrogen which is cathodically evolved during various corrosion processes. This is substantially prevented by providing an active substance in the vicinity of the metal substrate, and in electrical contact therewith, the active substance being one on which cathodic hydrogen evolution occurs in preference to the metal, thereby reducing the amount of hydrogen available for diffusion into the substrate. The active substrate is preferably a sulphide, for example FeS, or mixed sulphide, for example NiCo.sub.2 S.sub.4, and is advantageously applied as a coating on the surface of the substrate, a further coating of, for example, a thermosetting resin, preferably being employed for mechanical and environmental protection.