NOVELTY - Heating or cooling a carbon containing reducing gas having a carbon monoxide content of at least 0.5 vol.%, involves heating the gas to a temperature of at least 400 degrees C; cooling the gas from a temperature exceeding 400 degrees C; and passing the gas along a surface of a heating or cooling unit comprising a heat conductive metal or metal alloy body and a protective layer.    USE - For heating or cooling a carbon containing reducing gas such as carbon monoxide, alkane, and carbon dioxide; as an anti-metal dusting or anti-carburization coating (claimed); or for protecting metallic surfaces from high temperature corrosion in a reducing atmosphere, particularly in a carburizing atmosphere. The method is used in petrochemical technical processes such as coal liquefaction and coal gasification, in synthesis gas reactors, such as steam reformers and in plants for processing of synthesis gas, such as ammonia production, in Fischer-Tropsch reactions, Direct Reduction Iron (DM) plants or coal gasification coal liquefaction plants; and also used in industrial furnaces for hardening of steels.    ADVANTAGE - The method protects metallic surfaces from high temperature corrosion in a reducing atmosphere, particularly in a carburizing atmosphere. The protective layer protects the metal surface against corrosion from the gas phase; and does not require catalytic action.    DETAILED DESCRIPTION - Heating or cooling a carbon containing reducing gas having a carbon monoxide content of at least 0.5 vol.%, involves heating the gas to a temperature of at least 400 degrees C; cooling the gas from a temperature exceeding 400 degrees C; and passing the gas along a surface of a heating or cooling unit comprising a heat conductive metal or metal alloy body and a protective layer, where the protective layer provides the surface, and the protective layer is made from a coating composition comprising colloidal amorphous silicate, crystalline oxide particles, optionally an emissivity agent, and optionally a stabilizer/binding agent. An INDEPENDENT CLAIM is included for applying a protective coating to a metal or metal alloy surface of a heating or cooling unit comprising a heat conductive metal or metal alloy body, involving applying a coating composition to the metal or metal alloy surface.