Abstract: An iron-based heat-generating material excellent in oxidation resistance at an elevated temperature which comprises an iron-based alloy capable of generating heat by passing electricity therethrough and a coating of aluminum and oxygen formed on the surface of the alloy, the amount of the oxygen in the coating is less than the stoichiometric amount of oxygen in Al.sub.2 O.sub.3. The material can be prepared by vacuum evaporation of Al onto the surface of the iron-based alloy wherein an oxygen partial pressure in a vacuum gaseous atmosphere for the vacuum evaporation is adjusted so that there is formed on the surface of the alloy a coating consisting of aluminum and oxygen, the amount of the oxygen in the coating being less than the stoichiometric amount of oxygen in Al.sub.2 O.sub.3. When the material is heated in ambient or oxidizing atmosphere, an outermost layer of the coating is rapidly converted to Al.sub.2 O.sub.3.

Abstract: An iron-based heat-generating material excellent in oxidation resistance at an elevated temperature which comprises an iron-based alloy capable of generating heat by passing electricity therethrough and a coating of aluminum and oxygen formed on the surface of the alloy, the amount of the oxygen in the coating is less than the stoichiometric amount of oxygen in Al.sub.2 O.sub.3. The material can be prepared by vacuum evaporation of Al onto the surface of the iron-based alloy wherein an oxygen partial pressure in a vacuum gaseous atmosphere for the vacuum evaporation is adjusted so that there is formed on the surface of the alloy a coating consisting of aluminum and oxygen, the amount of the oxygen in the coating being less than the stoichiometric amount of oxygen in Al.sub.2 O.sub.3. When the material is heated in ambient or oxidizing atmosphere, an outermost layer of the coating is rapidly converted to Al.sub.2 O.sub.3.

Abstract: The surface of a steel material is irradiated with ion beams, held at a temperature of 100.degree.-400.degree. C. and then subjected to vapor deposition plating in vacuo. The vapor deposition plating may be performed by successively or simultaneously depositing different plating metals. The temperature control may use the sensible heat of the steel material, wherein the vapor deposition plating is applied to the surface of the steel material, which is in the temperature range of 100.degree.-400.degree. C. during cooling after ion beam irradiation, in a vacuum atmosphere. Since the surface of the steel material is held at a temperature of 100.degree.-400.degree.C., a lot of active spots remain on the surface. The active spots serve as starting points for the vapor deposition of the plating metals. The obtained plating layer is excellent in adhesiveness, workability, corrosion resistance and conformability to paint.