Abstract: A surface treated steel materials coated with manganese having a film of MmOOH (manganic hydroxide) formed thereon, which show excellent corrosion resistance, workability and weldability. The surface treated steel materials may be further coated with zinc as a base coating underlying the manganese coating or further coated with a coating of at least one selected from the group consisting of P, B, Si, Cu, Mn, Cr, Ni, Co, Fe, Zn, Al, Ca, Mg, Ti, Pb, Sn, inorganic carbon and their compounds and still further coated with an organic coating. The film of MmOOH (manganic hydroxide) is formed by a treatment in an aqueous solution containing Cr.sup.6+.

Abstract: Manganese coated steel materials having a compact film of hydrated manganese oxide formed on the manganese coating by heating and drying. Manganese coated steel materials of the present invention show very excellent corrosion resistance in ordinary corrosive environments as well as special corrosive environments such as marine environments and young plant cultivation in mountaineous forests. For further improvement of corrosion resistance, organic coating and metal coatings are applied.

Abstract: A stainless steel pipe having a surface layer with excellent resistance against vanadium pentoxide attack experienced upon boiler heating tubes for power generation, corrosion by sulfates, corrosion by chlorides experienced upon boiler heating tubes for various burning furnace and high-temperature gas corrosion experienced upon tubes for heating furnaces in the chemical industry, and also relates to methods for forming the surface layer.