Abstract: A steel product (or copper-plated steel product) with heat-resistant, corrosion-resistant plating layers which are composed of a 0.2-10 .mu.m thick nickel plating layer formed on said steel product, a Zn-Ni alloy plating layer formed on said nickel plating layer, and a chromate film formed on said Zn-Ni alloy plating layer.

Abstract: Disclosed is a method of producing a welded steel tube with excellent inner surface corrosion resistance, in which at least one surface of a steel strip is coated with a first plate layer made of at least one of nickel, cobalt and alloys based on the metals, the plated steel strip is formed into a welded tube with the plated surface being inside, a film-forming material of at least one of tin and tin-based alloys is inserted into the inside of the welded tube and is then heat-treated at a temperature not lower than the melting point of the film-forming material by passing the tube through a continuous heating furnace having a non-oxidizing gas atmosphere therein so that the film forming material as inserted into the welded tube is fused and spread over the first plate layer to form a second plate layer thereon, and the tube is finally cooled.

Abstract: A corrosion resistant metal pipe having an outer surface coated with a zinc film, a chromate film, an intermediate layer consisting substantially of an epoxy resin, and a polyvinyl fluoride film formed one upon another in the order listed.

Abstract: A seam welded steel pipe proofed against corrosion and prevented from oxidizing a fluid such as gasoline to be passed therethrough is produced by a process comprising forming an Ni layer by electroplating on at least one of the opposite surfaces of a steel strip, abutting the opposite edges of said steel strip in the direction of width with the Ni layer on the inside and fusing the abutted edges, subjecting the resultant steel pipe to a heat treatment in an oxidizing atmosphere thereby forming an oxide coating on the surface of the Ni layer, acid dipping the resultant steel pipe thereby removing the oxide coating from the portion of the skin of steel exposed in the neighborhood of a bead part in consequence of the fusion, and introducing a chemical Ni plating liquid through the interior of the steel pipe thereby coating the inner surface in the neighborhood of the bead part with a Ni alloy layer by chemical plating.