PURPOSE: To impart excellent corrosion resistance so as to withstand severe corrosive environments to a shape material by forming a Zn allay diffused layer having certain concn. and depth on the outer surface of a pipe.

CONSTITUTION: The maximum Zn concn. of a Zn or Zn allay diffused layer is regulated to 1 to 20%, the depth of the diffused layer is regualted to ≤300μm, furthermore, after the formation of the Zn or Zn allay diffused layer, cold reduction working of ≥1% is executed to form into a corrosion resistant piping material. More concretely, in the process of hot extrusion pipe-making, a Zn wire is used, and the surface of the pipe material is continuously thermal sprayed to form a Zn layer. After that, it is subjected to diffusing treatment of 520°C×1hr served also as solution treatment, and after the treatment, immediately, forced cooling is executed. Furthermore, it is subjected to cold reduction working of 5 to 40% and is thereafter subjected to aging treatment of 170°C×4hr. Thus, the pipe material usable over a long period without executing surface treatment such as coating after piping even in severe corrosive environments can be formed.