Manufacturing method of cast iron pipe and surface corrosion protection method of cast iron pipe

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a cast iron pipe having improved outer surface corrosion resistance by using it as a corrosion resistant layer without removing a part of the oxide film, and a method for protecting the outer surface of the cast iron pipe. SOLUTION: A method for manufacturing and casting a cast iron pipe in which a cast iron pipe after an annealing treatment is subjected to high-pressure water treatment and a zinc-based metal is directly sprayed onto the surface of the cast iron pipe after the high-pressure water treatment to form a zinc-based metal sprayed film. The subsequent cast iron pipe is annealed, and high-pressure water is sprayed onto the outer surface of the cast iron pipe after the annealing treatment to remove the oxide film layer having a high passivation on the outer surface of the cast iron pipe, and then on the remaining dense oxide film layer. High-pressure water is applied to the surface layer of the cast iron pipe formed on the outer surface of the cast iron pipe by the method of manufacturing the cast iron pipe by spraying a zinc-based metal or painting a paint, and the cast iron pipe after casting, which has a high passivation ratio. A method for preventing corrosion of the outer surface of a cast iron pipe, which comprises a step of removing by spraying and a step of spraying a zinc-based metal or applying a paint on the remaining dense oxide film layer. [Selection diagram] Fig. 1