| 摘要 |
PURPOSE:To make it possible to maintain the life of piping over a long period of time by suppressing the spreading and advance of corrosion, by forming projections to the inner or outer surface of the piping to which a film is applied. CONSTITUTION:The inner surface of a pipe is cut so that the shape of each projection is a quadrangular pyramid and triangular grooves can be formed in both spiral and pipe axial directions. The height of each projection is set to about 1.5mm. and the angle of each side surface of the quadrangular pyramid to 60 deg.. By this structure, even if a flaw is generated in a film, the flaw is stopped at the leading end of each projection while the liquid sump surrounded by the interface of the film and a metal can be formed as the flaw part is corroded and corrosion advances and an electrolyte is held at high concn. and, therefore, the advance of corrosion is reduced.
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