| 摘要 |
PURPOSE:To prevent corrosion of a member due to contact with fluid, by applying galvanization of Ni-Sn-P alloy onto the surface of the member for supplying/ discharging the fluid through cooperation at the contacting portion with the fluid, while furthermore applying galvanization of Ni-P series or Ni-B series alloy. CONSTITUTION:A screw vacuum pump 1 associated with a member for supplying/discharging fluid through cooperation comprises a tubular casing 3, covers 4, 5 and male/female screw rotors 13, 12 contained therein. The surface 20 of the composition member of the screw vacuum pump 1 at the contacting portion with fluid is applied with fine alloy galvanization 21 of Ni-Sn-P with scarce defect such as pin hole, followed by further galvanization 22 of corrosion resistant Ni-W-P or Ni-W-B alloy. Consequently, even when highly corrosive gas or gas containing water is employed, the surface 20 at the contacting portion with fluid does not corrode thus enabling cost reduction of material. Furthermore, the surface 20 at the contacting portion with fluid is made smooth through galvanization, thereby degradation of efficiency due to adsorption can be prevented.
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