PURPOSE: To easily prevent the corrosion of a bolt and nut over a long period of time by screwing a screw member consisting of a metallic material having the corrosion potential lower than the corrosion potential of the constituting material of the bolt and nut consisting of an iron material to the bolt and nut.

CONSTITUTION: Fastening of a pipe, etc., is executed by combining the bolt 1 consisting of a head 1a, a shaft 1b and a thread part 1c and the nut 2 to be screwed to the thread part 1c. The screw member formed of the metallic material (preferably zinc or zinc alloy) having the corrosion potential lower than the corrosion potential of the material constituting the bolt and nut is used as the screw member 3 to be screwed to the bolt and nut consisting of the iron material at this time. The current corresponding to the potential difference between the bolt 1 and the nut 2 and the screw member 3 flows from the bolt 1 and the nut 2 to the screw member 3 by screwing the screw member 3 to the thread part 1c and using such member. The screw member 3 is then eluted and consumed by as much as the electrochemical equiv. corresponding to the potential difference, by which the corrosion of the bolt and nut is prevented.