To resolve a problem in a joining method by a bolt joint wherein a state of rust generated on a joining surface is a largely affecting factor of friction coefficient when carrying out tightening, but, since there is no effective means of controlling progress of rust by a known rust generating method, the rust progresses along with passage of time and will not stop, becomes excessive, defective rust such as bossing rust is found frequent, and as a result, deterioration of joint strength is incurred.

In a friction improvement measure of the joining surface for the joint part in the bolt joint construction method, by applying a volatile corrosion inhibitor in due time or carrying out coexistence in a closed or nearly closed state, in response to a progress of rust generated on the joining face by an optional rust generating method, the progress of rust is inhibited, and a favorable rust face is maintained, which becomes effective in maintenance of the strength of the bolt joint.