In cases of repairing and reinforcing steel bridges using high-strength bolted frictional joints, it is assumed to apply a contact surface treatment method that generates red rust by applying a rust accelerator to contact surfaces of existing members. In this study, we discussed the effect of the rust condition by the improved rust accelerator to the slip coefficient on results of slip tests focused on the exposure period of 1 2 ~ 48 hours after applying the rust accelerator. Following result was obtained. The slip coefficient of test specimens (contact surface of splice plates: zinc rich paint) exposed to the rust accelerator for 24 hours after applying the rust accelerator was 0.55 and over 0.40.
