Evaluation of Surface Modification Methods to Mitigate Rusting and Pitting in Weathering Steel Bridges

摘要

The rusting and weathering characteristics of ASTM A-588 structural steel in bridge sections under the hot and humid conditions of Louisiana were studied using laboratory and field tests. Field tests included periodic section thickness measurements at several locations in eight bridges in order to determine the actual section losses due to corrosion, as well as analysis of corroded field coupons exposed at bridge sites for up to two years. Laboratory tests included exposure of steel coupons to simulated atmospheric conditions in chambers, exposure to hot and humid conditions in fog chambers, total immersion in plain as well as in salt water and potentiostatic polarization tests. Tests were also undertaken after coating the surfaces of cleaned steel coupons with rust stabilizer-type inhibitors, such as phosphoric acid, benzoic acid and tannic acid in various combinations. Results indicated that treatment with phosphoric acid is beneficial for preventing excessive rusting through stabilization of an amorphous form of rust, and such treatments were found to be effective even in the hot and humid coastal and near-marine environments.