Abstract
The application of impressed current cathodic protection to the inner surface of the steel aqueduct bridge in which river water flows has been studied by site tests. The site tests were conducted on two aqueduct bridges, which bring the river water for tap water supply. The span of the test site was 5 meters. The each inner surface of the aqueduct bridges is covered with tar epoxy resin. However, the painting has failed through 40 years of use. Many painting blisters and tubercles were observed on the inner surface. Even under these imperfect painting conditions, the cathodic protection was applicable to one of the two aqueduct bridges. The main reason why the cathodic protection was successful was the improvement of current distribution by the remaining paint coating. The potential measured around the inner surface became uniformly more negative than the protective potential at a cathodic current density of 16mA/m2 in the test.
