| Atmospheric corrosion-resistant steel is unique in forming a tight and stable rust layer on its surface、 which acts as a protective film that retards the corrosion of steel. Once stable rust forms、 no coating is needed for many years、 thereby reducing maintenance costs. However、 on some bridges with such steel、 stable rust has failed to form and the base metal has become corroded; as a result、 the specification has been changed to painting. There are also cases where serious corrosion has required a bridge to be reconstructed. It is necessary to fully understand corrosion conditions through inspections or investigations and to conduct proper maintenance such as by removing and minimizing the causes of corrosion. Hokkaido Development Bureau is developing a technique for evaluating the deterioration of bridges built with weathering steel. The evaluation method is suited to the severe natural environment of Hokkaido. In 2003、 this development program started with corrosion investigations on a corrosion-resistant bridge on Muroran Shindo(National Highway 36). This paper explores the extent of corrosion and factors of corrosion progress by comparing investigation results obtained in 2003 with those of 1987. |
