Corrosion Mechanism and Protection Methods for Suspension Bridge Cables

The main cables of several Japanese suspension bridges were found to be corroded. To determine the corrosion mechanism, the environments inside the cables were investigated, and corrosion simulation tests of galvanised wires were carried out. These studies showed that the corrosion environment depends on the position within the cable, with the side parts being most susceptible to corrosion. A new anti-corrosion system was developed using S-shaped wrapping wires and improved pastes to overcome this problem. Cables protected by this system were compared in long-term exposure tests with cables protected by conventional systems, and showed improved anti-corrosion performance. Another new method, namely to pass dry air through the cables, is proposed. Preliminary tests showed this system to be promising in terms of improving the anti-corrosion properties of the cables.