Bridges

Corrosion damage of steel elements is the main driver for development of corrosion management strategies by Asset Managers, the implementation of which draws significant amount from the government treasury. Since economic viability of any project is the key to sustainability, it is imperative to reduce the potential for corrosion. This paper presents a case study on corrosion of elements of a tunnel wall panel system, intricately identifying the underlying reasons and the options that could have led to its avoidance. These wall panels were mounted on galvanized steel frames using stainless steel screws through aluminum strips. The specification for the wall panel system was based on performance and it required the system to have 25 years design life. However, the elements of the wall panel system started showing signs of corrosion within ten years of installation. An investigation into the root cause of the problem was carried out. This involved visual examination of the elements of the wall panel system and sampling of the water, present due to seepage from the tunnel walls, for testing. The failure analysis identified presence of chloride in water around the support frames and the contact of dissimilar metals resulting in galvanic corrosion of the elements. A critical review of the submitted investigation report revealed that the recommended remedial measures were inadequate for the long term durability of the wall panel system, thus compromising its sustainability. The paper describes the corrosion behavior of the metals involved, explains possible corrosion mechanisms and reviews the proposed remedial measures. It is envisaged that the lessons learned may help adopt measures to achieve enhanced durability of bridges.