The application of abrasive water-jet treatment on severely corroded weathering steel bridge

In some environments where the amount of road salts or airborne sea salt particles are relatively high, weathering steels can be corroded remarkably. Under such conditions, weathering steel is unable to form its protective layer of rust, necessitating additional protective measures such as painting. Before repainting weathering steel, it is essential to completely remove not only the protective layer of rust but also any corrosion products. These corrosion products are physically very hard, necessitating chipping before abrasive blasting. However, a single blast treatment is often insufficient to completely remove the corrosion products, requiring multiple repetitions. Despite this, it can be challenging to fully remove chlorides remaining in deeply corroded areas. Such residual chlorides often cause localized corrosion under the coating. Abrasive water-jet treatment (AWT) has been developed as a new method for preparation of weathering steel surface. Abrasive waterjet is one of the cutting technology for cutting harder materials, which has been developed in the 1980s. AWT can remove rust layer containing corrosion easily with the ultra-high pressure water of Mach 2 and abrasive materials. Additionally, during AWT process, the water temperature rises, which effectively helps wash away residual substances containing chlorides. Due to these merits, AWT is superior to conventional surface treatment methods in terms of the removal of thick rust as well as the cleaning of surface residues. In this study, AWT was applied to an actual corroded bridge where it located in Japan, and it was verified the efficiency of removing corrosion products and chlorides. The results demonstrated that both the corrosion products and residual surface chlorides were completely removed in a very short period of time.