REMEDIAL WORK TO CORRODED CAST-IRON PIERS

In certain aggressive environments, such as saltwater, cast iron corrodes in a peculiar manner quite different from the more familiar open-air rusting form of corrosion. This softening process, called graphitization, is potentially serious because, to a visual examination, the corroding metal appears sound under an encrustation of marine growth. The cast iron piles of 2 RTA bridges on the NSW North Coast were discovered to be severely affected by this type of corrosion, after years of regular inspection had failed to detect it. This paper describes the general process of graphitization, the extent of deterioration evident on the cast iron piles at McFarlane Bridge, and the repair works utilizing fabric form pile jackets.