Corrosion of vertical mild steel strips in seawater

This paper describes the corrosion loss profiles of 1 m long vertical steel strips attached to a raft and exposed for 1 year in calm natural seawater on the Australian eastern seaboard. The upper parts of the strips were exposed to the atmosphere and the lower parts immersed to depths varying from 0.3 to 0.9 m. It was found that, irrespective of the precise ratio of atmospheric/immersion exposure, corrosion in the splash zone was much higher than that at the waterline and in the atmosphere. There was also significant corrosion in the immersion zone, immediately below the waterline, consistent with classical observations. Above the water line there was only moderate variability in corrosion between the strips but there was much greater variability in corrosion loss for the parts of the strips fully immersed. Mass loss observations are compared with observations of the corrosion and pitting patterns observed in the various zones. Potential reasons for these observations are considered. The observations have implications for explaining aspects of accelerated low water corrosion (ALWC).