Effect of Orientation and Shielding in the Early Corrosion of Mild Steel in Tidal Marine Conditions

There is remarkably little quantitative information in the literature regarding the marine corrosion expected for steel exposed at different levels in the tidal region. There are no data that describe the effects of orientation, shielding, and water wave action. Coupons exposed at two locations on the eastern Australian seaboard produced corrosion profiles with elevations that are generally consistent with data reported in the literature. Estimates made of the statistical variability in corrosion losses showed a typical coefficient of variation around 0.02 to 0.05. Coupons boldly exposed between the mean high tide and the average mean tide levels were found to have a higher degree of corrosion for orientations associated with more aggressive exposure conditions. This is attributed mainly to differences in solar radiation and in weather conditions. There is little effect of orientation at higher and lower elevations. Where the waters and the coupons are subject to wave action such as from shipping, the mean tide water level for effective corrosion tends to be raised, in the case described, by about 0.25 m.