Effect of tensile strain on the rate of marine corrosion of steel plates

It has been observed in the shipping industry that the rate of corrosion of steel plate may increase with longer duration of exposure, typically over many years. This effect has been attributed to the flexure of ships plates causing the loss of protective rust layers. The present paper describes the results of laboratory experiments in which plates with pre-existing rusts were subject to high levels of tensile strain, with and without subsequent exposure and corrosion. All rusts were obtained by exposing the steel to a natural marine environment, including the atmospheric and tidal zones. Careful observation of the rusts under tensile strain conditions showed that only strains near and beyond the elastic limit of the steel have the capacity to cause significant damage to the rust layers. Subsequent short-term exposure tests on pre-corroded and pre-strained steel coupons showed that there can be a moderate (10–15%) increase in the short-term corrosion rate.