Long-term immersion corrosion of steels in seawaters with elevated nutrient concentration

• Bi-linear model for long-term immersion corrosion of steel in seawater is proposed.
• Parameters describing model calibrated against multiple sources of literature data.
• Model allows for data uncertainty and seawater temperature.
• Greater dissolved inorganic nitrate concentration increases immersion corrosion loss.

Data from a variety of field exposure programs is used to quantify the effect of concentration of dissolved inorganic nitrogen (DIN) on long-term seawater immersion corrosion loss of structural steels. A linear correlation model that asymptotes the long-term part of the previously proposed bi-modal corrosion loss model is used. It allows for average seawater temperature. Model parameters and their variability are determined and reported. The model permits prediction of long-term corrosion loss in nutrient polluted waters of known average temperature. An example shows that anthropological pollution of seawater potentially is a major hazard for corrosion of steel infrastructure.