Effect of Nutrient-Based Water Pollution on the Corrosion of Mild Steel in Marine Immersion Conditions

Water pollution is often thought to cause accelerated corrosion of steels, particularly in harbors where levels of oxygenation of the waters may be low and where there may be industrial and shipping wastes. Harbors and coastal regions may also be prone to nutrient pollution from sewage or agricultural run-off. Offshore oil fields also are known to provide sources of nutrient pollution. There are some anecdotal observations but there appear to have been no systematic field or laboratory studies. Recent field observations have been reported on the effect of nutrient-based pollution on the corrosion of mild steel corrosion coupons. These are interpreted in terms of the phenomenological model previously described in the literature for the corrosion of mild steel under marine immersion conditions. A selection of field data previously reported in the corrosion literature is then considered and shown to have characteristics not inconsistent with nutrient-based water pollution. The effect of dissolved oxygen concentration is noted also.