Field experiments designed to evaluate deoxygenation of natural seawater as a corrosion control measure for unprotected seawater ballast tanks demonstrated decreased corrosion in hypoxic (< 0.2 ppm O2) seawater using weight loss and linear polarization measurements. The experiments also demonstrated the difficulty of maintaining hypoxic seawater. Using a gas mixture it was possible to displace dissolved oxygen in natural seawater. However, aerobic respiration and corrosion reactions consumed oxygen and produced totally anaerobic conditions within the first days of hypoxia. When gaskets and seals failed oxygen was inadvertently introduced. The impact on corrosion depended on the amount of dissolved oxygen in the system at the time of the inadvertent oxygen introduction. Steels exposed to cycles of hypoxic seawater and oxygenated atmosphere had the highest corrosion rate and severity.

Subject
Ballast, Water, Corrosion rate, Atmosphere, Instantaneous corrosion rate, Natural seawater, Seawater, Weight loss, Oxygen, Dissolved oxygen, Carbon steel, Corrosion coupons, Electrodes
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2005
GOV
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