Corrosion of an aluminum alloy chilled in flowing seawater and the effect of cathodic prevention

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A new type of jet-in-slit testing apparatus for a specimen, chilled with a peltier element, was developed to investigate corrosion on the heat transfer surface of an aluminum alloy heat exchanger, in contact with a liquefaction gas at cryogenic temperature and in flowing seawater. The specimen can be chilled, even under flowing conditions, using this apparatus. Corrosion tests and polarization measurements of a specimen chilled by a peltier element were carried out in flowing seawater at various temperatures. The effect of chilling a specimen was equivalent to the effect achieved for a test in solution at a lower temperature. The process was dependent on a passive film, formed on the surface of the aluminum alloy specimen, as evidenced by polarization measurements. The extent of corrosion damage increased with increasing temperature of the solution, and showed maximum damage at high temperature. At high temperatures, erosion-corrosion was found at the central part of the specimen, but the effect of flow was negligible at low temperature. Corrosion tests for a cathodically polarized specimen were conducted under flowing conditions. Corrosion damage was accelerated by cathodic polarization at lower temperatures.