The spray ash desalination system continues to attract the interest of researchers owing to its application in ocean thermal energy conversion. The system consists of a ash chamber, fresh water tank, vacuum pump, and plate type condenser. The desalination system requires a plate type condenser with good performance in order to improve overall system performance. The material used for the heat transfer plate of the condenser is usually titanium. However, the use of another material, such as

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... num alloy, is proposed by the author to achieve cost reduction and improve heat transfer performance. Furthermore, a special coating aluminum alloy plate is proposed as material for plate condenser of spray ash desalination system because the aluminum alloy has low corrosion resistance against seawater. In this study, the heat transfer performance of the material and its corrosion against seawater were investigated using deep and surface sea water of Kume island of Okinawa Prefecture. The plate heat exchanger incorporates three kinds of aluminum alloy plate coating, and its overall heat transfer coe cients under owing seawater were derived. The three coating materials are 25 μm and 100 μm thick PEEK and 5 μm WIN KOTE ® , respectively. In addition, evaluation test for heat transfer and corrosion test of the heat exchanger under owing seawater were also conducted for a ve months period. Results show that out of the three materials, the 25 μm-thick PEEK coating plate had the largest overall heat transfer coe cient. The overall heat transfer of the three materials did not change during the ve months test period. However, only the WIN KOTE ® coating plate corroded owing to corrosion e ects of the seawater.