Corrosion Resistance of Anodized A5052 Aluminum Alloy Under Long-Term Deep Seawater Exposure for OTEC Applications

To assess the feasibility of replacing titanium heat transfer plates with aluminum in ocean thermal energy conversion (OTEC) system heat exchangers, an investigative study on the resistance to seawater corrosion of aluminum plates was conducted. In this study, a long-term field corrosion test was conducted using deep seawater continuously supplied from an operational deep seawater facility in Kumejima, Japan. Flat A5052 aluminum plates with and without anodizing were installed in a plate heat exchanger, allowing corrosion behavior to be evaluated under realistic flow conditions for 12 months. The corrosion behavior of the plates was evaluated at 1, 3, 6, and 12 months. The results showed that, for the A5052 aluminum plates with anodizing, no apparent corrosion was observed on the anodized specimens throughout the test period. Although localized corrosion developed on the untreated specimens, the overall mass loss remained limited. Surface deposits containing inorganic and organic constituents were observed. The maximum corrosion rate of untreated A5052 was 2.56 × 10−2 mm/y. Overall, the results suggest that anodized A5052 has potential as a heat-transfer material for OTEC systems under the tested conditions.