Cyclic salt‐spray study of pitting corrosion of coastal air‐conditioner aluminum fins with varying spacing, surface flatness, and placement angle

Abstract Pitting corrosion of aluminum fins in coastal air‐conditioner units degrades heat‐exchange performance. This study quantifies pitting corrosion of 6063 aluminum fin assemblies under cyclic neutral salt spray. A salt‐spray protocol (720 h, 42 cycles) was applied to fins with different spacings, surface flatness, dehumidification/desalination strategies, and placement angles. Net mass change was measured by a loss‐on‐drying gravimetric method and analyzed statistically. Fins with smaller spacing and corrugated surfaces showed a mass increase of approximately 2% from adherent corrosion products after 31 cycles. This increase was substantially larger than for smooth, widely spaced fins, indicating that narrow spacing and poor flatness intensify pitting damage. Under summer conditions, periodic water‐mist spraying combined with enclosure and desiccant produced the lowest cumulative mass change among all mitigation measures. In contrast, ozone treatment yielded only modest. The installation angle also significantly affected pitting corrosion. After 42 cycles, vertically mounted fins exhibited a corrosion weight‐loss ratio of 12.1%, approximately three times that of horizontal fins (4.0%), while tilted orientations showed intermediate behavior. These results demonstrate that liquid‐film thickness and renewal significantly influence the pitting corrosion of coastal aluminum fins, providing quantitative guidance for fin geometry, dehumidification scheduling, and placement angle in coastal air‐conditioning design.