Nanosecond Laser Fabrication of Superhydrophobic 7075 Aluminum Alloy with Underwater Gas Film for Enhanced Buoyancy and Wear Resistance

Nanosecond laser etching combined with surface modification presents a promising method for fabricating superhydrophobic surfaces with enhanced functionality. In this study, superhydrophobicity is achieved on 7075 aluminum alloy via nanosecond laser treatment followed by lauric acid modification to reduce surface energy. Additionally, carbon black coatings derived from candle soot are applied for comparison. The impact of surface structure and the formation of underwater gas films on buoyancy is systematically explored. A composite sample with laser‐etched microstructures and soot coating demonstrated excellent superhydrophobicity. After injecting air beneath the sample to form a stable gas film, the maximum load‐bearing capacity and the deepest surface vortex are observed. Without an air film, superhydrophobic properties degraded within 3 days of immersion, while samples with gas films maintained performance for up to 20 days. A repair mechanism for the air film is also examined. Experimental results showed a 313% increase in buoyancy for treated surfaces compared to untreated ones. Characterization confirmed that the fabricated surfaces exhibit high durability, superior buoyancy, and strong wear resistance, indicating their potential for marine engineering and buoyancy‐enhancing applications.