Long-term corrosion performance of superhydrophobic vs. superhydrophilic laser-modified AA2024 surfaces under ambient storage

Abstract Laser surface treatments are a promising tool for controlling both wettability and corrosion resistance. However, the long-term relationship between these two properties, remains poorly understood. In this study, the wettability and corrosion behaviour of laser-treated AA2024-T351 aluminium alloy was investigated over a two-year period. This alloy was selected due to its widespread aerospace use, where high mechanical properties are outweighed by its susceptibility to corrosion. Two nanosecond laser treatments were employed, Direct Laser Interference Patterning (DLIP) to produce periodic line-like patterns, and Direct Laser Writing (DLW) to create non-periodic structures. Morphological analysis revealed no degradation after two years of ambient storage. Wettability tests showed that DLIP-treated samples retained their superhydrophobic properties, with water contact angles (WCA) above 153° and roll-off angles below 10°. In contrast, the DLW-treated surfaces exhibited superhydrophilic properties, characterised by WCAs below 6.5°, strong capillary action, and water penetration into the porous layer. Electrochemical impedance spectroscopy (EIS) confirmed up to a tenfold increase in the total resistance of the treated samples, as result of the thicker oxide layer. The corrosion current density decreased from 1026 nA·cm ⁻² (reference) to 329 nA·cm ⁻² for both laser-treated surfaces, corresponding to a reduction in corrosion rate from 10.8 µm·yr ⁻¹ to 3.48 µm·yr ⁻¹ . After 730 days, both treatments outperformed the reference, with DLIP surfaces showing slightly greater stability due to the formation of a more compact oxide layer. These results fill the gap of knowledge in the correlation of these properties and confirms the reliability of laser treatments for generating long-lasting functional properties.