Synergistic optimization of wettability and surface durability via femtosecond laser scanning pitch-regulated micro-nano structures on 7075 aluminum alloy

In this study, different micro-nano structural morphologies, including cylindrical and square-columnar micro-nano structures, were induced on the surface of 7075 aluminum alloy by adjusting the scanning interval of the femtosecond laser. The influence of the micro-nano structural morphology on surface wettability was characterized using a contact angle (CA) goniometer, while the correlation between structural morphology and corrosion resistance was revealed through electrochemical measurements. In addition, standardized salt spray tests, immersion corrosion tests and friction-wear tests were conducted to evaluate the effect of surface morphology on the durability of the treated samples. The results show that the CA of the femtosecond laser-processed samples increased significantly, exhibiting superhydrophobic behavior. The micro-nano structures effectively reduced the solid–liquid contact area, thereby markedly suppressing liquid infiltration. During electrochemical tests, the femtosecond laser treatment formed a hierarchical surface composed of periodic microcolumn arrays and nanoscale roughness. On the one hand, these features promote an air-trapping effect that reduces the actual contact area between the electrolyte and the substrate, leading to a lower corrosion current density; on the other hand, they improve the compactness and stability of the passive film, resulting in a significant increase in polarization resistance and thus enhanced corrosion protection. In the immersion corrosion test, the laser-treated samples maintained structural integrity and good surface morphology after 168[Formula: see text]h of immersion. Furthermore, in the salt spray corrosion test, the laser-structured surfaces demonstrated excellent corrosion resistance, confirming that the presence of micro-nano structures effectively enhances corrosion durability. The friction-wear tests revealed that the femtosecond laser-treated samples exhibited a lower friction coefficient and wear rate, indicating superior mechanical durability of the structured surfaces. Overall, femtosecond laser processing enables the simultaneous achievement of superhydrophobic modification and long-term protective enhancement on the surface of 7075 aluminum alloy. Among the tested conditions, the sample processed with a scanning interval of 50[Formula: see text][Formula: see text]m exhibited the most stable micro-nano structures with minimal processing defects, showing the best overall surface performance.