Effect of Nanosecond Laser Ablation and Oxidation on the Surface Wettability and Microstructure of Cu-ETP Copper Sheets

Nanosecond laser ablation effectively modifies Cu-ETP copper surfaces by controlling wettability and microstructure. This study examines the effects of nanosecond fiber laser processing and subsequent oxidation on surface evolution. The analyzed parameters include fluence (25.46–1018.59 J/cm2), wavelength (1064 nm), repetition rate (25–1000 kHz), and pulse duration (2–500 ns). To investigate high energy densities, fluence values were set above typical ablation thresholds, inducing hierarchical surface structures affecting wettability. Post-ablation oxidation was examined under two conditions: natural oxidation in ambient air and accelerated oxidation via low-temperature annealing (200 °C) in air. Contact angle measurements revealed that over time, the initially hydrophilic (θ < 90°) laser-textured surfaces exhibited a transition toward hydrophobicity (θ > 90°), which can be attributed to the adsorption of airborne organic compounds rather than oxidation alone. In contrast, annealing significantly accelerated hydrophobicity, attributed to controlled copper oxide growth. SEM and EDS analyses confirmed that higher fluences enhanced roughness and oxidation, forming multi-scale textures and oxide layers, which influenced water repellency. These findings demonstrate that high-fluence laser ablation, combined with controlled oxidation, enables precise wettability engineering. This method provides an efficient strategy for tuning surface properties, offering potential applications in anti-corrosion coatings, self-cleaning surfaces, and heat exchangers, where hydrophobicity and durability are essential.