Formation and effect of rough surface in pulsed laser removal of thick paint layer on 2024 aluminum

When using pulsed laser to remove a thick paint layer from a 2024 aluminum alloy substrate, the paint layer should be removed layer by layer, and the substrate should remain intact after the paint layer is completely removed. In this process, the formation of a rough surface on the paint increases laser absorption, changing the removal mechanism, which becomes an unstable factor for nondestructive paint removal. This study investigated the laser paint removal mechanism of fluorocarbon paint and found that when the laser fluence was 0.91 J/cm2, the main removal mechanisms were thermal stress and combustion-decomposition removal, while at 94.36 J/cm2, the main mechanism was sputtering removal. The study also investigated the relationship between surface roughness and the number of laser scans, which showed a positive linear correlation. Additionally, an equivalent model of a rough surface was established to analyze the changes in absorption, though this model has yet to be verified and further research and validation is required to confirm our findings.