The removal mechanism of surface coatings from aluminum alloys via high-power nanosecond pulsed laser interlaced cleaning

With the rapid advancement of high-power lasers, the accumulation of thermal effects has emerged as a critical factor influencing processing quality. To investigate an efficient and non-destructive coating removal technique, this study utilizes high-power nanosecond pulsed lasers for cleaning paint layers from aluminum alloy surfaces. Experimental and numerical simulations were performed under various scanning methods and laser frequencies, demonstrating that the laser interlaced cleaning method achieves superior and non-destructive coating removal compared to traditional techniques. Laser frequency and energy density are identified as key parameters affecting cleaning efficiency. At a frequency of 15 kHz and an energy density of 3.75 J/cm², the paint layer is completely removed while preserving optimal substrate integrity. While complete removal is achieved at 10 kHz and 5 J/cm², slight substrate damage occurs; conversely, at a frequency of 20 kHz with insufficient energy density (2.5 J/cm²), incomplete coating removal and noticeable surface residues result. Scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) analyses confirm that interlaced cleaning significantly enhances uniform contaminant removal and reduces substrate damage. Further Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses reveal chemical changes on the surface after laser interlaced cleaning, indicating effective exposure and cleaning of the aluminum alloy substrate. The mechanisms of laser interlaced cleaning primarily involve ablation, vaporization, plasma shock, and elastic vibrations induced by thermal stress, all contributing to the removal of the paint layer while minimizing substrate damage.