Effect of scanning speed on laser cleaning of composite paint layer on aluminum alloy

To explore the effect of varying scanning speeds on laser cleaning of the composite paint layer on the surface of civil aircraft skin, the paint removal transient process by laser ablation was simulated, and laser paint removal experiments of the acrylic polyurethane composite paint layer on the aluminium alloy surface were conducted using nanosecond pulse laser-cleaning equipment at three scanning speeds (v = 900 mm/s, 720 mm/s and 540 mm/s). The experiments show that the topcoat is entirely removed and the primer is partially removed when the scanning speed is 900 mm/s, and the actual paint removal depth is significantly less than the simulation result. The residual primer thickness is further reduced, and the partial oxide film is damaged when the scanning speed is 720 mm/s. The composite paint layer is removed, and part of the aluminium alloy substrate is slightly melted when the scanning speed is 540 mm/s. This study indicates that the ablation behaviour triggers three action mechanisms: plasma shielding, plasma shock-wave and thermal stress paint removal during laser paint removal. With the gradual decrease in scanning speed, the behaviour of ablation paint removal progressively strengthens, the effect of plasma action gradually weakens and the impact of thermal stress remains constant.