Optimised laser cleaning of paint from aluminum alloy based on thermal stress-induced integral peeling strategy

Abstract

The anodic oxide film is susceptible to damage during laser paint removal of aluminum alloy aircraft skins. In response to this issue, we proposed a cleaning strategy named Thermal Stress-Induced Integral Peeling (TSIP). Under the guidance of this strategy, we conducted laser paint removal experiments using an infrared nanosecond pulsed laser. The microscopic morphology, elemental composition, corrosion current density (5.4 × 10⁻⁷ A/cm²), and contact angle (70.28°) of the cleaned surface were highly consistent with the original oxide film, indicating that optimum cleaning was successfully realized. Furthermore, the oxide film damage mechanism was revealed by combining macro/micro morphology analysis and thermo-mechanical simulation. The thermal stress at the bottom of the paint layer exceeds its fracture strength, causing it to fragment and detach from the surface, forming holes. Subsequent pulses then pass through these holes to directly irradiate the oxide film, thereby damaging it. The process window for optimum cleaning, obtained through thermal stress simulation, is 2.32–3.20 J/cm², which is in good agreement with the experimental results. The research provides a new approach for optimum cleaning and contributes to advancing the engineering application of laser paint removal on aircraft skins.