Numerical simulation and experimental investigation on laser cleaning of a steel gate primer

In order to investigate the effect of laser cleaning technology on removing coatings from the surface of hydraulic steel gates, a finite element model of the epoxy zinc-rich primer on Q235 steel gate surfaces was constructed using COMSOL Multiphysics. A classical Gaussian pulsed heat source was applied to the surface to simulate the laser cleaning process, focusing on how laser cleaning parameters such as laser energy density and scanning speed, influence the temperature field, the stress field, and the ablation depth of the paint layer. Simulation results indicate that effective removal of the epoxy zinc-rich primer without damaging the Q235 substrate can be achieved under the following conditions: a laser repetition rate of 100 kHz, a pulse width of 200 ns, a laser energy density of 15.59<i>J</i>/<i>c</i><i>m</i>², and a scanning speed of 750 mm/s. To verify the accuracy of the simulation, laser cleaning experiments were conducted using a 100 W pulsed fiber laser. The microscopic morphology and composition of the material surface were analyzed via scanning electron microscopy and energy dispersive X-ray spectroscopy), while confocal microscopy was used to observe surface roughness before and after cleaning. Experimental results confirm that the epoxy zinc-rich primer can be effectively removed at energy densities ranging from 15.59<i>J</i>/<i>c</i><i>m</i>² to 18.19<i>J</i>/<i>c</i><i>m</i>² with a scanning speed of 750 mm/s, consistent with the simulation findings. However, when the energy density reaches 20.79<i>J</i>/<i>c</i><i>m</i>², the Q235 substrate becomes damaged during cleaning. Additionally, a scanning speed below 500 mm/s increases surface roughness, which negatively impacts the material's subsequent recoating performance. The research focuses on laser cleaning technology for critical components of hydraulic steel gates (epoxy zinc-rich primer on Q235 steel substrates), providing reference values for industrial applications.