Removal of Paint on Al Alloy Substrate without Destruction by Air Jet with Ultrahard Ice Particles

Aluminum (Al) alloy is widely used and coated with a protective layer. When the layer ages, it needs to be removed before re-coating, but conventional methods frequently cause substrate damage, environmental contamination, or require secondary cleaning. While ice particle jets offer a promising alternative, existing approaches using micron-sized or low-hardness ice particles often lack sufficient kinetic energy for efficient cleaning. In this paper, the air jet technology with ultrahard ice particles as abrasives (AJUIP) was utilized to experimentally investigate the removal of epoxy organic silicon paint layer from the surface of Al alloy. The results showed that, driven by high-speed air, the ice particles could effectively remove the paint layer from the substrate without causing any damage to the substrate. By optimizing cleaning processing parameters, the efficiency and quality of the cleaning could be improved. The study established a four-stage removal process (nucleation, growth, fusion, cleaning) characterized by circular paint peeling units. Elemental analysis and scanning electron microscopy images revealed nearly no residual paint in the cleaned area. Numerical simulations of the air flow field elucidated the asymmetric gas velocity distribution influencing the distinct morphologies of the removal region boundaries. Finally, an elastic contact theory explanation for the paint removal mechanism of the AJUIP was provided, i.e., the size and velocity of the ice particles were the main factors affecting the paint removal effect. Therefore, the AJUIP exhibited significant potential for application in surface cleaning.