High Pressure Cryogenic Nitrogen Jet for Clean Coating Removal: Experimental Study of Polyamide Ablation

Abstract

The potential of a recently developed technique that uses a clean supercritical High Pressure Cryogenic Nitrogen Jet (HPCryoN2Jet) for surface ablation and cleaning is depicted. In contrast to existent coating-removal techniques (chemical stripping, hydro-blast, water jet cleaning...), as nitrogen is naturally recycled in the air, this process has a high potential for surface treatment without any chemical and physical effluents or sewage disposal. The treatment consists in impacting the surface with a high pressure (up to 3500 bar) cryogenic nitrogen jet (down to-160°C). The pressurized cryogenic nitrogen exits from a nozzle - having generally a 0.2 to 0.5 mm diameter outlet - to form the high velocity (supersonic) nitrogen jet. In this contribution, the ability of the process to remove polymeric (PA) coatings is evaluated on different types of metallic substrates (Cu, Al, E24, 316L stainless steel). The mechanisms of chip formation have been visualized using a high speed camera. Coating failure is shown experimentally to occur downstream of the jet and the influence of the substrate thermal properties on the stripping efficiency of the PA coating is highlighted.