The observation and Raman analysis of the surface of a PET polymer after the impact of an aluminium particle, combined with thermal modelling, have shown the presence of a zone with modified crystallization. This heat affected zone, with a thickness of a few microns, has different shapes depending on the geometry of the splat particle which is at its origin. This is the sign of a sharp temperature increase followed by a very rapid cooling. As a result, the proposition of crystallized phase is gradually decreased, and an amorphous phase is formed in a thin layer close to the surface. These results have been used to develop a protective plasma spraying technique for the coating of organic parts.