2. Dry ice spray cleaning, also known as cold spraying, uses compressed air as the power and carrier, and dry ice particles as accelerating particles, which are sprayed onto the surface of the cleaned object through a special spray cleaning machine. Using energy conversion such as momentum change (δ MV), sublimation and melting of high-speed solid dry ice particles, the dirt, oil stains and residual impurities on the surface of the cleaned object can be quickly frozen, so as to coagulate, embrittle and freeze. It will not cause any damage to the surface of the cleaned object, especially the metal surface, and will not affect the smoothness of the metal surface.