Abrasive blast cleaning

In order to clean steel or remove rust from iron or scale from metal, sand or some other powder substance is forced by air pressure through a nozzle. In this way the small particles of abrasive can penetrate the metal where sanding with sandpaper cannot. Also, very small craters are formed on the surface of the metal from the blasting action. When thoroughly cleaned the metal is ready for painting. Paint adheres better to these "craters and imperfections than to a perfectly smooth surface".