Sandblasting

https://www.yxtechco.com/sandblasting.html

Sandblasting from Yixing Technology is a common process of surface treatment for sheet metal parts. Using compressed air as the power, a high-speed jet beam is formed to spray materials (copper ore, quartz sand, diamond sand, iron sand, sea sand) at high speed onto the surface of the workpiece to be treated, causing changes in the appearance or shape of the workpiece surface.