Shot blasting is a process that is often used to clean the surface of a material. The process usually involves a gun or a ride-on rolling blasting machine that is used to shoot various types of media, or shot, at the object being blasted. This is a particularly effective method for removing scale, rust, paint, and minor surface flaws from metal objects. Depending on the shot blast equipment and the type of shot that is used, various surface finishes or textures can also be applied to a work piece for decorative purposes, or to prep the surface for paint or powder coating.
There are many different types of shot blasting machines, from small hand held guns to riding lawnmower size machines to massive blast booths large enough to hold a tractor trailer. Regardless of the size or configuration, the majority of them are made up of the same components. A basic shot blasting setup includes an air compressor, a shot blaster gun, a blast booth or cabinet, and a hopper to deliver the shot to the gun.
Any holes that may be machined into the component being anodized should be bored or machined slightly oversize to take into consideration the anodized finish adding slightly to the inside dimensions of the hole. Failure to do this could result in a hole that is too tight to allow the pin or component into the hole once the part is assembled. For anodized surfaces that are not critical to any lubrication properties, sealing is often required for the surface once the anodizing has been completed. Immersion in very hot water is usually all that is required to close the small holes left in the surface of the anodized metal.
By placing the aluminum into a bath of liquid chemicals that are often nothing more than acetone and applying an electrical current through the aluminum component, a chemical reaction occurs that is similar to a type of rust forming on the aluminum. This rust-like material is the anodized finish and actually works to increase the strength of the aluminum's surface. Similar to gold or silver plating, the color of the anodized finish is dependent on the types of metal sheets immersed into the liquid chemicals.