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Mechanical Derusting Methods: Shot Blasting Machine vs. Sandblasting Machines

Mechanical Derusting Methods: Shot Blasting Machine vs. Sandblasting Machines 2012-02-21

Q69 Series Steel Sheet Shot-blasting Pre-treatment Line

In the casting, storing and transporting process of metal parts, there might be a layer of oxidation scale or rust on the surface because of vibration or atmospheric corrosion. This layer has to be removed before painting or coating. Otherwise, it will affect the service life of the equipment or instrument. For derusting methods, there are manual derusting, mechanical derusting and chemical derusting. Among these derusting methods, mechanical derusting is a more widely used method.

Mechanical derusting is to throw shots (silica sand, iron shot, steel shot or glass bead) from the nozzle or high-speed running impeller to the surface of the parts by compressed air or mechanical power. This process can remove not only the rust, high temperature oxidation or old coating, but also the burr or welding slag. Mechanical derusting can help to achieve different levels of surface roughness. Appropriate surface roughness can increase the practical contact area between the metal and the coating, improve the adhesive power of coating and prolong the service life of the product.

There are mainly three kinds of mechanical derusting methods, sandblasting, shot blasting and hydro-blasting.

Sandblasting machines 

According to the different shot materials, there is shot peening and sandblasting. For cleaning of ferrous metals, the shot materials of the shot peening machine are iron shot, steel shot or glass bead. For the cleaning of non-ferrous metals, the shot materials of the shot peening machine are lead shot or brass shot.

The shot material of sandblasting is mainly silica sand. Considering the cleaning quality of the parts surface, sandblasting is able to get bright pattern and fine surface. Therefore, sandblasting is usually used in the cleaning process of the parts which have higher requirements. However, quantity of dust may be produced in the sandblasting process, which will influence the health of personnel seriously. Thus, the application of sandblasting machines is limited to some extent.

Shot Blasting

Shot blasting machine is to throw the shot from the blade of the shot blasting machine to the surface of the parts by the high speed running impeller. Shot blasting machine is widely applied for its high production efficiency and low energy consumption. Meanwhile, shot blasting machine is convenient for the realization of mechanized production. In mass production, shot blasting machine can function as part of the production line.

Hydro-blasting

Hydro-blasting, or high pressure water explosion blasting, is to remove rust or oxidation layer by the explosion of high pressure water on the surface of the parts. Compared with sandblasting, hydro-blasting will not produce any dust which may pollute the environment. For hydro-blasting, it's very important to choose clean water. Otherwise, the water may also bring pollution to the surface. In addition, this method can clean the surface perfectly, but it will not produce enough surface roughness.

These are the comparative analysis of the three main mechanical derusting methods. In the practical application, these methods should be chosen according to practical requirements and demands.