Sand blasting & shot/grit blasting difference & types of abrasives medias?

What is Sand Blasting?

Sandblasting is the process of propelling that abrasive media using compressed air for cleaning the surface. This cleaning and preparation procedure takes compressed air as a power source and directs a high-pressure stream of abrasive media toward the part to be blasted. That surface could be welded parts being cleaned before painting, or auto part being cleaned of dirt, grease and oil or anything that require surface preparation before applying paint or any coating. So ,in the sand blasting process, Sandblasting media is accelerated pneumatically by compressed air (instead of a centrifugal turbine). The sand or other abrasive passes through the tube driven by the compressed air, allowing the user to control the direction of the blast, and is finally blasted through a nozzle onto the part.

sand blasting vs grit blasting

Sand blasting process is being used from a long time. Although, with time abrasive medias are changes from Sand to more environment friendly & efficient abrasives.

Despite the change in equipment and materials, sandblasting is still the most common and preferred abrasive treatment method. It’s particularly suited to soft and sensitive materials being readied for final finishes. Sandblasting is also a more economical equipment system to purchase, easier to operate and offers excellent quality to the consumer.

What is Shot Blasting or Grit Blasting?

Shot blasting or grit blasting is the process of propelling abrasive media material with centrifugal or mechanical force instead of using compressed air. Shot blasting has an entirely different pressurizing system than sandblasting as you can understand from above. Shot blasting technique uses a device similar to a spinning wheel to centrifugally accelerate shot-like material and blast it against a surface or other example of centrifugal pump used for hydro jetting where water is accelerated with high pressure.

Shotblasting is highly powerful blasting method than sandblasting. Shot blasting is used for larger and more difficult parts (high hardness, stiff oxide layers, removal of thick coating) that need a strong application force and a denser media material (such as steel shots) to clean and prepare a surface. Shotblasting also requires strict containment (use of full PPE armour for the blaster, enclosed blasting room) as the force of blasted shot could cause collateral damage if the process isn’t confined.

You can find shot blasting setup in large-scale companies such as heavy fabrication, big automobile companies. That could be in shot blasting tanks where steel shot or grit blasts rough surfaces like automobile frames being restored or steel containers being recycled.

Watch this Video to Learn What is Sand Blasting & Shot blasting, Various abrasives medias used in Shotblasting & their properties.

Sand Blasting or Shot Blasting, which is better?

Sandblasting is basically a softer and less invasive abrasion process. But it also depends on the compressed air pressure being used and the types of the abrasive media e.g. sand or glass or steel. Because sandblasting is less forceful than shot blasting, the depth of surface cleaning is not very high. With light pressure and soft media materials like organics or glass, sand blasting can be used on very thin parts, sheet metals, electronic parts etc.

Shotblasting is better option when you require deep abrasive penetration on having hard, denser materials. Where sandblasting might be too gentle and time-consuming for treating casting and steel plates, shot blasting will quickly remove thick rusting & oxides films easily.

Shotblasting is mostly used with coarse abrasion media like steel shot and steel grit. These are heavy-duty media materials that hit into a part surface to remove rust, scale, oxides very easily.

shot peening vs shot blasting

Peening is a metallurgical term for metal to increase strength and durability. Peening helps improve materials fatigue strength and reduces the geometrical stress concentration.

Shotblasting is actually a peening process used for tougher surfaces but mainly used as a surface cleaning process.

Types of shot media abrasive

Various types of basting medias are used in the industry for shot blasting. Most common used materials are:

  1. Steel grit
  2. Steel Shot
  3. Coal slag
  4. Copper slag
  5. Garnet
  6. Olivine
  7. Glass Grit
  8. Glass beads
  9. Aluminum oxides

Application of Shot blasting/ Sand blasting

Surface cleaning

Shot blasting equipment is initially used in the foundry industry to remove sand and oxide scale from the surface of steel and iron castings. This is not only to remove the oxide scale and sticky sand on the surface of the casting, but also an indispensable preparation process before the quality inspection of the casting.

Workpiece strengthening

According to modern metal strength theory, increasing the dislocation density inside the metal is the main direction to improve the strength of the metal.

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