What is Sand Blasting?
Sandblasting is the surface preparation & cleaning method of blasting the abrasive media using compressed air for cleaning the surface. Compressed air is used as the main power source to force the abrasive media on the surface to be blasted. That surface can be welded job requires cleaning before painting or other items that need surface preparation before applying paint or any coating. So, in the sandblasting process, Sandblasting particles are accelerated pneumatically using compressed air. The sand or other abrasive passes through the tube-driven by the compressed air, allowing the blaster to control the blasting direction, and is finally blasted via a gun onto the part.
Sandblasting process is being used for a long time. Although, with time abrasive media are replaced to better environment-friendly & efficient abrasives in place of sand. Sandblasting is a widely used surface treatment process for painting and coating applications. The process requires a closed area usually but can be applied in field application by giving a temporary enclosure around the blasting zone.
What is Shot Blasting or Grit Blasting?
During the Shot blasting or grit blasting process, an abrasive media is forced using a mechanical/ centrifugal force in place of the compressed area as used in sandblasting. Shot blasting uses a different equipment setup compared to sandblasting as you can understand from above. The shot blasting technique uses a mechanism like a rotating pump to force the abrasive media and hit it on the 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 big and more critical parts (high hardness, stiff oxide layers, removal of thick coating) that require more powerful pressure & a heavy abrasive media (such as steel shots) for clean & blast the part. As the process uses strong force, the area for the shot blasting is required to be confined (use of full PPE armor for the blaster, enclosed blasting room) for safety concerns.
You can notice shot blasting setup in big companies such as heavy fabrication, big automobile companies.
Watch this Video to Learn What is Sand Blasting & Shot blasting, Various abrasives media used in Shotblasting & their properties.
Sand Blasting or Shot Blasting, which is better?
Sandblasting is basically a soft surface preparation process. But abrasive media type and pressure of compressed air can increase the power of blasting to make it more invasive but it is still less powerful compared to the grit blasting so depth of depth of surface cleaning is not very high. Using low air pressure & soft blasting particles such as glass, sandblasting can be used on very thin parts, sheet metals, electronic parts, etc.
Shotblasting is a better option for higher depth surface preparation which is beneficial for surface of metals having hard, heavy metals. If sandblasting is used on such materials, it will be very soft & require long time for surface preparation on casting and steel plates, but in such cases shot blasting is rapid to remove thick rusting & oxides films easily.
Shotblasting (Grit Blasting) is mostly used with coarse abrasion shots of heavy-density that hit on a part surface to remove rust, scale, oxides very easily.
Shot Peening vs Shot Blasting
When we say Peening, it is a method used for materials & weld to improve strength, reduce stresses and increase durability. Peening helps to improve materials fatigue strength and reduces the geometrical stress concentration.
Shotblasting method is a type of peening method employed for hard surfaces but mainly used as a surface cleaning process.
Types of shot blasting media abrasive
Various types of basting media are used in the industry for shot blasting. The most common used materials are:
- Steel grit
- Steel Shot
- Coal slag
- Copper slag
- Glass Grit
- Glass beads
- Aluminum oxides
Application of Shot blasting/ Sand blasting
To Clean the material surface
This process is mainly carried out to perform the surface preparation for other processes such as coating and painting. Surface cleaning before visual inspection for overhauling components is also one of the area for the shot blasting.