Key Technical Points for Selecting Abrasives (Steel Shot, Cut Shot, Steel Grit)

　　Abrasives are a general term for granular solid materials used in shot blasting and sandblasting processes. They can be categorized by material type into metallic and non-metallic abrasives. They are also categorized by particle form into pellets, sand, and columnar particles. Abrasives have a direct impact on the efficiency, cost, and quality of steel surface cleaning. Abrasive selection in steel structure shot blasting and sandblasting should be based on the following:

　　According to ISO 8501, the original condition of the steel surface should be investigated. For thick, severely corroded Grade C or higher steel plates, high-quality, high-hardness abrasives should be selected. Abrasives should be selected based on the cleanliness standards and roughness levels specified in the coating design. For higher cleanliness levels, the abrasive particle size and density should be moderate; for higher roughness levels, the abrasive particle size should be larger.

　　The surface preparation method and equipment should also be considered. For example, for steel shot and grit used in shot blasting lines, a particle size of 1.0-1.2mm is appropriate; for copper slag used in open sandblasting equipment, a particle size of 0.6-1.8mm is appropriate. Furthermore, the coating type and the required film thickness also factor into the abrasive selection.

　　Because different primers have different requirements for steel cleanliness and roughness, especially when using alcohol-soluble inorganic silicate primers, it is best to use angular steel grit for sandblasting to increase the roughness's ability to bind the primer. Generally, a roughness of one-third of the coating thickness is ideal.

　　When selecting a specific abrasive, the following factors should be considered: Particle size: Within the same abrasive, larger particles have stronger cleaning properties. Conversely, smaller particles have a faster speed reduction and weaker cleaning properties. Shape: The shape of the abrasive particles determines the appearance of the steel surface after shot blasting. Hardness: The hardness of the abrasive must be greater than that of the steel surface. Density. Abrasive density is related to abrasive recovery rate; the higher the density, the higher the recovery rate.

　　For example, quartz sand can only be used once, while slags like copper slag can generally be used three times, and steel grit and cut wire shot can be used over 100 times. Abrasives should be free of oil, dust, and moisture. Using contaminated abrasives can lead to coating failure and premature damage to the coating. In the coating of steel structures, strict requirements are placed on the chlorine content of the abrasive.