The increased brightness of metal after shot blasting is mainly caused by surface cleaning, changes in the material’s microstructure and modified light reflection properties.
Main Reasons
Removal of oxide layers and contaminants
High-speed abrasive impact effectively strips rust, scale, grease and other surface coatings from the metal, exposing the base metal and restoring or enhancing its natural metallic luster.
Formation of a uniformly textured rough surface
Abrasive bombardment creates microscopic indentations and plastic deformation across the surface, generating a consistent micro-rough structure. Under specific operating conditions, this surface structure improves either diffuse or specular light reflection, making the workpiece appear brighter.
Process matching according to workpiece material
When treating non-ferrous metals such as aluminum alloys, stainless steel abrasives (grades 410 or 304) can produce high-gloss finishes with properly calibrated process parameters (abrasive hardness, particle size, etc.).
For example, the bright silvery-white finish of aluminum workpieces after shot blasting is commonly achieved by mixing a small proportion of aluminum shot with stainless steel abrasive.
