What is the difference between shot blasting and shot peening?

Shot blasting is a surface treatment process whose objective is to clean and prepare the surface of metal parts. On impact, the abrasive removes rust, mill scale, foundry sand, old paint and other contaminants, generating a controlled roughness profile — the anchor profile — that ensures maximum adhesion of paints, anticorrosive coatings and metallizing. It is the standard process in foundry, steel structures, shipbuilding, siderurgy and any industry requiring surface preparation prior to coating.

Shot peening is a mechanical treatment process whose objective is to increase the fatigue resistance of components. It uses exclusively spherical abrasives that, on impact, plastically deform the surface inducing residual compressive stresses in a layer 50 to 250 microns deep. These compressive stresses counteract the tensile stresses that generate fatigue cracks during component service. The result is a stronger component with longer service life. The process is controlled using the Almen test in accordance with SAE J443 and is always performed after heat treatment and grinding.