Sandblasting cleanliness is typically measured using the Sa grade standard.
There are two globally recognized standards for Sa cleaning grades:
The Sa grades established by Sweden in 1976.
The SSPC grades established by the United States in 1985.
Since Sweden was the first to formulate this standard, the Sa grades are now the primary benchmark used to measure cleaning levels.
The Sa grading system consists of four levels: Sa1, Sa2, Sa2.5, and Sa3.
Sa1:
This level typically involves simple manual methods-such as brushing or sanding with abrasive cloth-to clean the workpiece surface. It represents the lowest of the four cleanliness levels, offering a level of coating protection only marginally superior to that of an untreated workpiece. The technical standard for Sa1 treatment requires that the workpiece surface be free of visible contaminants such as oil stains, grease, residual mill scale, rust spots, and residual paint.
Sa2:
This level typically involves cleaning via sandblasting. Sa2 represents a lower tier within the sandblasting treatment spectrum-often considered the "general requirement" level-yet it offers significantly enhanced coating protection compared to manual cleaning methods. The technical standard for Sa2 requires that the workpiece surface be free of visible oil stains, mill scale, rust scale, corrosion products, and other foreign matter. However, if the workpiece surface contains pits or depressions, slight traces of rust and paint may still remain at the bottom of these recesses.
Sa2.5:
This level is widely utilized in industrial settings and frequently serves as the technical requirement and standard for acceptance criteria. The technical standard for Sa2.5 treatment mirrors the initial requirements of Sa2; however, it permits the presence of minor surface imperfections (defects) covering no more than 5–8% of the total surface area per square meter. These permissible imperfections may include slight shading, minor discoloration resulting from defects or corrosion, and residual traces of mill scale or paint.
Sa3:
This level represents the highest standard of surface treatment requirements in industrial applications. The technical standards for Sa3 treatment are identical to those of the Sa2.5 level; however, it removes shadows, rust, and similar contaminants even more thoroughly than the Sa2.5 level-to the point where such traces are completely absent.
