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The degree of surface contaminant is defined in ISO 8501-1. Sa 2,5 is required for most coating processes which is possible with the QGB Range of shot blasting systems.
Rust grades Preparation grades
| STANDARD | METHOD | DESCRIPTION OF FINISH |
| Sa 1 | Light blast cleaning | When viewed without magnification, the surface shall be free from visible oil, grease and dirt, and from poorly adhering mill scale, rust, paint coatings and foreign matter. |
| Sa 2 | Thorough blast cleaning | When viewed without magnification, the surface shall be free from visible oil, grease and dirt and from most of the mill scale, rust, paint coatings and foreign matter. Any residual contamination shall be firmly adhering. |
| Sa 2,5 | Very thorough blast cleaning | When viewed without magnification, the surface shall be free from visible oil, grease and dirt and from mill scale, rust, paint coatings and foreign matter. Any remaining traces of contamination shall show only as slight stains in the form of spots or stripes. |
| 3 | Blast cleaning to visually clean steel | When viewed without magnification, the surface shall be free from visible oil, grease and dirt and shall be free from mill scale, rust, paint coatings and foreign matter. It shall have a uniform metallic color. |
