Which standard represents brush-off blast cleaning with the lowest quality requirement?

The standard that represents brush-off blast cleaning with the lowest quality requirement is SSPC-SP 7. This standard outlines a process for surface preparation that is specifically intended for light cleaning of steel surfaces prior to the application of coatings. It allows for the removal of loose rust, loose mill scale, and other contaminants but does not require the surface to be free of all contaminants.

By contrast, other standards such as SSPC-SP 5 and SSPC-SP 10 represent higher quality cleaning requirements. SSPC-SP 5, for example, requires a near-white metal surface, which is much cleaner than the criteria set forth in SSPC-SP 7. Similarly, SSPC-SP 6 involves a commercial grade clean, which is still more rigorous than the brush-off cleaning defined in SSPC-SP 7. Therefore, when focusing on a quality requirement for surface preparation that is less stringent and suitable for less critical applications, SSPC-SP 7 is indeed the appropriate standard to refer to for brush-off blast cleaning.