SSPC-SP5/NACE 1 limits staining to what percentage per each unit area?

The SSPC-SP5/NACE 1 standard specifies that for a surface to be considered "white metal blast cleaned," it must be free of all visible contaminants such as rust, mill scale, and paint, resulting in a uniform appearance. This translates to having 0% staining or corrosion products allowed per unit area. This standard sets a high cleanliness threshold to ensure optimal adhesion and performance of subsequent coatings. Meeting the 0% stipulation is crucial for achieving the desired level of surface preparation before coating application, as any presence of contaminants could negatively affect the coating's integrity and longevity. High standards like this ensure that the coating system will bond effectively and perform as intended.