What is the maximum allowable staining according to SSPC-SP6/NACE 3?

According to SSPC-SP6/NACE 3, which pertains to commercial blast cleaning for steel surfaces, the standard allows for a maximum of 33% staining from rust and other contaminants. This level of staining acknowledges that some residual contaminants can remain after the cleaning process, but it ensures that the majority of the surface is cleaned to provide adequate performance for subsequent coatings. This percentage represents a balance, ensuring surfaces are sufficiently prepared without the necessity of achieving perfection, which can be impractical in many field situations. The allowance for up to 33% staining helps in practical applications while still aiming to achieve a surface profile conducive to coatings adhesion and effectiveness.