Surface preparation grade Sa 3

Sa 3 is the white-metal blast-cleaning grade in ISO 8501-1, one step above Sa 2.5 and the highest cleanliness in the standard. The blasted steel must be 100% free of visible mill scale, rust, old coating, and other contamination, with a uniform metallic appearance and no shadows or stains. It costs more in time and abrasive than Sa 2.5, so it is reserved for the most demanding service: immersion in aggressive electrolytes, thermal-spray substrates, and high-build coatings where any residual contaminant would cause early failure. Like all ISO 8501-1 grades it is assessed against the standard’s reference photographs, then checked for surface profile and soluble-salt levels before coating.