Abrasive blast cleaning to SSPC-SP 10/NACE No. 2, or Sa 2.5 in ISO 8501-1: all visible oil, mill scale, rust and old coating removed, with random light stains and shadows allowed on no more than 5 percent of each unit area. It is the common choice for immersion service and high-performance coating systems. One step down, commercial blast (SP 6, Sa 2) allows staining on up to a third of each unit area and suits many atmospheric jobs.
Spec calls for near-white blast, so those streaks down in the pits need another pass.
Also heard as
- SP 10
- NACE No. 2
- Sa 2.5
- Sa 2 1/2
Do not mix it up with
- White metal blast: White metal blast allows no staining at all; near-white allows light shadows on up to 5 percent of the surface.
Related terms
White metal blast
Top abrasive blast cleaning grade: bare, uniform steel with no visible residue, rust or staining.
Anchor profile
Peak-to-valley roughness that blasting cuts into steel so a coating can grip, given in mils or microns.
Soluble salts
Invisible chloride, sulfate and nitrate contamination on steel that causes blistering and early coating failure.
Dew point
Temperature at which moisture condenses from air; specs keep steel at least 3 C above it for blasting and painting.