Surface Preparation Methods and Standards
Naming the standards
Joint NACE/SSPC abrasive blast standards map directly onto ISO 8501-1 visual grades. SSPC-SP 5 / NACE No. 1 = white metal (ISO Sa 3). SSPC-SP 10 / NACE No. 2 = near-white (ISO Sa 2½). SSPC-SP 6 / NACE No. 3 = commercial blast (ISO Sa 2). SSPC-SP 7 / NACE No. 4 = brush-off (ISO Sa 1). Hand and power tool cleaning are SSPC-SP 2 and SP 3 (ISO St 2 and St 3); solvent cleaning is SSPC-SP 1; SSPC-SP 11 is power-tool bare metal; SP 13 and SP 14 cover concrete and masonry. Visual acceptance uses SSPC-VIS 1 or ISO 8501-1 photographs - the grade is defined by the remaining stains and tightly adherent material, not by blasting time.
Profile
Anchor profile is measured by replica tape (ASTM D4417 Method C) or stylus (Method B), with visual/tactile comparators (ISO 8503 grit and shot comparators) for field checks. Angular grit profiles are preferred over rounded shot for most coatings. Profile must be sufficient for the specified DFT but not so deep it exceeds film thickness at peaks.
Soluble salts and contamination
Salt contamination drives osmotic blistering and premature failure. Test by Bresle extraction with conductivity measurement (ISO 8502-6 and 8502-9), and compare against the project's µg/cm² limit rather than a generic number. Oil, grease, and visible contamination are removed by SSPC-SP 1 before any blasting.
Traps
Questions swap ISO and SSPC names, or claim SP 6 removes all mill scale. In practice, tightly adherent mill scale may remain at SP 6 but not at SP 10. Environmental limits (surface at least 3 °C / 5 °F above dew point, RH typically under 85%) apply during preparation as well as application.
Rule of thumb
Profile should be roughly one-third to one-half of the total system DFT - deep enough to anchor, shallow enough that peaks stay covered.