SSPC and AMPP surface preparation standards: complete guide to all grades

• SP 5 / NACE No.1 — White metal: the surface must be completely free of oil, grease, dust, rust, mill scale and paint residues without exception. The most demanding grade. Specified for extremely severe conditions: acids, salts in solution, marine or aggressive industrial environments.
• SP 10 / NACE No.2 — Near-white metal: up to 5% of contaminant residues are acceptable, appearing only as different colouration per unit area. The most widely used grade industrially — balances preparation quality and work speed. Recommended for moderate to severe conditions and high-performance coating systems.
• SP 6 / NACE No.3 — Commercial: mill scale residues must not exceed 33% per unit area, visible only as different colouration. Specified in lightly loaded zones without corrosive environments.
• SP 7 / NACE No.4 — Brush-off: removes loose mill scale, loose rust and flaking paint. Tightly adherent mill scale may remain. Only for very mild conditions or as a pre-treatment.
• SP 14 / NACE No.8 — Industrial: allows up to 10% tightly adherent mill scale, rust and coating residues, uniformly distributed. Specified for maintenance of heavily pitted steel where complete removal from pits is impractical.

• SP 1 — Solvent cleaning: removes oil, grease, dust and soluble salts using solvents, steam, alkaline solutions or detergents. Does not remove rust or mill scale. Mandatory pre-treatment before all other methods.
• SP 2 — Hand tool cleaning: wire brushes, sandpaper and scraping to remove loose rust, aged paint and weld residues. Does not remove tightly adherent contaminants.
• SP 3 — Power tool cleaning: more effective than SP 2 but applicable only in localised areas. Does not guarantee complete removal of adherent mill scale.
• SP 8 — Pickling: chemical or electrolytic reaction cleaning. Acceptable results but high-risk method: hydrogen embrittlement risk on high-strength steels and generation of toxic waste.
• SP 11 — Power tool cleaning to bare metal (updated Dec. 2020): produces bare metal with minimum 25 µm roughness profile. The 2020 revision added two additional cleaning levels and expanded the permitted methods for profile measurement (replica tape, drag stylus). Suitable where abrasive blasting is not feasible.
• SP 15 — Commercial grade power tool cleaning: produces surface with minimum 25 µm roughness profile. Allows random staining up to 33% of the area. Equivalent to SP 6 without projected abrasive.

The four SP WJ standards replaced SP 12 from 2014 and define four levels of high-pressure water jet cleaning:
• SP WJ-1: bare metal — equivalent in cleanliness to SP 5 by water jetting.
• SP WJ-2: very thorough cleaning.
• SP WJ-3: thorough cleaning.
• SP WJ-4: light cleaning.

Waterjetting does not generate a roughness profile; it generally requires prior or subsequent blast cleaning to create the mechanical anchor for the coating.

• SP 13 / NACE No.6 (revised 2024): surface preparation of concrete, cement, slabs and masonry. The surface must be free of laitance, weakly bonded concrete and contaminants.
• SP 16: light brush-off blast cleaning of non-ferrous metals — galvanised, stainless steel, copper, aluminium and brass. Minimum roughness: 19 µm (0.75 mil).
• SP 17 (new 2019): specific standard for preparation of stainless steel, aluminium, copper and non-ferrous alloys before applying coatings. Complements and partly replaces certain uses of SP 16 for these materials.