This guide covers all SSPC surface preparation standards currently in use — from solvent cleaning (SP-1) through the highest blast cleaning levels and water jetting (WJ) standards — with ISO equivalents, definitions, typical applications and verification methods. It is intended as a practical reference for coating specifiers, inspectors, maintenance engineers and contractors.
Who Publishes SSPC Standards?
SSPC standards were historically published by SSPC: The Society for Protective Coatings. In 2021, SSPC merged with NACE International to form AMPP — the Association for Materials Protection and Performance. Joint SSPC-NACE standards are now published under the AMPP umbrella. Legacy SSPC designations (SP-1, SP-3, SP-10, etc.) remain in active use across the industry and in existing specifications.
The Structure of SSPC Standards
SSPC surface preparation standards are grouped by method:
- SP-1: Solvent cleaning
- SP-2 and SP-3: Hand tool and power tool cleaning
- SP-5, SP-6, SP-7, SP-10, SP-14: Abrasive blast cleaning (increasing cleanliness levels)
- SP-11 and SP-15: Power tool cleaning to defined cleanliness levels
- SP-12: High-pressure and ultra-high-pressure water jetting (legacy, largely replaced by WJ standards)
- SP-13: Concrete surface preparation
- SP-16: Brush-off blast cleaning of non-ferrous metals
- WJ-1 through WJ-4: Water jetting cleanliness standards
SP-1 — Solvent Cleaning
SSPC-SP1 is not a cleanliness standard in the structural sense — it defines the process of removing oil, grease, soluble salts, drawing compounds and other surface contaminants using solvent wiping, steam cleaning, alkaline cleaning or emulsion cleaning.
SP-1 is a prerequisite for all other surface preparation standards. If oil or grease contamination is present on the steel, it must be removed by SP-1 methods before any other preparation begins. Mechanical cleaning or blasting over oil-contaminated steel drives the contamination into the surface profile rather than removing it, and the resulting surface cannot comply with any subsequent standard regardless of visual appearance.
Verification: No visual standard exists for SP-1. Compliance is verified by the water break test — clean steel is uniformly wetted by water, while oil-contaminated steel causes water to bead or break.
SP-2 — Hand Tool Cleaning
SSPC-SP2 defines hand tool cleaning: scraping, sanding, hand wire brushing, and chipping to remove loose rust, loose mill scale and loose coatings. Tightly adhered mill scale, rust and coatings may remain after SP-2 cleaning.
SP-2 is appropriate only for atmospheric coatings in low-corrosivity environments and for primer coats in non-critical applications. It is rarely specified for industrial or marine maintenance on performance-critical coating systems.
SP-3 — Power Tool Cleaning
SSPC-SP3 defines power tool cleaning using grinding discs, wire cup brushes, needle guns or other power-driven tools to remove loose rust, loose mill scale and loose coatings. As with SP-2, tightly adhered residue may remain. SP-3 does not require a defined anchor profile.
ISO equivalent: approximately St 2 (ISO 8501-1). SP-3 is commonly specified for maintenance overcoating with surface-tolerant coating systems in moderate environments.
| Standard | Method | Residue Permitted | ISO Equivalent |
|---|---|---|---|
| SP-2 | Hand tool | Tightly adherent mill scale, rust, coatings | St 2 |
| SP-3 | Power tool | Tightly adherent mill scale, rust, coatings | St 2 |
SP-5 — White Metal Blast Cleaning
SSPC-SP5 / NACE No. 1 / ISO Sa 3 — the most stringent abrasive blast cleaning standard. All visible oil, grease, mill scale, rust, coatings, oxides and other foreign matter are removed. Zero staining permitted on any area of the surface.
Required for: immersion service, thermal spray coatings (TSA/TSZ), inorganic zinc silicate primers, and highly aggressive service environments where any residual contamination is unacceptable.
Detailed guide: SSPC-SP5 White Metal Blast — When Is It Required?
SP-6 — Commercial Blast Cleaning
SSPC-SP6 / NACE No. 3 / ISO Sa 2 — all oil, grease, mill scale, rust, coatings and other contaminants are removed except for random staining. Staining is limited to no more than 33% of each unit area.
Required for: atmospheric protective coating systems in moderate environments. Commonly specified for maintenance repainting of industrial structures, bridges and process piping with compatible coating systems.
Detailed guide: SSPC-SP6 vs SP10 — Which Standard Does Your Project Need?
SP-7 — Brush-Off Blast Cleaning
SSPC-SP7 / NACE No. 4 / ISO Sa 1 — the lightest abrasive blast level. All loosely adhered mill scale, rust and coatings are removed. Tightly adherent mill scale, rust and old coatings may remain on the surface.
Required for: application of shop primers on new construction before further fabrication; temporary protection before a more thorough blast cleaning operation; overcoating of sound, intact existing coatings that require only surface cleaning.
SP-10 — Near-White Metal Blast Cleaning
SSPC-SP10 / NACE No. 2 / ISO Sa 2½ — all oil, grease, mill scale, rust, coatings and other contaminants are removed except for random staining. Staining is limited to no more than 5% of each unit area.
The most commonly specified standard for high-performance coating systems in industrial, marine and offshore applications. High-build epoxy, organic zinc-rich primers, polysiloxane and polyurethane topcoat systems are routinely applied over SP10-prepared steel.
Detailed guide: SSPC-SP10 Near-White Metal Blast — Complete Technical Guide
SP-11 — Power Tool Cleaning to Bare Metal
SSPC-SP11 — the highest cleanliness level achievable by power tool methods. All visible oil, grease, mill scale, rust, coatings and other contaminants are removed. Zero staining permitted. The prepared surface must have a minimum anchor profile of 25 µm Rz.
ISO equivalent: approximately St 3 (enhanced). Required for: spot repairs on maintenance projects, areas inaccessible to blast equipment, ATEX Zone 1 environments, and projects where abrasive blasting is not feasible. The Bristle Blaster® achieves SP-11 with a typical anchor profile of 65–85 µm Rz.
Detailed guide: SSPC-SP11 Power Tool Cleaning to Bare Metal
SP-12 — Surface Preparation and Cleaning of Metals by High- and Ultrahigh-Pressure Water Jetting
SSPC-SP12 was the original standard for pressure water cleaning of steel. It has largely been superseded by the more detailed WJ-1 through WJ-4 standards (see below) and NACE No. 5. SP-12 remains in some older specifications and legacy contracts.
SP-13 — Surface Preparation of Concrete
SSPC-SP13 defines surface preparation requirements for concrete substrates. It is outside the scope of steel surface preparation and is not covered in this guide.
SP-14 — Industrial Blast Cleaning
SSPC-SP14 / NACE No. 8 — a blast cleaning level between SP-7 and SP-6. All oil, grease, mill scale, rust, coatings and other contaminants are removed except for random staining and residues in pits. Staining is limited and streaks of rust, mill scale or coating may remain on up to 10% of each unit area. Remnants may remain in pits and valleys.
SP-14 is specified where SP-6 is considered excessive but SP-7 is insufficient — most commonly for maintenance repainting of heavily pitted steel where complete removal from pit surfaces is impractical without excessive blast time.
SP-15 — Commercial Grade Power Tool Cleaning
SSPC-SP15 is the power tool equivalent of SP-6 commercial blast. All oil, grease, mill scale, rust, coatings and other contaminants are removed, with random staining limited to no more than 33% of each unit area. The surface must have a minimum anchor profile of 25 µm Rz (same as SP-11).
SP-15 sits below SP-11 in cleanliness and is appropriate for maintenance repainting where SP-6 cleanliness is required but blasting is not feasible.
| Power Tool Standard | Cleanliness | Anchor Profile | Blast Equivalent |
|---|---|---|---|
| SP-3 | Tightly adherent residue permitted | Not specified | SP-7 / Sa 1 (approx.) |
| SP-15 | ≤33% staining per unit area | Min. 25 µm Rz | SP-6 / Sa 2 |
| SP-11 | 0% staining — bare metal | Min. 25 µm Rz | SP-10 / Sa 2½ (approx.) |
Water Jetting Standards: WJ-1 Through WJ-4
Water jetting (waterjetting) standards define cleanliness levels for surfaces cleaned by high-pressure or ultra-high-pressure water without abrasive media. Unlike blast cleaning standards, WJ levels do not define anchor profile — waterjetting cleans but does not create profile.
| WJ Standard | Cleanliness | Blast Equivalent (visual) |
|---|---|---|
| WJ-1 (Bare Substrate) | 0% staining — bare, matte metal | SP-5 / Sa 3 |
| WJ-2 (Very Thorough Cleaning) | ≤5% staining | SP-10 / Sa 2½ |
| WJ-3 (Thorough Cleaning) | ≤33% staining | SP-6 / Sa 2 |
| WJ-4 (Light Cleaning) | Adherent residue, any amount | SP-7 / Sa 1 |
Detailed guide: Water Jetting Standards WJ-1 to WJ-4
Complete Standards Reference Table
| SSPC Standard | NACE Equivalent | ISO 8501-1 | Method | Cleanliness |
|---|---|---|---|---|
| SP-1 | — | — | Solvent cleaning | Oil/grease removal (prerequisite) |
| SP-2 | — | St 2 | Hand tool | Loose material removed |
| SP-3 | — | St 2 | Power tool | Loose material removed |
| SP-5 | No. 1 | Sa 3 | Abrasive blast | White metal — 0% staining |
| SP-6 | No. 3 | Sa 2 | Abrasive blast | Commercial — ≤33% staining |
| SP-7 | No. 4 | Sa 1 | Abrasive blast | Brush-off — adherent residue permitted |
| SP-10 | No. 2 | Sa 2½ | Abrasive blast | Near-white — ≤5% staining |
| SP-11 | — | St 3 (enhanced) | Power tool | Bare metal — 0% staining, min. 25 µm Rz |
| SP-14 | No. 8 | — | Abrasive blast | Industrial — limited staining, pit residue permitted |
| SP-15 | — | St 2–3 | Power tool | Commercial — ≤33% staining, min. 25 µm Rz |
| WJ-1 | WJ-1 | — | Water jet | Bare substrate — 0% staining (no profile) |
| WJ-2 | WJ-2 | — | Water jet | Very thorough — ≤5% staining (no profile) |
| WJ-3 | WJ-3 | — | Water jet | Thorough — ≤33% staining (no profile) |
| WJ-4 | WJ-4 | — | Water jet | Light — adherent residue permitted (no profile) |
Verification Standards
Each preparation method has an associated visual reference standard used during inspection:
| SSPC Standard(s) | Visual Reference | Profile Measurement |
|---|---|---|
| SP-5, SP-6, SP-7, SP-10, SP-14 | SSPC-VIS 1 / ISO 8501-1 | ASTM D4417 Method C (replica tape) |
| SP-2, SP-3 | SSPC-VIS 3 | ASTM D4417 (where profile required) |
| SP-11, SP-15 | SSPC-VIS 3 | ASTM D4417 Method C (mandatory — min. 25 µm Rz) |
| WJ-1 through WJ-4 | NACE VIS 7 / SSPC-VIS 4 | ASTM D4417 (existing profile verification) |
Choosing the Right Standard
The surface preparation standard for any project is not a free choice — it is defined by the coating system being applied and the service environment. The decision framework:
- Start with the coating TDS: What is the minimum surface preparation standard specified by the coating manufacturer for this product?
- Consider the service environment: Immersion service, aggressive offshore or marine environments, and long repainting intervals all argue for specifying at the higher end of what the coating system allows.
- Consider the method available: Can abrasive blasting be performed? If not, what is the highest cleanliness level achievable with the available tools?
- Consider site constraints: ATEX classification, containment requirements, operating equipment, and environmental restrictions all affect method selection and therefore achievable cleanliness.
- Document the specification: The required standard, verification method, inspector qualifications and hold points must be written into the project specification before work begins.
Key Takeaways
- SSPC surface preparation standards define the cleanliness — and in some cases the anchor profile — required before protective coating application.
- The most commonly specified standards in industrial and marine maintenance are SP-10 (near-white blast), SP-6 (commercial blast), SP-11 (power tool to bare metal) and SP-3 (power tool, loose material removal).
- Water jetting standards (WJ-1 through WJ-4) define cleanliness achieved by water alone — they do not create or define anchor profile.
- The correct standard for any project is determined by the coating TDS and service environment — not by convention or default.
- All standards require independent verification — visual assessment against the appropriate reference standard, anchor profile measurement where required, and soluble salt testing in aggressive environments.
Detailed Guides
- SSPC-SP5 White Metal Blast: When Is It Required?
- SSPC-SP6 vs SP10: Which Standard Does Your Project Need?
- SSPC-SP10 Near-White Metal Blast: Complete Technical Guide
- SSPC-SP11 Power Tool Cleaning to Bare Metal
- Water Jetting Standards WJ-1 to WJ-4
- Flash Rust: Causes, Effects and Prevention
- Soluble Salt Contamination and Coating Failure
- Anchor Profile Measurement: Field Guide for Inspectors
- How to Write a Surface Preparation Specification