SSPC-SP10 Near-White Metal Blast: The Complete Technical Guide

SSPC-SP10, Near-White Metal Blast Cleaning, is one of the most commonly specified surface preparation grades for high-performance protective coating systems on steel in industrial, marine, offshore and infrastructure work. This guide sets out what the standard requires, how it maps to ISO 8501-1, how to verify it in the field, which methods can reach it, and how it differs from SSPC-SP11. It is written for coating specifiers, inspectors and contractors.

What is SSPC-SP10?

SSPC-SP10 is a surface preparation standard originally published by SSPC: The Society for Protective Coatings, which merged with NACE International in 2021 to form AMPP (Association for Materials Protection and Performance). It defines a level of cleanliness for steel surfaces prepared by abrasive blast cleaning. Other methods, such as bristle blasting, can produce a result that is comparable to it, but the standard itself describes a blast-cleaned surface.

The standard is formally titled SSPC-SP10 / NACE No. 2, Near-White Metal Blast Cleaning, a joint standard. Its usual counterpart under ISO 8501-1 is Sa 2½.

These designations are generally treated as corresponding grades in coating specifications, although their wording is not identical:

What SSPC-SP10 requires

The SSPC-SP10 standard defines near-white metal blast cleaning as follows:

When viewed without magnification, the surface shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter, except for staining. Staining shall be limited to no more than 5% of each unit area of surface and may consist of light shadows, slight streaks or minor discolorations caused by stains of rust, stains of mill scale or stains of previously applied coating.

In plain terms: all visible mill scale, rust, coating and foreign matter must be removed from the whole surface; only light staining is tolerated, on no more than 5% of each unit area. That staining allowance is the only distinction from SSPC-SP5 (white metal), which allows no staining.

What SSPC-SP10 does not define

SSPC-SP10 defines cleanliness, the removal of contaminants. It does not specify an anchor profile (surface roughness). The required anchor profile is set by the coating manufacturer's technical data sheet (TDS) and the project specification. Many high-performance marine and offshore systems call for a profile somewhere in the range of about 50 to 100 µm, and some systems, including certain shop primers and surface-tolerant coatings, accept lower minimums. Always consult the specific coating TDS.

SSPC-SP10 in the hierarchy of surface preparation standards

For the full set of grades from SP1 to SP16 and the water-jetting levels, see the complete guide to SSPC surface preparation standards.

How to verify SSPC-SP10 in the field

Verification of SSPC-SP10 normally involves three independent checks: the cleanliness grade itself, plus the profile and soluble salt limits that the coating specification adds. All three must pass. A surface that passes the visual check but fails on profile or contamination does not meet the specification.

Step 1: Visual cleanliness assessment

Compare the prepared surface against the reference photographs in ISO 8501-1 (Sa 2½ panels for the appropriate original rust grade A, B, C or D) or SSPC-VIS 1. Assess under good, even lighting; ISO 8501-1 calls for diffuse daylight or equivalent artificial illumination, and many specifications set a minimum light level for inspection.

Identify the original steel rust grade (A = largely covered with adherent mill scale with little rust, B = beginning to rust with mill scale flaking, C = mill scale rusted away or scrapable with slight pitting, D = general pitting) and compare against the Sa 2½ photograph for that grade. Estimate and record the percentage of any remaining random staining. If staining exceeds 5% of any unit area, the surface does not comply and preparation must continue.

Step 2: Anchor profile measurement

Measure the anchor profile using ASTM D4417 Method C: Testex Press-O-Film® replica tape read with a spring micrometer or replica tape reader. It is the most widely used field method for anchor profile and is named in many coating project specifications. More detail is in our anchor profile measurement field guide.

Procedure:

1. Select the correct tape grade: Coarse (about 20–64 µm / 0.8–2.5 mil) for lighter profiles; X-Coarse (38–115 µm / 1.5–4.5 mil) for most blasted or Bristle Blaster®-prepared surfaces; X-Coarse Plus (about 100–150 µm / 4.0–6.0 mil) for deep profiles where X-Coarse reads at its upper limit.
2. Apply the tape to the dry, dust-free surface and burnish the foam firmly with the burnishing tool until the impression is uniform, following the tape manufacturer's instructions.
3. Remove the tape and place it in the micrometer. Read the total thickness.
4. Subtract the incompressible polyester film (50 µm / 2 mil) to obtain the peak-to-valley profile height.
5. Take the number of readings the specification requires (commonly at least three per representative area), calculate the mean, and compare it with the coating TDS minimum and maximum.

Reference values for the Bristle Blaster® on API 5L pipeline steel: 65–85 µm Rz (2.6–3.3 mil) in documented tests, and up to 120 µm Rz depending on belt and test conditions. Results vary with steel grade, rust grade, belt and technique. The 65–85 µm Rz range falls within the profile range specified by many high-performance marine and industrial coating systems; always verify against the specific coating TDS.

Step 3: Soluble salt contamination measurement

SSPC-SP10 does not set a chloride limit, but the coating specification or manufacturer's TDS usually does. The standard field method is the Bresle patch method (ISO 8502-6 extraction with ISO 8502-9 conductometric measurement). Follow the extraction procedure the specification requires; on rough, profiled steel a single short extraction may not recover all of the salt present.

Acceptance limits are set by the specification and vary widely. Examples seen in practice include:

• Marine and offshore coatings: often low single-digit µg/cm² limits, with the strictest offshore systems at around 2 µg/cm² chloride
• Pipeline heat-shrink sleeve and field-joint systems: limits set by the sleeve or coating manufacturer, often in the low single-digit µg/cm² range
• Standard atmospheric industrial coatings: higher limits, set by the coating manufacturer

If contamination exceeds the limit, wash the surface with fresh water, allow it to dry, retest, and re-prepare as needed. Re-blasting, or re-treating with the Bristle Blaster®, after washing is the usual corrective action.

Methods that reach SSPC-SP10 cleanliness

Abrasive blast cleaning

The traditional method, and the one the SSPC-SP10 standard is written for. With appropriate media, pressure and technique it reaches SP10 on all steel grades and rust conditions. It requires containment, dust control and abrasive disposal, and in live hazardous areas (ATEX zones) it normally needs gas-freeing, permits or shutdown before it can proceed.

Bristle Blaster® (grit-free power tool)

The Bristle Blaster® produces surface cleanliness comparable to ISO 8501-1 Sa 2½ / SSPC-SP10 through repeated impact of wire bristle tips, without abrasive media. This has been documented in published tests on several steel grades, including shipbuilding steels, and Jotun has published a bristle blast cleaning code (BIPoT) with its own grades. Results vary with steel grade, rust grade, belt and technique, and acceptance on a project is set by the specification and the inspector.

The Bristle Blaster® Pneumatic is fully pneumatic with no electrical parts and has been evaluated under ATEX 2014/34/EU as Category 2 equipment for zone 1 explosive gas (group IIA) and zone 21 explosive dust (group IIIC). That makes it usable in many hazardous areas where blasting and electric tools are excluded. See surface preparation in ATEX zone 1.

For the step-by-step procedure, see our guide on how to achieve SSPC-SP10-comparable results without sandblasting. For a direct technical comparison with conventional sandblasting, see Bristle Blaster® vs. sandblasting.

Documentation requirements

A complete SSPC-SP10 inspection record should include:

• Date, time, ambient temperature, relative humidity, steel temperature and dew point at the time of preparation and inspection
• Original steel rust grade (ISO 8501-1 grade A, B, C or D)
• Preparation method and equipment reference
• Cleanliness grade achieved (Sa 2½ / SP10, or "comparable to" for non-blast methods, confirmed against the reference photographs)
• Percentage of any random staining (must not exceed 5% per unit area)
• Anchor profile: method (ASTM D4417 Method C), tape grade, individual readings and mean
• Soluble salt result: method, value measured, acceptance limit
• Inspector name and AMPP / FROSIO certification reference where applicable

SSPC-SP10 vs. SSPC-SP11: understanding the difference

SSPC-SP11 (Power Tool Cleaning to Bare Metal) is sometimes confused with SP10. The key differences:

If the specification states SSPC-SP10, an angle grinder with a fibre disc does not comply, even if the surface looks clean. The profile produced by grinding is shallower and directional, which is materially different from the angular, dense profile produced by blasting or bristle blasting. Any non-blast method needs to be written into the specification as an accepted alternative. See our SSPC-SP11 technical guide.

Frequently asked questions

What is the difference between SSPC-SP10 and SSPC-SP5?

SSPC-SP5 (white metal) requires the whole surface to be free of all visible contaminants, with no staining permitted. SSPC-SP10 (near-white metal) permits random light staining on up to 5% of each unit area. SSPC-SP5 is typically specified for immersion service, thermal spray and the most aggressive exposures; SSPC-SP10 covers most high-performance atmospheric and splash-zone systems.

Is SSPC-SP10 the same as ISO 8501-1 Sa 2½?

They are generally treated as corresponding grades and are often written side by side in specifications. They are not word-for-word identical: SSPC-SP10 sets a 5% staining limit per unit area, while ISO 8501-1 defines Sa 2½ by a written description and reference photographs. If a specification names one, inspect against that one.

Does SSPC-SP10 specify a minimum anchor profile?

No. SSPC-SP10 defines cleanliness only. The required anchor profile comes from the coating manufacturer's technical data sheet and the project specification. Many high-performance epoxy, zinc silicate and polysiloxane systems call for a profile somewhere in the range of about 50 to 100 µm, but always check the specific data sheet before fixing the preparation procedure.

Can a power tool achieve SSPC-SP10?

SSPC-SP10 is a blast-cleaning standard, so a power tool result is assessed as comparable to SP10 rather than as SP10 itself. Bristle blasting has documented results comparable to Sa 2½ / SSPC-SP10 with a 65–85 µm Rz profile on standard steel. Results vary with steel grade, rust grade, belt and technique, and acceptance is set by the specification and the inspector.

How do I verify a Bristle Blaster® surface against SSPC-SP10-comparable cleanliness?

Use the same checks as for abrasive blasting: visual comparison against ISO 8501-1 Sa 2½ reference photographs or SSPC-VIS 1, anchor profile measurement with ASTM D4417 Method C replica tape, and soluble salt testing with the Bresle patch method. The surface is judged against the same criteria and acceptance limits as a blasted surface.