SSPC-SP6 или SP10: какой стандарт подготовки поверхности нужен вашему проекту?

The difference between SSPC-SP 6 and SSPC-SP 10 is often misunderstood — and the consequences of getting it wrong run in both directions. Specifying SP 10 where SP 6 is sufficient adds cost and schedule time without a performance benefit. Specifying SP 6 where the coating system requires SP 10 leads to premature failure. Knowing which standard applies is a basic competence for maintenance engineers, coating specifiers and inspectors.

This article explains what each standard requires, how they differ in practice, which coating systems need which grade, whether either can be reached without abrasive blasting, and a step-by-step decision path for your project.

The standards at a glance

What does SSPC-SP 6 require?

SSPC-SP 6 / NACE No. 3 — Commercial Blast Cleaning — defines a surface from which all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides and other foreign matter have been removed, except for random staining. Staining is limited to no more than 33% of each unit area of surface and may consist of light shadows, slight streaks or minor discolorations caused by stains of rust, mill scale or previously applied coating.

In plain terms: at least two thirds of every unit area must be completely clean, and up to one third may show light staining. The blasting will normally leave an anchor profile, but SP 6 itself does not set a profile depth — that comes from the coating specification.

What does SSPC-SP 10 require?

SSPC-SP 10 / NACE No. 2 — Near-White Metal Blast Cleaning — requires the same removal of all visible contaminants, but with staining limited to no more than 5% of each unit area. At least 95% of every unit area inspected must be free of residues, with only light shadows, slight streaks or minor discolorations permitted on the rest.

The distinction is significant in practice: achieving SP 10 requires considerably more blasting effort, careful abrasive selection and closer quality control than SP 6 — particularly on steel with heavy mill scale, deep pitting or previous coating residue.

The practical difference in the field

The gap between SP 6 and SP 10 is not as visually dramatic as it might seem on paper, but it matters to the coating system. On lightly rusted steel with no previous coating, the difference in blasting time between SP 6 and SP 10 is modest. On heavily corroded steel, deeply pitted surfaces, or steel with stubborn mill scale or old paint residue in crevices, reaching the 5% threshold of SP 10 can require significantly more time, abrasive and passes than SP 6.

This is why SP 6 is commonly specified for atmospheric maintenance repainting — where cost and production rate are primary considerations — while SP 10 is the usual choice for high-value assets, offshore structures and new construction in aggressive environments.

How to determine which standard your project needs

The correct surface preparation standard is not a matter of habit — it is defined first by the coating system being applied. The starting point is always the coating manufacturer's technical data sheet (TDS) for the specific primer.

Step 1: Check the coating TDS

Every coating data sheet specifies a minimum surface preparation standard. This is the floor: applying the coating over a lower standard typically falls outside the manufacturer's recommendations, can jeopardise any warranty and often results in premature failure.

Step 2: Consider the service environment

Even if a coating manufacturer offers SP 6 as a minimum, the service environment may justify specifying SP 10:

• Marine and offshore atmospheric zones: high salt load, UV exposure and condensation cycling demand maximum adhesion. Sa 2½ / SP 10 is the common requirement for primary structure even where SP 6 would technically meet the TDS minimum.
• High humidity or tropical environments: residual staining at the SP 6 level can provide initiation sites for underfilm corrosion, accelerated in persistently humid conditions.
• Long repainting intervals: if the asset will not be repainted for 15–25 years, the extra cost of SP 10 at the start of the coating cycle is usually justified by lifecycle cost.
• Immersion or splash zone: SP 6 is typically not acceptable for submerged or splash-zone service. Most immersion systems require SP 10 or SP 5.

Step 3: Consider the coating system type

Typical minimums are shown below; the specific product TDS always governs.

Can you achieve SP 6 or SP 10 without abrasive blasting?

Strictly, no: SP 6 and SP 10 are written for abrasive blast cleaning, so a power tool result is assessed against power-tool standards or described as comparable to a blast grade. In practice, both cleanliness levels have non-blast routes.

The power-tool counterpart of SP 6

SSPC-SP 15 (Commercial Grade Power Tool Cleaning) mirrors SP 6: it permits staining on up to 33% of each unit area and requires a minimum 25 µm (1 mil) profile. Tools that both clean and profile — such as needle guns, rotary impact flap assemblies and the Bristle Blaster® — can meet it on suitable steel. Grinding discs and conventional wire brushes generally do not, because they tend to polish rather than profile. Where no staining is allowed, SSPC-SP 11 (Power Tool Cleaning to Bare Metal, minimum 25 µm profile) applies.

Near-white cleanliness without blasting

Bristle blasting has documented results comparable to Sa 2½ (ISO 8501-1) / SSPC-SP 10 with an anchor profile of 65–85 µm Rz on standard carbon steel, including API 5L pipeline steel. MontiPower field projects report similar results: the field joint coating project for Total E&P in Bolivia reported cleanliness comparable to Sa 3 / SP 5, and engineers trained on the GASNORP project in Piura, Peru reached a result comparable to Sa 2½ / SP 10. Results vary with steel grade, rust grade, belt and technique; on heavily pitted or very heavily corroded steel, consistent SP 10-comparable cleanliness may need a two-step approach or blasting.

The practical advantage of a power-tool route is that it eliminates grit, containment, abrasive disposal and the logistics of blast operations — valuable for maintenance on operating assets and in confined spaces. In ATEX-classified areas, only equipment evaluated for the zone may be used, such as the fully pneumatic Bristle Blaster® Pneumatic.

Common specification mistakes

Defaulting to SP 10 for all work

Some maintenance specifications apply SP 10 universally, regardless of coating system or service environment. Where SP 6 is genuinely sufficient, this adds blasting time and cost with no performance benefit. Review the coating TDS and specify accordingly.

Accepting an SP 6 system in an aggressive environment

A coating system rated for SP 6 in a coastal atmospheric environment is not necessarily adequate for an offshore structure. The service environment must drive the specification — not just the coating TDS minimum.

Not verifying anchor profile

Neither SP 6 nor SP 10 defines a profile depth; the coating TDS or project specification does. Meeting the visual cleanliness requirement without verifying profile is an incomplete inspection. Measure per ASTM D4417 and record the result.

Decision framework

Use this decision path to determine the correct standard for a maintenance painting project:

1. Check the primer TDS — what is the minimum surface preparation grade?
2. Is the service environment immersion or splash zone? If yes, minimum SP 10, often SP 5.
3. Is the asset offshore or in a high-salinity environment? If yes, specify SP 10 even if the TDS accepts less.
4. What is the planned repainting interval? If greater than 15 years, favour SP 10.
5. Is abrasive blasting feasible? If not, what cleanliness and profile can the available tools reach, and does that meet the coating manufacturer's minimum (confirm acceptance in writing)?
6. Document the specified standard and the verification method in the project specification before work begins.

Key takeaways

• SSPC-SP 6 permits random staining on up to 33% of each unit area; SSPC-SP 10 permits up to 5%. The performance difference lies in what that residue does to long-term coating adhesion in the service environment.
• The correct standard is determined by the coating system TDS and the service environment — not by convention or default.
• SP 6 is appropriate for atmospheric service with compatible coating systems. SP 10 is usual for high-performance systems, aggressive environments and long repainting intervals.
• Both cleanliness levels have non-blast routes — SP 15 for commercial grade, bristle blasting for results comparable to SP 10 — eliminating the logistics and hazards of blast operations in many maintenance scenarios.

Related articles

• SSPC-SP10 Near-White Metal Blast: Complete Technical Guide
• SSPC-SP5 White Metal Blast: When Is It Required?
• SSPC-SP11 Power Tool Cleaning to Bare Metal
• How to Achieve SSPC-SP10-Comparable Results Without Sandblasting
• Complete Guide to SSPC Surface Preparation Standards

Frequently asked questions

What is the difference between SSPC-SP 6 and SSPC-SP 10?

Both require removal of all visible oil, grease, dirt, mill scale, rust, coating and foreign matter. The difference is residual staining: SP 6 (Commercial Blast) permits light shadows, streaks or discolorations on up to 33% of each unit area, while SP 10 (Near-White Metal Blast) permits them on no more than 5%.

What are the ISO 8501-1 equivalents of SP 6 and SP 10?

SSPC-SP 6 / NACE No. 3 is generally treated as equivalent to ISO 8501-1 Sa 2, and SSPC-SP 10 / NACE No. 2 to Sa 2½. The correspondence is approximate: SSPC standards are written definitions with staining percentages, while ISO 8501-1 grades are assessed visually against reference photographs.

Can a power tool achieve SP 6 or SP 10?

Not formally, because both are blast-cleaning standards. The power-tool counterpart of SP 6 is SSPC-SP 15 (Commercial Grade Power Tool Cleaning, 33% staining, minimum 25 µm profile). For near-white work, bristle blasting has documented results comparable to Sa 2½ / SP 10 with a 65–85 µm Rz profile, depending on steel, rust grade, belt and technique.

Do SP 6 and SP 10 specify an anchor profile?

No. Both standards define cleanliness only; the required profile depth comes from the coating manufacturer's data sheet or the project specification. Measure it with replica tape or a depth micrometer per ASTM D4417 and record the result alongside the visual cleanliness grade.