What is the difference between SSPC and NACE standards?

SSPC and NACE have merged to form AMPP. Many of their surface preparation standards were already joint standards (e.g., SSPC-SP10 is the same as NACE No. 2). They are functionally identical.

What is the ISO 8501 equivalent to SSPC-SP10?

The ISO 8501-1 equivalent to SSPC-SP10 (Near-White Metal Blast) is Sa 2 ½.

Does SSPC-SP1 Solvent Cleaning remove mill scale?

No. SSPC-SP1 only removes soluble contaminants like oil, grease, and dirt. It does not remove rust, mill scale, or old paint. Mechanical methods must follow SP1 if those need removing.

SSPC-SP1 to SP11: Surface Preparation Degrees Comparison

Surface preparation is the foundation of any protective coating system. It is also the variable most often blamed after a premature failure — usually with a percentage attached, quoted from memory and traceable to no published study. This guide does not repeat it. What the standards themselves establish is enough: SSPC-SP 6 and SSPC-SP 10 exist as separate grades precisely because the amount of residual mill scale, rust and contaminant left on the steel changes what the coating can bond to, and every manufacturer datasheet states a minimum preparation grade below which its own performance claims no longer apply.

In North America, surface preparation is governed by the joint standards of SSPC and NACE (now merged as AMPP). This guide compares the most common SSPC surface preparation degrees and maps them to their NACE and ISO 8501 international equivalents.

All eight SSPC surface preparation grades in order, each with its NACE and ISO 8501-1 equivalent where one exists. The abrasive blast grades have ISO equivalents; the hand and power tool grades only partly do. — The full ladder. Note where the equivalences stop: SSPC-SP 11 and SSPC-SP 1 have no ISO counterpart, which is exactly where a specification written in one system and read in the other goes wrong.

The Standard Equivalency Table

When reading a Technical Data Sheet (TDS) or an engineering specification, you might see SSPC, NACE, or ISO designations used interchangeably. Use this table as your definitive cross-reference guide.

SSPC surface preparation standards with their NACE and ISO 8501 counterparts
SSPC Standard	NACE Equivalent	ISO 8501 Equivalent	Description	Typical Use Case
SSPC-SP 1	None	None	Solvent Cleaning: Removal of oil, grease, dirt, soil, salts, and contaminants.	Mandatory first step before any mechanical preparation.
SSPC-SP 2	None	St 2	Hand Tool Cleaning: Removal of loose rust, loose mill scale, and loose paint by hand chipping, scraping, sanding.	Minor touch-ups, benign environments (C1-C2).
SSPC-SP 3	None	St 3	Power Tool Cleaning: Same as SP2 but using power tools. More thorough, but does not achieve a profile.	Maintenance repainting where blasting is impossible.
SSPC-SP 5	NACE No. 1	Sa 3	White Metal Blast Cleaning: 100% removal of all visible rust, mill scale, paint, and foreign matter.	Immersion service (tanks), extreme chemical environments (CX).
SSPC-SP 6	NACE No. 3	Sa 2	Commercial Blast Cleaning: Removal of all visible contaminants. Random staining limited to 33% of each unit area.	Standard exterior industrial environments (C3-C4).
SSPC-SP 7	NACE No. 4	Sa 1	Brush-Off Blast Cleaning: Removal of loose rust, mill scale, and paint. Tightly adherent material may remain.	Sweeping galvanizing, overcoating sound existing paint.
SSPC-SP 10	NACE No. 2	Sa 2 ½	Near-White Metal Blast Cleaning: Removal of all visible contaminants. Staining limited to 5% of each unit area.	Severe environments (C5), typical for most high-performance epoxies.
SSPC-SP 11	None	None	Power Tool Cleaning to Bare Metal: Removal of all visible rust/paint using power tools, while also producing a surface profile (minimum 1 mil).	Spot repairs in C4/C5 areas where blasting is prohibited.

Source: SSPC-SP COM-2017 and ISO 8501-1:2007. The SSPC and ISO grades are close counterparts, not exact equivalents — a specification that cites one and is inspected against the other invites an argument on site.

The Difference Between SSPC-SP6 and SSPC-SP10

A common source of confusion in industrial maintenance is choosing between Commercial Blast (SP6) and Near-White Metal Blast (SP10).

The difference lies entirely in the allowable staining:

SSPC-SP10 (Near-White): Allows light shadows, streaks, or minor discolorations on a maximum of 5% of each 9 square inch area.
SSPC-SP6 (Commercial): Allows staining on up to 33% of each 9 square inch area.

The near-white grade has its own page, covering how that 5% is judged in the field and when SP10 is the right call rather than SP6 or SP5.

Specifying SP10 for a structural beam in a dry warehouse (C2) is a waste of abrasive and labor. Specifying SP6 for a chemical tank exterior (C5) risks premature failure. Always match the preparation degree to the ISO 12944 Corrosivity Category of the asset.

Don’t Forget the Profile

Standards like SP5, SP6, and SP10 dictate the cleanliness of the steel. They do not dictate the depth of the surface profile (anchor pattern).

You must specify the required profile (e.g., 2.0 to 3.0 mils) separately in your specification, as dictated by the coating manufacturer’s TDS.

SSPC Surface Preparation Degrees Compared

The Standard Equivalency Table

The Difference Between SSPC-SP6 and SSPC-SP10

Don’t Forget the Profile

Frequently asked questions

Sources and references

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