Surface preparation selector
The SSPC / ISO 8501-1 grade commonly required for a given substrate, initial condition, environment and system — and above all, what drives the requirement.
What this selector is for
The grade is almost never the hard question. The system data sheet gives it, and it is rarely disputed. What gets disputed is the gap between that grade and what can actually be achieved on equipment in service, in a shutdown window, with the access available.
That is why the "equipment stays in service" box changes the output. When the required grade exceeds what power tools can produce, the selector says so rather than passing over it. At that point two decisions exist: find a window, or change to a system the achievable grade supports. Specifying an unreachable grade is not one of them.
The second useful output is the driving factor. Knowing it is the system says a different product would change things. Knowing it is the condition of the steel says no change of product will.
Reference system equivalences
| SSPC / NACE | ISO 8501-1 | Designation |
|---|---|---|
| SSPC-SP 5 / NACE No. 1 | Sa 3 | White metal blast |
| SSPC-SP 10 / NACE No. 2 | Sa 2½ | Near-white blast |
| SSPC-SP 6 / NACE No. 3 | Sa 2 | Commercial blast |
| SSPC-SP 7 / NACE No. 4 | Sa 1 | Brush-off blast |
| SSPC-SP 11 | — | Power tool to bare metal |
| SSPC-SP 3 | St 3 | Power tool cleaning |
| SSPC-SP 2 | St 2 | Hand tool cleaning |
| SSPC-SP 1 | — | Solvent cleaning |
Method and sources
The grades come from ISO 8501-1 (preparation of steel substrates — rust grades and preparation grades) and the corresponding SSPC/AMPP standards. The combinations proposed reflect common data sheet practice; they are not normative and commit no manufacturer.
- ISO 8501-1:2007 — ISO, accessed 8 August 2026
- ASTM D4417 — field measurement of surface profile, ASTM International, accessed 8 August 2026
Safety
Abrasive blasting produces respirable dust and, on old coatings, can release lead or other heavy metals. Characterising the existing coating comes before choosing the method, not after.
Limits of use
- The product data sheet governs. No standard says "for this environment, prepare to this grade". ISO 8501-1 and the SSPC standards define what each grade means and how it is assessed; the system manufacturer sets the requirement. Where this selector and the data sheet differ, the data sheet applies.
- Equivalences between the two systems are working correspondences, not identities. Sa 2½ and SSPC-SP 10 are close and written differently: the first refers to reference photographs, the second to a percentage of area. A specification cites one reference, never both interchangeably.
- The anchor profile given is an order of magnitude. Actual profile depends on abrasive, pressure and angle, and is measured to ASTM D4417 — replica tape, comparator or depth micrometer. Three methods which do not give exactly the same figure.
- The selector does not address soluble salts, which are invisible and independent of the visual grade. A white-metal surface can still carry enough chloride to blister.
- Nor does it address dew point, recoat window or substrate temperature — three conditions that fail as many jobs as preparation itself.
How to cite this page
Maintenance Blueprint, « Surface preparation selector », maintenanceblueprint.com/en/tools/surface-preparation/