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Surface prep standards, in plain language
A coating is only as good as the surface under it. SSPC and NACE grades say how clean that surface has to be. Your coating data sheet names the grade. Here is what each one means.
| Grade | Name | What is left on the steel | Typical use |
|---|---|---|---|
| SSPC-SP7 NACE No. 4 | Brush-off blast | Loose rust, loose mill scale and loose paint are gone. Anything tightly stuck can stay. | Light duty recoats |
| SSPC-SP6 NACE No. 3 | Commercial blast | All visible rust, scale and paint removed. Light staining allowed on up to a third of the surface. | General industrial coating |
| SSPC-SP10 NACE No. 2 | Near-white blast | As above, with staining limited to 5 percent of the surface. | Harsh outdoor and industrial service |
| SSPC-SP5 NACE No. 1 | White metal blast | Nothing. Clean, uniform metal with no staining. | The most demanding specs |
Grade is half of it. Profile is the other half.
Blasting also leaves a texture in the steel, called the profile, that the coating grips. Too shallow and the coating has nothing to hold. Too deep and the peaks poke through.
The media decides the profile. We run steel grit and shot in the large room for ferrous parts and garnet in the second room for non-ferrous parts.
How each job is checked
- Blast profile measured with DeFelsko test equipment
- Coating thickness measured with DeFelsko test equipment after cure