Converted Values
Mils (thousandths inch)
3.0mils
1 mil = 25.4 μm
ISO 8503 Grade
Medium (G)
Most common for marine epoxy coatings
Rugotest No. 3 (Approx.)
N8 – N9
Visual comparator reference
ISO 8503-2 Reference Table — Grit (G) Abrasive
| ISO Grade |
Description |
Range (μm) |
Range (mils) |
Typical Use |
| Fine (G) |
Segment 1 |
≤ 25 |
≤ 1.0 |
Light duty / touch-ups |
| Fine to Medium |
Transition |
25 – 60 |
1.0 – 2.4 |
Thin-film coatings, primers |
| Medium (G) |
Segment 2 |
60 – 100 |
2.4 – 3.9 |
Standard marine epoxy (most coatings) |
| Coarse (G) |
Segment 3 |
100 – 150 |
3.9 – 5.9 |
Thick epoxies, tank linings, glass flake |
| Very Coarse |
Beyond Segment 3 |
> 150 |
> 5.9 |
Specialty / rubber linings (check PDS) |
Specification note: Most marine paint manufacturers specify surface profile as "60–100 μm, comparator Medium (G) per ISO 8503-2" for standard epoxy systems. For PSPC ballast tank coatings (IMO MSC.215(82)), a profile of 30–75 μm is typical with a required surface standard of Sa 2½ per ISO 8501-1. Always confirm against the specific coating Technical Data Sheet.