Here we are presenting a cross-cut adhesion test classification comparison between ISO 2409 and ASTM D3359 standards. Both are widely used to evaluate how well a paint or coating adheres to a substrate.
How the Test Works
- A series of cuts (usually 6 × 6 or 11 × 11) are made through the coating to the substrate using a special cross-cut tool or a sharp blade.
- Adhesive tape is applied and pulled off rapidly.
- The coating’s adhesion is rated based on how much coating detaches along the cuts.
| ISO Class: 0 / ASTM Class: 5B The edges of the cuts are completely smooth; none of the squares of the lattice is detached. |  |
| ISO Class: 1 / ASTM Class: 4B Detachment of small flakes of the coating at the intersections of the cuts. A cross-cut area not significantly greater than 5% is affected. |  |
| ISO Class: 2 / ASTM Class: 3B The coating has flaked along the edges and/or at the intersections of the cuts. A cross-cut area significantly greater than 5%, but not significantly greater than 15%, is affected. |  |
| ISO Class: 3 / ASTM Class: 2B The coating has flaked along the edges of the cuts partly or wholly in large ribbons, and/or it has flaked partly or wholly on different parts of the squares. A cross-cut area significantly greater than 15%, but not significantly greater than 35%, is affected. |  |
| ISO Class: 4 / ASTM Class: 1B The coating has flaked along the edges of the cuts in large ribbons, and/or some squares have detached partly or wholly. A cross-cut area significantly greater than 35%, but not significantly greater than 65%, is affected. |  |
| ISO Class: 5 / ASTM Class: 0B Any degree of flaking that cannot even be classified by classification 4. |  |
Comparison table between ISO 2409 class & ASTM D3359 class
| ISO 2409 Class | ASTM D3359 Class | Description | Visual Effect |
|---|---|---|---|
| ISO 0 | ASTM 5B | Best adhesion. Edges of cuts are smooth. No squares detached. | Clean lattice, no coating loss. |
| ISO 1 | ASTM 4B | Very good adhesion. Small flakes detach at intersections of cuts. Area affected ≤ 5%. | Tiny flakes only at cut lines. |
| ISO 2 | ASTM 3B | Good adhesion. Flaking along edges/intersections, >5% but ≤15% affected. | Noticeable coating lift around cuts. |
| ISO 3 | ASTM 2B | Moderate adhesion. Large flaking in ribbons, >15% but ≤35% affected. | Strips of coating detached along cuts. |
| ISO 4 | ASTM 1B | Poor adhesion. Large flakes/ribbons, some squares partly or wholly removed, >35% but ≤65% affected. | Many squares detached. |
| ISO 5 | ASTM 0B | Very poor adhesion. Coating flaked off beyond classification 4, >65% affected. | Severe removal of coating. |
In Simple Words
- ASTM 5B / ISO 0 → Excellent adhesion, coating is solidly bonded.
- ASTM 0B / ISO 5 → Terrible adhesion, coating easily peels off.
- Classes in between show increasing levels of coating failure.
This test is critical in paint, coatings, automotive, aerospace, construction, and plastic industries to check whether a coating will stay on its surface under stress, handling, or environmental exposure.
