Cross-Hatch Adhesion Testing (ASTM D3359)
Key facts
| Coating removed | ASTM D3359 (Method B) | ISO 2409 / GB/T 9286 |
|---|---|---|
| None — cut edges smooth | 5B | 0 |
| Small flakes at intersections, under 5% | 4B | 1 |
| 5–15% | 3B | 2 |
| 15–35% | 2B | 3 |
| 35–65% | 1B | 4 |
| Over 65% | 0B | 5 |
How the test is done
A cutting tool scores a grid of parallel lines through the coating in two directions. The cut spacing depends on the film thickness — typically 1 mm for thin films. Pressure-sensitive tape is pressed over the grid and pulled off, and the grid is compared with the classification pictures in the standard.
ASTM D3359 also has an X-cut method (Method A), used mainly for thicker films and field checks.
Watch the scale
The two scales run in opposite directions. In ASTM D3359, 5B is best. In ISO 2409 and GB/T 9286, 0 is best. A report that says “grade 0” without the standard can mean the best or the worst result.
What it tells you about coils
Adhesion confirms surface preparation and cure. A poor result on a batch panel usually points to contamination or under-cure — the two most common causes of coating failure.
Related
- CoatingsWaterborne Polysiloxane (Sol-Gel) Coil Coating
- StandardsMeasuring Dry Film Thickness on Fins
- GuidesHow to Verify a Supplier's Salt Spray Claims
- CompanyQuality Control and Inspection
- CoatingsWaterborne Two-Component Coil Coatings
- StandardsASTM B117 Neutral Salt Spray: What the Hours Mean
Also see
- GuidesWhy Do Coil Coatings Fail?
- CompanyTest Data Library
What does 'Grade 0' mean on a PG data sheet?
PG-S1 reports Grade 0 to GB/T 9286, the ISO 2409 scale, which means no coating removed — the best grade. PG-W also reports Grade 0.
Can adhesion be tested on the fins?
Not reliably. Fins are too thin and too small for a cutting lattice. Adhesion is tested on flat panels of the same metal coated and cured with the batch.
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