Standard · Adhesion, cure and holidays
ISO 4624
The pull-off test for adhesion of coatings.
In a pull-off test a dolly is glued to the coating, and a tester pulls it off at right angles. The result is the tensile stress at failure, and where the break happened.
Reading the result
- Adhesive failure: between two layers, or between coating and substrate.
- Cohesive failure: within one layer.
- Glue failure: the adhesive broke first, so the coating is at least as strong as the reading.
The letters for the break
Each place a break can run has a code: A in the substrate; A/B between substrate and first coat; B in the first coat; B/C between first and second coat; -/Y between the final coat and the glue; Y in the glue; Y/Z between glue and dolly. Each share is estimated to the nearest 10 %. A complete report gives the stress in MPa with the shares, for example "6 MPa, 70 % C, 30 % Y" for a break mostly in a second coat.
The test itself
- Dollies are 20 mm nominal, up to 100 mm on concrete.
- The stress rises at no more than 1 MPa/s, so that the assembly breaks within 90 s.
- Carry out at least six determinations.
- Method B pulls one dolly from one side and suits rigid substrates only.
- Below 150 µm the cut round the dolly may be left out, if agreed; report whether it was cut.
The parties agree the acceptance criteria for each type of failure. Destructive tests are outside the scope of CIP 1.
9 practice items in the members area mention ISO 4624 (CIP 2: 7 · FROSIO written: 2).
Related
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Also published openly: Elcometer 510 pull-off tester instructions, nature of fracture codes.
This page describes the subject of ISO 4624 in our own words; it does not reproduce the standard. For the full text, buy the current edition from ISO. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.