# ISO 4624

Source: https://coatmentor.com/standards/iso-4624/ · Updated 2026-10-14

The pull-off test for adhesion of coatings.

**Publisher**: ISO

**Area**: Adhesion, cure and holidays

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

- **Concepts:** [Adhesion testing](https://coatmentor.com/learn/adhesion-testing/)
- **Standards:** [ASTM D4541](https://coatmentor.com/standards/astm-d4541/) · [ISO 16276](https://coatmentor.com/standards/iso-16276/) · [ISO 2409](https://coatmentor.com/standards/iso-2409/)
- **Defects:** [Flaking and delamination](https://coatmentor.com/defects/flaking/) · [Delamination (intercoat adhesion failure)](https://coatmentor.com/defects/delamination/)

## About this page

**Also published openly:** [Elcometer 510 pull-off tester instructions, nature of fracture codes](https://www.southampton.ac.uk/assets/imported/transforms/content-block/UsefulDownloads_Download/ED337B88B6D74F43B030846FDB393223/510.pdf).

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](https://coatmentor.com/method/). CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.