# Flaking and delamination

Source: https://coatmentor.com/defects/flaking/ · Updated 2026-10-04

Pieces of coating lifting and falling away, either a top coat from the coat below (intercoat) or the whole system from the substrate.

*Figure: Flaking and delamination: the surface as you see it, and a schematic cross-section.*

## Causes

- A contaminated surface between coats: dust, salts, amine blush, chalk.
- The maximum recoat interval was exceeded without abrading.
- Incompatible coatings.
- Poor surface preparation under the system.
- Moisture or condensation on the surface when the coat was applied.

## Prevention

- Clean and check each coat before the next; remove blush and chalk.
- Overcoat inside the recoat window, or abrade as the data sheet says.
- Keep the steel at least 3 °C above the dew point while coating.

## How it is assessed

Rate under ISO 4628-5 and record at which interface it failed (destructive tests such as a knife or adhesion test are CIP 2).

## Repair

Remove loose coating to a sound edge, clean or abrade the exposed surface, and rebuild the missing coats. The specification and the coating manufacturer have the final word on the repair procedure.

**32** practice items in the members area mention flaking and delamination (CIP 1: 9 · CIP 2: 11 · FROSIO written: 12).

## Related

- **Concepts:** [Dew point and the 3 °C margin](https://coatmentor.com/learn/dew-point/) · [Drying, curing and recoat windows](https://coatmentor.com/learn/cure-and-recoat/) · [Adhesion testing](https://coatmentor.com/learn/adhesion-testing/)
- **Standards:** [ISO 4628](https://coatmentor.com/standards/iso-4628/) · [ISO 4624](https://coatmentor.com/standards/iso-4624/)

## About this page

Written from coating practice and the published rating standards, in our own words; the drawing is schematic. Checked on 2026-10-04; 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.