# Peeling

Source: https://coatmentor.com/defects/peeling/ · Updated 2026-10-14

The film lifts in larger, flexible sheets or strips, often from edges, seams or penetrations.

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

## Causes

- Poor surface preparation or a contaminated surface.
- Contamination between coats, or a coat applied after its recoat window.
- Alkyd paint on galvanizing: the zinc saponifies the binder and leaves a soapy layer.

## Prevention

- Prepare and clean the surface as specified.
- Use coatings suited to the substrate, for example no alkyd directly on zinc.

## How it is assessed

Visual, with adhesion tests round the area. Peeling is in soft, pliable films; flaking is in hard, brittle ones.

## Telling it apart

- **[Flaking and delamination](https://coatmentor.com/defects/flaking/):** Flaking breaks hard, brittle films into small chips. Peeling lifts soft, pliable films in sheets.
- **[Delamination (intercoat adhesion failure)](https://coatmentor.com/defects/delamination/):** When a coat parts cleanly from the coat below, the defect is an intercoat failure. Peeling is the wider term for a film that comes off in sheets.

## Repair

Remove all loose coating to a sound edge, find and correct the cause, then prepare and recoat. The specification and the coating manufacturer have the final word on the repair procedure.

**9** practice items in the members area mention peeling (CIP 1: 3 · FROSIO written: 6).

## Related

- **Concepts:** [Surface cleanliness grades](https://coatmentor.com/learn/surface-cleanliness/) · [Adhesion testing](https://coatmentor.com/learn/adhesion-testing/)
- **Standards:** [ASTM D3359](https://coatmentor.com/standards/astm-d3359/) · [ISO 2409](https://coatmentor.com/standards/iso-2409/)

## About this page

Written from coating practice and the published rating standards, in our own words; the drawing is schematic. 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.