Coating defect
Flaking and delamination
Pieces of coating lifting and falling away, either a top coat from the coat below (intercoat) or the whole system from the substrate.
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
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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. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.