Coating defect

Amine blush

A greasy, waxy or hazy film on the surface of an amine-cured epoxy, sometimes with white staining. It is water-soluble.

Amine blush: the surface as you see it, and a schematic cross-section.

Causes

Cold, damp curing conditions: the amine hardener reacts with moisture and carbon dioxide at the surface.
Condensation on the curing film.

Prevention

Keep temperature and humidity within the data sheet limits during cure.
Respect any induction time; keep the steel above the dew point.

How it is assessed

Assess it visually and by touch. A field test kit can confirm it. Check before every overcoat in cold, damp weather. Amine blush is water-soluble: makers usually ask for a wash with detergent and water before overcoating.

Telling it apart

Blushing (solvent blush): Solvent blush is moisture caught in the film of a fast-drying coating. Amine blush is a product of the epoxy hardener, on the surface.
Undercure: Under amine blush the film can be fully cured. An undercured film stays soft through its depth.

Repair

Wash it off with water (often warm, with scrubbing), then dry the surface before overcoating. Overcoating blush causes intercoat adhesion failure. The specification and the coating manufacturer have the final word on the repair procedure.

20 practice items in the members area mention amine blush (CIP 1: 9 · CIP 2: 5 · FROSIO written: 6).

Try it in an exam-style question. The free readiness check shows the question style, explains every answer and gives you a dated study plan.

Take the free readiness check See the tracks

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. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.