Coating defect

Bleeding

Stains or a colour change in a new top coat, as patches, halos or an overall shift, where colour moved up from below.

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

Causes

Solvent in the new coat dissolves a coloured coat below.
Coal tar or bitumen under an ordinary top coat.
Some red organic pigments under a light top coat.
A strong solvent in the new coat over an old coating of unknown type.

Prevention

Seal a bleeding coat with a barrier coat, for example an aluminium-pigmented sealer, before the top coat.

How it is assessed

Visual. Another coat of the same top coat does not cure it: the colour comes back.

Telling it apart

Fading and discoloration: Fading is paler colour from sunlight. Bleeding is a foreign colour coming up from below, often soon after the new coat.
Contamination and inclusions: Stains from outside, such as rust run-off, sit on the surface and often wash off. Bleeding stains are inside the new film.

Repair

Apply a suitable sealer or barrier coat, then the top coat. The specification and the coating manufacturer have the final word on the repair procedure.

2 practice items in the members area mention bleeding (CIP 2: 1 · FROSIO written: 1).

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.