Coating defect

Cratering (fish eyes)

Small round holes or dimples where the wet paint has pulled away from a spot, often with a raised rim.

Cratering (fish eyes): the surface as you see it, and a schematic cross-section.

Causes

Oil, grease or silicone on the surface.
Oil or water in the compressed air supply.
Contaminated spray equipment.

Prevention

Solvent clean (SSPC-SP 1) before blasting and painting.
Check the compressed air with the blotter test (ASTM D4285).

How it is assessed

Visual inspection; trace the contaminant to its source before work continues. Craters in a pattern along the spray passes point to the air or the equipment; craters in patches point to the surface.

Telling it apart

Pinholes: Pinholes are tiny holes that go deep into the film, often where air or solvent escaped. Craters are wider round dimples where the paint moved away from a contaminated spot.
Crawling and cissing: Crawling pulls the paint back into beads or islands over a wider area. Craters are separate round spots with a rim.

Repair

Clean off the contamination, abrade and recoat the affected area. The specification and the coating manufacturer have the final word on the repair procedure.

6 practice items in the members area mention cratering (CIP 1: 1 · CIP 2: 1 · FROSIO written: 4).

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.