Coating Craters

Coating craters represent a local depression in the coating and are often a consequence of wetting defects. The coating is pushed in the defective area outwards, thereby reducing the coating thickness in the crater area. The effect can range from a slight reduction in coating thickness to a complete absence of coating, thus locally exposing the component surface.

If the cause of the coating crater is a particle in the crater’s center, similar analyses are used as for pinholes. Usually, the particles are already freely accessible from the surface. Their elemental composition is then analyzed using Scanning Electron Microscopy (SEM-EDX) for a more detailed analysis.

If no particles are visible, an analysis of the coating crater is often still possible. Release agents, greases, or oils can often be detected using highly surface-sensitive analytical methods such as ESCA on the coating surface.

In addition, mechanical damage in underlying coating layers (flaking) or in the unpainted component, such as (dents or scratches), can also lead to coating craters. In such cases, it would be necessary to create a cross-section through the defect.

In the case of a multi-layer coating structure, a cross-section can also help determine which coating layer is responsible for the coating crater.