Intercoat Contamination

Definition - What does Intercoat Contamination mean?

Intercoat contamination is the presence of a contaminant between two layers of a multi-coat paint system, and is generally caused by inadequate cleaning of the inner surface before applying the outer coat. Intercoat contamination is a problem because it can cause a variety of coating defects, such as:

  • Adhesion defects (intercoat delamination, peeling)
  • Blistering
  • Crackling
  • Craters
  • Fish eyes

This coating problem is prevented by properly cleaning a coating's surface before applying the next coat. The cleaning method should be compatible with the coating type. To fix intercoat contamination, the coating must be removed and re-applied.

Corrosionpedia explains Intercoat Contamination

Intercoat contamination can interfere with intercoat adhesion and proper coat layering. Adhesion between two surfaces is due to intermolecular interactions, in which contaminates prevent the two surfaces from having adequate interactions. Without contamination, two compatible surfaces stick together due to favorable intermolecular interactions (polar-polar or non-polar-non-polar). These interactions are strengthened by a higher surface area of the interaction between the two layers. Contaminants can interrupt both of these factors and lead to weakness in the adhesion. The resultant defects can cause peeling of the outer surface or delamination.

Contamination between coats can also interfere with the setting of the top coat. The contamination may prevent the top coat from forming a complete film over the inner coat, or cause fish eye or crater type defects in the surface.

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