Flaking-off

Coming off of the coating on a substrate in the form of small fragments due to insufficient adhesion. Potential causes:

  1. From the start, insufficient wettability of the substrate surface for the coating material.
  2. Weathering of the coating material due to ageing in connection with embrittlement and cracking. This is often associated with the penetration of moisture through cracks and microcracks in the coating, which initially dissolves the substrate surface locally, causing it to weather or swell, followed by spreading on the substrate surface below the coating.
  3. Weathering of the substrate surface below the coating caused by penetration of substances through the coating, from behind through the substrate or by lateral migration parallel to the substrate surface.

Flaking-off can by prevented by a plasma treatment of the uncoated or sometimes also the coated substrate:

  1. By suitable cleaning, activating and surface enlargement through etching, every substrate can be pretreated in such a way that sufficient wetting by the coating material is ensured.
  2. By applying additional protective coats by plasma coating, the coat can be protected from weathering.
  3. Plasma treatment can prevent weathering of the substrate. Beispielsweise kann durch Hydrophobing can for example be used to prevent the penetration of moisture at the border between substrate and coating.

See also:⇒ Improving adhesion⇒ Pretreatment In the cross-cut test, flaking off of the coat shows insufficient wettability of the substrate for the coating material.

Video of the execution of the cross-cut test

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