Definition - What does Disbonding mean?

Disbonding is the failure of a coating to adhere to the substrate to which it was applied. It is a loss of adhesion between a cathodic coating and its metal substrate due to the products of a cathodic reduction reaction (corrosion reaction).

Cathodic protection (CP) systems are intended to prevent corrosion of metal. Coating disbondment occurs when coatings in a cathodic protection system interact either chemically or physically, ultimately causing corrosion beneath the coating.

Disbonding is also known as cathodic disbondment.

Corrosionpedia explains Disbonding

In cathodic protection (CP) systems, an electric current passing through the metal can free hydrogen atoms, causing coating disbondment. This current passes only through a fault in the metal coating, and the amount of current flow depends on the size of the coating fault. As the size of the fault increases, the current forces the coating away from the metal, resulting in a voltage drop at the interface, causing cathodic disbondment. If there is no coating fault, then cathodic disbondment does not occur.

Cathodic disbondment performance is much more consistent at thicknesses over 200 µm; therefore, thicknesses less than 200 µm should be avoided in order to achieve good cathodic disbondment protection.

Factors affecting disbondment:

  • Thickness
  • Formulation of the product
  • Cure percentage

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