Corrosion Prevention and Control Practice Test

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What is cathodic disbondment and what factors influence it?

Cathodic disbondment is the delamination of coating from the substrate near CP boundaries due to electrochemical driving forces; it is influenced by coating adhesion, cure, environment, and CP current density.

Cathodic disbondment is coating growth due to CP.

Disbondment occurs only under high temperature.

Disbondment is unrelated to CP and only due to moisture.

Cathodic disbondment is the loss of adhesion of a coating to the metal surface caused by cathodic protection. The cathodic polarization drives electrochemical reactions and movement of water and ions at the coating–substrate interface, creating stresses and osmotic conditions that push the coating away from the metal, especially near CP boundaries where current density changes are greatest. The likelihood and rate depend on how well the coating adheres to the substrate (adhesion), how well it was cured (crosslinking and solvent removal), and the environment (humidity, temperature, salinity) as well as the level and distribution of CP current density. A strong, well-cured coating in a mild environment with moderate CP current is less prone to disbondment, whereas poor adhesion, inadequate cure, harsh conditions, or high CP current accelerate it. The other choices miss the role of CP or mischaracterize the phenomenon as growth or moisture-driven only.