Moisture penetration under the coating film leads to what type of coating failure?

Moisture penetration under the coating film leads to osmotic blistering, which is a specific failure mechanism that occurs when water or moisture becomes trapped beneath the surface of a coating. This moisture can originate from environmental humidity, damp substrates, or even contamination. When moisture penetrates under the coating, it often disrupts the bond between the coating and the substrate, leading to the formation of blisters.

These blisters form as the moisture tries to escape, causing localized areas of pressure that can lift the coating away from the surface. Over time, osmotic blistering can compromise the protective properties of the coating, exposing the substrate to potential corrosion and degradation.

Understanding this type of failure is crucial for ensuring that coatings adhere properly and perform their intended protective functions. Other types of failures, such as cohesion failure, cracking, and peeling, may occur due to different reasons and mechanisms that are not directly related to moisture penetration in the same way.