What Does Intercoat Delamination Mean?
Intercoat delamination is a type of coating adhesion failure where two layers of coating do not stick together and the coating breaks or peels. As such, the coatings fail to provide their protective value or aesthetic appeal. Delamination problems often originate from mistakes at the time of application or errors in overseeing the compatibility between two different coating products.
Delamination between two coatings can be prevented by understanding the possible causes. Failure to plan multiple coatings leaves the system at risk for intercoat delamination and results in costs to fix the coatings and can make the underlying material prone to corrosion.
Corrosionpedia Explains Intercoat Delamination
Specific reasons for intercoat delamination include:
- Surface contamination
- Lack of primer
- Inadequate acid etching or blast profile
- Excessive moisture
- Presence of a solvent
- Intercoat incompatibility
Understanding molecular interactions is necessary to explain why intercoat delamination occurs. Adhesion between coatings is induced through intermolecular interactions between the molecules on each of the interacting surfaces. Favorable interactions, such as large surface areas of non-polar to non-polar interactions or polar to polar interactions help the coatings stick together.
Contaminants, such as dust, moisture or a solvent can interfere with adhesion by competing with the coating's surface for intermolecular interactions. These competing interactions prevent the coat as a whole from sticking, leading to weakness and eventual delamination. Intermolecular interactions are stronger as the surface area increases. Thus, acid etching or sand blasting a surface before applying a coating can lead to strong adhesion and prevent intercoat delamination.
Incompatibility, such as a polar and a non-polar surface, will prevent the two surfaces from interacting. Sometimes coatings are incompatible after they have fully cured, but can be successfully adhered by applying the second coat before the first coat has finished curing. This trick works because coatings such as epoxies undergo chemical reactions during curing before generating a hard non-stick surface. Before the first coat has finished curing, the second coating can intermix with the first coating and form chemical bonds between the two coats, thus forming a strong interaction between the two layers.