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Adhesion of organic coatings I

 
Why do coatings adhere?

The adhesion of organic coatings to a metal substrate is determined by various factors:

• Surface roughness I
• Impurities at the surface II
• The chemical status of the surface III
• The functional groups of the coating IV

The surface roughness plays normally only a very limited role. When impurities stick to a surface (see also Less sticking due to Micropeening) roughness is very important, but for good adherence of a coating mechanical pinning is seldom sufficient. A strong chemical bond is needed.

In this figure we can see an example where due to an extreme interpenetration nevertheless a strong effect results: a nice exception.

pseudoboehmite= oxyhydroxide layer

From PhD Thesis J. Van den Brand, TU delft 2004.