Adhesion characterisation of fouling release coatings

Abstract

Fouling release coatings (FRCs) are a new generation of anti-fouling systems for marine applications, relying on surface properties instead of biocides. Their non-stick behaviour derives from silicone oils that limit fouling adhesion, which is then removed by hydrodynamic action. However, due to their softness and weak interlayer adhesion, traditional adhesion tests cannot be applied. This work investigates the adhesion of FRCs containing silicone-based oils. The coating system consists of an epoxy primer and a silicone topcoat. Electrochemical impedance spectroscopy was used to evaluate the barrier properties, while cathodic disbonding tests examined adhesion at the substrate–primer interface. Since pull-off or cross-cut tests cannot be performed on these soft coatings, a new method was developed to assess adhesion at the primer–topcoat interface. The method relies on scratching the coating with a tribometer in a pin-on-flat configuration. By progressively increasing the applied load, the critical load inducing complete delamination of the topcoat was identified. Coating damage was then evaluated using a stylus profilometer. This approach highlights the effect of silicone-based oil content in the topcoat on adhesion at the primer–topcoat interface.