Bronze propellers used in pleasure boats are commonly protected by zinc sacrificial anodes in combination with antifouling coatings. However, the simultaneous use of organic coatings and cathodic protection can promote coating degradation and cathodic delamination at the metal–coating interface, highlighting that, in these systems, high barrier properties alone are not sufficient and must be combined with strong adhesion to the metallic substrate to ensure durable performance. Owing to increasing environmental constraints, new-generation eco-compatible coatings are required; consequently, fouling release coatings (FRCs), consisting of an epoxy primer and a polydimethylsiloxane (PDMS) elastomer topcoat, are progressively replacing conventional biocide-containing systems. In the absence of specific standards for these coating architectures, the present work evaluates their resistance to cathodic delamination at the primer–substrate interface and their barrier properties by means of electrochemical impedance spectroscopy (EIS), while coating morphology was investigated by scanning electron microscopy (SEM). The effects of introducing a silane-based additive and modifying the resin-to-hardener ratio in the epoxy primer formulation were studied in order to improve adhesion to the bronze substrate, while preserving the coating resistance to cathodic disbonding. After an initial screening of these parameters, the subsequent in-depth investigation focused on the silane content, as it emerged as the most influential factor affecting coating performance. The results show that variations in primer stoichiometry do not significantly affect the overall performance of the organic coating. In contrast, the silane-based additive markedly improves resistance to cathodic delamination. However, excessively high silane contents lead to coatings with inconsistent delamination resistance, despite retaining comparable barrier properties. These findings demonstrate that optimizing the metal–coating interface is crucial for enhancing resistance to cathodic disbonding. While stoichiometric variations have a negligible effect, the silane-based additive plays a key role in improving interfacial performance. Its concentration, however, must be carefully controlled, as excessive amounts can adversely affect long-term electrochemical stability.
Effect of silane content on barrier properties and adhesion of fouling release coatings for naval applications
Rondinella A.;Fedrizzi L.;Andreatta F.
2026-01-01
Abstract
Bronze propellers used in pleasure boats are commonly protected by zinc sacrificial anodes in combination with antifouling coatings. However, the simultaneous use of organic coatings and cathodic protection can promote coating degradation and cathodic delamination at the metal–coating interface, highlighting that, in these systems, high barrier properties alone are not sufficient and must be combined with strong adhesion to the metallic substrate to ensure durable performance. Owing to increasing environmental constraints, new-generation eco-compatible coatings are required; consequently, fouling release coatings (FRCs), consisting of an epoxy primer and a polydimethylsiloxane (PDMS) elastomer topcoat, are progressively replacing conventional biocide-containing systems. In the absence of specific standards for these coating architectures, the present work evaluates their resistance to cathodic delamination at the primer–substrate interface and their barrier properties by means of electrochemical impedance spectroscopy (EIS), while coating morphology was investigated by scanning electron microscopy (SEM). The effects of introducing a silane-based additive and modifying the resin-to-hardener ratio in the epoxy primer formulation were studied in order to improve adhesion to the bronze substrate, while preserving the coating resistance to cathodic disbonding. After an initial screening of these parameters, the subsequent in-depth investigation focused on the silane content, as it emerged as the most influential factor affecting coating performance. The results show that variations in primer stoichiometry do not significantly affect the overall performance of the organic coating. In contrast, the silane-based additive markedly improves resistance to cathodic delamination. However, excessively high silane contents lead to coatings with inconsistent delamination resistance, despite retaining comparable barrier properties. These findings demonstrate that optimizing the metal–coating interface is crucial for enhancing resistance to cathodic disbonding. While stoichiometric variations have a negligible effect, the silane-based additive plays a key role in improving interfacial performance. Its concentration, however, must be carefully controlled, as excessive amounts can adversely affect long-term electrochemical stability.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
