Development of multi-component fluoropolymer based coating on simulated outdoor patina on quaternary bronze

Overview & Synopsis

Bronze reacts with oxygen, humidity, and pollutants in the atmosphere so that a patina forms. Natural exposureto an outdoor atmosphere can be simulated and accelerated in order to achieve a patina that mimics outdoorancient patina. In order to avoid the uncontrolled dissolving of either the natural or artificially formed patina,protection of the patina is needed.In this study, a multi-componentfluoropolymer based coating for the protection of bronze patina was de-veloped. In order to provide various functionalities of the coating (such as the hydrophobicity of the coatingsurface, obtaining interactions within the coating itself as well as a bronze substrate and inhibiting the corrosionprocesses), afluoroacrylate coating with appropriate adhesion promoter was suggested, with and without asilane modified benzotriazole inhibitor. The protective efficiency and durability of the applied coatings wereinvestigated electrochemically using potentiodynamic tests and electrochemical impedance spectroscopy in asimulated acid rain solution. All of the developed coatings showed a significant decrease in the corrosion currentdensity. The self-assembled single layer coating (FA-MS) also showed 100% inhibition efficiency. After ageingthe coating remained transparent and did not change by UV exposure and/or thermal cycling. The patina andcoating investigations using FIB-SEM and EDX showed that the latter coating (FA-MS) successfully covered thesurface of the patinated bronze. The mechanism of the bonding was proposed and supported with the spec-troscopic observation of a thin and even coating