Corrosion protection of brown and green patinated bronze

Researchers have developed two fluoropolymer coatings (FA-MS and FA-MS-SH) for the protection of artificial patinas for outdoor application.

A bronze sculpture with patina under the left eye.
Test results show that the protective efficiency of menthol coating increases as its thickness increases.  Image source: joseph_Berardi - Pixabay (symbol image).

Bronze surfaces, whether bare or patinated, tend to change when exposed to an outdoor atmosphere. Art made of bronze which is exposed to the outdoors is usually artificially patinated. This patina changes when exposed to rain, especially in polluted rain, where sulphuric, nitric or carbonic acids are present.

Fluoropolymer based coating

In order to gain optimal protection of different patinas and consequently reduce the patina changes over the time different protection systems were developed, tested and tailored. Three types of patina (brown, green sulphate, and green persulphate) were prepared, protected and subsequently studied. The protections were based on two coatings (i) fluoropolymer based coating (FA-MS) and (ii) newly developed fluoropolymer based coating with addition of mercaptopropyl groups, named as alternative fluoropolymer coating (FA-MS-SH).

It was shown that a fluoropolymer coating (FA-MS) provided the most efficient protection to bare bronze and the sulphate patina, while a newly proposed alternative fluoropolymer coating (FA-MS-SH) offered good protection to bare and brown patinated bronze.

The study has been published in Progress in Organic Coatings, Volume 161, December 2021.

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