Electrochemical Characterization of Bronze Exposed to Outdoor Atmosphere

Marijana Marcelja,Dajana Mikić,Helena Otmačić Ćurković,Ema Kovačević,Luka Bera

doi:10.15255/cabeq.2021.1926

Abstract

The aim of this work was to examine corrosion behaviour of bare and artificial patinated bronzes during exposure to urban outdoor atmosphere. Studies were conducted on <br /> copper and two different bronzes in order to evaluate the influence of substrate composition on patina composition and electrochemical behaviour. Additionally, two different patination methods were compared. Corrosion behaviour was examined using electrochemical impedance spectroscopy with gel-electrolyte electrochemical cell. The composition of patina was determined by ATR-FTIR spectroscopy. The obtained results showed that all studied artificial patinas initially decrease the corrosion resistance of copper and bronzes but in time their corrosion resistance improves, and even for certain combinations, artificial patina-bronze corrosion resistance is higher than that of naturally patinated bronze.

Highlights

Copper and its alloys, when exposed to outdoor environment, corrode under the influence of moisture, rainwater and corrosive species in the air
Various methods of artificial patination have been developed over time.[3]
The patinas were analysed by ATR-FTIR spectroscopy using a Perkin Elmer Spectrum One FTIR spectrometer, within the scan range from 4000 to 650 cm–1, and with resolution of 0.5 cm–1; the results shown in this paper are averages of 25 scans

Summary

Introduction

Copper and its alloys, when exposed to outdoor environment, corrode under the influence of moisture, rainwater and corrosive species in the air. Atmospheric corrosion firstly leads to formation of brown layer of cupric oxides, which gradually turns black due to the formation of cuprous oxides, and afterwards the greenish-blue layer of patina is formed.[1,2]. Duration of this process, and especially the formation of terminal patina layer, depends on the concentration of various pollutants, such as SO2, NOX, or Cl–. As the natural formation of patina on copper and bronze takes years, artificial patina is commonly applied. This is done for aesthetic reasons, as well as for the protection of the bronze base.

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Conclusion