An Electrochemical and Spectroscopic Study of Surfaces on Bronze Sculptures Exposed to Urban Environment

Abstract

Polluted urban environment enhances dissolution of patina and underlying bronze material of recent and historical bronze sculptures exposed outdoors. In this work, two bronze statues, situated in one of the most polluted Croatian cities, were examined in order to characterize composition of patina and its electrochemical stability. The composition of patina on several positions on each sculpture was determined by EDS, Raman spectroscopy, and FTIR measurements. Electrochemical impedance spectroscopy measurements were conducted in order to evaluate the corrosion stability of both patina and underlying bronze. Results obtained in this work show that the two examined bronze sculptures were covered with patina layer that was mainly composed of copper sulfides and sulphates, which is in accordance with the high concentrations of H2S and SO2 in the atmosphere. However, the variations in the appearance of FTIR and Raman spectra revealed that the amount of each species differed from spot to spot, as well as the fact that other compounds, such as carbonates, were present at some areas. This difference in patina composition was reflected in electrochemical behavior as observed by electrochemical impedance spectroscopy.

The Effect of Corrosion Conditions on Aging of Artificial Patina on Three Bronzes

“…The strongest peaks were observed for RG7 bronze. The band at 610 cm −1 may be assigned with the presence of a bond between either copper or tin and oxygen [9,31], while the 1071 cm −1 band can be attributed to SO 4 2− vibration [32,33]. Both peaks indicate the formation of copper and tin oxides as well as sulphate patina, as observed by Kosec at al.…”

“…Many researchers have studied the formation of patina on bare bronze under various aging conditions, simulating processes that occur during outdoor exposure [5][6][7][8]. In addition, studies have been conducted on real artistic or historical objects covered by a decades-or centuries-old patina [9][10][11][12]. However, studies on freshly patinated bronzes are mainly conducted with the aim to evaluate different coatings used for their protection [3,13,14].…”

Application of low-temperature plasma for the removal of copper chloride layers on bronze Wares

“…Bronzeware is of vital importance in the river of human civilization, bronze has been used for utensils, decorative and artistic objects since ancient times due to its good corrosion resistance, casting performance, and longlasting characteristics [1,2]. Bronze is a composite alloy based on copper with the additions of lead, tin, and other metals [3].…”

Protection of Patinated Bronze with Long-Chain Phosphonic Acid/Organic Coating Combined System

“…In urban atmospheres, patinas directly exposed to rain are subjected to significant dissolution, which leads to the corrosion of underlying bronze [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Many studies have been conducted with the aim of understanding better the mechanism of bronze atmospheric corrosion and the influence of various factors such as alloy composition [ 4 , 5 , 6 ], presence of pollutants [ 2 , 9 , 10 ], and weathering conditions [ 7 , 11 , 12 , 13 ]. These factors influence not only the corrosion rate value but also the composition and structure of the patina layer.…”