A Thermodynamic Perspective of Copper Tarnishing in Moist Air—SO₂

Abstract

The open-circuit potential (E"p) of alloy 600 in lithiated water at 25 to 200°C is more negative than the RHE potential, which indicates that the alloy exhibits a mixed electrode potential under these conditions. In the 200 to 350°C range, E op is close to the RHE potential.The inner layer of the oxide film formed at 200°C and above is composed of MeO, white its outer layer is probably composed of Me00H or Me(OH) 2 .With increasing temperature, the film thickness increases moderately between 25 and 200°C, but increases drastically above 200°C.The AC impedance measurements show significant changes in the electrochemical properties of films starting from 150°C.At 250°C, semiconductivity of the film changes from p-type at lower temperatures to n-type at higher temperatures.The occurrence of changes in the properties of oxide films was established by ex situ and in situ experiments (AES, semiconductivity, and AC impedance, respectively). ABSTRACTA thermodynamic perspective of the initial stages of copper tarnishing in moist air-S02 is presented. Previous experimental work has shown that in such a system the initial tarnish film consists mostly of a mixture of copper(I) oxide and copper(1) sulfide. Equilibrium criteria are used to calculate the Tonic composition of the adsorbed water layer on the surface of the untarnished and the tarnished metal at various gas precursor concentrations. Using the adlayer chemistry, the electrode potentials of the redox reactions in the system are determined. Thermodynamically stable corrosion products are then calculated. The ability of S02 dissolved in water to act as a cathodic depolarizer in this system, thereby forming sulfide in the tarnish film, is demonstrated.

Mechanism of Atmospheric Corrosion of Copper in the Presence of Ammonium Sulfate Particles

“…For example, for copper it was not possible to produce a surface layer similar to the naturally formed patina using gaseous pollutantes like SO 2 and NO 2 . [1][2][3][4][5][6][7][8][9] However, the 1930s, Vernon demonstrated that dust particles, especially dust particles consisting of ammonium sulfate, significantly influence the corrosion of copper and lead to higher corrosion rates. [10][11][12][13][14][15][16] The factors that determine the amount of ionic surface contamination relevant for atmospheric corrosion on metal surfaces was later studied by Sinclair et al [17][18][19][20][21][22][23] The extent of ionic deposition on indoor surfaces is influenced by the concentration of dust particles in the outdoor air, the air exchange rate between indoors and outdoors, efficiency of air filtration systems, the velocity of the air, the surface area to volume ratio, the temperature of the surface, the distance between surfaces and source of particles, and the orientation of the surface.…”

Slowing down the corrosion of metal structures using polymeric materials

“…Grossman [6] has investigated the atmospheric factors which determined the time of wetness of the outdoor structures. A thermodynamic perspective of copper tarnishing by SO 2 in the presence of moisture was reported by Chawla and Payer [7]. Walters [8,9] carried out some exhaustive studies on the laboratory simulation of atmospheric corrosion by SO 2 detailing the apparatus, electrochemical techniques, and example results.…”