Effect of NO2 and/or SO2 atmospheric contaminants and relative humidity on copper corrosion

Abstract

A study has been made of the individual and combined roles of NO₂ and SO₂ atmospheric contaminants on corrosion and patina formation on copper in humid atmospheres. In most cases the combined effect of the two contaminants has been greater than the sum of their individual effects, although exception have been found with the mixture of 800 μg/m⁺³NO₂ + 800 μg/m⁺³ SO₂- XPS analysis has revealed important composition changes in the outermost layer of films formed on copper, depending on the nature of the atmospheric contaminant and humidity level. The presence of sulphates and sulphites has been clearly observed in exposure to atmospheres contaminated with SO₂ at 50, 70 and 90 % RH. Nitrates and nitrites have been detected in exposure to NO₂ at 50 and 70 %RH, but not at 90 % RH. A hydrogenated nitrogen compound has been detected with the mixture of NO₂ and SO₂ at 90 % RH .In this atmosphere, a certain inhibiting effect has been seen.