The Early Stage of Atmospheric Corrosion of Copper by Sulfur Dioxide

Abstract

The early stage of corrosion of copper by moist air containing 0.5% sulfur dioxide (75% relative humidity at 25°C) has been studied. Scanning electron microscopy, Auger electron spectroscopy, and transmission electron microscopy have been used to examine the surface topography, surface chemistry, and microstructure of copper foils before and after exposure to the corrosive atmosphere. The analyses show that in the initial stage of corrosion a mixture of copper oxide and copper sulfide forms on the surface. Reduction of sulfur dioxide to sulfide on the metal surface indicates that sulfur dioxide is a cathodic depolarizer in the early stages of corrosion.