The Evolution of the Adsorbed Solution Layer during Atmospheric Corrosion and Its Effects on the Corrosion Rate of Copper

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Abstract
A better understanding of the atmospheric corrosion of materials requires an improved knowledge of the adsorbed electrolyte layer. Such insights include the ionic constituents present and their concentrations as well as how these depend on experimental variables such as time, pollutant gas, and relative humidity. The present work describes experiments which combine quartz crystal microbalance measurements with ion chromatography to study the evolution of the adsorbed electrolyte layer during the exposure of Au and Cu to low levels of . These measurements show that it takes up to 20 h for the electrolyte layer to approach a steady‐state composition in which the nitrate concentration is on the order of 1M. The dominant nitrogen specie is nitrate, though both nitrate and nitrite are detectable. The results support the idea that metal surfaces preferentially catalyze one of the reaction pathways. The corrosion rate of copper was shown to increase only after a sufficiently aggressive solution chemistry was developed in the adsorbed electrolyte.