Atmospheric Corrosion of Silver in Outdoor Environments and Modified Accelerated Corrosion Chambers

Abstract

The accelerated corrosion of pure silver (Ag) exposed in a standard salt spray test chamber under standard conditions (5 wt% sodium chloride [NaCl] solution at 95°F and 95% relative humidity), as well as in a modified salt spray chamber test that included ozone (O3) and ultraviolet (UV) irradiation with 5 wt% NaCl, was investigated. The effects of O3 and UV on the atmospheric corrosion of exposed samples were determined with coulometric reduction and scanning electron microscopy–energy dispersive spectroscopy. The coulometric reduction is based on the cathodic reduction of the film, which forms on the Ag surface during exposure. A quantitative value of film formation on Ag sample could be indicative of the cumulative corrodent level present at the exposure sites. Coulometric reductions on exposed Ag coupons were performed in 0.1 M Na2SO4. The corrosion rates of the samples exposed in the modified ASTM B117 corrosion chamber under UV and O3 conditions were much higher than the standard B117 salt spray test...