Influence of UV irradiation and ozone on atmospheric corrosion of bare silver

The corrosion of Ag in an atmosphere of ozone and humidity with or without irradiation by ultraviolet (UV) light was investigated. A modified coulometric reduction technique was used, substituting sulphate solution for chloride solution, to prevent the spontaneous transformation of silver oxide corrosion product to chloride in the reduction solution. The presence of both ozone and UV radiation was required for fast corrosion of Ag to occur. The amount of corrosion product for a given exposure time increased with ozone concentration, whereas the relative humidity had little effect. An incubation time for the corrosion reaction was observed. The presence of both ozone and UV radiation were necessary for rapid corrosion because the photodissociation of ozone generates reactive atomic oxygen, which reacts with Ag rapidly to form Ag2O. The corrosion reaction on bare silver was minimally affected by the relative humidity in the environment, which is contrary to common atmospheric corrosion experience.