The Role of Sulfur in the Atmospheric Corrosion of Silver

X-ray photoelectron spectroscopy was used to investigate the corrosion products formed on silver (Ag) samples that were exposed at various outdoor sites. Silver chloride (AgCl) and silver sulfide (Ag 2 S) were identified, as well as silver sulfite (Ag 2 SO 3 ) and silver sulfate (Ag 2 SO 4 ). The presence of these oxidized sulfur species on field-exposed Ag samples has been contested. Yet, evidence here suggests that Ag 2 SO 3 is a stable intermediate in the formation of Ag 2 SO 4 . Furthermore, the presence of alkali cations, such as Na + , correlates with the final oxidation state of the sulfur species found on the Ag samples. When cations were present, Ag 2 SO 4 was the final state, whereas Ag 2 SO 3 was found in the absence of alkali cations. In addition, silver carbonate (Ag 2 CO 3 ) was identified on samples exposed at one site with higher altitude. Here, we present for the first time the detection of Ag 2 SO 3 , in addition to Ag 2 CO 3 , on field-exposed Ag. These findings improve the ability to use Ag as an atmospheric corrosion monitor for the simultaneous detection of AgCl and Ag 2 S as well as Ag 2 SO 3 and Ag 2 SO 4 .