STUDY OF THE CONTAMINATION OF CONTACT MATERIALS, SILVER AND SILVER-PALLADIUM ALLOYS IN AIR CONTAINING HYDROGEN SULPHIDE AND NITROGEN DIOXIDE

摘要

A detailed study of silver sulfidation in air containing either hydrogen sulfide or mixtures of hydrogen sulfide and nitrogen dioxide has been realized. It shows an acceleration of the sulfidation rate in presence of nitrogen dioxide. The kinetics become linear, depend on air flow and on H_2S and NO_2 concentrations. The rate increase is explained by the formation of sulfur. Several possible reactions are proposed. The study realized with silver-palladium alloys shows that the sulfidation rate is clearly slowed down only when the alloy contains fifteen to twenty per cent of palladium.