Effect of Arsenic on Permeation of Hydrogen Through Steel Membranes polarized cathodically in aqueous solution

A sensitive technique is developed for studying the effect of As and its compounds on the permeation of hydrogen through steel membranes electrolytically charged at various pH values. Use of a rotating disc electrode permits to change pH at the cathode over a large range without changing composition of the bulk electrolyte. The results of this study strongly support previous conclusions as to the dominant part played by promoter hydrides as species accelerating the entry of hydrogen into metals. In the case under consideration, AsH3 has been found to promote the permeation of hydrogen evolved from acid and alkaline media. On the other hand, surface films, deposits, and precipitates of As impede the entry of hydrogen into the steel.