Effect of Thiosulfate and Sulfite on the Permeation Rate of Hydrogen Through Iron

Effects of thiosulfate (S2O32-) and sulflte (SO32-) on hydrogen evolution and permeation within iron have been studied in acid and neutral solutions. Results show that thiosulfate increases the hydrogen permeation rate and depolarizes the hydrogen evolution reaction at concentrations as low as 0.1 mM, in acid or neutral media. Sulfite showed similar and somewhat less pronounced effects in the acid medium and no effect on either process in the neutral medium. Results are discussed in light of the stability of the various sulfur species and their effects on the rates of both processes.