EFFECT OF CHLORIDE-IONS ON ADSORPTION AND PERMEATION OF HYDROGEN IN IRON

Effects of chloride ions (Cl-) OR hydrogen absorption into iron and on the hydrogen evolution reaction (HER) on an iron surface were studied in acid and alkaline solutions at 23 degrees C using the permeation m ethod of Devanathan and Stachurski. Cl- ions reduced the overpotential (eta) for HER and in turn, reduced hydrogen coverage and permeation. Effects on hydrogen permeation were more pronounced in alkaline than i n acid solutions. Permeation transients at constant electrode potentia l of the charging surface and subsequent surface analyses of the upper most atom layers of the hydrogen-charged iron surface indicated a reve rsible or low coverage with Cl- ions, a low hydrogen coverage that was not influenced significantly by Cl- ion concentration at low eta, and a marked effect of Cl- ions in reducing hydrogen coverage of the surf ace and permeability in alkaline solutions at high cathodic polarizati ons.