Radiotracer study of embedding of SO42− and Cl− ions into the surface film formed on Mn corroding in perchlorate solution

The adsorption of radiolabelled Cl− and SO4− ions from aqueous perchlorate solutions onto powdered Mn metal was studied. It was found that the extent of the adsorption is determined by the continuous increase of the thickness of the surface oxide/hydroxide layer formed as a consequence of the slow corrosion of the metal in neutral or quasi-neutral media. At low pH values (pH < 6) the extent of the adsorption decrease significantly owing to the dissolution of the surface layer. At high pH values (pH > 10) the adsorption decreases presumably owing to the competitive adsorption of OH− ions or the modification of the adsorption centres by some kind of deprotonation.