Mechanism of the initial stages of iron passivation in acidic sulfate solutions

Abstract

Anodic and cathodic potentiostatic current transients of freshly formed iron (99.95%) electrodes in 0.5 M aqueous acidic (pH 1.7–3.2) sulfate solutions are examined. The initial stages of iron passivation are confirmed to be determined by the following several processes each prevailing in a definite period: the formation of surface charge-transfer complexes (H2O) δ+ ads (first 3–5 ms) and their transformation into adsorbed OH− groups (subsequent 10–50 ms) with the concurrent adsorption of hydrogen atoms Hads by iron.