Tafel Constants and Changes in Hydrogen Coverage during Corrosion of Fe18Cr

Abstract

Cathodic Tafel constants associated with the hydrogen reaction at Fel8Cr in H2-saturated 1N H.~SO4 were determined by computer analysis of the potential decay following current interruption at fixed starting potentials positive to the corrosion potential. The values of b = -2.3 RT/aF were evaluated from the general current-interruptive equation, E = Ei + b 9 log [1 + t/v], from its linear log form. and from a modification of the general equation that was derived to analyze multiple TafelElectrochemical Society Active Member.

The kinetics of Anodic dissolution of iron‐chromium alloys in weak acid solutions. Part I. Potentiodynamic and potentostatic investigations

“…The slope b; is attributed to the Volmer-Tafel mechanism with the electrochemical discharge (reaction 1) as the rate-determining step [18-201: This is indicated by values of the reaction order rpH = (6 log i/6 pH)u from -0.4 to -0.5; theoretically -0.5 according to [19]. According to [22] such slopes can be expected if the chemical recombination (reaction 2) is the rate determining step. Relatively unusual are the slopes b near the corrosion potential with -50 to -60 mV for medium and nearly -30 mV for higher chromium contents.…”