Comments on E. Huttunen-Saarivirta et al., “Kinetic Properties of the Passive Film on Copper in the Presence of Sulfate-Reducing Bacteria” [ J. Electrochem. Soc. , 165, C450 (2018)]

Abstract

© 2019 Electrochemical Society Inc.. All rights reserved. TheHuttunen-Saarivirta et al. study1 offers no undisputed evidence regarding the presence of a passive Cu2S film. The authors misinterpreted both electrochemical and surface analysis data, ignoring the abundance of literature that concludes that Cu2S films grown under similar conditions are in fact porous in nature. Using vacancy concentration values generated by their Equation 3 without considering that they were many orders of magnitude beyond what is physically pos-c sible led to a nonsensical output from the calculations. The majority of the argument regarding the barrier layer lies within the impedance data analysis, for which the conclusion about passivity is, a priori, made inescapable by applying the PDM. Considering the previous literature and the critical examination presented here, we posit that the Cu2S films analyzed by Huttunen- Saarivirta et al.1 were porous in nature and the susceptibility of Cu to localized corrosion processes, such as SH-induced pitting, under the investigated conditions is of low probability.