Electrochemistry of mackinawite electrodes in sour aqueous solutions

Abstract

Iron sulfide, frequently found on carbon steel exposed to sour conditions, is under certain conditions expected to act as a (large area) cathode thereby increasing the corrosion rate of the underlying steel through galvanic coupling. In this work electrochemical reactions taking place at mackinawite (the most common low temperature polymorph of iron sulfide) electrodes in sour aqueous solutions have been studied using electrochemical techniques and the effect of mass transport was obtained using a jet impingement setup. The main objective was to obtain current-potential relations for iron sulfides which can be taken into a modelling framework, thereby allowing the estimation of the galvanic coupling between carbon steel and iron sulfides under different environmental conditions. In order to do so a method to produce mackinawite electrodes was developed. Part of this paper is therefore devoted to describing the FeS manufacturing process and to some physical characteristics to the produced mackinawite and the electrode itself. Paper reproduced with permission from CORROSION/2017 Annual Conference and Exhibition. www.nace.org