Impact of oxygen contamination on the electrochemical impedance spectroscopy of iron corrosion in H2S solutions

• Published in: Corrosion science Vol. 164; p. 108302
• Main Authors: Deffo Ayagou, Martien Duvall, Joshi, Gaurav R., Mai Tran, Thi Tuyet, Tribollet, Bernard, Sutter, Eliane, Mendibide, Christophe, Duret-Thual, Claude, Kittel, Jean
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.03.2020; Elsevier BV; Elsevier
• Subjects: Chemical Sciences; Contamination; Corrosion; Corrosion tests; Critical components; EIS; Electrochemical corrosion; Electrochemical impedance spectroscopy; ELectrochemical methods; H2S; Hydrogen; Hydrogen charging; Hydrogen permeation; Hydrogen permeation studies; Hydrogen reduction; Hydrogen sulfide; Impedance spectroscopy; Iron; Iron sulfides; Material chemistry; Materials selection; Oxygen; Oxygen contamination; Penetration; Permeation; Pollution induced corrosion; Safety critical; Safety critical components; Safety engineering; Saturated solutions; Spectroscopy; Spectrum analysis; Sulfur compounds; Weight loss measurement; H2S; Oxygen; Iron; Corrosion; EIS; H 2 S; iron; oxygen
• ISSN: 0010-938X; 1879-0496; 1879-0496
• DOI: 10.1016/j.corsci.2019.108302

•Corrosion of pure iron in H2S saturated water leads to the formation of a thick and porous scale of conductive iron sulfide.•Due to its conductive and porous nature, this scale has a huge impact on the impedance of the metal at the corrosion potential.•O2 contamination significantly affects this scale, by decreasing the thickness, porosity, and adherence to the metal.•O2 contamination also aggravates the corrosion rate. Oxygen pollution in hydrogen sulfide (H2S) saturated test solutions can compromise the results of standardized tests, which guide materials selection in safety-critical components. To examine the temporal evolution of such contamination, we have used the electrochemical methods of impedance spectroscopy and hydrogen permeation to study the corrosion of iron exposed to oxygen-polluted H2S-saturated solutions. EIS analyses were performed with a previously developed model, which explicitly accounts for the contribution of a conductive and porous iron sulfide overlayer. A good correlation is found between corrosion estimates from EIS and weight loss, measured to be higher than the O2-free case. Hydrogen permeation studies across the iron membrane were conducted to qualitatively evaluate the impact of dissolved O2 on hydrogen entry. We observe that O2 contamination was found to significantly reduce hydrogen charging into the metal.