The influence of sulphide, bicarbonate and carbonate on the electrochemistry of carbon steel in slightly alkaline solutions

• Published in: Corrosion science Vol. 169; p. 108607
• Main Authors: Goldman, Maxwell, Tully, Claire, Noël, James J., Shoesmith, David W.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01-06-2020; Elsevier BV
• Subjects: Alkaline corrosion; Anodic dissolution; Bicarbonates; Carbon steel; Carbon steels; Cyclic voltammetry; Dissolution; Electrochemistry; Passivity; Pyrite; Raman spectroscopy; Sulfides; Cyclic voltammetry; Alkaline corrosion; Carbon steel; Raman spectroscopy; Passivity
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2020.108607

•Sulphides (< 10−6 M) interfere with the passivity of FeIIIoxides in alkaline conditions.•Sulphides are able to chemically reduce FeIIIoxides.•Surface analysis shows the presence of elemental S and SO42−.
The influence of sulphide on the electrochemistry of carbon steel in neutral to slightly alkaline sulphide solutions was investigated using electrochemical and surface analytical techniques. Small concentrations of sulphide were found to promote anodic dissolution as FeII carbonate complexes and to destabilize FeIII oxides leading to the loss of passivity, especially at pH ≤ 9. The dominant phase formed was mackinawite, while reactions between FeIII and sulphide led to the formation of oxidized S species (elemental Sand sulphate), polysulfides, and pyrite.