Author:
Berntsen T.,Seiersten M.,Hemmingsen T.
Abstract
The effect on corrosion of carbon steel of varying bicarbonate (HCO3−) and ferrous ion (Fe2+) concentrations in carbon dioxide (CO2) purged in 1 wt% sodium chloride (NaCl) and 50 wt% monoethylene glycol (MEG, C2H6O2) solutions was studied. The iron carbide (Fe3C) in the steel was exposed by pre-corrosion to explore its role in the iron carbonate (FeCO3) film formation process at pH-stabilized conditions. The corrosion layers formed ranged from being protective and showing passive behavior (corrosion potential approximately −0.5 V vs. silver/silver chloride [Ag/AgCl]) to being non-protective despite highly supersaturated solutions and long exposure times. The corrosion rate and potential development are discussed based on thermodynamic, kinetic, and electrochemical principles. The corrosion potential increased sharply after a protective FeCO3 film was established, indicating passivation. New reaction mechanisms are proposed at these high potentials, which are more anodic than that obtainable by H+ reduction. Dissolved Fe3C and magnetite (Fe3O4) are important factors in this passive potential range.
Subject
General Materials Science,General Chemical Engineering,General Chemistry
Cited by
49 articles.
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