Investigation of Pseudo-Passivation of Mild Steel in CO2 Corrosion

Abstract

The iron carbonate corrosion product layer formed on mild steel in carbon dioxide (CO 2 ) environments is known to retard corrosion. When not fully covering the steel surface, it may also lead to initiation of localized corrosion, due to a galvanic effect. In this work, the stability of a protective iron carbonate layer has been studied at 80°C over a relatively wide range of bulk pH. Experiments were done in a glass cell using a threeelectrode system. Electrochemical techniques such as linear polarization resistance (LPR) and potentiodynamic polarization (PP) were used. Surface analysis techniques (scanning electron microscopy [SEM], x-ray diffraction [XRD], and transmission electron microscopy [TEM]) were used to confi rm the composition and structure of the protective layer. Experimental results confi rmed a pseudo-passive behavior, indicated by a positive shift in the open-circuit potential and a signifi cantly retarded corrosion rate for systems at pH 6.0 and above. However, a stable and protective pseudo-passive layer could not be formed at pH 5.6 or lower.

Effect of graphene oxide nanoplatelets on electrochemical properties of steel substrate in saline media

“…8 where polarization resistance efficiency was increased up to 60%. These results are accordance with the EIS result and also indicate that precipitation on the WE slows down the easy transfer of corrosion products and reactant from bulk solution to WE surface [34].…”

The Coupling Effect of O2 and H2S on the Corrosion of G20 Steel in a Simulating Environment of Flue Gas Injection in the Xinjiang Oil Field

“…Once Fe 2+ and CO 3 2 − are present at the steel/solution interface at sufficiently high concentrations, which make the product of [Fe 2+ ] × [CO 3 2 − ] exceed the solubility product of FeCO 3 , precipitation and crystal growth will occur [26], as described in Equation (11):Fe 2+ + CO 3 2 − → FeCO 3 .…”

“…This is attributed to the relatively high CO 2 partial pressure and high pH in the experimental environment. The CO 2 partial pressure in each condition was up to 2.25 MPa, and the pH in corrosive solution was 7.0, which favored the formation of FeCO 3 [26]. …”

Corrosion Behavior of Carbon Steels in CCTS Environment

“…Significant increase in open circuit potential and a decrease of the corrosion rate were observed at pH 8, owing to the formation of a mixed film of FeCO 3 and magnetite (Fe 3 O 4 ). Li et al reported that the pseudopassivation could not be achieved at pH 5.6 [19]. At pH 3, the scale is mainly constituted by siderite, which does not promote a passive or pseudopassive state.…”