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Speciation and electrochemistry of brines containing acetate ion and carbon dioxide

Speciation and electrochemistry of brines containing acetate ion and carbon dioxide
Speciation and electrochemistry of brines containing acetate ion and carbon dioxide
The corrosion of carbon steel, oilfield pipelines is accelerated when the anion of a weak acid (usually considered to be acetate) is present in the carbon dioxide saturated brines that usually accompany the production of the oil. This paper reports the voltammetry of such media at both platinum and carbon steel (X65) rotating disc electrodes in order to demonstrate that the solution composition as well as the surface films determine the rate of corrosion. It is shown that the cathode reactions at Pt and in the corrosion process at steel are the parallel reduction of free proton and the strongest proton donor in the solution. In these solutions, the strongest proton donor is acetic acid and at the usual pH of the brines, the concentration of acetic acid is substantially higher than that of the free proton. As a result, the concentration of the proton donor, the undissociated weak acid, rather than the pH. is a critical factor determining the rate of corrosion of the steel. A quantitative interpretation of the voltammetry and the corrosion behaviour requires a knowledge of the speciation within these complex aqueous solutions and in this paper, the speciation is calculated using equilibrium constants from the literature and a computer package (PHREEQC 2.2).
acetate/carbon dioxide solutions, acetic acid reduction, steel corrosion, steady-state voltammetry, weak acids, supporting electrolyte, hydrogenevolution, microelectrodes, corrosion
1572-6657
285-297
Garsany, Yannick
699dc832-7052-4820-80f4-ade41a7180d0
Pletcher, Derek
f22ebe69-b859-4a89-80b0-9e190e6f8f30
Hedges, Bill
005e9d9a-1f03-4d54-b1cb-e7b521daf163
Garsany, Yannick
699dc832-7052-4820-80f4-ade41a7180d0
Pletcher, Derek
f22ebe69-b859-4a89-80b0-9e190e6f8f30
Hedges, Bill
005e9d9a-1f03-4d54-b1cb-e7b521daf163

Garsany, Yannick, Pletcher, Derek and Hedges, Bill (2002) Speciation and electrochemistry of brines containing acetate ion and carbon dioxide. Journal of Electroanalytical Chemistry, 538-539, 285-297. (doi:10.1016/S0022-0728(02)00728-3).

Record type: Article

Abstract

The corrosion of carbon steel, oilfield pipelines is accelerated when the anion of a weak acid (usually considered to be acetate) is present in the carbon dioxide saturated brines that usually accompany the production of the oil. This paper reports the voltammetry of such media at both platinum and carbon steel (X65) rotating disc electrodes in order to demonstrate that the solution composition as well as the surface films determine the rate of corrosion. It is shown that the cathode reactions at Pt and in the corrosion process at steel are the parallel reduction of free proton and the strongest proton donor in the solution. In these solutions, the strongest proton donor is acetic acid and at the usual pH of the brines, the concentration of acetic acid is substantially higher than that of the free proton. As a result, the concentration of the proton donor, the undissociated weak acid, rather than the pH. is a critical factor determining the rate of corrosion of the steel. A quantitative interpretation of the voltammetry and the corrosion behaviour requires a knowledge of the speciation within these complex aqueous solutions and in this paper, the speciation is calculated using equilibrium constants from the literature and a computer package (PHREEQC 2.2).

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More information

Published date: 13 December 2002
Keywords: acetate/carbon dioxide solutions, acetic acid reduction, steel corrosion, steady-state voltammetry, weak acids, supporting electrolyte, hydrogenevolution, microelectrodes, corrosion

Identifiers

Local EPrints ID: 19742
URI: http://eprints.soton.ac.uk/id/eprint/19742
ISSN: 1572-6657
PURE UUID: b2c09649-91f0-4648-b607-759942eb2678

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Date deposited: 20 Feb 2006
Last modified: 08 Jan 2022 06:46

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Contributors

Author: Yannick Garsany
Author: Derek Pletcher
Author: Bill Hedges

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