Corrosion Consequences of Secondary Oxidation of Microbial Corrosion

Jack, Thomas R.; Wilmott, M.; Stockdale, J.; Boven, Greg Van; Worthingham, Robert; Sutherby, Robert

doi:10.5006/1.3284850

Cited by 24 publications

(37 citation statements)

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“…However, there are particular situations in which SRB-induced biocorrosion can be further exacerbated. Ingress of molecular oxygen (32)(33)(34)51) into previously anoxic systems can lead to the formation of highly corrosive sulfur species from the partial oxidation of dissolved H 2 S and biogenic FeS deposits at steel surfaces (123)(124)(125). This can even further impair metals that have already been damaged by SRB.…”

Section: Discussionmentioning

confidence: 99%

“…Under anoxic conditions or in systems with only temporary O 2 ingress, microbial corrosion tends to be even more pronounced. Here, corrosion results from microbial metabolic products such as organic acids (27,28), hydrogen sulfide (12,29,30), or other corrosive sulfur species (31)(32)(33)(34). In addition to these indirect effects, more-direct interactions between certain microorganisms and iron have been demonstrated (12,(35)(36)(37)(38)(39).…”

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confidence: 99%

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Corrosion of Iron by Sulfate-Reducing Bacteria: New Views of an Old Problem

Enning

Garrelfs

2014

Appl Environ Microbiol

680

414

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About a century ago, researchers first recognized a connection between the activity of environmental microorganisms and cases of anaerobic iron corrosion. Since then, such microbially influenced corrosion (MIC) has gained prominence and its technical and economic implications are now widely recognized. Under anoxic conditions (e.g., in oil and gas pipelines), sulfate-reducing bacteria (SRB) are commonly considered the main culprits of MIC. This perception largely stems from three recurrent observations. First, anoxic sulfate-rich environments (e.g., anoxic seawater) are particularly corrosive. Second, SRB and their characteristic corrosion product iron sulfide are ubiquitously associated with anaerobic corrosion damage, and third, no other physiological group produces comparably severe corrosion damage in laboratory-grown pure cultures. However, there remain many open questions as to the underlying mechanisms and their relative contributions to corrosion. On the one hand, SRB damage iron constructions indirectly through a corrosive chemical agent, hydrogen sulfide, formed by the organisms as a dissimilatory product from sulfate reduction with organic compounds or hydrogen ("chemical microbially influenced corrosion"; CMIC). On the other hand, certain SRB can also attack iron via withdrawal of electrons ("electrical microbially influenced corrosion"; EMIC), viz., directly by metabolic coupling. Corrosion of iron by SRB is typically associated with the formation of iron sulfides (FeS) which, paradoxically, may reduce corrosion in some cases while they increase it in others. This brief review traces the historical twists in the perception of SRB-induced corrosion, considering the presently most plausible explanations as well as possible early misconceptions in the understanding of severe corrosion in anoxic, sulfate-rich environments. E ver since its first production roughly 4,000 years ago, iron has played a central role in human society due to its excellent mechanical properties and the abundance of its ores. Today, iron is used in much larger quantities than any other metallic material (1) and is indispensable in infrastructure, transportation, and manufacturing. A major drawback is the susceptibility of iron to corrosion. Corrosion of iron and other metals causes enormous economic damage. Across all industrial sectors, the inferred costs of metal corrosion have been estimated to range between 2% and 3% of gross domestic product (GDP) in developed countries (2, 3). These costs are to a large extent caused by corrosion of iron, due to its abundant use and particular susceptibility to oxidative damage. Estimates of the costs attributable to biocorrosion of iron lack a computed basis so that they vary widely, and definite numbers cannot be given with certainty. Still, microbially influenced corrosion (MIC) probably accounts for a significant fraction of the total costs (4-7), and, due to its effects on important infrastructure in the energy industry (such as oil and gas pipelines), costs in the range of billions of...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Corrosion of Iron by Sulfate-Reducing Bacteria: New Views of an Old Problem

Enning

Garrelfs

2014

Appl Environ Microbiol

680

414

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“…[8][9][10][11][12][13]15,16,18,19,21,23,33 However, it is difficult to correlate local potential values with corrosion rates without more information regarding the local conditions. Corrosion rates are related to the anodic dissolution kinetics which are constantly influenced by factors such as CP potential, as well as changes in oxygen concentration, [11][12][13]17,18,22,23,32 pH, 10,12,13,[16][17][18][19]21,22,[33][34][35] and concentration of other species 16,17,22,35 present under disbonded coatings, which affect the passivity of the metal.…”

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confidence: 99%

“…26,27 Electrochemical monitoring methods, on the other hand, are characterized by a high sensitivity to corrosion processes. These methods, which include potential monitoring, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS), have been employed for measuring corrosion related parameters in soil, at open circuit potential (OCP).28,29 However, CP introduces significant challenges when using such techniques for measuring corrosion rates, since these traditional electrochemical methods are not directly applicable at an externally fixed CP potential.30,31 Furthermore, given that disbonded coatings promote the development of a local environment that significantly differs from the bulk, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]32,33 the use of either corrosion coupons or sensors directly exposed to the bulk soil does not adequately represent the corrosion susceptibility under disbonded coatings. Therefore, the development of a sensor that could use electrochemical means to evaluate corrosion under more realistic conditions would be an important step.…”

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confidence: 99%

“…This phenomenon is particularly serious for buried pipelines, because the typically resistive soil solution could prevent CP current from reaching deep into the crevice created by the disbondment. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Disbonded coatings are generally considered a 'worst case scenario' for pipeline corrosion. Therefore, early detection of insufficient CP and corrosion within such crevice environments is critical.…”

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Electrochemical Method for Studying Localized Corrosion beneath Disbonded Coatings under Cathodic Protection

Varela

Tan

Forsyth

2015

J. Electrochem. Soc.

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This paper presents a new method for measuring localized corrosion under disbonded coatings by means of an electrochemical sensor, denoted differential aeration sensor (DAS). It measures the distribution of electrochemical currents over an electrode array surface partially covered by a crevice that simulates a disbonded coating. The DAS has been evaluated using immersion tests at open circuit and under cathodic protection (CP) conditions. Under both conditions, anodic as well as cathodic current densities were detected within the crevice. A fundamental understanding for the detection of anodic currents under CP has been explained in terms of basic electrochemistry. Based on the current distribution data provided by the sensor, two different analysis methods have been used to estimate corrosion and its distribution. These methods consisted of a direct application of Faraday's Law to the anodic currents detected by the array, and on a sensor-specific method denoted 'corrected currents' method. It has been demonstrated that under diffusion controlled conditions this latter method produces a better corrosion estimation than the direct application of Faraday's Law. The 'corrected currents' method allowed the estimation of corrosion patterns outside the crevice under CP. Good correlation between electrochemical calculations and surface profilometry results has been obtained. Cathodic protection (CP) is typically applied in combination with barrier coatings to prevent corrosion of steel on buried structures such as in water and energy pipelines. However, this combination is not always effective. Industrial experience has shown that severe localized corrosion issues such as pitting, microbiological induced corrosion and stress corrosion cracking can still occur within these structures, and these occurrences are often related to disbonded coatings. [1][2][3][4][5][6] Coating disbandment is common in buried pipes, particularly when CP is applied, 3,7 leading to the formation of a crevice (or gap) between the metal surface and the disbonded coating layer. Solution from the surrounding environment can access these crevices, resulting in enclosed corrosive environments. Furthermore, the effectiveness of the applied CP is believed to decrease significantly within the crevice due to a phenomenon often referred to as cathodic shielding. This phenomenon is particularly serious for buried pipelines, because the typically resistive soil solution could prevent CP current from reaching deep into the crevice created by the disbondment. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Disbonded coatings are generally considered a 'worst case scenario' for pipeline corrosion. Therefore, early detection of insufficient CP and corrosion within such crevice environments is critical.Potential survey methods, currently used by the pipeline industry, are not able to provide information about the CP effectiveness under a disbonded coating.Whilst the use of in-line metal loss inspection tools can detect pipeline corrosion (includ...

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