Study of criterion for assuring the effectiveness of cathodic protection of buried steel pipelines being interfered with alternative current

He, Xingwei; Jiang, Guancheng; Qiu, Yubing; Zhang, G.; Jin, Xing; Xiang, Zheng; Zhang, Z.; Tang, Hui

doi:10.1002/maco.201006036

Cited by 10 publications

(7 citation statements)

References 13 publications

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“…Although the ratio between the current densities is equal in the two conditions, they represent a different corrosion risk, i.e., 3 A•m −2 AC density is not recognized as a threat, dissimilarly from 30 A•m −2 . As discussed in Paragraph 3, several authors [21][22][23][24][25][26][27] investigated the effect of i AC /i DC ratio on corrosion rate, proposing different threshold limits. ISO 18086 standard [4] reports that AC corrosion can be mitigated by maintaining the i AC /i DC ratio less than 3 over a representative time (e.g., 24 h) and it is valid for DC density greater than 10 A•m −2 (severe over-protection condition) and AC density over 30 A•m −2 .…”

Section: Ac/dc Current Density Ratiomentioning

confidence: 99%

“…In 2012, He et al [24] report that the average corrosion potential of X65 steel in loam soil moves to more positive values by increasing AC density from 5 to 150 A•m −2 . At 150 A•m −2 , a positive shift of about 200 mV has been measured with respect to the condition without interference.…”

Section: Positive Shift Of Potentialmentioning

confidence: 99%

“…For instance, at 0.1 A•m −2 DC density, the maximum allowed AC density is 2.5 and 20 A•m −2 , considering the corrosion criterion of Figures 4 and 5, respectively. [24]).…”

Section: Acceptable Ac Interference Levels-protection Criteriamentioning

confidence: 99%

“…In 2012, He et al [24] reported a similar approach based on current densities: the AC density threshold increases linearly with CP current density. The criterion (Figure 5) suggests there is not corrosion risk if i AC < 10 + 100•i DC (with i DC ≥ 0.01 A•m −2 ).…”

Section: Acceptable Ac Interference Levels-protection Criteriamentioning

confidence: 99%

“…Fu et al [60] proposed a criterion based on both potential and current densities: potentials more positive than −0.95 V vs. CSE are considered not safe in the presence of AC. The maximum acceptable [24]).…”

Section: Acceptable Ac Interference Levels-protection Criteriamentioning

confidence: 99%

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AC Corrosion of Carbon Steel under Cathodic Protection Condition: Assessment, Criteria and Mechanism. A Review

2020

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Cathodic protection (CP), in combination with an insulating coating, is a preventative system to control corrosion of buried carbon steel pipes. The corrosion protection of coating defects is achieved by means of a cathodic polarization below the protection potential, namely −0.85 V vs. CSE (CSE, copper-copper sulfate reference electrode) for carbon steel in aerated soil. The presence of alternating current (AC) interference, induced by high-voltage power lines (HVPL) or AC-electrified railways, may represent a corrosion threat for coated carbon steel structures, although the potential protection criterion is matched. Nowadays, the protection criteria in the presence of AC, as well as AC corrosion mechanisms in CP condition, are still controversial and discussed. This paper deals with a narrative literature review, which includes selected journal articles, conference proceedings and grey literature, on the assessment, acceptable criteria and corrosion mechanism of carbon steel structures in CP condition with AC interference. The study shows that the assessment of AC corrosion likelihood should be based on the measurement of AC and DC (direct current) related parameters, namely AC voltage, AC and DC densities and potential measurements. Threshold values of the mentioned parameters are discussed. Overprotection (EIR-free < −1.2 V vs. CSE) is the most dangerous condition in the presence of AC: the combination of strong alkalization close to the coating defect due to the high CP current density and the action of AC interference provokes localized corrosion of carbon steel.

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Section: Ac/dc Current Density Ratiomentioning

confidence: 99%

Section: Positive Shift Of Potentialmentioning

confidence: 99%

“…For instance, at 0.1 A•m −2 DC density, the maximum allowed AC density is 2.5 and 20 A•m −2 , considering the corrosion criterion of Figures 4 and 5, respectively. [24]).…”

Section: Acceptable Ac Interference Levels-protection Criteriamentioning

confidence: 99%

Section: Acceptable Ac Interference Levels-protection Criteriamentioning

confidence: 99%

Section: Acceptable Ac Interference Levels-protection Criteriamentioning

confidence: 99%

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AC Corrosion of Carbon Steel under Cathodic Protection Condition: Assessment, Criteria and Mechanism. A Review

2020

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Effect of pH value on corrosion of carbon steel under an applied alternating current

Tang

et al. 2015

Materials & Corrosion

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In this work, corrosion behavior of carbon steel under the application of alternating current (AC) was investigated in electrolyte solutions with five different pH levels, from near-neutral to alkaline condition, through weight loss measurements, potential monitoring techniques, potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS) tests, and surface examination. It is found that the corrosion rate of carbon steel decreases with increasing pH value toward the alkaline end while increases with increasing AC current density. When the solution pH becomes highly alkaline, say, 12, passivation occurs on carbon steel surfaces, with an enlarging passive region as pH increases. However, it is worth noting that the passive film suffers from mechanical breakdown when the applied AC current density reaches a critical level. Based on these results, an AC corrosion mechanism of carbon steel in near-neutral and alkaline environment is proposed.

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Electrochemical studies of the galvanic coupling zinc/pipeline steel in the presence of an applied alternating current

Tang

Long

et al. 2015

Materials & Corrosion

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The effects of alternating current on the galvanic coupling zinc/pipeline steel were investigated in 4 g/L Na 2 SO 4 simulated backfill solution by weight-loss measurements for 96 hr, electrochemical measurements, and surface examinations. Alternating current accelerates the dissolution of zinc significantly but reduces the corrosion rate of pipeline steel. Under an applied alternating current, zinc DC potential shifts negatively while the DC potential shift direction of pipeline steel is closely related to the value of alternating current density. When the alternating current density is low the DC potential shifts negatively. It, however, shifts positively under higher alternating current density. Besides, the coupling current increases with alternating current density.

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Study of criterion for assuring the effectiveness of cathodic protection of buried steel pipelines being interfered with alternative current

Cited by 10 publications

References 13 publications

AC Corrosion of Carbon Steel under Cathodic Protection Condition: Assessment, Criteria and Mechanism. A Review

AC Corrosion of Carbon Steel under Cathodic Protection Condition: Assessment, Criteria and Mechanism. A Review

Effect of pH value on corrosion of carbon steel under an applied alternating current

Electrochemical studies of the galvanic coupling zinc/pipeline steel in the presence of an applied alternating current

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