An In-Situ Galvanically Coupled Multielectrode Array Sensor for Localized Corrosion

Yang, Lietai; Sridhar, Narasi; Pensado, Osvaldo; Dunn, Darrell S.

doi:10.5006/1.3280789

Cited by 55 publications

(31 citation statements)

References 7 publications

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“…WBE, [36][37][38][39][40][41] CMAS 42 or any other 10,15,23 ) exposed to an electrolyte at OCP. In order to satisfy the principle of conservation of charge, the summation of the net current measured at all the electrodes must equal zero.…”

Section: Calculation Of Metal Loss Distribution Based Of Faraday'smentioning

confidence: 99%

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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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Section: Calculation Of Metal Loss Distribution Based Of Faraday'smentioning

confidence: 99%

“…Two-dimensional electrochemically integrated electrode arrays such as the wire beam electrode (WBE) 36-41 and the coupled multielectrode array sensor (CMAS) 42 have been previously used to study non-homogeneous corrosion conditions. The DAS takes advantage of the higher spatial and temporal resolution of the WBE compared to segmented electrodes used in …”

mentioning

confidence: 99%

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

Varela

Tan

Forsyth

2015

J. Electrochem. Soc.

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“…Another limitation of these methods is that they are based on ideally homogenous electrodes and could only provide spatially averaged corrosion information. In an attempt to evaluate the maximum local corrosion rate produced under CP, Sun 10,11 used the method developed by Yang et al 12 based on a coupled multi-electrode array to estimate the largest anodic current density based on statistical parameters by assuming that the local current densities measured at each electrode follow a normal distribution. Unfortunately they did not correlate individual local current density values with visual observation of localized corrosion damage on the array.…”

mentioning

confidence: 99%

An Electrochemical Method for Measuring Localized Corrosion under Cathodic Protection

Varela

Tan

Forsyth

2014

ECS Electrochemistry Letters

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A new method has been developed to measure metal corrosion rates and their distribution under cathodic protection (CP). This method uses an electrochemically integrated multi-electrode array to take local measurements of cathodic current density while simulating a continuous metallic surface. The distribution of cathodic current densities obtained under CP was analyzed to estimate the anodic current component at each electrode of the array. Corrosion patterns determined by this new method have shown good correlation with visual inspection and surface profilometry of the multi-electrode array surface.

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“…Identical electrodes were used as the working, counter, and reference electrodes for LPR measurements. A CMAS measuring system described in [6] was used with the CMAS probes. A multichannel potentiostat was used to automatically conduct the polarization on the LPR electrodes for corrosion rate measurements and to measure the open circuit potential of the electrodes between the polarization measurements.…”

Section: Methodsmentioning

confidence: 99%

Boric Acid Corrosion of Concrete Rebar

Pabalan

Yang²,

Chiang

2013

EPJ Web of Conferences

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Abstract. Borated water leakage through spent fuel pools (SFPs) at pressurized water reactors is a concern because it could cause corrosion of reinforcement steel in the concrete structure and compromise the integrity of the structure. Because corrosion rate of carbon steel in concrete in the presence of boric acid is lacking in published literature and available data are equivocal on the effect of boric acid on rebar corrosion, corrosion rate measurements were conducted in this study using several test methods. Rebar corrosion rates were measured in (i) borated water flowing in a simulated concrete crack, (ii) borated water flowing over a concrete surface, (iii) borated water that has reacted with concrete, and (iv) 2,400 ppm boric acid solutions with pH adjusted to a range of 6.0 to 7.7. The corrosion rates were measured using coupled multielectrode array sensor (CMAS) and linear polarization resistance (LPR) probes, both made using carbon steel. The results indicate that rebar corrosion rates are low (~1 µm/yr or less) when the solution pH is ~7.1 or higher. Below pH ~7.1, the corrosion rate increases with decreasing pH and can reach ~100 µm/yr in solutions with pH less than ~6.7. The threshold pH for carbon steel corrosion in borated solution is between 6.8 and 7.3.

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An In-Situ Galvanically Coupled Multielectrode Array Sensor for Localized Corrosion

Cited by 55 publications

References 7 publications

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

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

An Electrochemical Method for Measuring Localized Corrosion under Cathodic Protection

Boric Acid Corrosion of Concrete Rebar

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