In Situ Assessment of Pitting Corrosion and Its Inhibition Using a Localized Corrosion Monitoring Technique

Moloney, Jeremy; Mok, W.Y.; Menendez, Carlos M.

doi:10.5006/1.3452399

Cited by 9 publications

(3 citation statements)

References 4 publications

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“…Although the OCP for each experiment was only measured once per day, the fluctuations in these values during the last 20 d of each experiment seemed to indicate a higher probability of localized corrosion. Moloney, et al, 16 found that potential transients in a continuously measured OCP can be directly attributed to pitting activity on the metal surface. Although the data in this current study only reviewed the OCP on a daily basis, when the OCP was not stable (more than ±10 mV fluctuation) Table 4).…”

Section: Setmentioning

confidence: 99%

Comparison of Mono- to Diphosphate Ester Ratio in Inhibitor Formulations for Mitigation of Under Deposit Corrosion

Brown

Saleh

Moloney³

2015

Corrosion

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Mitigation of localized under deposit corrosion (UDC) in upstream oil and gas pipelines is an important research topic for both industry and academia. In a research program to better define the various inhibitor components that provide mitigation of UDC, this initial research investigates the effect of varied ratios of mono-to dinonylphenol phosphate esters (PE) by testing a set of specifically formulated inhibitors. Inhibitors with three monoto di-PE ratios were tested in the presence and absence of 2-mercaptoethanol (ME). Using two 1.25 in (3.18 cm) diameter API 5L X65 pipeline steel samples and 250 μm silica sand, UDC testing was conducted for 28 d in a CO 2 saturated solution at 70°C and 1 bar (100 kPa) total pressure. Analysis has shown that localized corrosion (pit penetration rate) increased for ME-free nonylphenol PE as the concentrations of di-PEs and mono-PEs approached equivalency. The nonylphenol PE inhibitor with a 50:50 mono-to di-PE ratio at 100 ppm concentration failed to protect the surface of the sample under the individual sand grains. Even the base product inhibitor package with no PE provided better mitigation under these test conditions than the 50:50 mono-to dinonylphenol PE. However, it was observed that the addition of ME provided a dramatic improvement in the mitigation of UDC for each mono-to di-PE ratio of the nonylphenol PE tested. From this research, it is seen that the mono-to di-PE ratio is important to consider when developing corrosion inhibitors containing PEs.

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Section: Setmentioning

confidence: 99%

Comparison of Mono- to Diphosphate Ester Ratio in Inhibitor Formulations for Mitigation of Under Deposit Corrosion

Brown

Saleh

Moloney³

2015

Corrosion

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“…Additionally, the LPR method found application in other fields where galvanic and hence uniform corrosion occurs, such as in water supply systems [ 24 ] or for monitoring pipelines in the oil and gas industry. [ 25 ]…”

Section: Introductionmentioning

confidence: 99%

A new perspective on measuring the corrosion rate of localized corrosion

Angst

Büchler

2020

Materials & Corrosion

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Many corrosion phenomena are nonuniform, which means that anodic and cathodic locations are spatially separated. An example is macrocell corrosion of steel in concrete. Under these conditions, determining the corrosion rate from polarization resistance measurements and using the Stern-Geary equation is fundamentally not possible. We present a novel theoretical approach for the interpretation of galvanostatic pulse measurements, to make them applicable as a method for corrosion rate measurements in situations of localized corrosion. Experiments show that it is important to consider that (a) only a fraction of the applied current flows through the anode of the macrocell, and (b) this current is not constant over time. We propose an approach to quantify and consider these two effects, based on information generally accessible in condition assessment of concrete structures. Our results show that galvanostatic pulse measurements are a robust method to determine the corrosion current. With the traditional empirical approach, the measurement error was generally below factor 3, and occasionally up to factor 10. With the novel approach, this error could be reduced to a factor of maximum 2 in all cases. K E Y W O R D Scorrosion rate, galvanic corrosion, localized corrosion, macrocell corrosion, test method

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“…The linear polarization resistance method has been used in many applications where galvanic corrosion is likely to occur, such as in water supply systems and for pipelines in the oil and gas industry . To determine instantaneous corrosion rates of steel in concrete, the linear polarization resistance method was first applied in the 1970s .…”

Section: Introductionmentioning

confidence: 99%

On the applicability of the Stern–Geary relationship to determine instantaneous corrosion rates in macro‐cell corrosion

Angst

Büchler

2014

Materials & Corrosion

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The well‐known Stern–Geary equation was derived on the basis of the theory by Wagner and Traud and relies on the so‐called mixed potential of an electrode subject to uniform corrosion. Nevertheless, it is common practice to apply the linear polarization method to determine instantaneous corrosion rates in situations of galvanic corrosion. In the present work, the applicability of the Stern–Geary equation to galvanic corrosion was in detail discussed both with help of theoretical considerations and experimental measurements. The primary reason why the application of the Stern–Geary equation to galvanic corrosion is fundamentally incorrect is the fact that a well‐defined mixed potential does for galvanic elements not exist. In this work, equations were derived that allow a correct calculation of the corrosion rate for galvanic cells. However, the required variables can, in usual practical situations, not be measured. Application of the Stern–Geary equation to galvanic cells is in the literature claimed (or assumed) to yield adequate results. An explanation for this apparent applicability was identified in the fact that two major errors have a compensating effect so that they tend to cancel each other out. The extent to which this is possible depends strongly on the actual conditions such as the geometry of the galvanic cell as well as on the position of the counter and the reference electrode (RE). Nevertheless, since this apparent applicability is owing to specific conditions rather than a fundamental applicability of the method, further research is clearly needed to characterize these conditions and their limits in detail.

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In Situ Assessment of Pitting Corrosion and Its Inhibition Using a Localized Corrosion Monitoring Technique

Cited by 9 publications

References 4 publications

Comparison of Mono- to Diphosphate Ester Ratio in Inhibitor Formulations for Mitigation of Under Deposit Corrosion

Comparison of Mono- to Diphosphate Ester Ratio in Inhibitor Formulations for Mitigation of Under Deposit Corrosion

A new perspective on measuring the corrosion rate of localized corrosion

On the applicability of the Stern–Geary relationship to determine instantaneous corrosion rates in macro‐cell corrosion

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