Corrosion Monitoring Techniques Research Articles

Performance Evaluation of Potassium Dichromate and Potassium Chromate Inhibitors on Concrete Steel Rebar Corrosion

This study investigated the performance of potassium dichromate and potassium chromate inhibitors on the corrosion of steel rebar in concrete partially immersed in sulfuric acid and sodium chloride medium. The open circuit potential corrosion monitoring technique was employed for the acidic and marine simulating environments, and potential readings were taken in accordance with ASTM C 876. Inhibiting quality and uniformity of the inhibitors were then analyzed using an extreme value statistical modeling approach of the Weibull probability density distribution for determining the most efficient inhibitor. In the inhibitor concentrations used, the statistically analyzed experimental results identified 0.145 M potassium chromate as exhibiting the best inhibiting quality in sulfuric acid whereas the synergetic admixture of 0.032 M potassium dichromate and 0.097 M potassium chromate was predicted as showing the lowest probability of corrosion risk in sodium chloride solution. However, the overall probabilistic results rated potassium chromate as the best inhibitor compared to potassium dichromate in most of the other concentrations investigated in the study, especially in concrete structures exposed to saline environments.

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

Abstract Pitting corrosion of pipelines remains a serious concern to operators in the oil and gas industry. Pitting is a particularly insidious and extremely rapid form of attack of a metal structu...

Longitudinal Guided Waves for Monitoring Chloride Corrosion in Reinforcing Bars in Concrete

Corrosion of reinforcing steel in concrete is one of the major durability problems faced by civil engineers as they maintain an aging infrastructure. The problem accelerates since steel is embedded inside concrete. If it remains unnoticed inside concrete, it further accelerates and can cause loss of life and property. This article discusses a nonintrusive corrosion monitoring technique for early detection of damages in steel embedded in concrete. Corrosion manifests itself in debond and pitting steel bars. Guided ultrasonic waves offer a potentially attractive solution for this problem. But it is imperative to excite the right mode for detection of a particular type of corrosion. In the present work, longitudinal guided ultrasonic waves have been utilized to monitor notch and debond defects in steel bars in concrete simulating pitting and delamination phenomena caused by corrosion. Two ultrasonic techniques of pulse transmission and pulse echo were used to monitor the healthy and damaged specimens. The developed methodology is successfully applied for real time monitoring of RC beam specimens undergoing accelerated chloride corrosion. The ultrasonic signals effectively relate to the state of reinforcing bars.

The Efficiency of Corrosion Inhibitor as Given by Electrochemical Impedance Spectroscopy Tafel Polarization and Weight-Loss Measurements

ABSTRACT The compound 6-methylquinoxalin-2(1H)-one (Q-CH3) was synthesized, and its inhibiting action on the corrosion of mild steel in 1M HCl was investigated by various corrosion-monitoring techniques: electrochemical and weight-loss measurements. Results showed that this compound has fairly good inhibiting properties for steel corrosion in acidic medium, with efficiencies of around 97% at a concentration of 10−2 M. The protection efficiency of this inhibitor decreases slightly with the rise of temperature, and it is improved with the immersion time.

Assessment of EFM as a new nondestructive technique for monitoring the corrosion inhibition of low chromium alloy steel in 0.5 M HCl by tyrosine

Electrochemical frequency modulation (EFM), a nondestructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is applied here to investigate the inhibition performance of tyrosine (Tyr) toward corrosion of low chromium alloy steel in 0.50 M HCl. Measurements were conducted under various experimental conditions in the range of temperature (20–60 °C). Results obtained from EFM were compared with other traditional corrosion monitoring techniques, namely Tafel extrapolation, impedance, and weight loss. Polarization measurements showed that Tyr acted as a mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protected the metal against corrosive agents. Energy dispersive X-ray spectroscopy and scanning electron microscopy examinations of the electrode surface confirmed the existence of such an adsorbed film. The inhibition efficiency increased with increase in Tyr concentration, while it decreased with solution temperature. The adsorptive behavior of Tyr on the electrode surface followed Temkin-type isotherm. Thermodynamic functions for the adsorption process were determined. The data obtained from the different methods were in good agreements, which indicated that the EFM technique was valid for monitoring the corrosion inhibition under the studied conditions.

Techbits: Subsurface Corrosion Spotlighted at Workshop

Techbits Corrosion remains a major challenge to maintaining the integrity of infrastructure in oil and gas fields, particularly at the subsurface. A recent SPE Applied Technology Workshop in Abu Dhabi, UAE called "Subsurface Corrosion Risks and Challenges" highlighted critical aspects of subsurface corrosion control, including selection of corrosion-protection methods, improving drilling practices to minimize corrosion, and assessing downhole corrosion-monitoring techniques. The welcome address by Qasem al-Kayoumi of Zadco highlighted the importance of organizations working together to identify critical subsurface corrosion challenges, share and agree on best practices, and identify the best existing downhole corrosion-mitigation technologies. To understand the technical areas where additional focus is required, networks must be formed between the operators, well engineers, and service providers. Al-Kayoumi said that Zadco has gained valuable subsurface experience by creating a seamless co-operative relationship with other operators. Zadco has also sponsored projects for downhole corrosion-modeling programs. Materials for Oil and Gas Production The first technical session of the work-shop highlighted materials used in oil and gas production. Keynote speaker Bijan Kermani of KeyTech opened by stating that hydrocarbons will continue to be the world's principal energy source in the foreseeable future. The expected growth in energy demand will spur increases in production, which will become more multiphase in nature and contain higher percentages of harsh components such as hydrogen sulfide (H2S) and carbon dioxide (CO2). These acid gases in high water-cut production systems present major corrosion concerns. Therefore, material selection must become more specific to mitigate corrosion, and the impact of corrosion with regards to health, safety, and the environment; capital expenditure; and operational expenditure must receive continued serious consideration. Kermani said that materials selection must be coupled with ‘near-realistic’ corrosion modeling and prediction for optimum integrity assurance. Zadco's Obadah Al-Sawadi next discussed the principles of corrosion modeling and prediction as they relate to materials selection. He stated that any useful model should be able to accurately predict corrosion rates as operating conditions change and account for actual tubing conditions rather than predict the phenomena at only one set of design conditions. A successful modeling program should also clearly define target corrosion rates to assess whether carbon steel or a corrosion-resistant alloy (CRA) should be employed. Finally Al-Sawadi highlighted several continuing challenges for accurate modeling programs, including obtaining accurate field data, the large number of variables involved and their relevance, and changes in the operating regime.

Proper Inventory Management Requires Sound Analysis and Technology

Management Corrosion remains a major challenge to maintaining the integrity of infrastructure in oil and gas fields, particularly at the subsurface. A recent SPE Applied Technology Workshop in Abu Dhabi, UAE called "Subsurface Corrosion Risks and Challenges" highlighted critical aspects of subsurface corrosion control, including selection of corrosion-protection methods, improving drilling practices to minimize corrosion, and assessing downhole corrosion-monitoring techniques. The welcome address by Qasem al-Kayoumi of Zadco highlighted the importance of organizations working together to identify critical subsurface corrosion challenges, share and agree on best practices, and identify the best existing downhole corrosion-mitigation technologies. To understand the technical areas where additional focus is required, networks must be formed between the operators, well engineers, and service providers. Al-Kayoumi said that Zadco has gained valuable subsurface experience by creating a seamless co-operative relationship with other operators. Zadco has also sponsored projects for downhole corrosion-modeling programs. Materials for Oil and Gas Production The first technical session of the work-shop highlighted materials used in oil and gas production. Keynote speaker Bijan Kermani of KeyTech opened by stating that hydrocarbons will continue to be the world's principal energy source in the foreseeable future. The expected growth in energy demand will spur increases in production, which will become more multiphase in nature and contain higher percentages of harsh components such as hydrogen sulfide (H2S) and carbon dioxide (CO2). These acid gases in high water-cut production systems present major corrosion concerns. Therefore, material selection must become more specific to mitigate corrosion, and the impact of corrosion with regards to health, safety, and the environment; capital expenditure; and operational expenditure must receive continued serious consideration. Kermani said that materials selection must be coupled with ‘near-realistic’ corrosion modeling and prediction for optimum integrity assurance. Zadco's Obadah Al-Sawadi next discussed the principles of corrosion modeling and prediction as they relate to materials selection. He stated that any useful model should be able to accurately predict corrosion rates as operating conditions change and account for actual tubing conditions rather than predict the phenomena at only one set of design conditions. A successful modeling program should also clearly define target corrosion rates to assess whether carbon steel or a corrosion-resistant alloy (CRA) should be employed. Finally Al-Sawadi highlighted several continuing challenges for accurate modeling programs, including obtaining accurate field data, the large number of variables involved and their relevance, and changes in the operating regime.

Corrosion inhibition of mild steel in acidic media by [BMIm]Br Ionic liquid

The inhibiting behavior of 1-butyl-3-methylimidazolium bromide [BMIM]Br on mild steel corrosion in 1.0 M HCl as corroding solution at 25 °C was evaluated by various corrosion monitoring techniques. The obtained results showed that [BMIM]Br is a good inhibitor for mild steel in 1.0 M HCl solution. Potentiodynamic polarization data indicated that the [BMIM]Br acts essentially as a mixed-type inhibitor. The effect of inhibitor concentration on zero charge potential (ZCP) of the mild steel in 1.0 M HCl was studied and its comparison with OCP has been made for evaluation of the mechanism of adsorption of [BMIm] + cation. The effect of temperature on corrosion behavior of mild steel in 1.0 M HCl with addition of [BMIM]Br was studied in the temperature range of 25–45 °C. The inhibition efficiency decreases with the rise of temperature.

Monitoring of stress corrosion cracking of sensitised 304H stainless steel in nuclear applications by electrochemical methods and acoustic emission

AbstractA hybrid monitoring technique for stress corrosion cracking (SCC) has been developed that employs simultaneously localised corrosion monitoring, electrochemical noise and acoustic emission (AE) techniques. The application of the hybrid technique for detection of SCC initiation and propagation in sensitised 304H stainless steel in dilute tetrathionate solutions at ambient temperature is reported. Initial result shows that SCC initiation and its early stage propagation can be detected by the localised corrosion monitoring and electrochemical noise methods. The dimensions of the crack can be estimated from the charge values derived from the detected transients. The locations of AE events determined using two sensors are in good agreement with the locations of cracks observed in the specimen. The AE technique is sensitive to rapid crack propagation, but does not appear to be sensitive to SCC initiation and early stage propagation for the present material environment load combination. It is postulated ...

Corrosion inhibition of X70 steel in saline solution saturated with CO 2 by thiourea

Corrosion monitoring techniques were performed on X70 steel in saline solution saturated with CO2 with and without thiourea additives within the concentration range 5–25 mg/L. It was found that when the concentration of the inhibitors were increased, the inhibitor efficiencies (IE) of thiourea varied with solution temperature and immersion time. The results indicated that thiourea had the highest inhibition efficiency. The potentiondynamic polarization studies revealed that thiourea are mixed-type inhibitor that mainly restrains the anodic process.

The inhibition effect of the new Schiff base, namely 2,2′‐[bis‐N(4‐choloro benzaldimin)]‐1,1′‐dithio against mild steel corrosion

Abstract2,2′‐[bis‐N(4‐choloro benzaldimin)]‐1,1′‐dithio has been synthesized and its inhibiting action on the corrosion of mild steel in 0.5 M sulfuric acid was investigated by various corrosion monitoring techniques, such as weight loss and potentiodynamic polarization techniques. The experimental results suggest that this compound is a good corrosion inhibitor for mild steel and the inhibition efficiency increases with the increase in inhibitor concentration. This organic compound is a mixed type inhibitor in the acid solution, and its adsorption on the mild steel surface is also found to obey the Langmuir adsorption isotherm.

Corrosion inhibition of Armco iron by 2-mercaptobenzimidazole in sodium chloride 3% media

The effect of 2-mercaptobenzimidazole (2MBI) on the corrosion of Armco iron in NaCl media has been investigated in relation to the concentration of the inhibitor by various corrosion monitoring techniques. Surface morphology was studied by scanning electron microscopy (SEM). Results obtained revealed that 2MBI is a good anodic inhibitor. The addition of increasing concentrations of 2MBI moves the corrosion potential towards positive values and reduces the corrosion rate. EIS results show that the changes in the impedance parameters ( R t and C dl) with concentrations of 2MBI is indicative of the adsorption of these molecules leading to the formation of a protective layer on iron surface. The adsorption of this compound is also found to obey Langmuir’s adsorption isotherm in NaCl.

The Inhibitory Effect of Diethanolamine on Corrosion of Mild Steel in 0.5 M Sulphuric Acidic Medium

The inhibitory effect of diethanolamine (DEA) on corrosion of mild steel in 0.5 M H2SO 4 was investigated by various corrosion monitoring techniques. Galvanostatic polarization study revealed that this compound is a very good inhibitor. The inhibition efficiency (I%) varies in the range of 88.7% to 55.3 % for a concentration range of 10 -3 M to 10 -7 M at 303 K, respectively. A study of corrosion potential (E corr ) reveals that DEA is a mixed type inhibitor. DEA inhibited mild steel corrosion due to physical adsorption of the inhibitor on the metal surface. The study at higher temperatures indicates that the inhibition efficiency decreases with the increase in temperature. The adsorption of DEA on the mild steel surface in 0.5 M H 2SO 4 follows the Frumkin’s adsorption isotherm. The results of potentiostatic polarization study revealed that DEA is a strong passivating additive. The results of infra red (IR) spectroscopy, scanning electron microscopy (SEM) and quantum chemical study supplement the results of the electrochemical techniques.

Detection of Corrosion Using Piezoelectric Impedance-Based Structural Health Monitoring

C ORROSION is an extremely costly problem for industries and business sectors throughout the world and results in severe economic impact. In 1998, Congress funded the Department of Transportation and the Federal Highway Administration to estimate the total cost of corrosion on theU.S. economy and provide corrosion prevention guidelines. The final results of the survey estimated the extrapolated total direct corrosion cost to be $278 billion per year, which is 3.14%of the gross domestic product in theUnited States [1]. In 1996, the U.S. spent $1.7 billion on commercial aircraft maintenance and lost $0.3 billion due to corrosion downtime [2]. The “find it and fix it” maintenance practices of the airline industry are costly and, in some cases, inadequate. The present note will focus on identifying a detection method for the galvanic type of corrosion that plagues aircraft. Many techniques exist for detecting corrosion in aircraft; however, these methods are typically inadequate due to the intrinsic human error present and are difficult and time-intensive to implement. Two general categories of corrosion monitoring techniques exist, nondestructive evaluation (NDE) and structural health monitoring (SHM). NDEmethods include techniques such as visual, eddy current, ultrasonics, electrochemical impedance spectroscopy, color visual imaging, radiography, and infrared imaging [3]. The second class of detection is SHM and is typically superior due to the automated nature of the sensing system. Examples of SHM systems used in aircraft include the monitoring of pH and humidity, acoustic emissions, ion concentration, and chemical potential detectors. The present study will provide results on a series of tests performed using piezoelectric-based impedance techniques, which are a newer and less developed method of performing SHM. These methods use the electromechanical coupling present in piezoelectric materials to determinewhen structural changes have occurred.When the piezoelectric material is bonded to the structure, its electrical impedance is coupled to themechanical impedance (a function of the mass, stiffness, and damping) of the structure, providing a means for characterizing it. As damage occurs or progresses, the electrical impedance measured from the piezoelectric materials shifts, which can be quantified using statistical methods, providing a method of measuring the damage present. For a detailed review of the impedance method and it application see Park et al. [4] However, the ability to use this technique to measure the small changes associated with the onset of corrosion has not been identified. This note will experimentally evaluate the use of piezoelectric materials in conjunction with the piezoelectric-based impedance method to detect, locate, and quantify precrack surface corrosion damage. The impedance variations caused by changes in corrosion location, pit depth, and surface coverage will be correlated to the damage metric, which is calculated from the measured impedance signatures.

Corrosion monitoring using electrochemical noise and linear polarization resistance in fuel oil combustion gas environment

Corrosion monitoring of different steels is carried out online in a combustion rig firing 32 kg/h of fuel oil. Two temperature-controlled probes are designed to allow control of the specimens temperature and the use of electrochemical noise (EN) and linear polarization resistance (LPR) techniques for corrosion monitoring. Two probes are placed where the combustion gas reached a temperature of 850–900°C, and another one at the combustion gas exit where the rig was at 200–240°C. Corrosion rates of an austenitic and a ferritic steel are obtained where the temperature of the combustion gas is 850–900°C, firing fuel oils with different content of Na-V-S. Corrosion monitoring of mild steel is carried out in the test burning a fuel oil with the higher content of Na-V-S by placing a corrosion probe in the low combustion gas temperature zone. The EN results show that this technique is able to assess the corrosion rate in an environment at high temperature where fuel oil ashes deposited and at a temperature high enough where they start to melt and a corrosion process proceeds. Results show that this technique is able to assess the corrosivity of fuel oil ashes originated from fuel oil containing different amounts of sodium, vanadium, and sulfur as corrosion causing impurities. Results of the low-temperature probe show that EN and LPR are able to detect the onset of corrosion on mild steel as a result of sulfuric acid condensation on the probe. However, the corrosion rates are not the same, because localized corrosion is taking place as detected by the EN technique. It is demonstrated that the use of two techniques for corrosion monitoring can give a better understanding of the corrosion process. Electrochemical techniques used to assess the corrosion resistance of alloys at high and low temperatures prove to be a valuable tool for the purposes of materials selection or controlling the main process variables that affect the corrosion resistance of materials in industrial equipment.

The inhibition of mild steel corrosion in acidic medium by 2,2′-bis(benzimidazole)

A new corrosion inhibitor, namely 2,2′-bis(benzimidazole) has been synthesised and its inhibiting action on the corrosion of mild steel in acidic bath (1 M HCl) has been investigated by various corrosion monitoring techniques, such as corrosion weight loss test and potentiodynamic polarisation. The results of the investigation show that this compounds have fairly good inhibiting properties for steel corrosion in hydrochloric acid, and is a mixed inhibitor in (1 M HCl). The adsorption of this inhibitor is also found to obey the Langmuir adsorption isotherm.

On-line corrosion monitoring in geothermal district heating systems. I. General corrosion rates

General corrosion rates in the geothermal district heating systems in Iceland are generally low, of the magnitude 1 μm/y. The reason is high pH (9.5), low-conductivity (200 μm/y) and negligible dissolved oxygen. The geothermal hot water is either used directly from source or to heat up cold ground water. The fluid naturally contains sulphide, which helps keeping the fluid oxygen-free but complicates the electrochemical environment. In this research on-line techniques for corrosion monitoring were tested and evaluated in this medium. Electrochemical methods worked well as long as frequency was kept low but ER worked better if oxygen was present.

Corrosion inhibition of steel pipelines in oil fields by N, N-di(poly oxy ethylene) amino propyl lauryl amide

The effect of non-ionic surfactant, namely N, N-di(poly oxy ethylene) amino lauryl amide, on the corrosion rate of carbon steel in produced water has been investigated by various corrosion monitoring techniques. The strong adsorption ability of the surfactant molecules leads to formation of a mono-layer, which isolates the surface from the environment and thereby reduces the corrosion attack on the surface. The adsorption process was found to obey the Langmuir adsorption isotherm. The potentiostatic polarization results clearly revealed that the inhibitor behaves as a mixed type. The maximum percentage inhibition efficiency ( η%) approached 94.87% in presence of 250 ppm of the inhibitor molecules. The effect of temperature on the corrosion rate of carbon steel was studied in the temperature range from 30 to 70 °C. Finally, scanning electron microscopy was used to examine the surface morphology of carbon steel samples in absence and presence of the inhibitor.

Monitoring the corrosion and remediation of reinforced concrete on-site: An alternative approach

Difficulties associated with the interpretation of site data collected over long periods of time from commonly used electrochemical corrosion monitoring techniques often make it difficult to assess the corrosion of reinforcing steel. An alternative approach for the interpretation of data is proposed, based on a model of the quality of passive film upon the steel surface. This model leads to a representation of the corrosion state by means of the relationship, over a long period of time, of the corrosion potential and the logarithm of the Linear Polarization Resistance, since both are functions inter alia of corrosion rate. It is shown that for the reinforced concrete panels tested, data points representing this relationship closely fitted a family of results; allowing the development of a “monitoring control diagram”, MCD. The MCD reveals that for a fixed geometry and experimental conditions, a relationship between the corrosion potential and polarization resistance of steel exists, facilitating a useful monitoring tool for assessment of both the corrosion and remediation of reinforced concrete structures. Particular emphasis is placed on the latter in this work. Monitoring the corrosion of steel embedded within concrete presents certain challenges, especially in terms of physical inspections. On-site electrochemical techniques that have been developed to monitor corrosion processes that may be occurring at the reinforcement surface, but of which there is as yet no evidence on the concrete surface, include: half cell potential measurements and linear polarization resistance measurements [1]. Such techniques are in good relation to the technical and financial scope of those conducting routine nondestructive testing. Up to the present, measuring the corrosion potential, E corr , of reinforcing steel is the commonest of the corrosion monitoring methods available [2], and is widely used in practice as an indication of the possible corrosion risk. Corrosion potential monitoring is outlined in ASTM C876 [3], in which the value of E corr is only claimed to indicate the relative risk of corrosion, with is no provision of quantitative information regarding corrosion rates. The standard suggests that passivity of the reinforcement may be lost at potentials more negative than � 150 mV (Cu/CuSO4) [3]. In the LPR technique (originally developed for metals in solution in the late 1950’s [4]), the potential of the steel is scanned over a small range in the vicinity of the corrosion (open-circuit) potential. As the current densities and potential shifts associated with the technique are small, it was considered in the original derivation of the theory that mass transport effects could be neglected. The slope of the polarization curve (viz. the potential change divided by the applied current) at the point at which the applied current equals zero is defined as RP, the Polarization Resistance, and is considered a measure of the opposition to metallic dissolution. Each of these techniques provides some information as to what is going on within the concrete, but none give the complete story [5, 6]. In particular the changes in the environment that are an inevitable feature of site measurements introduce random variations into the data that can often mask underlying fundamental changes in the corrosion process [7 – 9]. As opposed to the presentation of alternative techniques to replace E corr and LPR monitoring, this paper attempts to introduce an approach to analyzing data from such techniques; which aims to lead to more meaningful conclusions. The paper will illustrate this technique by using it in the context of ranking different corrosion remediation techniques.

Pipe corrosion and deposit study using neutron- and gamma- radiation sources

The problems of corrosion and deposit are crucial issues in the pipelines of the chemical, nuclear and petrochemical industries. Radiography (neutron, gamma, X-ray) has long been used as a technique for pipe inspection and corrosion monitoring. The 10 MW Budapest research reactor site is a source of various energy neutron (thermal and epithermal) and gamma radiation. The detector system was a Peltier-cooled LLL CCD camera controlled by a PC with Image ProLite software and imaging plate equipment with a BAS 2500 scanner that used AIDA software. The objects inspected were corroded tubes and various kinds of test specimens with a large wall thickness (25 mm) inside and outside steps. In the evaluation part we used tomographic algorithms. A software simulation study was made as well. Fan-beam projections were computed of the given software phantoms and a new discrete tomography method was used to reconstruct the unknown objects from these projections.