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Collaborating Authors
CORROSION 2010
Distributed Node Electrodes For Corrosion Monitoring Of Concrete Rebars And Buried Pipes
Yang, Lietai (Department of Earth, Material, and Planetary Sciences Geosciences and Engineering Division) | Chiang, K.T. (Department of Earth, Material, and Planetary Sciences Geosciences and Engineering Division) | Shukla, Pavan (Center for Nuclear Waste Regulatory Analyses Geosciences and Engineering Division Southwest Research Institute®)
INTRODUCTION Background ABSTRACT A node electrode system can be defined as a system with a network of electrodes. A new node electrode concept is proposed for real-time monitoring of the degradation of concrete rebars and buried pipes and to measure the corrosion rate of the metals at selected locations over a large area. In this concept, a selected number of long metal bars are used as the working electrodes for the monitoring system. The long bars are coated such that only selected sections are exposed to the concrete or soil. Each exposed section has a well-defined surface area for corrosion rate measurement. The collection of the exposed sections forms a network of electrodes, and each exposed section is a node electrode. The network of node electrodes can be used to conveniently monitor the health conditions of the metals it represents over a large area with only one instrument channel. If a potential problem is identified from the node electrode monitoring system, a counter electrode can be placed near the individual nodes that are suspected to have the high corrosion rates to measure the corrosion rate of these nodes. Therefore this concept allows surveillance of the corrosion of concrete rebar or buried pipes over a large area and measurement of the rate of corrosion on the metal that is aged in the same concrete or same soil for the same time duration as the actual concrete rebar or buried pipes. For the case of concrete rebars, the long bars used as the working electrode can themselves be actual rebars in the concrete structure. Experiments were conducted to determine the optimum distance between neighboring nodes for corrosion rate measurement in concrete blocks. The relationship between the corrosivity of the concrete or size of the node electrodes and the distance required to minimize the effect of neighboring electrodes on the accuracy of the corrosion rate measurements are discussed. In concrete structures, corrosion of concrete reinforcement is often the major cause of the concrete structure failures. The corrosion rate of the reinforcement bars (rebars) is one of the most important parameters in assessing the remaining life of a concrete structure and the risk of failure. For buried pipes, the external corrosion of the pipes in soil is often the major concern for pipeline integrity. An effective corrosion monitoring program requires corrosion sensors with the following characteristics: Able to detect corrosion over large areas of a structure; Have low cost and high reliability for deployment in large numbers to form a network of monitoring systems; Provide signals easily interpreted by operators; Be easily automated and interfaced with a central data system during a monitoring period; Provide accurate measurements of rates of corrosion taking place on the actual metal structure at the worst-case locations. Limitations of Existing Corrosion Rate Measurement Devices Electrochemical methods are often used to assess the corrosion rate of rebar in concrete structures and buried metal structures in soil. However, measuring the corrosion rate of actual rebar materials.
Application Of An Electrochemical Microcell For Corrosion Measurements On Stainless Steels
Sorg, Matthias (Aalen University of Applied Science Aalen) | Ladwein, Thomas (Aalen University of Applied Science) | Wiegers, Karsten (Aalen University of Applied Science) | Schilling, Sebastian (Aalen University of Applied Science) | Maier, Jens (Curtin University of Technology) | Oehler, Mike (Curtin University of Technology)
INTRODUCTION ABSTRACT With an electrochemical microcell it is possible to make measurement without effects of edges or different surface modifications on one specimen. It allows you to measure base material and welds separately. The preparation of the specimen is simple because you only need a small area for the measurements. For statistics it is possible to make a few measurements on one specimen to check the reproducibility. For this work the following electrochemical techniques were tested with the microcell: linear polarization curves, electrochemical impedance spectroscopy and electrochemical potentiokinetic reactivation test (double-loop EPR). The results of the measurements were reproducible and in some cases better for interpretation than measurement with a standard cell. The values of the pitting potential, determined with the linear polarization technique, were higher in average than the values from the standard cell. With the electrochemical impedance spectroscopy it was possible to study the passivation behaviour of a stainless steel over time on one specimen. Double-loop EPR-test with the microcell allows the separate investigation of sensitization on base material, weld and heating zone. Electrochemical microcells have been widely used in the corrosion science. They are beside techniques that expose the whole specimen to an electrolyte like SECM or SRE able to conduct electrochemical experiments on fractions of the total specimen surface. Other techniques proposed therefore include covering the surface with photoresist coatings to expose limited surfaces to the electrolyte or using wire electrodes embedded in resin to create small working electrode surfaces. [1] Microcells of the capillary type were designed to expose just limited surface areas of a larger test specimen to the corrosive environment in order to preserve the remaining surface for further test work or in order to focus on locally limited phenomena like inclusions [2], or focus on heat affected zones created in stainless steels during welding. [3] Several different electrochemical techniques have been applied in order to characterize stainless steels for their corrosion properties. Localized pitting corrosion potential measurements were conducted in order to investigate the locations of pitting initiation around inclusions and grain boundaries of stainless steels. [4] Local electrochemical impedance measurements were conducted in order to achieve locally resolved surface analysis. [5, 6] In this work the main focus are corrosions measurements on stainless steels. Different techniques, like pitting potential measurements, electrochemical potentiokinetic reactivation tests or electrochemical impedance measurements shows the availability of an electrochemical microcell in corrosion research. Test specimens EXPERIMENTAL The test specimens comprised of a range of commercially available austenitic stainless steels and heat-treated weldable martensitic stainless steels in different chemical compositions. Detailed information on the grade is given in the actual experimental procedure. The test specimens were embedded in epoxy resin with an attached metal wire to make contact to the potentiostat's WE cable. The surface preparation was done with an automatic grinding / polishing machine. The contact pressure for grinding was 40 N per specimen, for diamond polishing it was 20 N and for aluminium oxide polishing it was 15 N.
- Materials > Metals & Mining > Steel (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.49)
INTRODUCTION ABSTRACT A variety of electrochemical techniques has been used for the evaluation of protective performance of coated steel. For example, one of them is electrochemical impedance spectroscopy. (EIS) Each method has its own characteristic and is suitable to determine some kinds of anti-corrosive mechanisms of coating film. We developed a new evaluation method of protective coatings using current interrupter technique. Generally the equivalent circuit of coated steel is simplified as a connection of the resistance of test solution. the impedance of paint film and impedance of mild steel surface in series. When the time constant of the paint film is much smaller and very different from that of the metal substrate as coated steel in general, the two equivalent circuits can be separated from each other. Thus the polarization resistance of metal substrate was determined by separating the measured paint film impedance from the metal substrate impedance. Electrochemical parameters can be measured by using current interrupter technique. Results of protective coating performance obtained by some experiment were discussed. Corrosion protection by organic coatings is a popular and an important technology. High performance organic coatings have been developed for the protection of steel structures so far. So the evaluation method for these protective paints has been required because of the reduction of developing time for high performance coatings. Several methods of AC method such as EIS, DC method such as CI (current-interrupter technique) and RV(relaxation voltammetry) can be listed as electrochemical techniques. EIS technique is based on from low frequency to high. Current interrupter technique for coated steel was developed which enables to measure protective performances in short measuring time. The measurement starts with applying small current to coated steel at first. Generally the equivalent circuits of coated steel are simplified as a connection of the resistance of test solution, the equivalent circuit of paint film and the equivalent circuit of metal surface under paint film in series. When the time constant of the equivalent circuit corresponding to paint film is much smaller and very different from that of the metal substrate under paint film. the two equivalent circuits can be separated from each other. Thus the polarization resistance of metal substrate was determined by separating the metal substrate impedance from paint film impedance. So current interrupter method allows to obtain electrochemical parameters such as film resistance, film capacitance, polarization resistance, double layer capacitance and natural potential. Simplified circuit for measurement Principle of measurement using current interrupter technique The circuit for the measurement of five electrochemical parameters of coated steel is shown in Fig.1. Small current is applied to coated steel from the potential change of 10 mV to 50 mV by current pulse generator and then current is turned off. A potential decay curve was detected and plotted for obtaining five electrochemical parameters. (Figure in full paper) technique The principle of measurement on electrochemical parameters by current interrupter The current interrupter method is the way that the transitional polarization behavior of coated steel is measured to obtain polarization resistance.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Electrochemical Evaluation Of Corrosion Inhibitors In CO2 Containing Brines. An Rce And Flow-Loop Comparison
Genesca, J. (Departmento Ingenieria Metalurgica.Facultad Quimica.UNAM.Ciudad Universitaria) | Olalde, R. (Departmento Ingenieria Metalurgica.Facultad Quimica.UNAM.Ciudad Universitaria) | Garnica, A. (Exploracion y Produccion. Instituto Mexicano del Petroleo) | Balderas, N. (Exploracion y Produccion. Instituto Mexicano del Petroleo) | Mendoza-Flores, J. (Exploracion y Produccion. Instituto Mexicano del Petroleo) | Duran-Romero, R. (Exploracion y Produccion. Instituto Mexicano del Petroleo)
INTRODUCTION ABSTRACT The purpose of this work was to study the effect that turbulent flow has on the electrochemical behaviour of a 3-amino-1,2,4-triazole (aminotriazole or 3-AT) based corrosion inhibitor. The experiments were carried out in a rotating cylinder electrode (RCE) and a 4 l laboratory flow-loop. The test environment used in all experiments was a 3% NaCl solution saturated with CO2 at 20 C. Potentiodynamic polarization curves, polarization resistance and electrochemical impedance spectroscopy (EIS) measurements were used to determine the electrochemical behaviour of the steel in the environment at different flow rates and inhibitor concentrations. The inhibiting effect of the tested substance is strongly dependent on the hydrodynamic conditions of the environment. As the turbulence of the environment increases, the efficiency of the inhibitor also increases. This increment could be associated to an increased migration of the inhibitor, from the bulk of the solution towards the surface of the corroding electrode. This increased migration can generate a better coverage of the surface of the corroding electrode and therefore a decrement of icorr. When the efficiency of this inhibitor is estimated, controlled hydrodynamic conditions must be taken into account. Otherwise the value of efficiency that is calculated can be underestimated. In oil and gas production industry, internal corrosion of carbon steel pipeline is a well-known problem, and inhibition is the most effective and flexible method of corrosion control. Therefore, the knowledge of the mechanisms of the corrosion inhibition process is highly desirable in the design and proper selection of inhibitors. In the petroleum industry, organic inhibitors containing nitrogen (amines) are often used due to their effectiveness and availability. When a corrosion inhibitor is added to a system, adsorption of inhibitor molecules at the metal-solution interface occurs. This adsorption is accompanied by a change in potential difference between the metal electrode and the solution, due to the non-uniform distribution of electric charges at the interface. The use of film-forming inhibitors has been a widely used practice in the control of corrosion in hydrocarbon transport pipelines. The performance of these types of inhibitors depends on their ability to form a continuous film upon the surface of the metal that will be protected against corrosion, isolating it from the aggressive environment. In most cases, the corrosion environment is in constant movement. This is a common situation in the transport of hydrocarbons in steel pipelines. In industrial processes fluid flow in pipes is usually turbulent. In order to obtain information about the performance of film forming inhibitors, laboratory tests are carried out. The most common type of laboratory tests are based on weight loss of metallic coupons, which have been exposed to a test environment for a certain period of time. Some other tests use electrochemical measurements such as linear polarization resistance (LPR) or electrochemical impedance spectroscopy (EIS) to measure and monitor the rate of general corrosion. At the same time, it is known that, with limited success, the electrochemical techniques can be used for measuring the corrosion rate controlled.
- North America > Mexico (0.29)
- North America > United States (0.28)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.48)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
INTRODUCTION Copenhagen Metro ABSTRACT During the construction of the Copenhagen Metro from 1996 until the inauguration between 2002 and 2007 corrosion monitoring probes were installed and embedded in the concrete structures. One hundred and seventy sets of corrosion monitoring probes were installed each comprising 4 mild steel electrodes; a counter electrode (platinised titanium), reference electrode, temperature sensor and a reinforcement connection. The overall objective of the installation is to have a prewarning system for corrosion in the concrete cover, so as to spot the onset of corrosion at reinforcement depth. This provides the basis for being able to apply preventive measures for corrosion protection, such as cathodic protection. For the first three years the potential, zero resistance ammeter, temperature, impedance measurements were conducted manually. The metro trains have since commenced operating 24 hours a day, 7 days a week which made manual data collection unpractical. For this reason and also in order to have continuous monitoring, the Metroselskabet developed a data collection system, where each corrosion probe is connected to a measuring board and data is being collected on a regular basis and transferred to a server using databus cables and fibre optics. A software system controls the measurements being conducted and presents the data. This article describes the monitoring system and results from the pilot installation. is a rapid transit serving Copenhagen, Frederiksberg and Tårnby in Denmark. The system opened in 2002, and has two lines, M1 and M2, following the 2007 extension to Copenhagen Airport. The system is a driverless metro that supplements the larger S-train rapid transit system. (Figure in full paper) The system operates 34 three-car trains built by Ansaldobreda. The Metro is owned by Metroselskabet, which in turn is owned jointly by Copenhagen Municipality (50%), the Danish State (41.7%) and Frederiksberg Municipality (8.3%). Trains operate every six minutes during day, every four minutes during rush hour and every fifteen minutes at night. Line M1 has 15 stations and is 14.3 kilometres (8.9 mi) long, while line M2 has 16 stations and is 19.2 kilometres (11.9 mi) long. The City Circle Line is scheduled to open in 2018. Served by lines M3 and M4, it will connect the central parts of the city together. The Metro was built largely as a result of a 1992 report on the future of transport in Copenhagen. A metro was chosen over i.e. a tramway system, because it was thought to have the highest capacity, speed, and security while not hampering the city environment. The final plans (in 1996) for the initial construction of the Metro consisted of two lines. Construction began in 1997 and the first phase was opened by Queen Margrethe II on October 19, 2002 followed by two more openings in 2003 and 2004 and in September 2007 also the line from the city centre to the airport was opened. The Metro runs underground as well as above ground on standard-gauge tracks, and it operates at 750 V DC provided by a third rail.
- Transportation > Ground > Rail (0.68)
- Transportation > Infrastructure & Services (0.68)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
INTRODUCTION ABSTRACT It is known that, in addition to corrosion processes, the generation of electrochemical noise (EN) can be caused by other disturbances such as mass transfer and flow turbulence. In this work the effect of laminar and turbulent flow on the generation of electrochemical noise has been studied using a carbon steel rotating cylinder electrode (RCE) in aerated sodium chloride solution and in inhibited solution. EN experiments have been performed in free corrosion conditions (i.e. no applied current), and with applied cathodic polarisation in the regions of hydrogen evolution and oxygen reduction. It has been found that laminar flow had a negligible effect on the noise produced, but a significant increase in the amplitude of the noise was observed in turbulent flow, particularly when the electrode was cathodically polarized. Spectral analysis showed that the noise produced by turbulent flow had power at significantly higher frequencies than is normal for corrosion-related noise. Flow is an important parameter that can influence corrosion processes. Previous work on the measurement of electrochemical noise (EN) has shown that variations in flow can have a noticeable influence on the measured EN parameters [1]. This work was qualitative in nature, recording a marked increase in noise when a peristaltic pump was switched on, with a periodicity to the noise that was consistent with the pulsation frequency of the pump. From the few studies that have been performed under different flow conditions, it was clear that an additional source of potential and current fluctuations could be represented by stirring of solution [2-4]. In this study, the rotating cylinder electrode (RCE) has been used to investigate the effect of flow on EN generation. RCE is considered to be a good tool to simulate field geometry and provide a better understanding of corrosion, corrosion inhibition and mass transfer processes that are associated with turbulent flow conditions. The selection of the RCE is based on advantages such as achieving a turbulent flow regime at very low Reynolds numbers and the small amount of test solution used [5,6]. To avoid rapid damage to the specimen by corrosion, many of the measurements have been made with an applied cathodic current, so that the noise generation process is predominantly hydrogen evolution or mass-transport limited oxygen reduction. The last part of this work was performed in free corrosion with and without inhibitor in the solution in order to evaluate the influence of flowing conditions on the measured EN. This paper updates a previous publication on this project [7], and a proportion of the prior work is reproduced here for the convenience of readers. The major developments have been the measurement under a wider range of conditions, and the use of a faster data acquisition system that has allowed the EN to be studied at frequencies up to 500 Hz. EXPERIMENTAL All tests were carried out in 0.1 M NaCl solution with pH adjusted to 7. All tests were performed at room temperature and the solutions were open to air.