Anode Location Research Articles

Inverse modelling of potential measurements on reinforced concrete to assess localized corrosion: Sensitivity with respect to the corrosion state and concrete properties

We present a novel, fundamentally sound approach for the determination of corrosion rate and anode location in reinforced concrete. In this contribution, we focus on the sensitivity of this non-destructive method with respect to the state of corrosion and concrete properties. Corrosion is often the main cause for the premature deterioration of reinforced concrete structures. Especially the type of pitting (or localized) corrosion poses great danger, as it can result in fast local decrease of the steel diameter. Non-destructive testing (NDT) is essential to detect the corrosion at an early stage, without the need to damage the concrete. The most commonly applied NDT method for reinforced concrete is potential mapping. However, it only predicts the probability of corrosion at a certain location, and does not supply any information about the corrosion rate. Other electrochemical measurements targeting corrosion rate rely on the polarization resistance, based on the mixed-potential theory by Wagner and Traud [1938]. This theory, however, is not applicable to localized corrosion. A novel inverse modelling approach allows us to detect and quantify corrosion, based on electrical potential measurements at the concrete surface in combination with a small perturbation of the corroding system by an external electrode. Using a 3D finite-element model to describe the electrical potential field resulting from external polarization of the corroding steel, we estimate the location and rate of corrosion through the application of inverse methods. This study presents the sensitivity of the approach with respect to the degree of corrosion and the concrete properties themselves. We investigated effects of the width of the corroding spot, the cover thickness and the concrete resistivity. First, we analyzed the direct effect of the potentials measured at the surface, using the finite-element model. Secondly, we determine the range of these factors for which the inverse method is able to accurately estimate the corrosion rate and location. This information allows us to understand the limitations of inverse modelling of electrical potential in detecting corrosion in reinforced concrete.

Effects of anode position on pedicle screw testing during lumbosacral spinal fusion surgery

SUMMARY OF BACKGROUND DATAPedicle screws are commonly placed with lumbar/lumbosacral fusions. Triggered electromyography (tEMG), which employs the application of electrical current between the screw and a complementary anode to determine thresholds of conduction, may be utilized to confirm the safe placement of such implants. While previous research has established clinical thresholds associated with safe screw placement, there is variability in clinical practice of anode placement which could lead to unreliable measurements. PURPOSETo determine the variance in pedicle screw stimulation thresholds when using four unique anode locations (ipsilateral/contralateral and paraspinal/gluteal relative to tested pedicle screws). STUDY DESIGNProspective cohort study. Tertiary medical center. PATIENT SAMPLETwenty patients undergoing lumbar/lumbosacral fusion with pedicle screws using tEMG OUTCOME MEASUREStEMG stimulation return values are used to assess varied anode locations and reproducibility based on anode placement. METHODSMeasurements were assessed across node placement in ipsilateral/contralateral and paraspinal/gluteal locations relative to the screw being assessed. R2 coefficients of correlation were determined, and variances were compared with F-tests. RESULTSA total of 94 lumbosacral pedicle screws from 20 patients were assessed. Repeatability was verified using two stimulations at each location for a subset of the screws with an R2 of 0.96. Comparisons between the four anode locations demonstrated R2 values ranging from 0.76 to 0.87. F-tests comparing thresholds between each anode site demonstrated all groups not to be statistically different. CONCLUSIONThe current study, a first-of-its-kind formal evaluation of anode location for pedicle screw tEMG testing, demonstrated very strong repeatability and strong correlation with different locations of anode placement. These results suggest that there is no need to change the side of the anode for testing of left versus right screws, further supporting that placing an anode electrode into gluteal muscle is sufficient and will avoid a sharp ground needle in the surgical field.

Effect of optimum current‐collector design on electrochemical performance of Mg‐air primary batteries for large‐scale energy storage

Recent research has focused on the optimal current-collector design of a large Mg anode for large-scale Mg-air primary batteries. The study investigated the effects of different current-collector contact points (CCPs) on the electrochemical discharge performance and degradation of Mg anodes. The results revealed that the selection of CCPs on the Mg anode plays a critical role in improving the discharge capacity and power characteristics. The current values measured at several anode surface locations varied significantly depending on the CCP position on the Mg anode. This nonuniform current distribution is considered to be the major cause of undesirable degradation of the Mg anode upon discharge. Through numerical simulation based on electric field analysis, optimum multiple CCPs were designed to minimize the Mg anode degradation during the discharge process by alleviating the locally concentrated current in the vicinity of the CCPs of the Mg anode. The Mg anode with multiple CCPs exhibited a highly improved discharge capacity (46.2 Ah) and energy conversion efficiency (42%) compared to the Mg anode with single CCP (38.7 Ah and 35.2%). The multiple contact strategy and improved understanding of the correlation between the current distribution and anode degradation phenomena can be further applied for the optimal design and performance improvement of various types of metal-air batteries, including Li-, Al-, and Zn-air systems.

X-ray photons produced from a plasma-cathode electron beam for radiation biology applications

A compact low-energy and high-intensity x-ray source for radiation biology applications is presented. A laser-induced plasma moves inside a 30 kV diode and produces a beam of 1014 electrons at the anode location. An aluminum foil converts a part of the energy of these electrons into x-ray photons, which are characterized using filtered imaging plates. The dose that would be deposited by these x-ray photons in C. elegans larvae is calculated from Geant4 simulations. It can be set to a value ranging between 10 μGy and 10 mGy per laser shot by simply changing the aluminum foil thickness and the diode voltage. Therefore, this versatile and compact x-ray source opens a new path to explore the radiation effects induced by dose rates varying over several orders of magnitude.

Numerical Simulations of Factors Affecting Stray Current Corrosion on Pipeline

Stray current can cause severe corrosion on buried steel pipelines. To investigate the corrosion effect of stray current, originating from impressed current cathode protection system of pipeline, on interference pipeline, a numerical model based on boundary elements using commercial software COMSOL Multiphysics was developed to simulate corrosion potential and stray current density distribution on interference pipeline. The model geometry was comprised of the cathodically protected pipeline, interference pipeline and an auxiliary anode. The effects of crossing angle and crossing distance of the two pipelines, output current and location of anode, soil resistivity and coating surface resistivity were investigated. The results demonstrated that the impressed current cathode protection system substantially affects the corrosion potential and current density distribution of interference pipelines in vicinity of crossing. The crossing angle and vertical distance of two pipelines have no important influence while the anode output current, anode location, soil resistivity and coating surface resistivity have significant influence to stray current corrosion on interference pipeline.

Visualization of aquaionic splitting via iron corrosion

We report a water decomposition mode called ‘Aquaionic Splitting (AiS)’ by means of iron corrosion in aqueous solution. In this paper, we investigated the phenomenon by controlling the reaction between iron and water. A pseudo-sacrificial protection method with oil paint was employed to select the anode and cathode formation locations that govern iron corrosion. Then, the AiS reaction was visualized by using BTB solution, whose colour corresponds to pH, to produce colour patterning that corresponds to the aquaion distribution. It has become clear that water can be selectively separated into protons and hydroxide ions by corrosion control treatment. In this vein, the diffusion coefficient of protons was estimated by using the colour patterning of BTB solution that accompanies iron corrosion, and aquaion distribution was then computer simulated by solving the diffusion equation.

A versatile and compact high-intensity electron beam for multi-kGy irradiation in nano- or micro-electronic devices

A compact low-energy and high-intensity electron source for material aging applications is presented. A laser-induced plasma moves inside a 30 kV diode and produces a 5 MW electron beam at the anode location. The corresponding dose that can be deposited into silicon or gallium samples is estimated to be 25 kGy per laser shot. The dose profile strongly depends on the cathode voltage and can be adjusted from 100 nm to 1 μm. With this versatile source, a path is opened to study micro- or nano-electronic components under high irradiation, without the standard radioprotection issues.

Burial depth of anode affected the bacterial community structure of sediment microbial fuel cells

Sediment microbial fuel cells (SMFCs) are attractive devices to in situ power environmental monitoring sensors and bioremediate contaminated soils/sediments. Burial depth of the anode was verified to affect the performance of SMFCs. The present research evaluated the differences in microbial community structure of anodic biofilms located at different depth. It was demonstrated that both microbial diversity and community structure of anodic biofilms were influenced by the depth of anode location. Microbial diversity decreased with increased anodic depth. The number of the operational taxonomic units (OTUs) was determined as 1438 at the anode depth of 5 cm, which reduced to 1275 and 1005 at 10 cm and 15 cm, respectively. Cluster analysis revealed that microbial communities of 5 cm and 10 cm were clustered together, separated from the original sediment and 15 cm. Proteobacteria was the predominant phylum in all samples, followed by Bacteroidetes and Firmicutes. Beta-and Gamma-proteobacteria were the most abundant classes. A total of 23 OTUs showed high identity to 16S rRNA gene of exoelectrogens such as Geobacter and Pseudomonas. The present results provided insights into the effects of anode depth on the performance of SMFC from the perspectives of microbial community structure.

Enhanced Predictive Modelling of Steel Corrosion in Concrete in Submerged Zone Based on a Dynamic Activation Approach

A numerical model for enhanced service life prediction of concrete infrastructure is presented which includes transient analysis of processes during corrosion initiation as well as propagation stage. The temporal and spatial transition of Steel–Concrete Interface during depassivation events is described by a randomly varying chloride threshold function. As such random activation events can be accounted for, rather than having to pre-describe the anode size and location as in many existing models. The aim of the study is to investigate random spatial activation events in concrete structures in submerged zones based on dynamically changing boundary conditions on the rebar surface to control transition from passive to active state. Investigations are carried out to realize the sustainability of corrosion processes in limiting oxygen concentrations in dissolved seawater. The model showcases the numerical architecture, the associated concept of randomly varying chloride threshold and predicts that among other factors, the rate of oxygen strongly influences corrosion rate in submerged locations.

Optimizing anode location in impressed current cathodic protection system to minimize underwater electric field using multiple linear regression analysis and artificial neural network methods

Design of impressed current cathodic protection (ICCP)-anode locations to minimize underwater electric field is important to increase the survivability of naval ships. However, the evaluation of all ICCP-anode location scenarios is time-consuming process even though it is conducted by numerical simulation, especially boundary element method (BEM). To solve this problem, the randomly selected cases of ICCP-anode location in 3, 4 and 5-pair, which were produced by the beta distribution model, were simulated using BEM simulations. Then, the optimized ICCP-anode location scenario from the cases was verified by statistical methods (multiple linear regression and artificial neural network). Predictions of ICCP-anode location and underwater electric field were more correlated with the artificial neural network than the multiple linear regression analysis. Also, the selected ICCP-anode locations were verified by the artificial neural network considering data interactions. Thus, the application of an artificial neural network can be more useful for designing ICCP-anode location that minimizes underwater electric fields.

Anodic potentials, electricity generation and bacterial community as affected by plant roots in sediment microbial fuel cell: Effects of anode locations

A planted sediment microbial fuel cell (PSMFC) is a promising new technology for harvesting energy and remediating a contaminated geo-environment. In this study, the effects of roots (of Acorus tatarinowii) on oxygen profiles in sediment, power generation, and anodic bacterial community were investigated in PSMFCs and unplanted SMFCs with different anode locations to roots. The presence of plant did not improve the electricity generation when roots were placed on the surface of an anode because a high amount of oxygen loss from roots increased the redox potential at anode and made aerobic bacteria co-exit and compete with electrochemically active bacteria in substance utilization. It was suggested to place the anode under the roots with a proper distance, where the PSMFCs made use of root-derived organics, avoiding the negative effects of oxygen loss. Oxygen loss could control the diurnal rhythm of power generation in the PSMFCs.

Influence of anode location and quantity for the reduction of underwater electric fields under cathodic protection

To investigate the effect of anode location and quantities on underwater electric fields, numerical simulations were performed using the boundary element method. Simulations were performed for the cases of 3, 4, and 5 pairs and the installation locations of the anodes were set at 10 different hull regions. Although the potential difference was nearly unchanged with changes in the anode locations, the electric field was effectively diminished when the anodes were uniformly distributed through prevention of the current concentration at the specific region. Additionally, increasing the number of anodes decreased the underwater electric field, although the decrease rate of the electric field reduced. Thus, the locations of anodes should be uniformly distributed and an adequate number of anodes should be applied to effectively reduce the underwater electric fields.

Numerical simulation and re‐design optimization of impressed current cathodic protection for an offshore platform with biofouling in seawater

A finite element model (FEM) of the offshore platform with biofouling is developed here to predict the effectiveness of the ICCP under seawater. Remotely operated vehicle (ROV) test verified that the offshore platform was fully covered by a coating‐like biofouling to protect the structures from corrosion. FE‐SEM and EDS tests demonstrated that the biofouling deposits on the offshore platform mainly contained magnesium oxides, biofouling deposits, and corrosion products doped with calcium oxides. The polarization relationships of platform steel with biofouling coverage were used as boundary conditions for the numerical simulation. Furthermore, the factors including output current, anode location, seawater conductivity, and biofouling coverage rate, which influenced the protective effectiveness, were comparatively evaluated by FEM. Then, a re‐design two‐anode ICCP system was employed to keep offshore platform in protective condition. A ROV monitored the potential distributions of the legs and demonstrated that numerical simulation results of ICCP had a good agreement with measured data.

Electric Field Modified Bunsen Flame with Variable Anode Placement

A methane–air Bunsen flame was tested under dc electric field forcing with different ring anode sizes and locations. The anodes were placed within the flame to far outside the flame, both axially and radially. The focus of the work is to understand the limit of electrode placement and its effect on the flame under a dc field. A stoichiometric flame with voltages up to 9.1 kV was tested. The electrical current and flame height were measured as a function of the bias voltage and anode location. Plasma density measurements of the unmodified flame at various axial locations were used to corroborate that anode placement at regions of high electron density caused the largest reductions in flame height. The results showed the anodes closest to the burner at 35 mm caused the largest reduction (24%) in flame height. The effect of the electric field on flame height decreased as the anode moved farther downstream of the flame or radially outward. For the same voltage, larger currents were also observed for anodes close to the burner, whereas anodes placed far outside of the flame had minimal effects on current and, consequently, on the flame height. These differences are due to the variable electron density at the anode, which limits the net current collected and the strength of the field.

Electric fields of motor and frontal tDCS in a standard brain space: A computer simulation study

The electric field produced in the brain is the main physical agent of transcranial direct current stimulation (tDCS). Inter-subject variations in the electric fields may help to explain the variability in the effects of tDCS.Here, we use multiple-subject analysis to study the strength and variability of the group-level electric fields in the standard brain space.Personalized anatomically-accurate models of 62 subjects were constructed from T1- and T2-weighted MRI. The finite-element method was used to computationally estimate the individual electric fields, which were registered to the standard space using surface based registration. Motor cortical and frontal tDCS were modelled for 16 electrode montages.For each electrode montage, the group-level electric fields had a consistent strength and direction in several brain regions, which could also be located at some distance from the electrodes. In other regions, the electric fields were more variable, and thus more likely to produce variable effects in each individual. Both the anode and cathode locations affected the group-level electric fields, both directly under the electrodes and elsewhere. For motor cortical tDCS, the electric fields could be controlled at the group level by moving the electrodes. However, for frontal tDCS, the group-level electric fields were more variable, and the electrode locations had only minor effects on the group average fields.Our results reveal the electric fields and their variability at the group level in the standard brain space, providing insights into the mechanisms of tDCS for plasticity induction. The data are useful for planning, analysing and interpreting tDCS studies.

Optimization the quantity, locations and output currents of anodes to improve cathodic protection effect of semi-submersible crane vessel

In order to improve corrosion protection effect of semi-submersible crane vessel (SSCV), 3-D boundary element method combined with automatic movement of anodes and adjustment of currents is developed to optimize anode quantity, location and output current of impressed current cathodic protection system for SSCV. Numerical simulation results show that protection potential of SSCV is obviously smoothed after optimization. The protection effect of SSCV in four different states is also predicted and simulation results indicate that SSCV is well protected in the whole service life when the protective coating on hull is repainted every seven years. Finally, challenges associated with cathodic protection providing for marine engineering equipment are discussed.

Numerical analysis results of the cathodic protection for the underground steel pipe by anode installation method

This study aims to find out the best anode location for buried pipelines. Numerical simulation program known as CATPRO(Elsyca, Belgium) were used for confirming the best location of anodes and the effects of impressed current cathodic protection system. Applied conditions for numerical simulation were similar to on-site environmental conditions for optimal application of cathodic protection system. Used criterion of cathodic protection was NACE SP 0169, which describes that minimum requirement for cathodic protection is -850mV vs. CSE. Various layouts for anodes’ installation were applied, which were distance between anodes, anode installation location, and applied current. The areas where cathodic protection potential was lower than -850mV vs. CSE was limited up to 50m from anode installation locations. It was founded numerical analysis obtain cost-effective and efficient cathodic protection methods before design and application the impressed cathodic protection system to on-site environment.

Arc Discharge Anode Reattachment: Simple Model

Anode attachment of a nontransferred dc arc moves along the anode nozzle. Under the influence of the gas flow, it moves downstream thus elongating the arc. This leads to an increase of the arc voltage. The voltage across the cold layer that separates the arc column and the nozzle increases accordingly. This voltage increase leads to the breakdown of the cold anode layer. After this breakdown, the anode attachment jumps to the new upstream location (reattachment). The phenomenon of reattachment of the anode spot has not been completely understood yet. A simple model of the reattachment is suggested. Based on a suggestion that electron temperature inside the cold layer does not drop as low as the heavy particles' temperature does, it is assumed that some residue electrical conductivity (on the level of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> Ω <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) exists in this layer. It is shown that the voltage drop across the layer rises in time, leading to a fast developing overheating instability. This creates a electrically conductive column at an upstream location and results in reconnection of the arc to this new anode location. Simple estimations of the amplitude of the voltage oscillations and their frequency correspond to the experimental data.

Transcranial direct current stimulation facilitates cognitive multi-task performance differentially depending on anode location and subtask.

There is a need to facilitate acquisition of real world cognitive multi-tasks that require long periods of training (e.g., air traffic control, intelligence analysis, medicine). Non-invasive brain stimulation—specifically transcranial Direct Current Stimulation (tDCS)—has promise as a method to speed multi-task training. We hypothesized that during acquisition of the complex multi-task Space Fortress, subtasks that require focused attention on ship control would benefit from tDCS aimed at the dorsal attention network while subtasks that require redirection of attention would benefit from tDCS aimed at the right hemisphere ventral attention network. We compared effects of 30 min prefrontal and parietal stimulation to right and left hemispheres on subtask performance during the first 45 min of training. The strongest effects both overall and for ship flying (control and velocity subtasks) were seen with a right parietal (C4, reference to left shoulder) montage, shown by modeling to induce an electric field that includes nodes in both dorsal and ventral attention networks. This is consistent with the re-orienting hypothesis that the ventral attention network is activated along with the dorsal attention network if a new, task-relevant event occurs while visuospatial attention is focused (Corbetta et al., 2008). No effects were seen with anodes over sites that stimulated only dorsal (C3) or only ventral (F10) attention networks. The speed subtask (update memory for symbols) benefited from an F9 anode over left prefrontal cortex. These results argue for development of tDCS as a training aid in real world settings where multi-tasking is critical.

Spatial distribution of bacterial communities on volumetric and planar anodes in single‐chamber air‐cathode microbial fuel cells

Pyrosequencing was used to characterize bacterial communities in air-cathode microbial fuel cells across a volumetric (graphite fiber brush) and a planar (carbon cloth) anode, where different physical and chemical gradients would be expected associated with the distance between anode location and the air cathode. As expected, the stable operational voltage and the coulombic efficiency (CE) were higher for the volumetric anode than the planar anode (0.57 V and CE = 22% vs. 0.51 V and CE = 12%). The genus Geobacter was the only known exoelectrogen among the observed dominant groups, comprising 57 ± 4% of recovered sequences for the brush and 27 ± 5% for the carbon-cloth anode. While the bacterial communities differed between the two anode materials, results showed that Geobacter spp. and other dominant bacterial groups were homogenously distributed across both planar and volumetric anodes. This lends support to previous community analysis interpretations based on a single biofilm sampling location in these systems.