Corrosion Defects Research Articles

Model of an E-cored probe over layered conductor containing corrosion for eddy current testing

PurposeIn eddy current nondestructive testing, ferrite-cored probes are usually used to detect and locate defects such as cracks and corrosion in conductive materials. However, the generic analytical model for evaluating corrosion in layered conductor using ferrite-cored probe has not yet been developed. The purpose of this paper is to propose and verify the analytical model of an E-cored probe for evaluating corrosion in layered conductive materials.Design/methodology/approachA cylindrical coordinate system is adopted and the solution domain is truncated in the radial direction. The magnetic vector potential of each region excited by a filamentary coil is derived first, and then the expansion coefficients of the solution are obtained by matching the boundary and interface conditions between the regions and the subregions. Finally the closed-form expression of the impedance of the multi-turn coil is derived by using the truncated region eigenfunction expansion (TREE) method, and the impedance calculation is carried out in Mathematica. In the frequency range of 100 Hz to 10 kHz, the impedance changes of the E-cored coil and air-cored coil due to the layered conductor containing corrosion are calculated, respectively, and the influences of corrosion on the coil impedance change are investigated.FindingsAn analytical model for the detection and evaluating of corrosion in layered conductive materials using E-cored probe is proposed. The model can quickly and accurately calculate the impedance change of E-cored coil due to corrosion in layered conductor. The correctness of the analytical model is verified by finite element method and experiments.Originality/valueAn accurate theoretical model of E-cored probe for evaluating corrosion of multilayer conductor is presented. The analytical model can be used to detect the inhomogeneity of layered conductor, design ferrite-cored probe or directly evaluate the corrosion defects of layered conductors.

Study on response patterns and influencing factors of buried pipelines with corrosion defects under fault action

It is evident how corrosion flaws affect the tension and strain of pipelines that pass oblique-slip faults. The pipeline is very risky and is more likely to experience tensile and buckling damage when corrosion develops in the major deformation region of the pipeline. This will also significantly diminish the pipeline's failure slippage. This research uses a three-dimensional finite element modeling of trans-fault pipes to study the mechanical reaction and influencing factors of corroded pipelines under the action of oblique-slip faults. It is determined that the distribution of stress and strain as well as the pipeline's extension trend are changed when corrosion faults are present. The concentration of tensile and compressive strain along the corroded circular cross-section at the time of damage, followed by a gradual expansion through the entire corroded circumferential cross-section, and the pipeline's extrusion, folding, and bulging, are the manifestations of the influence of corrosion defects on the pipeline at damage. Tensile and compressive strains in the pipeline increase, failure slippage is reduced, and the pipeline experiences tensile damage and corrosion. The length of the pipeline corroded in the circumferential direction, the length of the corroded length in the direction of corrosion along the pipeline axis, and the corrosion depth increase all contribute to these outcomes. The location of corrosion defects has the greatest influence on the dynamics of the pipeline and is most dangerous in the large deformation section from -10 m to 10 m; the corrosion effect is very small when the corrosion is located on the right side of the fracture surface at 25 m. The risk of buckling damage is higher in this scenario, where the corrosion depth has the greatest effect. The conclusions of this paper can be used as a reference for the seismic and corrosion-resistant design of cross-fault pipelines.

Reliability index of a pipe transporting hydrogen submitted to seismic displacement

The reliability index was determined for a pipe presenting a corrosion defect, subjected to an internal hydrogen pressure, buried in a soil with a reaction and subjected to displacement due to seismic activity. The results are obtained by calculating the failure condition: strain demand greater than strain resistance, which is usually the basis of local strain-based design (LSBD). From a probabilistic point of view, this condition results from the product of the two probability distributions, Demand and Resistance. The Resistance is assumed to follow a normal distribution. The strain Demand is calculated assuming that the earthquake probability density follows a Gutenberg–Richter distribution. The reliability index is calculated by analytical method. This method is used to predict the reliability index of three different reference periods or seismic zones located in France.

Residual strength of a casing with corrosion semi-ellipsoid defect in high-sulfur gas wells

There are few studies on the residual strength of semi-ellipsoid defect casing considering the bending moment load in high sulfur gas well. In this paper, a numerical model of a casing with corrosion defects exposed to bending moment is proposed. The effect of the defect positions along the circumference on the residual strength of the casing with bending moment is investigated. Parametric studies highlight that defect size have significant effect on the residual strength of the casing, and the circumferential defect and the axial defect can change the critical internal pressure and the critical axial load. This finding has a significant guidance for residual intensity evaluation of a casing with defect.

Bond behavior between CFRP and steel structures with random corrosion defects

Steel structures in long-term service are difficult to avoid corrosion and can be reinforced by carbon fiber reinforced polymer (CFRP) bonding method. To investigate the corrosion effect on the bond behavior between CFRP and steel, a modified cohesive zone model was proposed and verified by experiment. Then, a series of random corrosion morphologies controlled by the size and the shape of corrosion pit were generated. Finally, by importing the random corrosion morphologies and the corresponding cohesive parameters distributions into the model, a parametric analysis was executed. Results showed that the ultimate load of CFRP-corroded steel bonding system was sensitive to the size of corrosion pit, while the stiffness had identical sensitivities to the pit size and pit shape. The ultimate load would reach the peak value when the average pit width Wp,avg was 1.0 mm and the average pit depth-to-width ratio (Dp/Wp)avg was between 0.12 and 0.14, whereas the stiffness would reach a high level when the Wp,avg was between 1.0 mm and 1.2 mm and the (Dp/Wp)avg was between 0.12 and 0.14. Moreover, the effective bond length would reach a high level when the Wp,avg was between 1.0 mm and 1.2 mm and the (Dp/Wp)avg was about 0.10.

Compositional and surface changes of retrieved stainless-steel hardware and its effects on surrounding soft tissues: A prospective study.

To evaluate the surface, compositional, and histological changes in the overlying soft tissues of retrieved stainless-steel mini-plates and screws used for rigid internal fixation in the maxillofacial skeleton. A prospective study was conducted comprising 60 patients who sustained maxillofacial trauma and underwent ORIF in our unit previously and who required hardware retrieval in the post-operative phase. The retrieved hardware was evaluated for surface and compositional changes with the help of a scanning electron microscope for surface roughness and corrosion changes. Energy-dispersive X-ray study was done to know the composition and metal release from the hardware. The data obtained from these results were compared with a control unused and a sterile stainless-steel mini-plate and screw. The effects of the corrosion changes of this hardware on the adjacent soft tissues were evaluated histologically to assess the cellular changes of the soft tissue cover overlying the stainless-steel mini-plates and screws. A total of 96 stainless-steel mini-plates and 380 stainless-steel screws were retrieved from 60 patients. The control plate was smooth without any surface and corrosion defects, while the retrieved mini-plates irrespective of the reason for removal have shown surface roughness. Fe and Ni ions were found to be significantly reduced in the retrieved mini-plates. The presence of CrC in the retrieved plates indicates corrosion, which was seen only in hardware retrieved from symptomatic patients. The histological study revealed chronic inflammatory cell infiltrate with hyalinized connective tissue in all the samples irrespective of the reason for the removal of the plate. Stainless-steel mini-plates and screws act as a potent foreign body material and initiate a localized inflammatory reaction due to its corrosive products with longer duration of stay. Hence, the authors advocate the overall shift in the use of stainless-steel hardware to titanium hardware for ORIF.

Quantifying the influence of corrosion defects on the failure prediction of natural gas pipelines using generalized extreme value distribution (GEVD) model and Copula function with a case study

Quantifying the influence of corrosion defects on the failure prediction of natural gas pipelines using generalized extreme value distribution (GEVD) model and Copula function with a case study

Development of a convolutional neural network model to predict the size and location of corrosion defects on pipelines based on magnetic flux leakage signals

This study employs the convolutional neural network (CNN) to predict the dimensions and locations of corrosion defects on steel pipelines based on magnetic flux leakage (MFL) signals. Extensive three-dimensional parametric finite element analyses are carried out to generate MFL signals corresponding to semi-ellipsoidal-shaped corrosion defects with different sizes and locations on a pipe model. The white noises characterized by different signal-to-noise ratios are considered in the analysis to represent the measurement errors in the real MFL inspection tool. The numerically generated MFL signals are used to train and validate the CNN model to predict the dimensions and locations of the corrosion defects. The results indicate that the developed CNN model achieves a high predictive accuracy. The study demonstrates the application of CNN model to improve the pipeline integrity management practice.

Silicon oxide anticorrosion coating deposition on alloy steel surface by low temperature plasma

In this work, honeycomb-like SiOx coating was successfully prepared on steel surface by atmospheric pressure low temperature plasma jet. The surface morphology, corrosion resistance and stability of the coating were systematically analyzed. In addition, the growth mechanism of the coating was discussed. The analysis revealed that the coatings were primarily composed of Si-O-Si and Si-OH groups, with a minor presence of Si-CH3 moieties. The coating obtained after two deposition cycles exhibits the highest level of uniformity and density, with minimal porosity and superior corrosion resistance. The increase in deposition cycles led to particle aggregation, augmented particle dimensions and porosity, which adversely affected the coating's performance. The dense SiOx coating resulted in a significant reduction in the corrosion current density of the alloy steel, and showed no significant corrosion defects when exposed to the crude oil simulant in 25 °C. The coating simultaneously enhanced the hydrophilicity and oil transfer of the steel surface. Finally, the coating exhibited self-cleaning properties, stability and high potential for safeguarding steel pipes against low-viscosity crude oil contamination. This study provides a general surface modification method for the preparation of corrosion-resistant coatings on metal surfaces under mild conditions.

Effects of two mild amino acids on benzotriazole residue desorption during cobalt post-chemical mechanical polishing cleaning: Experimental and theoretical studies

During the polishing process of the cobalt (Co) interconnect layer, the corrosion inhibitor in the polishing solution will leave an organic residue on the polished cobalt surface, which needs to be removed by the post-chemical mechanical polishing (CMP) cleaning process. However, given the active chemical properties of cobalt, the potent and corrosive complexing agents in traditional cleaning solutions have the drawback of generating new corrosion defects on the cobalt surface. In this study, an eco-friendly cleaning solution is developed utilizing tetraethyl ammonium hydroxide (TEAH), deionized water, and either sarcosine or serine, thereby ensuring the absence of any additional introduction of metal impurities. The removal effect of the cleaning solution on BTA was tested using atomic force microscopy (AFM) and X-ray photoelectron spectrometer (XPS). The results demonstrate that post-CMP cleaning with either sarcosine or serine yielded a cobalt surface with reduced roughness (2.78 nm and 2.63 nm), diminished Co-BTA content (10.6% and 9.5%), and a lowered contact angle (44.3° and 37.9°). To elucidate the mechanism of post-CMP cleaning, electrochemical measurements and molecular dynamics were employed. Initially, in the cleaning solution with a pH of 10.4, the adsorption of BTA and cobalt is minimized. Subsequently, as serine permeates through the BTA residue layer, the desorption of BTA is expedited through competitive adsorption. These findings contribute valuable insights into the mechanism of residue removal in post-CMP cleaning processes.

Quantitative method for evaluating corrosion defects and residual bearing capacity of bridge structural steel via MMM technique

The quantitative assessment of corrosion defects and residual bearing capacity is essential to ensure the safe operation of bridge steel structures. In this study, Q345qD steel was selected as the research object, and specimens with different corrosion levels were prepared using the electrochemical corrosion method. Metal magnetic memory (MMM) detection experiments and uniaxial tensile experiments on corroded steel plates were performed. A three-dimensional magnetic charge model of a corroded steel plate considering the end effect was built to explain the variation of the MMM signals. The finite element simulation results of the corroded steel plates were consistent with the experimental and theoretical results. Based on experimental and finite element data, the quantitative relationship between the corrosion depth h and the magnetic characteristic parameter Hn(z) is established with a relative error within 15 %. A quantitative relationship between the nominal tensile strength σu and the magnetic characteristic parameter Hn(z) is proposed with an evaluation accuracy within ±5 MPa. It is suggested that the proposed evaluation method is feasible in quantitatively evaluating the defects and residual tensile strength of corroded steel plates using the MMM technique.

High-Precision Corrosion Detection via SH1 Guided Wave Based on Full Waveform Inversion.

Corrosion detection for industrial settings is crucial for safe and efficient operations. Due to its high imaging resolution, the guided-wave full-waveform inversion tomography technique has significant potential for corrosion detection of plate metals. Limited by the long wavelengths of A0 and S0 mode waves, this method exhibits inadequate detection resolution for the earlier shallow and small corrosion defects. Based on the relatively short wavelength characteristics of the SH1 mode wave, we propose a high-precision corrosion detection method via SH1 guided wave using the full waveform inversion algorithms. By conducting finite element simulations of ultrasonic-guided waves on aluminum plates with varying corrosion defects, a comparison was made to assess the detection precision across A0, S0, and SH1 modes. The comparison results showed that, whether for regular or irregular defects, the SH1 mode wave always exhibited higher imaging accuracy than the A0 and S0 mode waves for shallow and small-sized defects. The corresponding experiments were conducted on an aluminum plate with simple or complex defects. The results of the experiments reconfirmed that the full waveform inversion method using SH1 guided wave can effectively reconstruct the shape and size of small and shallow corrosion defects within aluminum plates.

Synthesis of signal formation and processing blocks of diffuse light reflection sensor using FPGA PSoC5 microcontroller

The problem of partial implementing the functionality of the electronic blocks for forming and processing the diffuse light reflection sensor's signal using an FPGA-microcontroller PSoC5 is solved. The topicality of this problem is caused by necessity of precision and high resolution measurement of the difference between, on the one hand, the reference signal of light reflection from the clear sensor's working surface and, on the other hand, the signal of diffuse light reflection from the inspected corroded surface. For this purpose, in particular, a channels' multiplexer, measuring and reference operational amplifiers of the second stage, a delta-sigma ADC with differential inputs, as well as a PWM control and synchronization scheme are implemented on the built into microcontroller FPGA consisting of universal digital blocks (UDB) together with programmed logical devices (PLD). The only components implemented outside the FPGA-microcontroller are the first stage operational amplifiers (in amount of sixteen), the current pulses generator for LED, as well as power supply block. The combination of components synthesized on FPGA with a powerful 32-bit Arm Cortex-M3 core makes it possible to ensure flexibility of settings, to minimize the influence of dark currents of sensitive elements of the sensor's photodiode linear array as well as noises, to align programmatically the sensitivity of the measuring channels and to carry out sensor calibration. Thus, noise mitigation is implemented programmatically by ADC's data collection and averaging in measurement buffer or calibration buffer (for reference signal from clear working surface). Several software routines for mode selection and settings, channels scanning (including measurement and calibration with alignment), as well as for measurement data (difference between the measurement and calibration buffers) displaying and transfer to PC (via one of onboard communication devices) have been developed. These all features can allow implementing the algorithms for deep analysis of measurement data and for calculation of the characteristics of surface corrosion defects.

Objective characterisation of reinforced concrete with progressive corrosion defects through clustering and thresholding of infrared images

The research in this paper focuses on detection and quantification of subsurface damage in reinforced concrete (RC) structures by the analysis of infrared images. Experimental investigations were performed on RC slabs with embedded reinforcing bars (rebars). The corrosion mechanism in rebars was accelerated using an electrical circuit setup. The initial temperature of the slabs was adjusted in the environmental chamber and IR images were taken at regular intervals while they were exchanging heat to laboratory air through convection. Records of IR images were post-processed using an objective thresholding method proposed based on unsupervised k-means clustering. The results were discussed in context and with respect to the ASTM D 4788–03 recommendation for minimum detectable thermal contrast (0.5 °C) from delamination in bridge concrete by infrared thermography (IRT). The conclusions lead to recommendations for improved practical implementation of IRT that contribute to the broader prospects of structural health monitoring (SHM).

Effect and simulation of tensile stress on corrosion behavior of 7050 aluminum alloy in a simulated harsh marine environment

The corrosion behavior of the 7050 aluminum alloy was investigated in the presence of high concentrations of H+ and Cl- ions simulating the marine environment of high salinity and local acidification in tropical seas. The results highlight the significant influence of tensile stress on the corrosion rate of the aluminum alloy with higher stress levels resulting in faster corrosion. Under the influence of tensile stress, corrosion pits form on the alloy surface, and their depth increases with higher levels of applied stress. It is important to note that the presence of a corrosion defect leads to a pronounced stress concentration, resulting in a much faster rate of corrosion compared to other regions. However, when subjected to low tensile stress (≤174 MPa), the corrosion at the defect exhibits uniform characteristics similar to a uniform corrosion process. Moreover, the potential at the defect shifts positively with increasing stress level. Furthermore, stress has an effect on the diffusive behavior of the aluminum alloy, leading to a higher potential at the defect center compared to its surrounding region. Nevertheless, as the tensile stress is further increased, this behavior is disrupted and stress corrosion cracking becomes the dominant mode of corrosion.

Investigation into the mechano-electrochemical interaction of internal and external corrosion defects on pipe surfaces

Revealing the mechanical-electrochemical interactions (M-E) on internal and external defects in pipelines is of paramount importance for ensuring the safe operation of pipelines. The present study establishes a mechano-electrochemical multi-physics coupling model and develops a two-dimensional finite element (FE) model of internal and external defects on the pipe surface to investigate the M-E interaction of X100 steel pipe with corrosion defects on both internal and external surfaces. The results demonstrate that the M-E interaction is significantly influenced by the geometrical shape, relative position, and internal pressure of defects. Moreover, altering a single defect parameter can simultaneously impact the M-E interaction of two defects. As the depth of defects increases, the cross-sectional area between internal and external defects decreases, leading to an intensified interaction between mechanics and electromagnetics and a gradual concentration of M-E interaction at the center of defects. The magnitude of the M-E interaction exhibits a negative correlation with the length of the defect, while the presence of a long defect minimally impacts the M-E interaction on the opposing side. As the external defects gradually distance themselves from the internal defects, the M-E interaction diminishes and the concentration area of M-E interaction shifts in the opposite direction to defect migration, while stress in the non-defect region adjacent to both internal and external defects progressively intensifies. The increase in internal pressure significantly enhances the M-E interaction of internal and external defects, with the M-E interaction primarily focused on the minimum cross-sectional area of radial overlap between these defects. At low internal pressures, however, the M-E interaction becomes negligible.

Study on torsional response and ultimate loading of unbonded flexible risers under corrosion defects

During the process of deep-sea oil and gas exploitation, unbonded flexible risers (UFRs) are corroded by CO2 and other media over long periods of time, which causes serious damage to the tensile armor layers and threatens the safety of the UFRs in service. To study the effects of torsional response, ultimate loading, and failure mode on UFRs after corrosion, and to reveal the torsional failure mechanism of the UFR while considering corrosion defects, an 8-layer UFR torsional response model is established in this paper. Local bending of the UFR and lateral buckling failure of the inner tensile armor layer occur under counterclockwise ultimate torsion, whereas strength failure of the inner tensile armor layer occurs under clockwise torsion. When the degree of corrosion is 0.4 mm, the counterclockwise torsional stiffness of thickness corrosion, width corrosion, and combined corrosion decreases by 27.6%, 10.8%, and 28.4%, and the ultimate loading of counterclockwise torsion for thickness corrosion, width corrosion, and combined corrosion decreases by 37%, 13.4%, and 39.3%, respectively. Therefore, the influence of thickness corrosion and combined corrosion on the torsional response of UFRs is worthy of further attention.

Effect of Rinsing on Atmospheric Corrosion Environment of KT-1 Aircraft

Corrosion is difficult to predict and manage. Thus, understanding the characteristics of the atmospheric corrosion environment inside and outside the aircraft is necessary. A series of corrosion defects were found inside the KT-1 aircraft; hence, an atmospheric corrosion monitoring set was mounted inside the aircraft to measure the effect of external rinsing on the internal corrosion according to location (fuselage and wing). The effect of external rinsing was analyzed through surface analysis of the specimens and corrosion rate estimation using internal environmental parameters. Steel specimens within the monitoring set exhibited complete corrosion, while Ag specimens showed discoloration. External rinsing reduced the rate of chloride build-up inside the wing. Additionally, time of wetness (TOW) tended to increase with external rinsing regardless of location. Estimated and measured corrosion rates were positively correlated with TOW but negatively correlated with chloride accumulation rate. These results indicate the mixed effect of rinsing and require corrosion control for individual aircraft when deciding whether to apply cleaning for corrosion control.

Coil Spring Failure Analysis Reviewed from Residual Stress, Crytal Orientation, and Texture

Crystal defects can be identified through the crystallographic characteristics of crystal orientation (lattice), microstrain, and texture. Identification of crystal defects on the atomic scale through crystallography is very important in analyzing the mechanism of material properties due to the influence of dislocations. The slip mechanism is analyzed to minimize coil spring failure. This study aims to analyze the causes of coil spring failure based on crystallography. XRD testing was carried out for analysis of residual stress, crystal orientation, and texture using MAUD 2.94 version software. Hardness testing was carried out on the surface of the coil spring with locations near and far from the fracture using micro Vickers. The macro fracture morphology was analyzed using a DSLR camera and the micro fracture morphology was analyzed using SEM. The XRD result shows that the coil spring material has a tensile residual stress value of "202.4 ± 15.9 MPa" with the resulting crystal orientation showing the hkl (100), (200), (211), (200) fields. The plane (200) has a texture characteristic that is oriented towards the Rolling direction along the spring axis. Texture oriented towards Rolling Direction can be shown with a maximum probability value of 1.191. A high probability will have an impact on the presence of material surface defects. Surface defects are indicated by the presence of pit corrosion on micro and macro fracture morphology observations. The pit corrosion defects that occur in the failed coil springs are the beginning of the formation of crack initiation and cause stress concentration. The stress concentration will increase with loading and cause crack propagation.

Numerical investigation of the mechano-electro-chemical effect of X100 buried pipelines with pre-existing corrosion defects

This study investigates the corrosion kinetics and crack propagation in buried transmission pipelines made of high-strength low alloy steel API X100. Despite its cost-effectiveness and ability to withstand high operating conditions without increasing pipe wall thickness, the corrosion kinetics in near-neutral pH environments for this steel grade is not fully understood. To address this gap, two numerical models were developed. The first model, using COMSOL Multiphysics v5.6, showed higher electrolyte potential at the corrosion defect center due to stress-induced defect growth, increasing corrosion susceptibility. The second model, employing the XFEM approach, evaluated crack initiation, propagation, and von Mises stress distribution along the crack path. This research contributes to a better understanding of corrosion and crack behavior in corroded pipelines, aiding in their performance improvement in near-neutral pH soil environments.