Corrosion Defects Research Articles

Quantification of depth and morphology of internal corrosion defects by stepped eddy current thermography skewness under weak excitation conditions

In the nondestructive testing (NDT) of eddy current thermography of oil and gas tanks, the low and non-uniform temperature rise due to weak excitation conditions makes the quantitative estimation of the depth and area of defects still challenging. This work proposes a mathematical-physical model of skewness to characterize defect depth quantitatively. The skewness image is estimated in Gaussian scale space using the background difference method combined with the chunked threshold segmentation method to characterize the defect morphology. The experimental results show that the skewness is affected by the combination of defect depth and area. As the defect area decreases, the relationship between defect depth and skewness gradually degrades from nonlinear to linear, while the rate of change of skewness becomes insignificant. The skewness analysis model predicted the maximum MRE of 5.15%, the minimum R2 of 0.94 for defect depth, and the MRE of 8.39% for defect area. It shows that the skewness can effectively characterize the depth and morphology of internal corrosion defects.

Exploration of Interfacial Materials Chemistry Control to Improve Cu Wire Bonding Reliability

Copper wire bonding, with its advantages of higher electrical conductivity and better mechanical strength, has replaced gold wire bonding as a proven cost-effective electrical interconnection solution for IC packaging for the past 15 years. Early development of Cu wire bonding required overcoming of several technical challenges including bond pad damage caused by copper’s hardness and brittleness relative to gold. A more chemistry related challenge of using Cu as bonding wire is its well-known reactivity with oxygen. Inert atmospheric envelope of forming gas surrounding bonding capillary was developed to prevent oxidation of Cu wire during electronic flame off to enable a strong bonding. Another more elusive materials-chemistry related reliability challenge, with a typical low ppm occurrence, has been the chloride-induced corrosion defects between the Cu wire and Al bond pad. The opportunistic low-level chloride contaminations can originate from various points of packaging manufacturing process flow and often render it un-trackable. In this talk, we present recent efforts to systematically control interfacial materials chemistry across Cu bonding wire, Cu/Al bimetallic contacts and CuxAly intermetallic compounds with the aim to eliminate corrosion defects and improve the overall bonding reliability. The current prevailing manufacturing solution is to utilize Pd-coated Cu bonding wire that can only partially mitigate the CuxAly intermetallic corrosion vulnerability. We utilized a real-time corrosion screening metrology to explore the underlying interfacial materials chemistry drives vigorous corrosion between Cu wire and Al bond pad when exposed to trace level of chloride contaminant. Combining with SEM, sensitive infrared spectroscopy and electrochemical characterization, our data show strategic surface modification on both Cu bonding wire and exposed CuxAly intermetallic can have a significant impact on reducing corrosion defect rates. The obtained mechanistic insights provide several new strategies enabled by a novel Cu-selective passivation coating technology to effectively mitigate Cu wire bonding corrosion defects. Implications on further improving overall Cu wire bonding reliability will be present based on these new approaches that have low-cost and packaging friendly advantages.

Failure Pressure Evaluation of Corroded Pipeline Using Semi-Empirical and Finite Element Analysis

Abstract Computational simulation using the finite element method (FEM) has proven to be one of the most efficient methods for the correct evaluation of the structural integrity of pipelines with corrosion-induced defects. In this paper, the results of the failure pressure of corroded pipelines obtained with a computer tool called PIPEFLAW based on nonlinear finite element analyses are presented and compared with the failure pressures of corroded pipes obtained with twelve (12) advanced semi-empirical models from the literature. A computational code was created in the Python language to automatically obtain the failure pressure of randomly generated cases of corroded pipes, which allows the analysis of multiple piping cases with isolated external corrosion defects in an idealized configuration. For this purpose, the LHS (Latin Hypercube Sampling) approach was adopted for the design of experiments to obtain a better distribution of cases in the sample space. Comparisons between the results using the FEM and semi-empirical models show, as expected, that the semi-empirical solutions are more conservative in most cases analyzed in this work. A statistical model is proposed that adheres to the relative error distribution for some of the models used. Moreover, the influence of some parameters (pipeline thickness, defect depth, defect length, defect width, yield stress and ultimate stress) on the failure pressure was evaluated. It was found that in most of the studied models the error increases as the defect depth increases.

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

Possible Approaches to the Reconstruction of the Vyšehrad Bridge in Prague

Prague has two iconic views. The first is Charles Bridge with the silhouette of Prague Castle in the background, the second is the Vyšehrad Railway Bridge framed by the imposing structure of Vyšehrad. It has been a listed cultural monument since 2004. The Vyšehrad Railway Bridge was opened in its first form on 15 August 1872, its current appearance dates back to 1901. It is a riveted structure with three parabolic arches spanning about 70 m with verticals and diagonals in the shape of segmented cross-sections. The structure is an important technical cultural monument, which is also located in an exposed part of the Prague Monument Reserve. However, due to long neglected basic maintenance, the structure deteriorated to such an extent that the Railway Administration decided to demolish it. Having carried out an inspection and structural assessment of the bridge we are confident that it can be repaired, refurbished, and modified to provide a long and satisfactory additional service life for future operation of the railway and footways. In particular, localized corrosion defects resulting from inadequate maintenance over many years can be repaired and the structural components which fail to meet the assessment criteria in their current condition can be repaired or replaced. Expressed in weight, only 15 % of the structure by mass needs structural repair or improvement; the rest is satisfactory without further intervention, other than renewing the corrosion protection system. The paper is based on a study by Petr Tej, Andreas Galmarini and Ian Firth and will focus on a detailed survey of the bridge’s condition and the possibilities of its reconstruction for rail traffic. It describes the reconstruction system, replacement of individual elements and contact points. Part of the paper is also a proposal for the reconstruction and use of the stone viaduct for trade and services, including static and visual rehabilitation.

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.