Corrosion Pits Research Articles

The Role of Rare Earths on Steel and Rare Earth Steel Corrosion Mechanism of Research Progress

Corrosion has always been an important factor affecting the life of steel, which causes huge economic losses every year. How to improve the corrosion resistance of steel has always been a research focus. Adding rare earth elements into steel is an important method to improve the corrosion resistance of steel. In this paper, the effects of rare earth elements on steel are summarized, including the purification of molten steel, modification and modification of inclusions, improvement of grain boundaries by solid solution strengthening, the influence of phase transformation and the refinement of microstructure, and reduction in C and N desolubilization. On this basis, the progress of research on the corrosion resistance mechanisms of rare earth steel is summarized, focusing on rare earth-modified inclusions. This includes the changes in composition and sizes of inclusions by rare earth addition, promoting the transformation of MnS and Al2O3 in rare earth inclusions with regular shapes, smaller sizes and better performance, or composite rare earth inclusions. The corrosion pits that form in the early stages of corrosion are shallow in depth, fewer in number and light in corrosion degree. The effects of rare earth materials on the rust layer include: rare earth promotes the formation of a more stable corrosion product α-FeOOH, and rare earth promotes the formation of a dense rust layer, which covers the surface of the matrix and hinders the transmission of corrosion ions. The protective effect of the rare earth atomic layer on the substrate and the corrosion inhibition effect of rare earth ions are formed by the segregation of rare earth at the interface. In the end, the existing problems in the research into rare earth steel and future research directions are briefly put forward, including improving the addition process of rare earth steel, theoretical guidance on enhancing the corrosion resistance mechanism of rare earth steel, and extending the research from La, Ce, and Y steel to more rare earth steels.

Local–overall buckling behavior of corroded intermediate compression-bending H-section steel columns

The primary aim of this paper is to assess the impact of corrosion damage on intermediate H-section steel columns subjected to combined compression and bending about the strong axis. The study conducted a comprehensive investigation into the corrosion-induced transition in the buckling behavior of steel columns through experimental and numerical analyses. Six H-section Q355 steel intermediate columns were designed, with five undergoing an artificial spray-accelerated corrosion process. The three-dimensional scanning technology was employed to quantify the general corrosion and corrosion pits. Eccentric compression tests were carried out on intermediate H-section steel columns to investigate the effect of the different corrosion levels on the failure mode and load-displacement curves, as well as to determine local buckling load based on the load-strain curves. The test results showed that the corrosion characteristic parameters of each cross-section of the steel column exhibited irregularity and variation in all locations, reflecting the heterogeneity of corrosion. The density of corrosion pits exhibited a decreasing trend with increased corrosion duration. Corrosion remarkably reduced both the ultimate carrying capacity and local buckling capacity, with the most severely corroded specimen exhibiting an average cross-sectional area loss rate of 37 %, resulting in a 43 % and 51 % reduction in ultimate load and buckling load compared to the uncorroded specimen. Furthermore, the corrosion features substantially influenced the failure mode, resulting in a transition from overall buckling to local buckling or local-global interaction buckling. A numerical methodology was developed to incorporate the actual surface morphology of corrosion, and the reliability of the modeling method was validated through comparison with experimental results, further revealing the failure mechanism of corroded intermediate H-section steel columns under compression and bending about the strong axis.

Galvanic corrosion behavior of micro-arc oxidation coated Al-Zn-Mg-Cu alloy coupled with 316 L stainless steel in the salt-spray atmosphere

Micro-arc oxidation (MAO) coating with thickness, potential, current density, and impedance of 30 μm, −0.62 V, 7.2×10−8 A/cm2 and 88,730 Ω·cm2 was prepared on the surface of Al–Zn–Mg–Cu alloy to inhibit galvanic corrosion caused by its coupling with 316 L stainless steel. It was found that the MAO coating increased the potential of the galvanic corrosion zone (GCZ) from −0.67 V to −0.43 V, and decreased its current density from 3×10−3 A/cm2 to 4.4×10−7 A/cm2, resulted in a much lower corrosion rate and longer failure time. Salt-spray erosion can cause the MAO coating to detach gradually and formed the stepped corrosion pits at the GCZ. The galvanic corrosion process of the MAO coated 7085 alloy could be divided into three stages: (1) the electrolyte passes through the interconnected defects in the coating, leading to pitting corrosion beneath the coating; (2) the corrosion products block the interconnected defect channels in the coating, reducing the rate of galvanic corrosion; (3) the Al alloy substrate becomes fully exposed and contacts with 316 L stainless steel through the electrolyte, accelerating the galvanic corrosion and corrosion detachment. These findings confirm the effectiveness of MAO coatings in inhibiting galvanic corrosion and clarify the complex corrosion mechanisms involved, providing valuable insights for enhancing the durability of Al–Zn–Mg–Cu alloy in coupled environments.

Failure analysis of local effusion corrosion in small diameter gas pipeline: Experiment and numerical

In the later stage of gas well production, water–gas ratio increases, liquid carrying capacity decreases, gas field water accumulates in pipes for a long time, and the corrosion environment of pipelines becomes more and more severe. On the basis of carbon dioxide corrosion, microbial corrosion in gas field water accelerates catalytic pitting and finally leads to serious internal corrosion of pipelines. Therefore, accurate prediction of fluid distribution and flow characteristics in pipes is of great significance for engineering applications. In this work, the location and morphology of the corrosion pit were determined by physicochemical analysis. A computational fluid dynamics (CFD) model was established by using VOF and RNG k-ε models to predict fluid distribution characteristics and fluid accumulation locations in pipelines. The results showed that: 1) Corrosion and perforation occurred in the position of pipeline fluid accumulation. 2) The main elements of the corrosion pit on the inner surface of the pipe sample are O, Fe, C, S and Cl. The main corrosive substances in the pipeline corrosion pit are FeCO3 and Fe2O3. 3) The low-lying areas and uphill sections are prone to corrosion. A decrease in the fluid velocity in the pipe and a corresponding increase in the gas–liquid ratio will result in a greater accumulation of liquid in the pipe. 4) Magnetic flux leakage (MFL) detection method can be used to detect the characteristics and distribution of pipeline corrosion defects and determine the corrosion area. The research results are of great significance to the safety evaluation of small diameter pipelines for gathering and transporting in oil fields.

The effects of σ phase on localized corrosion of 2205 duplex stainless steel in the presence of Pseudomonas aeruginosa

Pitting and galvanic corrosion of 2205 DSS with σ phase were investigated in the presence of Pseudomonas aeruginosa. Pitting corrosion was accelerated by σ phase, and further promoted by P. aeruginosa. The σ phase changed the distribution of pitting sites from being concentrated on phase boundaries and α phase in the solution treated coupons to being around σ phase in the biotic medium. The galvanic corrosion between α and γ phases was enhanced by the bacterium, and σ phase led to anodic dissolution of γ phase instead of α phase in DSS with solution treatment.

Improving mechanical property and corrosion resistance of high electrical conductivity Al-Ce-Sc-Y and Al-Mg-Si-Ce-Sc-Y alloys by laser shock peening

The high electrical conductivity Al-Ce-Sc-Y and Al-Mg-Si-Ce-Sc-Y alloys were used to study the effects of laser shock peening on their mechanical property, pitting and intergranular corrosion resistance. The strength and elongation of the alloys were improved simultaneously at the expense of very low electrical conductivity after laser shock peening due to the gradient structure and residual compressive stress. After two side laser shock peening, the strength and elongation of Al-Ce-Sc-Y and Al-Mg-Si-Ce-Sc-Y alloys increased to 231 ± 3 MPa/16.2 ± 0.2 % and 359 ± 3 MPa/17.1 ± 0.3 %, respectively. The samples with two surface states were used to study the corrosion behaviors. The number and depth of corrosion pits can be significantly reduced by laser shock peening and the crystallographic corrosion morphology exists in the corrosion pits. After two side laser shock peening with polished surface, the intergranular corrosion depth of Al-Mg-Si-Ce-Sc-Y alloy can reach the minimum and the intergranular corrosion cracks are much finer at the same depth. The Al-Ce-Sc-Y alloy had no tendency of intergranular corrosion, but the unpolished surface was prone to form the deep corrosion pits rather than occurred uniform corrosion. According to the microstructure analysis, the corrosion mechanism of pitting and intergranular corrosion was revealed.

A microstructure-sensitive electro-chemo-mechanical phase-field model of pitting and stress corrosion cracking

An electro-chemo-mechanical phase-field formulation is developed to simulate pitting and stress corrosion in polycrystalline materials. The formulation incorporates dependencies of mechanical properties and corrosion potential on crystallographic orientation. The model considers the formation and charging dynamics of an electric double layer through a new general boundary condition for the solution potential. The potential of the model is demonstrated by simulating corrosion in polycrystalline materials with various grain morphology distributions. The results show that incorporating the underlying microstructure yields more extensive defects, faster defect kinetics, and irregular pit and crack shapes relative to a microstructurally-insensitive homogeneous material scenario.

Sparse reconstruction of ultrasonic guided wave signals of fluid-filled pipes by multistrategy hybrid DBO-OMP using dispersive Hanning-windowed chirplet model

Ultrasonic guided waves (UGWs) in fluid-filled pipes are subject to more severe dispersion and coherent noise than those of vacant pipes, posing significant challenges for defect identification and localization. To this end, a novel sparse signal decomposition method called multistrategy hybrid dung beetle optimization based orthogonal matching pursuit (MHDBO-OMP) using dispersive Hanning-windowed chirplet model was proposed, of which the model not only represents the nonlinear frequency and asymmetric envelope of the dispersive UGW, but also contains the mode and propagation distance information, and this model exhibits better matching and interpretability than the other UGW models. For dispersive perturbed UGW signals with multiple modes and features, MHDBO-OMP achieves high reconstruction accuracy in both signal reconstruction (RES < 0.3) and propagation distance estimation (RES < 3 cm). When applied to experimental UGW signals obtained from water/oil-filled pipes containing cracks and corrosion pits, MHDBO-OMP successfully reconstructs dispersion-compensated signals that solely contain feature signals, and the minimum location error is 0.72 cm while the average location error is 2.65 cm. © 2001 Elsevier Science. All rights reserved.

Revealing Crack Propagation and Mechanical Behavior of Corroded Aluminum Alloys

The mechanical properties and crack propagation behavior of aluminum alloys, both with and without corroded surfaces, were thoroughly investigated through molecular dynamic (MD) simulations. The study delved into the effects of corrosion depth and width on the mechanical properties of corroded aluminum alloys. It was found that as the corrosion depth increases, the yield strength experiences an initial decrease followed by a subsequent increase. This can be attributed to the impact of increased corrosion depth on the healing of surface roughness, which ultimately leads to significant changes in yield strength. Furthermore, the presence of corrosion pits was identified as a key factor in regulating the local microstructure evolution within the material, leading to pronounced differences in stress distribution localization. This, in turn, influenced the path of crack propagation within the material. These findings not only contribute to a deeper understanding of the behavior of aluminum alloys under corrosion, but also provide valuable insights for the development of aluminum alloys with enhanced mechanical properties.

Synergy effect of polyaspartic acid and D-phenylalanine on corrosion inhibition caused by Desulfovibrio vulgaris

Microbiologically influenced corrosion (MIC) poses a threat to various fields, particularly in piping and cooling water systems. As a green corrosion inhibitor, polyaspartic acid (PASP) faces challenges in achieving the intended corrosion inhibition against MIC due to biofilm. Therefore, mitigating biofilm might be the key to improving the corrosion inhibition of PASP. D-Phenylalanine (D-Phe) was selected as an enhancer to promote the inhibition of PASP on MIC caused by Desulfovibrio vulgaris due to its potential role in biofilm formation in this work. The joint application of PASP and D-Phe reduced the corrosion rate by 76.54% and obviously decreased the depth of corrosion pits with the maximum depth at 0.95 µm. Also, fewer cells adhered to the coupon surface due to the combined action of PASP and D-Phe, leading to thin and loose biofilm. Besides, both cathodic and anodic reactions were retarded with PASP and D-Phe, resulting in a low corrosion current at 0.530 × 10−7 A/cm2. The primary synergy mechanism is that D-Phe promoted the formation of PASP protective film via decreasing bacterial adhesion and thus inhibited electrochemical reaction and electron utilization of cells from metal surface. This study introduces a novel strategy to augment the effectiveness of PASP in inhibiting MIC.

Revealing the Nanoscopic Corrosive Degradation Mechanism of Nickel-Rich Layered Oxide Cathodes at Low State-of-Charge Levels: Corrosion Cracking and Pitting.

Ni-rich layered oxides have received significant attention as promising cathode materials for Li-ion batteries due to their high reversible capacity. However, intergranular and intragranular cracks form at high state-of-charge (SOC) levels exceeding 4.2 V (vs. Li/Li+), representing a prominent failure mechanism of Ni-rich layered oxides. The nanoscale crack formation at high SOC levels is attributed to a significant volume change resulting from a phase transition between the H2 and H3 phases. Herein, in contrast to the electrochemical crack formation at high SOC levels, another mechanism of chemical crack and pit formation on a nanoscale is directly evidenced in fully lithiated Ni-rich layered oxides (low SOC levels). This mechanism is associated with intergranular stress corrosion cracking, driven by chemical corrosion at elevated temperatures. The nanoscopic chemical corrosion behavior of Ni-rich layered oxides during aging at elevated temperatures is investigated using high-resolution transmission electron microscopy, revealing that microcracks can develop through two distinct mechanisms: electrochemical cycling and chemical corrosion. Notably, chemical corrosion cracks can occur even in a fully discharged state (low SOC levels), whereas electrochemical cracks are observed only at high SOC levels. This finding provides a comprehensive understanding of the complex failure mechanisms of Ni-rich layered oxides and provides an opportunity to improve their electrochemical performance.

Study of the Corrosion Behavior of Stainless Steel in Food Industry.

AISI 304L stainless steel is widely used in the processing equipment and food and beverage handling industries due to its corrosion resistance, hygienic properties, and cost-effectiveness. However, it is prone to pitting and crevice corrosion phenomena, the development of which can be influenced by factors such as chloride concentration, temperature, humidity, and bacterial presence. Surface treatments, including roughness levels and residual tensile stress, can significantly affect the corrosion behavior and resistance of the material. This study aims to evaluate the impact of three different surface treatments on the durability of AISI 304L steel. The correlation between surface roughness resulting from pre-treatment and pitting potential values will be examined. Additionally, the influence of different concentrations of biocide additives on surface durability will be assessed to determine the maximum effective concentration for preventing pitting phenomena. Passivation processes will also be evaluated as a potential solution for improving the pitting potential and overall durability of the components. By optimizing surface treatments and biocide concentrations, improved corrosion resistance and durability can be achieved, ensuring the long-term performance and reliability of AISI 304L steel components in critical applications such as food processing and beverage handling.

Effect of C content and annealing on dendrite structure evolution and corrosion resistance of CoCrFeMnNi alloys

In this study, a series of CoCrFeMnNiCx (0–0.8 at% C) high-entropy alloys (HEAs) were prepared by vacuum arc melting and subsequently vacuum annealed at 800°C or 1000°C for 120 h. The aim was to investigate the microstructure evolution and corrosion behavior of the as-cast and annealed CoCrFeMnNiCx alloys in a neutral corrosion solution. Experimental results revealed that the addition of C can refine the as-cast dendrite structure, with an optimal C content of 0.4 at%. Annealing treatment led to a decrease in C solubility in the face-centered cubic (FCC) phase, resulting in the precipitation of carbides. In a 3.5 wt% NaCl neutral solution, the as-cast alloy containing 0.4 at% C exhibited the highest corrosion resistance. After annealing at 1000°C, the alloy's pitting potential and corrosion resistance were further improved. The corrosion behavior of both the as-cast and annealed CoCrFeMnNiCx alloys was primarily composed of pitting and intergranular corrosion, although the dominant mechanism varied among these alloys. This study establishes a correlation between microstructure evolution and corrosion behavior, providing insights for the design of high-entropy alloys with superior corrosion resistance.

A Study of Accelerated Corrosion of Stainless Steels under Highly Oxidizing Conditions

The corrosion behavior of certain steels under extremely oxidative conditions, simulating the impact of water radiolysis on stainless steels, has been investigated. Radiolysis generates aggressive species, including radicals, solvated electrons, and hydrogen peroxide, potentially leading to corrosion over time in materials typically considered resistant. To expedite the kinetics of this phenomenon, drastic conditions were employed, involving high concentrations of peroxide in a strongly acidic environment. Under these conditions, corrosion can manifest rapidly. The varied responses of different steels are contingent upon their inherent nature and chemical composition, notably the chromium and nickel content. Steels with higher chromium and nickel concentrations exhibit increased resistance to corrosion, even in such severe environments. Microscopic corrosion mechanisms involve pitting and intergranular corrosion. Pitting results in the formation of craters on surfaces, while intergranular corrosion leads to the detachment of grains.

The role of lithium in hydrogen trapping and embrittlement of Al-Cu-Li alloys: Experimental study and DFT calculations

The role of lithium in hydrogen embrittlement (HE) and trapping of Al-Cu-Li alloys were investigated in experimental and density functional theory (DFT) calculations. The tensile curves and fracture morphology show that the Li-contained samples are more sensitive to HE than the Li-free samples and the HE sensitivity increases with the aging time expansion. The Transmission Electron Microscope (TEM) analyses reveal that the number density of T1 (Al2CuLi) precipitates increases about 66.8% with aging process, suggesting that HE sensitivity is exacerbated by T1 precipitates. In addition, the lithium in T1 precipitates, solid solution matrix and solute segregation grain boundaries (GBs) always has a high affinity to hydrogen according to DFT calculations, where T1 precipitates have the highest hydrogen trapping energy with 0.736 eV/H atom. Moreover, the influence of hydrogen on Al-Cu-Li alloys was investigated using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and electrochemical corrosion analysis. These analyses indicate that hydrogen exists in the form of hydrogen atoms, which results in a reduction in corrosion potential (Ecorr) from −676.3 mV to −699.3 mV by approximately 20 mV and an increase in corrosion current density (icorr) from 2.1×10−6 A/cm2 to 10.8×10−6 A/cm2 by an order of magnitude. The accumulated hydrogen atoms eventually lead to corrosion pits and blisters on the surface of alloys.

Corrosion of API 5L X60 Pipeline Steel in Soil and Surface Defects Detection by Ultrasonic Analysis

The corrosion steels phenomenon is one of the main problems in the oil industry, such as in buried transmission pipelines used for high gas pressure for long distances. Steels are protected from the external soil corrosion through a bituminous coating, whose action is coupled with a cathodic protection system, which aims to maintain steel in its protection field and thus to avoid any corrosion risk. However, steels in service may experience external surface defects like corrosion pitting and cracking due to electrochemical or mechanical interactions of bare steel with an aggressive soil solution after steel protection failure. These are concerning phenomena and are the major threats of the pipeline transmission system’s reliability and ecological safety. Corrosion mechanisms are varied and can be evaluated by different methods, such as electrochemical measurements, which are influenced by various factors like temperature, pH, soil characteristics, resistivity, water content, and as well mechanical stresses. Corrosion results from simulated artificial soil solutions showed that steel is sensitive to corrosion by soil. Surface defects detection was carried out using an ultrasonic non-destructive method such as C-Scan Emission testing and the time of flight diffraction technique (TOFD) ultrasonic non-contact testing method. After propagation of the ultrasonic waves, the diffracted ultrasonic reflected wave occurring at the edges of the defects appears due to the presence of a corrosion defect by generating defect echoes. The C-Scan ultrasonic image shows surface reflection, including corrosion defects on interfaces with varying acoustic impedances. The cross-transverse speed ultrasonic propagation through the plate including defect is modified, revealing more surface defects, and cross-transverse speed is shown to increase ultrasonic detection presents some advantages, such as precision and speed of detection without alteration to the structure. This method can be used in the industrial context as an intelligent industrial robotics technique.

Failure investigation of an elbow pipe used in sewage water treatment facility

AbstractIn this research work, a real case of failed ASTM A860 WPHY 65 long elbow pipe coated with inorganic zinc ethyl silicate primer is collected from a treatment facility to investigate the root causes of its failure, which was reported after approximately 28 months of use. The failure was investigated using visual observations, metallurgical analysis using optical emission spectroscopy, mechanical testing, X‐ray diffraction of corrosion product, chemical analysis of sewage and corrosion rate test of the elbow using a three‐electrode potential technique, fractographic analysis using scanning electron microscope along with computational analysis to confirm the results. Through the testing, it was observed that severe depletion in the strength can be attributed to erosion–corrosion caused by various impurities present in the sewage, leading to the generation of corrosion pits and turbulent eddies and stresses generated due to sudden changes in fluid flow direction along with gases present in sewage reacting with a base metal. Various failure mechanisms that have led to pipe failure are discussed in this paper, along with a listing of preventive measures to delay it.

Corrosion-induced fracture of Cu–Al microelectronics interconnects

We present a mechano-chemical model that couples corrosion, mechanical response, and fracture. The model is used to understand the failure of Cu wires on Al pads in microelectronic packages using a multi-phase field approach. Under high humidity environments, the Cu-rich intermetallic compounds (IMC), Cu9Al4, formed at the interface between Cu and Al, undergo a corrosion degradation process. The IMC expands while undergoing corrosion, inducing stresses that nucleate and propagate cracks along the interface between the Cu-rich IMC and Cu. Furthermore, the volumetric expansion of the IMC may cause damage to the passivation layer and enhance the nucleation of new corrosion pits. We show that the presence of a crack accelerates the corrosion process. The model developed here can be extended to other systems and applications.

Synergistic protection of borate and silicate salts composite for controlling the chloride-induced pitting and uniform corrosion of steel reinforcement bars embedded in mortars

In this study, the efficacy of the combined effect of borate and silicate alkali metal salts added to mortars for controlling the chloride-induced uniform and localized corrosion of embedded steel rebars is examined. The individually added salts in mortars are found to have insignificant effects in terms of reducing the uniform corrosion rate and localized damage. However, their combination (0.50% sodium tetra borate + 0.10% sodium silicate added with respect to the weight of the binder) provides complete protection to reinforcements tested for long durations under wet/dry treatments with mortars in saline water and laboratory atmospheres. Electrochemical impedance spectroscopy, direct current cyclic polarization, polarization resistance, and visual observations are used for quantitative and qualitative evaluations of the protective effects of the tested additives. X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analysis of the corrosion products formed on the embedded steel surfaces help explain the possible mechanisms behind the considerable improvement in the inhibitive effects of a mixed composition of borate and silicate. This combination also improves the compressive strength and workability of the mixed concrete. The results reveal that the synergistic protection provided by a mixture of borate and silicate can be attributed to the co-deposition of an iron-boron + ferrosilicate + cortensitite (an iron-silicon phase) film on the rebar surface.

Characteristics of the non-uniform corrosion of the steel bars extracted from the marine transportation infrastructures

This paper investigates the spatial morphological characteristics of non-uniform corrosion of reinforced concrete in coastal areas. A series of naturally corroded reinforced concrete specimens were retrieved from marine transportation infrastructure. Non-destructive tests were conducted by X-ray computed tomography (CT). The morphological propagations of the corrosion pits were explored, and the spatial distribution of non-uniform corrosion of the steel bars was analyzed in both longitudinal and circumferential directions. The results show that the non-uniformity of corrosion is related to both the corrosion degree and the morphology of corrosion pits. When the morphology of corrosion pits is similar, non-uniformity decreases exponentially with the corrosion degree of the steel bars. The morphologies of corrosion pits can be divided into two main categories: surficial corrosion pits and deep corrosion pits. The morphologies are related to the non-uniformity of the concrete surrounding the steel bar. When the corrosion degrees are similar, deep corrosion pits are more significant than surficial corrosion pits for the non-uniformity of the corrosion. The eccentricity was adopted to quantify the corrosion non-uniformity of bars with high corrosion degrees. These results provide a new perspective for evaluation on the non-uniform corrosion of steel bar in the marine transportation infrastructures.