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Unveiling materials corrosion pathways is significant for understanding the corrosion mechanisms and designing corrosion-resistant materials. Here, we investigate the corrosion behavior of Sn@Ni3Sn4 and Sn nanocrystals in an aqueous solution in real time by using high-resolution liquid cell transmission electron microscopy. Our direct observation reveals an unprecedented level of detail on the corrosion of Sn metal with/without a coating of Ni3Sn4 at the nanometric and atomic levels. The Sn@Ni3Sn4 nanocrystals exhibit pitting corrosion, which is initiated at the defect sites in the Ni3Sn4 protective layer. The early stage isotropic etching transforms into facet-dependent etching, resulting in a cavity terminated with low-index facets. The Sn nanocrystals under fast etching kinetics show uniform corrosion, and smooth surfaces are obtained. Sn nanocrystals show creeping-like etching behavior and rough surfaces. This study provides critical insights into the impacts of coating, defects, and ion diffusion on corrosion kinetics and the resulting morphologies.

The heat-treatment process exerts a substantial influence on both the quantity and morphology of reversed austenite in 17-4PH stainless steel. In this study, the effects of different ageing treatment methods on the microstructure and corrosion resistance of the steel were investigated. Through the observation of microscopic morphology, it was found that adjustment and ageing treatment and double ageing treatment were more conducive to the migration of elements in the steel than single ageing treatment, and they also improved the microstructure. In addition to improving the uniformity of alloy element distribution, uniformity also controls the reversed austenite content. By controlling the content and distribution of reversed austenite, the stability of the corrosion film formed at the interface can be improved, thereby improving the corrosion resistance of stainless steel. The stainless steel, after adjustment treatment and ageing treatment, has better corrosion resistance. The electrochemical corrosion resistance in a high-temperature and high-pressure underground environment was evaluated based on parameters including passivation current density and passivation potential. The results revealed a significant improvement of 50.5% in electrochemical corrosion resistance and a remarkable increase of 45.96% in pitting corrosion resistance. Furthermore, the FeCl3 pitting test demonstrated a substantial decrease of 63.16% in pitting density and a reduction of 27.96% in the uniform corrosion rate. [ABSTRACT FROM AUTHOR]

The corrosion failure of 304 and 2205 stainless steels in fuel cell was analyzed by measuring the chemical compositions of steel substrate and ions concentration of condensate as well as corrosion morphology observation. It revealed both of them, especially the 2205SS, were severely corroded after one-month exposure. The austenitic 304SS with higher Ni content was found to be more corrosion resistant than 2205SS in this environment. The primary cause for the pitting corrosion of stainless steels in fuel cell system was the acidic high-temperature condensate which contains chloride ions released from thermal insulation powders. To resolve or mitigate this problem, the flue gas leakage from the system shall be avoided or controlled. The aggressive substances (chlorides, acids, etc.) in the thermal insulation powders should be eliminated or reduced. In addition, other materials with higher Ni content (e.g., Ni-based alloys) might be feasible in this environment. [ABSTRACT FROM AUTHOR]

In this study, the corrosion experiments combined with first-principles calculations were used to study the adsorption behavior and pitting corrosion mechanism of Nb and S on the TiN surface. The results of SEM indicated that Nb and S were obviously enriched on the TiN surface, and the enrichment of S was stronger than that of Nb. The results of segregation energy indicated that Nb and S tended to segregate on the surface of Fe (110) and TiN (100), and the segregation of S was stronger than that of Nb. The results of adsorption energy indicated that the vacancy points and top points on the TiN (100) surface were the most stable for Nb and S, respectively, and the adsorption stability of S on the TiN (100) surface was stronger than that of Nb. The results of co-adsorption energy indicated that both Nb and S promoted the mutual adsorption on the TiN (100) surface, the co-adsorption stability of top adsorbed S on the TiN (100) surface with pre-adsorbed Nb was stronger than that of vacancy adsorbed Nb on the TiN (100) surface with pre-adsorbed S, and this co-adsorption effect was effective within a certain distance. These findings will be helpful to understand the pitting corrosion mechanism of rebar matrix induced by TiN. [ABSTRACT FROM AUTHOR]

The orientation of lamellar eutectoid (α2 + γ) structure in the Ti50Al48Mo2 alloy was controlled by in-situ directional solidification and thermal processing (DS-TP). The eutectoid orientation was parallel to the directional solidification direction by DS-TP, instead of 45 deg or being perpendicular during directional solidification. The spacing and orientation of lamellar eutectoid influenced corrosion resistance and the evolution of corrosion morphologies in both transverse and longitudinal sections. As the growth velocity decreased, temperature gradient increased, the lamellar spacing decreased and the directional orientation of eutectoid was significantly enhanced, the micro-galvanic effect between the γ and α2 phases was weakened, the sensitivity to pitting corrosion decreased, the corrosion resistance of the alloy increased. The alloy by DS-TP exhibited improved anti-corrosion performance with the minimum lamellar spacing (1.02 μm) and the eutectoid orientation being parallel to the directional solidification direction. On account of directional solidification, the corrosion resistance of longitudinal section was better than that of transversal section in directionally solidified alloys. Owing to the existence of only one eutectoid growth orientation and similar lamellar spacing in the transverse and longitudinal sections of the alloy by DS-TP, consequently the corrosion resistance of both transverse and longitudinal sections was improved synergistically and showed isotropic. [ABSTRACT FROM AUTHOR]

Surface particles on multiarc ion plated coatings are common defects, and their influence on the service performance of coatings is rarely defined. The CrAlN coatings were deposited on the tungsten steel (YG8) substrates using multiarc ion plating. The effects of the substrate bias voltages and nitrogen flow rates on the quantity of the surface particles were investigated, and the influence of the surface particles on the corrosion resistance of the coatings is quantitatively characterized. The morphology of surface particles was characterized using a scanning electron microscope. The quantity of the surface particles was counted by image software. The corrosion resistance of the coatings was evaluated through an electrochemical workstation. The results show that the quantity of surface particles decreased with the increase in the substrate bias voltage and nitrogen flow rate. The corrosion resistance of the coatings showed a positive correlation with the quantity of the surface particles, and it decreased dramatically when the quantity of the surface particles exceeded 111/10 000 μm2. The corrosion mechanism of the coatings was attributed to the defect-induced pitting corrosion. [ABSTRACT FROM AUTHOR]

Due to the increase in severe consequences of mild steel corrosion, the development of coatings with improvement in corrosion-resistant properties has become very essential. In this work, benzotriazole (BTA) was encapsulated into halloysite nanotubes (HNTs) for inhibiting the corrosion of mild steel surface. The BTA-encapsulated HNT exhibits pH-responsive properties over a wide range of pH. It was found that a large amount of BTA was released at pH 3 (48 %), followed by pH 7 (30 %) and least in the case of pH 10 (20 %). At neutral pH, a rapid release of BTA was observed during initial exposure, reaching a steady-state later, with no significant release further. A salt immersion test was carried out after immersing mild steel (MS) substrates in BTA-HNT nanopowder dispersion in 3.5 wt% NaCl at different pH. SEM images and EDS maps confirmed that corrosion product formation on MS surface at pH 3 was significantly more with corrosion pits along with HNTs throughout the surface. At pH 7 and 10, corrosion pits were observed with very few halloysite nanotubes on the surface. An optimum amount of BTA is required to inhibit corrosion, excessive release may cause more Cl− ions to penetrate, leading to more corrosion. Electrochemical data also reveals the same trend, where the i corr value was maximum for pH 3 (1.09 × 10−5 A/cm2) > pH 7 (4.74 × 10−6 A/cm2) > pH 10 (3.43 × 10−6 A/cm2). Therefore, results suggest that BTA-encapsulated HNT can be efficiently incorporated into the coating matrix for their controlled release to provide corrosion protection under varying neutral and alkaline marine environments. [Display omitted] [ABSTRACT FROM AUTHOR]

ABSTRACT Zr‐based conversion coatings represent an environmentally conscious alternative to traditional phosphating and chromating in the automotive industry. In this study, we employ XPS and LEIS to investigate the formation of Zr‐conversion layers on Zn–Mg–Al alloy after alkaline and acidic model pretreatments. On alkaline pretreated surfaces, a Zr‐oxide/oxyfluoride layer and an underlying Mg–Al–fluoride layer are formed, whereas acidic pretreatment results in only an oxidic layer. The thickness of the Zr‐layer depends on pretreatment pH and immersion time. Acidic treatment achieves an approximately 23 nm‐thick Zr‐oxide/oxyfluoride layer after 1 min, while prolonged treatment increases the thickness of the oxidic layer for strong alkaline and acidic conditions. Mild alkaline pretreatments, however, do not benefit from extended immersion. F‐induced corrosion pits are observed after mild alkaline treatment. The strong alkaline pretreatment proved to be the most efficient in creating a double‐layered Zr‐conversion coating with increased oxidic layer thickness over time. [ABSTRACT FROM AUTHOR]

Localized corrosion sometimes brings about unanticipated and catastrophic damages in petrochemical pipelines and pressure vessels. For localized corrosion modeling, multicomponent reactive transport and corrosion morphology evolution are two arduous problems that involve multi–physical‐(electro) chemical processes along with multi–temporal and spatial scales. In this study, the lattice Boltzmann method (LBM) is employed to shed some light on the evolution of localized corrosion on a heterogeneous surface focusing on the effects of electrolyte ohmic resistance and diffusion. The corrosion pit is always initiated at the junction of anode and cathode sites; however, quite different morphologies are prompted under ohmic control or ohmic‐diffusion control. Under ohmic control, the pit propagates along the interface of the anode and cathode. Under ohmic‐diffusion control, the pathway of reactive species is broadened, and the corrosion morphology is developed into a more regular shape, like a flattened semicircle in 2‐D modeling. This work presents the huge potential of LBM in long‐term corrosion modeling. [ABSTRACT FROM AUTHOR]

The electrochemical chlorine evolution reaction (CER) is an important electrochemical reaction for industrial applications, but it has serious problems, such as the short service life and low electrolytic efficiency in the extremely dilute chlorine-containing solution. In this paper, a RuO2–TiO2/IrO2–Ta2O5 (RuTi/IrTa) electrode was prepared via a thermal decomposition method involving alternate coating with precursor solutions with two active components, which significantly improved the service lifetime and CER selectivity of electrode materials with low Ir content. The experimental results indicate that the accelerated lifetime (AL) of the RuTi/HC–IrTa electrode with an Ir loading of 374 μg cm−2 can reach 602 h. Although the Ir loading of the HC–IrTa electrode (680 μg cm−2) is about twice that of the RuTi/HC–IrTa electrode, the AL of the HC–IrTa electrode is only 245 h, and the AL of the RuTi electrode (Ru loading: 180 μg cm−2) is only 5 h. If the precursor solutions of HC–IrTa and RuTi electrodes are simply mixed, the AL of the obtained RuTi–HC–IrTa electrode is only 41 h. This suggests that the increase in AL does in fact originate from changing the coating method, rather than simply the use of multiple active components. In addition, the SEM results indicate that the increase of the AL of RuTi/HC–IrTa is due to the change of the corrosion mechanism from pitting corrosion to surface corrosion of active components. Moreover, the CER selectivity of the RuTi/IrTa electrode has also been improved. This may be due to the change in the electronic structure, which is demonstrated through XPS characterization. The RuTi/IrTa electrode has a high electrolysis efficiency in the electrolysis of low-chlorine-concentration solutions. In the preparation of electrochemical disinfection technologies (EDTs), such as acidic electrolyzed water (AEW), more available chlorine content (ACC) can be obtained. [ABSTRACT FROM AUTHOR]

• The wooden structures unearthed at the Kasba Oudaya site exhibited cell wall collapse, while the nails displayed signs of surface weakening caused by chloride ion activity. • The presence of archaeological wood in the impregnation bath lowers the pH of the 10 % PEG-200 solution and accelerates its corrosive effect on steel. • Crevice corrosion develops at the nail-wood interface during impregnation with 10 % PEG-200 with significant diffusion of iron into wood. • The relative concentrations of chloride and sulfate in the 10 % PEG-200 impregnation bath change over time. • The 10 % PEG-200 soaking solutions provide favorable conditions for the development of various microorganisms. Electrochemical and biological analyzes were carried out on iron-wood composite archaeological objects from the "KASBA-OUDAYA" site in Morocco in 10 % PEG-200 solutions. Electrochemical measurements of steel combined with wood were made possible thanks to a proposed steel-wood configuration, with characterization of the surfaces after natural aging tests focused on the steel-wood interface by scanning electron microscope. The Mohr and Nephelometric method allow the determination of chloride and sulfate ions. While the biological study is ensured by isolation and enumeration of strains. The results revealed that the presence of wood in the PEG-200 solution decreased the pH of the solution and accelerated corrosion of steel. At the interface, we observe the development of pitting corrosion zones. In addition, PEG-200 solutions constitute a favorable environment for the proliferation of microorganisms. [Display omitted] [ABSTRACT FROM AUTHOR]

Al-based metallic glasses (MGs) effectively circumvent the longstanding tradeoff between corrosion resistance and mechanical properties inherent in commercial Al alloys due to their distinctive structural and compositional attributes. This article systematically elucidates the effects of composition and microstructure on the corrosion evolution process, particularly regarding pitting corrosion. This comprehensive examination encompasses aspects such as Cl− adsorption, passive film characteristics, and the stability of pit growth, and based on insights drawn from this exhaustive review of the literature, it advocates for further investigations aimed at advancing the development of corrosion-resistant Al-based MGs. [ABSTRACT FROM AUTHOR]

This study aims to examine the variation in corrosion characteristics and tensile properties of WE43 magnesium alloy in an actual marine atmospheric environment by means of outdoor exposure tests. The macroscopic corrosion morphology, microstructure, and tensile properties were analyzed. The results indicated that WE43 alloy will corrode rapidly during exposure under marine atmospheric environmental conditions, resulting in a loose and porous Mg(OH)2 layer on the surface. The Mg matrix was mainly consumed as an anode, leading to the occurrence of corrosion pits. With the increase in exposure time, both the tensile strength and plasticity of WE43 alloy gradually deteriorated. After exposure for six months, the elongation and area reduction were significantly reduced, with a reduction ratio of more than 50%. After 18 months of exposure, the ultimate strength of the alloy decreased from 359 MPa to 300 MPa. According to an analysis of fractures in the alloy, the corrosion pits on the sample surface were the main reason for the decrease in tensile properties. [ABSTRACT FROM AUTHOR]

Surface modifications not only improve the corrosion resistance of Co-Cr-Mo dental alloys (Bego Wirobond® C) but also ensure their long-term performance and reliability in dental applications. This paper describes the preparation of single-layer TiO2-ZrO2 sol–gel coatings on the Co-Cr-Mo dental alloy using the method of dip-coating. The TiO2-ZrO2 sol–gel coatings were sintered at 300 and 500 °C. SEM analysis shows that sintering at 300 °C produces a uniform, slightly dense structure without micro-cracks, while sintering at 500 °C results in a denser structure with micro-cracks due to higher stress and shrinkage. EDS confirms that sintering temperature affects the elemental composition of the coating, with higher temperatures causing the volatilization or diffusion of Ti and Zr. Roughness measurements indicate that the Ra value increases with the sintering temperature, meeting dental application requirements. Electrochemical measurements by open-circuit potential, EIS, and cyclic potentiodynamic curves demonstrate that sintering temperature and saliva composition affect corrosion resistance, with NaF and mouthwashes (Listerine Total Care Teeth Protection® and Meridol®) generally increasing charge transfer resistance and double-layer capacitance. The ceramic TiO2-ZrO2 coatings significantly reduce pitting corrosion susceptibility at physiological and acidic pH, with the 500 °C sintered coating showing better protective properties. These findings highlight the potential of TiO2-ZrO2 coatings in enhancing the performance of Co-Cr-Mo dental alloys. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to assess the pitting resistance of austenitic stainless steel welded joints fusion zone (FZ) with high density of inclusions before and after surface treatment, including potentiostatic pulse technique (PPT) and pickling. Design/methodology/approach: The potentiodynamic polarization tests and critical pitting temperature tests were carried out for estimating pitting resistance. The PPT and pickling were performed as surface treatment. Scanning electron microscope (SEM) and energy dispersive spectrometer were used for characterize the microstructure and elemental distribution. Electron back-scattered diffraction (EBSD) was used to assess the portion of phases and morphology of grains. Findings: The weld metal exhibits a higher degree of alloying compared to the base metal, and it contains d-phase and sulfur-containing inclusions. Sulfur-containing inclusions serve as initiation sites for pitting, and they diminish the pitting resistance of weld metal. Both PPT and pickling can remove sulfur-containing inclusions, but PPT causes localized dissolution of the weld metal matrix around the inclusions, while pickling does not. Because of the high density of inclusions, certain pits initiated by PPT are significantly deeper, which makes the formation of stable pitting easier. Because of the high density of inclusions, certain pits initiated by the PPT are deeper. This characteristic facilitates the progression of these initial defects into fully developed, stable pits. Originality/value: Analysis of pitting initiation in shielded metal arc welding FZ with PPT and ex situ SEM tracking observation. Explanation of why the PPT surface treatment is not able to enhance the pitting resistance of stainless steel with a high inclusion density. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the crevice corrosion behavior of carbon steel in neutral/alkaline environments utilizing a transient multi-physics field model. Design/methodology/approach: The crevice corrosion of carbon steel with different solution pH and crevice width was modeled, incorporating mass transfer, homogeneous phase and localized electrochemical reactions. The extent of crevice corrosion was evaluated by the geometric deformation of the model mesh. The hydro-chemical state inside the crevice was discussed through the Cl− concentration and potential distribution of the solution. Findings: Results revealed that the formation of pitting corrosion near the crevice mouth was accelerated in a neutral solution. When pH = 8 and pH = 9, the carbon steel matrix was dissolved and the Cl− content within the solution was significantly reduced due to the higher concentration of hydroxide ions (OH−). Originality/value: The crevice corrosion behavior of carbon steel in neutral/alkaline environments is closely associated with solution pH rather than the crevice width. The inhibition of crevice corrosion in alkaline environments was proved by finite element simulation. These findings provide valuable insights that can be applied in engineering applications to prevent and mitigate crevice corrosion in neutral/alkaline environments. [ABSTRACT FROM AUTHOR]

The corrosion resistance of Zr55Cu30Al10Ni5 amorphous alloys fabricated by twin-roll strip casting using various process parameters was systematically investigated compared with 316 stainless steel. Potentiodynamic polarization tests indicated that pure amorphous alloy sheets possessed the best passivation in NaOH and H2SO4 solutions, but pitting corrosion was observed in NaCl solution. In NaOH and H2SO4 solution, the corrosion current density of amorphous matrix is increased by nearly two times, and the corrosion rate increases accordingly. The presence of Al-rich microcrystallites retained from the melt in the amorphous matrix reduces the corrosion resistance of the sheets. The preferential attack occurs on the microcrystallites due to the formation of a passivation film of composition and structure different from that of the substrate. The study on the corrosion properties of twin-roll cast-rolling amorphous provides theoretical guidance for expanding its practical application. It provides new ideas to extend the application of amorphous alloys in practical environments. [ABSTRACT FROM AUTHOR]

Turbine blades recovered from the Apollo Saturn V rocket F-1 engines were examined to determine an appropriate conservation protocol. Significant corrosion damage was observed in the turbine blades which appear to be made of a nickel based γ–γ′ superalloy. Pitting corrosion appears to have breached the surface of the turbine blades, and subsequently a form of dealloying corrosion preferentially attacked the γ′ phase. This corrosion left behind a thin network of interconnected γ phase, causing a severe loss of density of the blades and fragility of the blades. The particular alloy used for these turbine blades does not appear to be a known production alloy and may have been developed specifically for use in the F-1 rocket engines, with an increased concentration of refractory (Mo, Nb) elemental additions. The analytical results helped conservators determine a suitable treatment protocol for more than 400 blades and 100 fragments from four recovered turbines. [ABSTRACT FROM AUTHOR]

This study investigates the corrosion behavior of dissimilar gas tungsten arc (GTA) welded joints between super duplex stainless steel (sDSS 2507) and pipeline steel (X-70) using electrochemical and immersion corrosion tests. The GTA welds were fabricated using ER2594 and ER309L filler metals. The study examined the electrochemical characteristics and continuous corrosion behavior of samples extracted from various zones of the weldments in a 3.5 wt.% NaCl solution, employing electrochemical impedance spectroscopy, potentiodynamic polarization methods, and an immersion corrosion test. EIS and immersion investigations revealed pitting corrosion in the X-70 base metal/X-70 heat-affected zone, indicating inferior overall corrosion resistance due to galvanic coupling. The corrosion byproducts identified in complete immersion comprised α-FeOOH, γ-FeOOH, Fe3O4, and Fe2O3, whereas γ-FeOOH and Fe3O4 were predominant in dry/wet cyclic conditions. Corrosion escalated with dry/wet cycle conditions while maintaining a lower level in complete immersion. The corrosion mechanism involves three wet surface stages in dry/wet cycles and typical oxygen absorption during complete immersion. Proposed corrosion models highlight the influence of Cl−, O2, and rust layers. [ABSTRACT FROM AUTHOR]

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Cable-stayed bridges have become the preferred bridge type for large-span bridges due to their unique advantages, and the long-term performance of the cable under the extreme conditions has been facing great challenges. An accelerated corrosion test was carried out using in-service cable, and the evolution model of the etch pit was established based on cellular automata to study the evolution law of corrosion damage to steel wire. This study showed that with the increase in the number of dry-wet cycles in the electrified accelerated corrosion, the macro- and micromorphology of the steel wire showed more serious corrosion damage, the tensile strength decreased, the ductility index decreased, and the tensile strength of the steel wire after corrosion decreased by nearly 5%; the geometric dimension of the steel wire etch pits all met a right-skewed distribution with a broader range of etch pit depth, mainly consisting of shallow spherical etch pits and deep ellipsoidal etch pits. The length, width, and depth sizes were mainly distributed in the range of 0.005 mm to 0.015 mm, 0.005 mm to 0.02 mm, and 0 mm to 0.04 mm; at the early stage of corrosion, the etch pits were first developed along the longitudinal direction. As the corrosion process progressed, the iron matrix participated in the electrochemical reaction, leading to the rapid expansion of the etch pits' dimensions. The stress concentration effect at the bottom of the etch pit caused the maximum stress to approach 1800 MPa, with a stress concentration coefficient of more than 3.0; when the cable anchorage system was located in the connecting sleeve and the threaded splice seam, where corrosion protection was prone to failure, the outer steel wire bore most of the corrosive effects, and the internal cable was less eroded by the corrosive medium. [ABSTRACT FROM AUTHOR]

In order to study the corrosion resistance of 904L composite plate pressure vessels under a high-temperature and high-pressure gas field environment, the pitting corrosion and stress corrosion cracking resistance of a 904L composite plate body and weld material were compared with those of a 2205 composite plate and 825 composite plate, which are used in high-temperature and high-pressure gas field environments. The results showed that the pitting resistance of the 904L composite plate was lower than that of the 825 composite plate and higher than that of a 2205 solid-solution pure material plate and a 2205 composite plate. The corrosion resistance of the 625 welding material is higher than that of the E385 welding material. In the simulation of the corrosion environment of a high-temperature and high-pressure gas field, the corrosion rates of the 904L composite plate body, welding seam, and surfacing welding were all less than 0.025 mm/a, indicating slight corrosion, and the sensitivity coefficient of chloride stress corrosion cracking was less than 25%, indicating low sensitivity. The 904L composite plate met the requirements of corrosion resistance for pressure vessel materials in a high-temperature and high-pressure gas field environment. [ABSTRACT FROM AUTHOR]

This study employed a high-pressure cold spray to apply a Zn30Al alloy coating to Q235 steel substrates to provide corrosion protection for steel in marine environments. The corrosion resistance of the coatings was investigated through full immersion tests, and the corrosion mechanisms were further analyzed using electrochemical experiments. The results were compared with those of traditional flame-sprayed Zn30Al alloy coating. The findings indicate that the high-pressure cold-sprayed Zn30Al alloy coating possesses a dense microstructure with a porosity of only 0.32%, providing effective cathodic protection to the substrate during the immersion tests. The cold-sprayed Zn30Al alloy coating maintained good integrity after 720 h immersion in 3.5 wt.% NaCl solution, whereas the flame-sprayed Zn30Al alloy coating exhibited significant pitting corrosion. [ABSTRACT FROM AUTHOR]

In this study, the effect of intermetallic compounds (ICMs) on the tribocorrosion behavior of the 7075 aluminum alloy was investigated. ICMs play important roles in the tribocorrosion resistance and mechanism of the sample. In the as-received sample, micron-sized Mg2Si, Al23Fe4Cu, and nanosized MgZn2 induced pitting corrosion and acted as abrasive materials. Accompanying the re-dissolution of Mg2Si and the growth of MgZn2, the pitting resistance worsened and adhesive wear took place. Subsequently, MgZn2 precipitated along the grain boundaries, which resulted in intergranular corrosion and aggravation of adhesive wear. [ABSTRACT FROM AUTHOR]

The present study aimed to understand the effect of nitrogen on the carbide precipitation and its influence on pitting corrosion of shielded metal arc welded high nitrogen 316SS weld. Nitrogen addition to weld reduces Cr availability sites in ferrite and enhances Cr in nearby austenite. Although higher carbon and continuous ferrite with ferritic austenitic mode exist, the changes in the degree of sensitisation were avoided at all the stages, and marginal changes in pitting potential (Epit) at 898 K/100 h and 998 K/24 h were observed. Nitrogen addition to weld further reduced the number of stable pits in ferrite and austenite, and the protectiveness of passive film was affected by nitrogen in ferrite and austenite, which affected pit propagation. This results in stable pits in ferrite and austenite, which affects pit propagation during thermal ageing. [ABSTRACT FROM AUTHOR]

Corrosion and biofouling are wetting‐related phenomena that limit the effective use of metals in aqueous media. Nonwettable surfaces can mitigate the adverse effects of wetting by minimizing contact with water. However, current achievements in this field fall short of meeting industrial requirements due to the short lifetime of plastrons. This study proposes a method to measure the protective sustainability of plastron. Superhydrophobic (SHS) and aerophilic (APhS) surfaces are constructed on lightweight aluminum and are initially analyzed by conventional goniometry, which show comparable values. However, the plastron that develops underwater is substantially different. While SHS exhibit unevenly broken plastron, APhS show uniform, continuous plastron. As an example of the sustained protective performance of plastron, the corrosion resistance of SHS and APhS is presented. Potentiodynamic polarization, impedance spectroscopy, and long‐term immersion in seawater show a drastic enhancement in corrosion resistance, exclusively for APhS. In fact, almost no electrochemical signals are measurable, and no pitting corrosion is observed after 415 days of immersion in seawater. Conversely, SHS show no noticeable improvement and corrode faster than bare Al due to plastron loss. Since goniometric measurements do not provide information on plastron, it is essential to analyze the plastron for any non‐wettable surface utilized underwater. [ABSTRACT FROM AUTHOR]

AbstractThis study investigates the inhibitory effects of poly(4-vinyl pyridine) (P4VP) and polyvinylpyrrolidone (PVP) on the corrosion of low carbon steel (LCSt) in 1 M H2SO4. Protection efficacy (%PE) was measured using mass loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Results showed %PE values increased with higher polymer concentration and lower temperature. At 450 mg/L, %PE reached 93.13% and 94.19% for P4VP and PVP, respectively. These polymers function as mixed inhibitors, adsorbing onto the LCSt surface per Langmuir’s model as a mode of physical adsorption. EIS indicated that higher polymer concentration increased charge transfer resistance and decreased effective double-layer capacitance. Both P4VP and PVP also reduced pitting corrosion in chloride-containing solutions. Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) optimized the molecular structures of the inhibitors, evaluating electronic parameters such as frontier molecular orbital (FMO) energies, energy gap, softness, hardness, electron transfer fraction, dipole moment, and hyperpolarizability (β°). Monte Carlo (MC) and molecular dynamics (MD) simulations provided insights into adsorption mechanisms, corroborating experimental findings and highlighting the effect of protonation. This comprehensive study enhances our understanding of the relationship between molecular structure and function in polymer inhibitors, improving their application in corrosion protection. [ABSTRACT FROM AUTHOR]

Microbial corrosion is the deterioration of materials associated with microorganisms in environments, especially in oil- and gas-dominated sectors. It has been widely reported to cause great losses to industrial facilities such as drainage systems, sewage structures, food-processing equipment, and oil and gas facilities. Generally, bacteria, viruses, and other microorganisms are the most important microorganisms associated with microbial corrosion. The destructive nature of these microorganisms differs based on the kind of bacteria involved in the corrosion mechanism. Amongst the microorganisms related to microbial corrosion, sulfate-reducing bacteria (SRB) is reported to be the most common harmful bacteria. The detailed mechanistic explanations relating to the corrosion of pipelines by sulfate-reducing bacteria are discussed. The mechanism of microbial corrosion in pipelines showing the formation of pitting corrosion and cathodic depolarization is also reported. The current review provides theoretical information for the control and protection of pipelines caused by microbial corrosion and how new eco-friendly protection methods could be explored. [ABSTRACT FROM AUTHOR]

The production of biocompatible ceramic–metal brazed joints is a subject of great interest. The development of new methods for obtaining biocompatible brazed joints will allow the production of new and more complex metal-ceramic implants with increased reliability and service life. At the same time, the titanium-zirconium-cobalt system is the most promising for the production of active rapid-quenched filler metals due to its low cost and low toxic effect on the human body. In this work, a ZTA-Ti joints manufacturing with various configurations using novel Zr-30Ti-20Co filler metal has been carried out. The filler metal contact angle on ZTA ceramic and titanium has been 78–80° and 53.2–33.0° in the 900–1000 °C interval. The XRD and EDS study revealed that the brazed joint consists of α-(Ti, Zr) and (Zr, Ti)2Co phases. Subsequent corrosion test according to the ASTM F 2129 standard showed that the brazed joint meets the biocompatibility criteria. However, there has been detected the (Zr, Ti)2Co phase pitting corrosion. At the same time, the content of cobalt ions in the Ringer-Locke solution after corrosion tests does not exceed the maximum safe limit. Mechanical shear strength tests have revealed that the joint fracture is brittle and the strength varies from 21.5 ± 2.5 up to 46.9 ± 19.2 MPa, depending on the joint configuration. [ABSTRACT FROM AUTHOR]

The parallel steel wires used in arch bridge suspenders experience random corrosion damage on their surfaces during service. Corrosion damage, including micro-cracks, pitting, and a combination of both, leads to significant stress concentration under axial loading, which affects the performance of the steel wires. The change in the stress field caused by surface damage alters the stress intensity factor at the crack tip, and the presence of adjacent crack tips significantly amplifies the stress intensity factor, thereby accelerating crack propagation. The development of small surface damages in the steel wires is difficult to control and observe through experiments. By utilizing finite element methods for simulation, it is possible to intuitively analyze the crack propagation process, the trend of stress changes at the crack tip, and the interaction between damages. Numerical simulation results based on Paris' law indicate that corrosion pits have a certain impact on the stress intensity factor at the crack tip. The propagation process of coplanar double cracks is highly sensitive to the initial crack size and the distance between adjacent crack tips. When the crack spacing is less than the crack depth, the stress intensity factor at the adjacent crack tips exhibits significant amplification. Based on this phenomenon, the coplanar double-crack system can be simplified to a complete single crack for analysis. By comparing the fatigue life of the double-crack system with that of the equivalent single crack, the effectiveness of the simplification rule has been validated. [ABSTRACT FROM AUTHOR]

The primary objective of this study is to investigate the corrosion resistance of Fe‐36Ni Invar alloys with varying Mg contents in a 3.5 wt% sodium chloride solution. The electrochemical results reveal that the incorporation of Mg amplified the corrosion behavior of Fe‐36Ni Invar alloy. The inclusion compositions undergo a transformation with the increase of Mg content, evolving from MnO–MnS in 0 Mg alloy to MnO–MnS–MgO in 0.0015 Mg alloy, and ultimately to MnS–MgO–MgS in 0.0030 Mg alloy. During the corrosion process, the small‐sized MnS–MgO–MgS inclusions exhibit greater stability compared to the MnO–MnS inclusions, rendering them less susceptible to attack and dissolution. Adding Mg diminishes the size and number density of inclusions, which effectively decreases the susceptibility to pitting initiation. The introduction of Mg refines the microstructure and elevates the fraction of twin boundaries, which also is responsible for the enhancement of corrosion resistance. [ABSTRACT FROM AUTHOR]

The present study aimed to examine how the corrosive environment affected the low‐velocity impact (LVI) characteristics and damage mechanisms of thermoplastic polyamide fiber‐reinforced polymer (PFRP) composites. In this regard, composite specimens were subjected to corrosive environment containing 10 wt.% diluted HCl for one week and one month before LVI tests. To investigate the hostile effects of the corrosive environment on the composites, scanning electron microscope (SEM) coupled with energy‐dispersive X‐ray system (EDX) analyses were carried out, and thus variations in the elemental composition and damage mechanisms for the composites were determined. According to the examinations, it was discovered that the degradation in LVI responses, such as contact stiffness, bending stiffness, and peak force, increased with longer aging time, as expected. Furthermore, when the aging effect was assessed based on absorbed energy, the specimens exposed to a corrosive environment for one month exhibited the highest energy absorption compared to the control and 1‐week‐immersed ones. The degrading effect of the HCI environment appeared as higher damage severity on the composites, which was also detected from the SEM images. According to the SEM analyses, matrix cracks, corrosion pits, and local surface imperfections caused by ion exchange are detected in 1‐week‐immersed specimens, while more serious damage mechanisms such as fiber breakage and fiber pull‐out are noted in specimens exposed to corrosive environment for 1 month. Furthermore, approximately 6.33 wt.% CI was identified in the composites after 1 month of aging, which was associated with the hydrolysis triggered by rise in the composite's damage severity. Highlights: Aging effects in mechanical properties of PFRP composites were investigatedLVI tests were conducted to determine dynamic responses of aged compositesLonger aging time led to more severe damages such fiber rupture, delamination etc.PFRP composites absorbed at least 68% of impact energy. [ABSTRACT FROM AUTHOR]

This study investigated the corrosion behaviour of dissimilar steel-to-aluminium laser-welded conduction, and keyhole mode (partial- and full-penetration) lap joints through electrochemical techniques and advanced microstructural characterisation. The corrosion resistance of the weld was found to be higher than the base materials, primarily due to the presence of cathodic FexAly (η-Fe2Al5, θ-Fe4Al13, β-FeAl) intermetallic compounds (IMCs) with high corrosion potential. The different micro and macro-galvanic corrosion mechanisms were found at various interfaces around the weld, resulting in localised pitting corrosion. The keyhole mode welding showed improved corrosion resistance, primarily attributed to the type, size, and distribution of IMCs. [ABSTRACT FROM AUTHOR]

ABSTRACT The ability to assess the risk of corrosion of metallic structures in particular environments holds considerable significance in the field of automotive industry. In recent years, machine learning has evolved into a crucial tool to evaluate the complex and multidimensional corrosion phenomena. In this paper, the special case of non‐aqueous alcoholate pitting corrosion of AA1050 in ethanol‐blended fuels with water and chloride contamination is examined via supervised machine learning techniques in order to distinguish between safe and unsafe conditions. The data space was created by conducting dedicated experiments with varying ethanol–fuel–water ratios, temperatures, and surface preparations. The classifier's performance rating of 0.87 (balanced accuracy) indicates an outstanding predictive ability and highlights the model's usefulness as decision support for subsequent experiments. [ABSTRACT FROM AUTHOR]

ABSTRACT The corrosion product competition and transformation process of J55 under an O2/CO2 environment in the temperature range of 50–350°C and 0–1 MPa oxygen partial pressure range, respectively, were studied using electrochemical and surface analysis techniques as well as thermodynamic calculations to determine its corrosion rate change law and pitting corrosion phenomenon. This study demonstrates that the uniform corrosion rate of J55 with increasing temperature shows a trend of first increasing, then decreasing, and finally increasing. The transformation of its corrosion products, from FeCO3 into Fe3O4, is consistent with the altering corrosion rate law with increasing temperatures. J55 corrodes faster at 350°C as the O2 partial pressure increases. When the O2 partial pressure is low, the predominant kind of corrosion product that is obtained is FeCO3; when the O2 partial pressure exceeds 0.2 MPa, all corrosion products are transformed into iron oxides. As the oxygen partial pressure increases, J55's corrosion product film becomes increasingly less protective of the substrate, making the substance more vulnerable to corrosion reactions. [ABSTRACT FROM AUTHOR]

Samples of the Ni-based superalloy, RR1000, were exposed to 98% Na2SO4/2% NaCl salts at 700 °C with a flux of 1.5 µg cm−2 h−1 in flowing air + 300 ppm SO2 for a total of 250 h. Three pre-exposure conditions were studied: a bare reference alloy; fast heating to the test temperature followed by a 100 h hold; heating at a rate of 5 °C min−1 to the test temperature following by a 100 h hold. The surface oxide formed under the latter two conditions were Cr2O3 or NiCr2O4, respectively. The results show corrosion pit formation on the surface of the base, reference sample, and no pits present on the sample with the preformed Cr2O3. Some protection was found for the sample heated at 5 °C min−1 with a delay in the progression to accelerated corrosion attack. Additional testing under moisture containing air was also conducted. This showed no obvious difference in surface oxide morphology under the two tested heating rates for the short-term exposures examined but a difference was noted to be dependent on the moisture content of the air. [ABSTRACT FROM AUTHOR]

The comparative investigation of the corrosion behavior of S32304 cast lean duplex and CF3M cast austenitic stainless steels was conducted in a chloride environment. The resistance to pitting corrosion of the S32304 alloy was "one" time higher than that of the CF3M alloy because the pitting potential, passive region, and critical pitting temperature of the low Ni-low Mo S32304 alloy were higher than those of the high Ni-medium Mo commercial CF3M alloy. There are two main reasons for the enhancement of the pitting corrosion resistance of high Cr-low Mo-medium N S32304 alloy compared to the low Cr-medium Mo CF3M alloy: First, the pitting resistance equivalent number (PRENδ+γ) value of the S32304 alloy is higher than that of the CF3M alloy. Second, the passive region of the S32304 alloy is larger than that of the CF3M alloy. It indicates that the synergistic effects of the three elements by adding high Cr and low Mo-medium N to the S32304 alloy enhance the passivity of the passive film, thereby increasing the resistance to pitting corrosion. It was verified that based on the PRENγ and PRENδ values calculated using an N-factor of 30, the pitting corrosion of the S32304 alloy was selectively initiated at the γ-phases and the inclusions of Mn oxy-sulfieds because the γ-phase's PRENγ value was smaller than the δ-phase's PRENδ, and finally propagated from the γ-phase to the δ-phase. [ABSTRACT FROM AUTHOR]

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This study explores microstructure, wear, and corrosion resistance properties of FeCoNiCrAl0.7Cu0.3Six (x = 0, 0.2, 0.3, 0.5) high-entropy alloys. The FeCoNiCrAl0.7Cu0.3Six alloy contains FCC and BCC structures; as the x increases, the FeCoNiCrAl0.7Cu0.3Si0.2, FeCoNiCrAl0.7Cu0.3Si0.4, and FeCoNiCrAl0.7Cu0.3Si0.5 high-entropy alloys transition to BCC structures. The morphological transition in FeCoNiCrAl0.7Cu0.3Six evolves from bamboo leaf-like intergranular features to a discontinuous intergranular structure as Si content increases. The hardness of these alloys gradually increases with higher Si content. The addition of Si promotes a uniform distribution of Cr within and between grains, reducing the intergranular segregation of Cu. Al and Ni show a consistent pattern of elemental distribution throughout the alloy. Wear measurements of FeCoNiCrAl0.7Cu0.3Six alloys demonstrate that adding Si enhances wear resistance, resulting in smoother wear surfaces with reduced deformation. The wear mechanism for all alloys is primarily abrasive, with no brittle fractures observed. Corrosion resistance is optimized when Si content is 0.2, with pitting corrosion being the primary corrosion form. [ABSTRACT FROM AUTHOR]

Titanium alloys are mostly used in high temperature and high pressure, which requires its high mechanical properties and corrosion resistance. As a good surface modification technology, arc surface cladding has been applied in various fields. In this study, the gas tungsten arc welding was used to clad titanium alloy and the nitrogen gas with different contents were added in the shielding gas. During the cladding process, the TiN strengthening phase was formed in the cladding layer. The effects of different nitrogen flow rates on the microstructure and properties of the cladding layer were studied. The scanning electron microscope (SEM) and the x-ray diffractometer (XRD) were used to observe microstructure and identify the formed phases. The mechanical properties and corrosion properties were studied by Vickers hardness and electrochemical experiments. The results show that after adding nitrogen, the grain size becomes smaller and the hardness increases from 247 to 363 HV. The formation of TiN also improves the pitting corrosion resistance of the cladding layer. The corrosion resistance of the cladding layer was the best when the nitrogen flow rate was 0.4 L/min. Therefore, adding suitable nitrogen gas in the titanium alloy arc cladding process can significantly improve the performance of the cladding layer. [ABSTRACT FROM AUTHOR]

The mechanical, thermophysical, and ablation properties of 2.5D C/HfC–SiC composites with various SiC/HfC ratios are studied. The S7‐C/HfC–SiC composite with a high SiC/HfC volume ratio of 30.4/15.2 has the highest flexural strength of 203.4 ± 26.8 MPa and fracture toughness of 10.0 ±.5 MPa·m1/2. All C/HfC–SiC composites have a similar low thermal conductivity of ∼2 W·m−1·K−1 and their CTEs are in the range of.45–4.0 × 10−6/K from 30°C to 1400°C. S5‐C/HfC–SiC with medium SiC/HfC ratio possesses the lowest mass ablation rate of.29 ±.02 mg·cm−2·s−1 and linear ablation rate of.003 ±.0002 mm/s. The C/HfC–SiC composites are endowed with a pitting corrosion feature according to the morphology and composition evolution of the ablated surface, which results from both high temperature and stagnation pressure gradients in the radial direction of the oxyacetylene torch. [ABSTRACT FROM AUTHOR]

Corrosion is widely known to be a major cause of the failures in process facilities. Prediction of corrosion damage is therefore essential for industries to manage the availability of their assets. This research aims to investigate the application of supervised machine learning methods for the classification of pitting corrosion damage. Several machine learning classifiers, namely ensemble methods, support vector machine (SVM), K‐nearest neighbours, and the decision tree are used to classify the extent of pitting corrosion damage in corroded steel samples. To simulate the corrosion of the steel samples, a series of laboratory experiments were conducted. After processing the results using appropriate statistical methods, the corrosion data was used to train the machine learning models. The trained models can predict the class of corrosion damage with acceptable accuracy using the material and environmental specifications of the samples. Additionally, a discussion on the selection of machine learning techniques which classify corrosion damage using a risk‐based approach is provided. With their optimal accuracy and lower risk of misclassification, the SVM and AdaBoost models perform better than the other studied models. [ABSTRACT FROM AUTHOR]

The pitting mechanism of 7 series high-strength aluminum (Al) alloys (7xxx) is investigated experimentally and numerically (finite element method, FEM) by comparing the characteristics of passive films and pitting kinetics of two types of 7xxx Al alloys. The point defect model (PDM) is used to evaluate the passive film properties in the two varieties of 7xxx Al alloy, and the FEM is employed to calculate the point defect diffusion process in detail. The results reveal that the two 7xxx Al alloys exhibit various microstructures, particularly the 7xxx-1, characterized by a robust (111) fiber texture and a lower proportion of low-angle grain boundaries than the 7xxx-2. The diffusivity D of point defects in 7xxx-1 (3.85 × 10−18–52.74 × 10−18 cm2 s−1) is lower than that in 7xxx-2 (5.47 × 10−18–66.61 × 10−18 cm2 s−1) and the diffusion duration of 7xxx-1 is longer than 7xxx-2, which is closely associated with the rupture of passive film. Additionally, FEM proved that the initial shapes of pits dictate the progression of pitting, manifesting that the shallow dish shape grows laterally while the deep hole shape grows longitudinally.

Regarding providing energy, few sectors are as massive as the oil and gas business. One of the most crucial parts of oil and gas production is the distribution pipes or pipelines that transport the production fluids, which include oil and gas, from one distribution point to another. The corrosion of A316 material, which can lead to holes or pitting, and the damage it causes in most industrial operations, particularly in the oil and gas industry, has resulted in substantial losses at high prices over an extended period of time. In the study, we will quickly examine what corrosion is, the different kinds of corrosion, inhibitors, and how to assess the corrosion rate of A316 stainless steel in salt water. Analysis of the electrochemical corrosion rate of Inconel 600 nickel alloy and stainless steel 316L subjected to varying amounts of saltwater (freshwater, seawater, mixed water). Because chlorine speeds up corrosion, alloys like Inconel 600 and 316L undergo pitting corrosion. The molybdenum component gives 316 stainless steel its superior corrosion resistance. That's why it works well for gas and oil pipelines that go through saltwater. Nevertheless, materials exposed to maritime environments must have cathodic protection or coating to prolong their life and stop the pipe from continuously corroding.

High-performance alloys such as super duplex stainless steels (SDSS) are of interest to the oil and gas industry, especially in deep and ultra-deep reservoirs where high pressures and highly corrosive environments are prevalent. SDSS have high nitrogen contents and pitting resistant equivalent number (PREN) values greater than 40, however, fusion welds of these alloys can exhibit unsuitable microstructures and defects that may result in failure during usage. Solid-state linear friction welding (LFW) offers an alternative for the effective joining of SDSS with a less detrimental effect on microstructure and properties. In this work, four LFW joints in UNS S32760 SDSS were produced and investigated by evaluating the process parameters required to achieve a high-quality joint with the desirable metallurgical, mechanical, and localized corrosion properties. These properties were assessed through metallography (optical microscopy and scanning electron microscopy), tensile and microhardness tests, and corrosion analysis according to the ASTM G48A standard. Results indicated that one specific combination of LFW parameters led to a defect-free joint, and that the mechanical properties of the weld in this case were comparable to those of the base material. Additionally, an adequate balance between ferrite and austenite phases was achieved throughout the microstructural gradients seen in the weld region. Microhardness values were below 350 HV, thus complying with the DNV–OS–F101 standard. Furthermore, no pitting corrosion was observed in this joint under the testing conditions suggested by ASTM G48A.

After conducting a compression test on rocket storage tanks, the presence of residual S2− and Cl− ions was detected in the remaining solution. These ions, when concentrated in areas prone to high residual concentrations such as weld seams, can cause corrosion. Therefore, this study focuses on the mechanical properties and corrosion behavior of resistance spot welded (RSW) joints in 2219 aluminum alloy storage tanks in a service environment with a mixed solution of 1 mg/L NaCl and 0.1 mg/L Na2S. The results indicate that the joint exhibits a tight mechanical bonding wires, with the fusion zone being isolated from the external environment, making it difficult for the corrosive solution to penetrate. However, some pitting corrosion is observed in the base metal and the heat affected zone. The corrosion products mainly consist of Al2O3 and AlCl3. The S2− ions are released in the form of H2S after hydrolysis. Comparing the mechanical properties of the joints before and after 60 days of immersion, no significant loss in mechanical performance is observed. The joint fractures exhibit a combination of brittle and ductile fracture modes. The presence of S2− and Cl− ions does not affect the safe operation of the rocket propellant tanks. [ABSTRACT FROM AUTHOR]

Fe90-6%Al2O3 coatings with the respective Cr and Ta mass fraction of 10% were prepared on Q235 steel by laser cladding. The microstructure, chemical elementals, surface roughness and phases of obtained coatings were analyzed using an optical microscope, energy-dispersive spectrometer, atomic force microscope and x-ray diffraction, respectively. The effects of Cr and Ta on the immersion corrosion and electrochemical performances of Fe90-6%Al2O3 coating in 3.5% NaCl solution were investigated using an electrochemical workstation, and the corrosion mechanism was discussed in detail. The results show that the (Fe90-6%Al2O3)-10%Cr coating has highest immersion corrosion resistance among the three kinds of coatings, and the corrosion mechanism of Fe90-6%Al2O3 and (Fe90-6%Al2O3)-10%Cr coatings is combined intergranular corrosion and pitting corrosion; while that of (Fe90-6%Al2O3)-10%Ta coating is intergranular corrosion and local crevice corrosion. Moreover, the polarization resistance of Fe90-6%Al2O3, (Fe90-6%Al2O3)-10%Cr, and -10%Ta coatings is 3.31 × 104, 3.95 × 104, and 4.11 × 104 Ω cm2, respectively, and the corresponding charge transfer resistance is 10280, 16460, and 16990 Ω cm2, respectively, showing that the (Fe90-6%Al2O3)-10%Ta coating has the best electrochemical corrosion resistance. [ABSTRACT FROM AUTHOR]