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The chloride-induced stress corrosion cracking (CISCC) is one of the major integrity concerns in dry storage canisters made of austenitic stainless steels (ASSs). In this study, an advanced duplex stainless steel (DSS) with a composition of Fe–19Cr–4Ni-2.5Mo-4.5Mn (ADCS) was developed and its performance was compared with that of commercial ASS and DSS alloys. The chemical composition of ADCS was determined to obtain greater pitting and CISCC resistance as well as a proper combination of strength and ductility. Then, the thermomechanical processing (TMP) condition was applied, which resulted in higher strength than ASSs (304L SS and 316L SS) and better ductility than DSSs (2101 LDSS and 2205 DSS). The potentiodynamic polarization and electrochemical impedance spectra (EIS) results represented the better pitting corrosion resistance of ADCS compared to 304L SS and 316L SS by forming a better passive layer. The CISCC tests using four-point loaded specimens showed that cracks were initiated at 24 h for 304L SS and 144 h for 316L SS, while crack was not found until 1008 h for ADCS. Overall, the developed alloy, ADCS, showed better combination of CISCC resistance and mechanical properties as dry storage canister materials than commercial alloys.

The effect of sulfides on the pitting corrosion behavior and film chemistry of 70/30 copper-nickel alloys in aerated seawater was investigated. Sulfides in seawater prevent the formation of protective oxides on the surface of the alloy and alter the morphology and composition of the corrosion products. It results in the corrosion product film consisting of the double layer structure of the loose and porous sulfide-containing outer layer and the dense inner layer. This double-layer structure of the corrosion product film can't alleviate corrosion, but instead accelerates the development of pitting corrosion. The statistical analysis method is used to study the corrosion process of 70/30 copper-nickel alloy in sulfide-containing environment. This work records the trend of pitting corrosion towards the horizontal and longitudinal directions.

Effects of Mo and C addition on the microstructural evolution and corrosion resistance in chloride solution of FeNiCrAl duplex alloy were investigated. The results showed that α phase stabilizing element Mo increased the α/γ volume ratio and γ phase stabilizing element C decreased its ratio in FeNiCrAl alloy, and the chemical composition of α and γ phases was changed by Mo and C addition, which affected the corrosion resistance of FeNiCrAl alloy. Pitting corrosion mainly occurred in α phase around NbC precipitated at α/γ interface due to the micro-galvanic corrosion (MGC) effect between α (anode), γ (cathode) and NbC (cathode) phases. The pitting corrosion resistance was improved by Mo and C addition, resulting from that Mo and C enhanced the passivity of passive films and decreased the MGC effect between α, γ and NbC phases.

This study presents a comprehensive analysis using the finite element method (FEM) to examine and evaluate the behavior of fuel carrier ship structure. Sandwich panels are effective structures for use in ship structures due to their lightweight yet robust nature. Sandwich panels used in ship structures have various core shapes, such as hexagonal, circular, and square, as needed. The sandwich panel structure can be widely implemented in ship construction, for example, on the deck, hull, and bulkhead of the ship’s cabin. Hydrogen is an alternative fuel that can replace fossil fuels. In this modern era, hydrogen is high valuable energy commodity, so accidents involving carrier ships could have significant consequences. Hydrogen is produced from liquefied natural gas (LNG), so if a leak occurs, for instance, in a storage tank or fuel tank, it has the potential to lead to accidents such as fires. Corrosion is a significant concern for the maritime industry, as it can jeopardize the structural integrity of these vessels and pose substantial safety and environmental risks. In this research, FEM was utilized to model and simulate the effects of corrosion on hydrogen carrier ships when exposed to fire, considering various environmental and operational factors. Through a systematic investigation, it is aimed to gain insights into the impact of corrosion on ship structural components during fires, such as hulls and storage tanks. The result of this study will contribute to improving corrosion and fire mitigation strategies, ensuring the safety and longevity of hydrogen and LNG carrier ships, and supporting the sustainable transportation of hydrogen to meet global energy demands. No research has been conducted on the structural behavior resulting from hydrogen fires and corrosion simultaneously. To achieve this, it is assumed to use the corrosion properties of steel in heavily traveled ship routes such as the Panama Canal Zone, Barent Sea, North Sea, and Suez Canal Zone. This study utilized an approach by modeling corrosion using shell thickness in Abaqus Quasi-Static and applying boundary conditions in the form of temperature increase up to 800°C and subsequent cooling back to the initial temperature. At the maximum temperature, the most significant mid-span displacement occurred in the circular core sandwich panel, with a value of 4 mm. The axial force in the structure was inversely proportional to the mid-span displacement. In the case of the circular core sandwich panel, the axial force was 96 kN. The most resilient core type was hexagonal because it experiences the least deformation when compared to circular and square cores.

Automobile structural components are subject to high stress, friction and corrosive environmental conditions. Though aluminum alloys exhibit lightweight and high corrosion resistance, there is a need to improve the high strength-to-weight ratio and resistance to friction. This paper presents microstructural analysis, hardness, dry sliding wear behavior, and corrosion behavior of AA7075 reinforced with silicon carbide (SiC) particles. The composite specimens were prepared at the concentration of 2.5 and 5wt.% SiC. The microstructure of AA7075 showed dendritic morphology while composite specimens showed nondendritic morphology grains. Reinforcement of SiC resulted in increased nucleation site and refinement of grain during solidification. XRD analysis of base alloy showed α matrix with η (MgZn2), T(Al–Zn–Mg–Cu) and Al7Cu2Fe phases, while the composite sample showed the presence of additional S(Al2CuMg) and θ (Al2Cu) phases. Composite samples showed higher hardness values than base alloy due to grain boundary strengthening and Orowan strengthening. The enhancement of hardness of AA7075 by 20% and 37.5% were obtained with the addition of 2.5 and 5wt.% SiC particles respectively and also predicted with less coefficient of friction and less wear rate at all the tested load conditions. At the same time, the respective reduction in wear rates of AA7075 was found to be 50 and 65%. The worn-out surface of the base alloy was found to have undergone extensive plastic deformation and resulted in delamination with extensive patches and no clear groove marks. The composite sample of 2.5wt.% SiC showed mild patches with clear groove marks, while the Composite of 5wt.% SiC showed groove marks with fine width parallel to sliding directions. The wear mechanism was found to be transferred from adhesive mode to abrasive mode through a mixed mechanical layer with an added concentration of SiC particles from 0wt.% to 5wt.%. Weight loss during immersion corrosion increases with an increase in the amount of SiC due to an increased amount of metallic phase which increases microgalvanic corrosion and pitting. Hence, composite samples showed decreased corrosion resistance than base alloy. [ABSTRACT FROM AUTHOR]

Sulfuric acid anodizing assisted by a hydrothermal sealing with inhibitors [Ce3+-Mo6+] was used to prevent pitting corrosion on spray-deposited hypereutectic Al–Si alloy (A390). An investigation concerning the evaluation of pitting corrosion resistance on the anodic oxide thin film with ions incorporated was carried out in NaCl solution using electrochemical measurements (i.e., potentiodynamic polarization and electrochemical impedance spectroscopy, EIS). The influence of Si phase morphology and size on the growth mechanism of an anodic oxide film was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results were then compared with those for its equivalent IM390 alloy (Al-17Si-4.5Cu-0.6Mg) produced through a conventional process ingot metallurgy, IM. The electrochemical findings indicate that sulfuric acid anodizing followed by a simple hot water sealing treatment was ineffective. In this manner, an intense attack was localized by pitting corrosion that occurred on the anodic oxide film in less than three days, as denoted by characteristic changes in the EIS spectra at the lowest frequencies. Improved results were achieved for Ce–Mo surface modification, which can provide better corrosion resistance on the aluminum alloys because no signs of pits were observed during the corrosion testing. [ABSTRACT FROM AUTHOR]

To combat abiotic CO2 corrosion of pipelines, chromium steels (CrSs) are used to replace carbon steels, but CrSs can suffer very severe pitting corrosion caused by microbiologically influenced corrosion (MIC) because their passive films are not as good as those on high-grade stainless steels, and their MIC often involves (semi-)conductive corrosion product films. In this study, severe pitting corrosion (2.0 cm/a pitting corrosion rate) with a 7-day weight loss of 3.8 ± 0.5 mg/cm2 (0.26 mm/a uniform corrosion rate) was observed on 13Cr coupons incubated anaerobically with a highly corrosive pure-strain sulfate reducing bacterium (SRB) Desulfovibrio ferrophilus IS5 in 125 mL anaerobic vials filled with 50 mL enriched artificial seawater at 28°C. A popular green biocide, namely tetrakis hydroxymethyl phosphonium sulfate (THPS), was enhanced by biofilm dispersing Peptide A (a 14-mer) to mitigate SRB MIC against 13Cr. The 7-day weight losses for coupons with 50 ppm (w/w) THPS, 50 ppm THPS + 100 nM (180 ppb) Peptide A and 100 ppm THPS were reduced to 2.2 ± 0.2 mg/cm2, 1.5 ± 0.5 mg/cm2, and 0.3 ± 0.2 mg/cm2, respectively. The pitting rates also decreased from 20 mm/a to 12 mm/a, 8.6 mm/a, and 1.5 mm/a, respectively based on the maximum pit depth data for the 7-day incubation. Electrochemical tests using a miniature electrochemical glass cell design supported the weight loss trend with additional transient corrosion rate information. THPS was found to be effective in mitigating severe pitting corrosion on 13Cr, and the enhancement effect of Peptide A for THPS was manifested. This work has significant implications in field applications when CrSs are considered as metal choices to replace carbon steels to combat abiotic CO2 corrosion in pipelines. When SRB MIC is a possible threat, a mitigation plan needs to be implemented to prevent potentially very severe pitting that can lead to pinhole leaks. [ABSTRACT FROM AUTHOR]

In Type 316 L stainless steel fabricated from gas-atomized powder via spark plasma sintering, lack-of-fusion pores and MnS inclusions were identified as possible pitting initiation sites. Through potentiodynamic polarization with different working electrode areas, the distribution density of the identified pit initiation sites was compared with that of sites found on wrought Type 316 L stainless steel. Surface observations of the sintered Type 316 L after polarization suggest that pitting corrosion was initiated at a location where both MnS and pores existed. By reducing the porosity and removing MnS, the roles of pores and MnS inclusions in the initiation of pitting corrosion were investigated. [ABSTRACT FROM AUTHOR]

The paper introduces a computer vision methodology for detecting pitting corrosion in gas pipelines. To achieve this, a dataset comprising 576,000 images of pipelines with and without pitting corrosion was curated. A custom-designed and optimized convolutional neural network (CNN) was employed for binary classification, distinguishing between corroded and non-corroded images. This CNN architecture, despite having relatively few parameters compared to existing CNN classifiers, achieved a notably high classification accuracy of 98.44%. The proposed CNN outperformed many contemporary classifiers in its efficacy. By leveraging deep learning, this approach effectively eliminates the need for manual inspection of pipelines for pitting corrosion, thus streamlining what was previously a time-consuming and cost-ineffective process. [ABSTRACT FROM AUTHOR]

Nacre-inspired metal matrix composites have received much attention due to their excellent deformation coordination ability, which can achieve the synergy of strength and ductility. The preparation of nacre-like Al matrix composites by freeze casting has been a promising application, but the continuous ceramic-rich layer affects the corrosion resistance of the composites, facing complex corrosion problems during service. In this work, the microstructure and corrosion behavior of the nacre-inspired (TiBw-TiB2)/Al composites fabricated by freeze casting and squeeze casting were systematically studied. The results indicated that the Al layers and ceramic-rich layers had little change, about 35 μm and 31 μm, respectively, with an increasing ratio of the Ti/TiB2. Meanwhile, a high Ti/TiB2 ratio resulted in an increase in the Fe-Ti intermetallic phases, which was detrimental to the corrosion performance of the composites and was prone to pitting. The electrochemical test results showed that the 3Ti7TiB2 composite had the lowest corrosion current density (15.9 μA) and intergranular corrosion depth (231 μm), indicating that it had the best corrosion resistance, which can be attributable to its stable and dense passivation film. Two different corrosion phenomena during the intergranular corrosion test existed in the present nacre-inspired (TiBw-TiB2)/Al composites: intergranular corrosion in the Al matrix layer and pitting corrosion in the ceramic-rich layer. Among all the composites, the corrosion depth of the 3Ti7TiB2 composite was the smallest and significantly less than that of the 2024Al alloy. In addition, the continuous ceramic-rich layer acted as a corrosion channel during corrosion, significantly degrading the corrosion resistance of the nacre-like Al composites. [ABSTRACT FROM AUTHOR]

To investigate the variation law of corrosion damage of steel wires for bridge cables, the accelerated stress-corrosion test was carried out. The corrosion surface of steel wires was collected by virtue of a three-dimensional topography instrument, and the surface characteristic parameters of steel wires were also statistically analyzed under different corrosion ages and initial strains. Finally, the maximum pit depth of steel wires was estimated by the analysis method of extreme value. The results showed that the stress corrosion intensified the corrosion degree of steel wires under the same corrosion age, and the maximum discrepancy was nearly 20%. However, the high strain level had a lower influence on the growth rate of corrosion degree in the later stage of corrosion. The pit depth of steel wires more conformed to the lognormal distribution under the unstressed condition, while the corrosion depth of steel wires more closely conformed to the normal distribution under the stress condition. The fractal dimension could not only reflect the unevenness of the corrosion surface, but also be used as one of evaluation indicators of corrosion degree. The maximum pit depth obtained from the sampling inspection data was hazardous, and it was safe and feasible to take the results from the analysis method of extreme value. [ABSTRACT FROM AUTHOR]

AISI 440C is a high carbon martensitic stainless steel with superior wear and abrasion resistance among all grades of stainless steel. Hydraulic amplifier valve (HAV) spools, made of AISI 440C stainless steel, are used in flow control devices of launch vehicle actuator systems. In the present case, a failure occurred near the undercut region of the HAV spool during the vibration test. The failure was observed specifically at M5 threaded region of the spool. A detailed investigation has been carried out to understand the root cause of the failure. 612 µm deep pit was observed with corrosion products on the fracture surface near to the undercut region of M5 thread. Elemental chemical composition analysis via energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of oxygen and chlorine in the pit location. Primary carbides exposed to the rough machined surface at the undercut region lead to the pit initiation and propagation because of the galvanic potential difference between matrix and primary carbides. Failure of the HAV spool is attributed to corrosion-assisted overload. [ABSTRACT FROM AUTHOR]

Weathering steel (WS) and high‐performance steel (HPS) have been widely used in bridge engineering. Investigating the corrosion performances of WS and HPS is of great significance to the safety evaluation and maintenance of uncoated WS or HPS bridges, especially aging bridges. This study focused on the correlation between the corrosion performance and composition of the rust layer. Accelerated corrosion tests were conducted on Q345CNH and HPS 70 W to observe their corrosion performance under salt‐spray corrosive environment. Based on the results of corrosion test and the existing corrosion attack evaluation theories, the empirical formulae of uniform corrosion and pitting corrosion were derived. X‐ray diffraction experiments were performed to analyze the composition of the rust layer formed on the surface of steel specimens after various corrosion cycles. The relationship between the composition of the rust layer and the corrosion performance was established. The test corrosive environment was verified to be consistent with the C3 environment. The conclusions of this study could provide guidance for the corrosion evaluation in the following test or practical application. [ABSTRACT FROM AUTHOR]

Microalloying is an effective method to improve the properties of Al–Mg alloys. The microstructure, mechanical properties and corrosion behaviours of Al–9.2Mg–0.8Mn–xCu (x = 0–1.2 wt-%) alloys are studied to promote the application of Al–Mg alloys. The addition of Cu increases the strength of the alloy, where the ultimate tensile strength of 0.6 wt-% Cu alloy is improved by 43 MPa. Moreover, the addition of Cu significantly affects the corrosion behaviours of alloys. For as-sensitised alloys, compared to the matrix, the 0.1 wt-% Cu alloy shows a 28.3% reduction in pitting corrosion mass loss, which is attributed to the Cu element can form a stable passivation film, and the 0.3 wt-% Cu alloy shows a 15% reduction in intergranular corrosion mass loss, which is attributed to the addition of Cu can restrict the β phase precipitation at grain boundaries. The study shows that Cu-alloying can improve the comprehensive properties of Al–9.2Mg–0.8Mn alloys. [ABSTRACT FROM AUTHOR]

To reduce the corrosion degradation of copper alloys, an equiatomic CoCrNi medium-entropy alloy (MEA) coating was successfully fabricated on a copper alloy plate using high-velocity oxygen-fuel (HVOF) spraying. The microstructure, corrosion behaviour, and passive film characteristics of the CoCrNi MEA coating in a 3.5 wt.% NaCl solution were investigated. The CoCrNi MEA coating mainly consisted of a face-centred cubic solid solution structure and a small amount of metal oxide. Compared to that of the widely used electroplated NiCo coating, the corrosion current density of the CoCrNi MEA coating dropped by 93%. The pitting corrosion of the CoCrNi MEA coating originated from the interface between the solid solution matrix and the oxide. Due to the strong protective passive film and low coincident site lattice boundaries, the CoCrNi MEA coating exhibited superior corrosion resistance in a NaCl solution. [ABSTRACT FROM AUTHOR]

In this investigation, electropolishing and plasma ion nitriding are applied to super austenitic stainless steel for the purpose of improving its corrosion and pitting resistance. Electrochemical experiments are conducted with washing water collected directly from the ship's scrubber. After electropolishing, the surface roughness is improved by about 73.6% compared to mechanical polishing. After plasma ion nitriding, CrN (precipitate), Fe4N (compound), and γN (solid solution) are observed on the surface. The thickness of the layer formed on the surface is measured to be about 10 μm. A hysteresis loop is observed in the cyclic potentiodynamic polarization curves of mechanical polishing and electropolishing, and the areas are calculated as 23.33 mW cm−2 and 0.17 mW cm−2, respectively. The polarization curve of plasma ion nitriding presents perfect passivation characteristics. Accordingly, mechanical polishing and electropolishing reveal local corrosion, whereas plasma ion nitriding presents a tendency towards general corrosion. In the mechanical polishing, electropolishing, and plasma ion nitriding, the corrosion current densities are 0.665 μA cm−2, 0.093 μA cm−2, and 16.47 μA cm−2, respectively, and the maximum damage depth is observed to grow progressively smaller from plasma ion nitriding to electropolishing and then mechanical polishing. [ABSTRACT FROM AUTHOR]

The pitting corrosion tendency of the as-extruded AA6063 alloy was investigated in this study through immersion corrosion and electrochemical corrosion tests at various aging temperatures. The morphologies of the corroded samples were characterized using OM, WLI, SEM, and TEM. The corrosion resistance of as-extruded alloys with various heat treatments was assessed using an electrochemical workstation and SECM. The surface potential at various positions on the alloy surface was measured using KPFM. The results indicate that as the aging temperature increases, the corrosion mode of the alloy shifts primarily from subcritical pitting corrosion to pitting corrosion. This shift eventually leads to the formation of stable pitting corrosion, and the alloy's pitting corrosion resistance gradually decreases. Surface potentials vary among different types of second-phase particles, with Mg2Si measuring 1.57 V and β-AlFeSi measuring 2.14 V. The existence of a potential difference between the matrix and the second-phase particles leads to the formation of both crystalline and cathodic pits. As the temperature increases, the number of active sites for pitting corrosion also increases. Longitudinal expansion of the pits takes place along densely packed (100) planes, forming a semi-cubic stepped crystal structure. Lateral expansion of pits occurs parallel to the <001>Al direction, demonstrating filamentous corrosion expansion. [ABSTRACT FROM AUTHOR]

Ti‐based bulk metallic glasses are envisioned for human implant applications. Yet, while their elevated Cu content is essential for a high glass‐forming ability, it poses biocompatibility issues, necessitating a reduction in near‐surface regions. To address this, surface treatments that simultaneously generate protective and bioactive states, based on nanostructured Ti and Zr‐oxide layers are proposed. An electrochemical pseudo‐dealloying process using the bulk glass‐forming Ti47Cu38Fe2.5Zr7.5Sn2Si1Ag2 alloy is defined. Melt‐spun ribbons are immersed in hot concentrated nitric acid solution, monitoring the anodic polarization behavior. From the current density transient measurements, together with surface studies (field‐emission scanning electron microscopy, transmission electron microscopy, and Auger electron spectroscopy), the surface reactions are described. This nanostructuring process is divided into three stages: passivation, Cu dissolution, and slow oxide growth, leading to homogenous nanoporous and ligament structures. By tuning the applied potential, the pore and ligament sizes, and thickness values are adjusted. According to X‐ray photoelectron spectroscopy, these nanoporous structures are Ti and Zr‐oxides rich in hydrous and nonhydrous states. In a simulated physiological solution, for those treated glassy alloy samples, complete suppression of chloride‐induced pitting corrosion in the anodic regime of water stability is achieved. This high corrosion resistance is similar to that of clinically used cp‐Ti. [ABSTRACT FROM AUTHOR]

Tartaric-sulfuric acid anodic (TSA) films were prepared on the surface of the 2024 Al alloy. These films were sealed with cerium salts at 25 °C and 65 °C, hot water, and dichromate. The morphology and corrosion resistance of the anodic films were investigated using a field emission scanning electron microscope/energy-dispersive spectrometer, an electrochemical workstation, an acidic spot test, and an immersion test. The results indicated that the surface of the TSA film sealed with cerium salt at 65 °C had a slightly lower cerium content compared to the TSA film sealed at 25 °C. It was found that increasing the sealing temperature of cerium salt could enhance the corrosion resistance of the TSA film. After immersion in a 3.5 wt.% NaCl solution for 336 h, no obvious corrosion pits were observed on the surface of the TSA film sealed at 65 °C, whereas many larger corrosion pits appeared on the surface of the TSA film sealed at 25 °C. The improved corrosion resistance of the TSA film sealed at 65 °C could be attributed to the synergistic effect of cerium oxide deposition and the hydration reaction. The corrosion resistance of the TSA film sealed at 65 °C was significantly better than that of the film sealed with hot water, but it was still lower than that of the TSA film sealed with dichromate. [ABSTRACT FROM AUTHOR]

This study describes the biofilm formation by sulphate-reducing bacteria (SRB) on different materials, which has implications for the biomedical, pharmaceutical, food and chemical process industries. SRB was chosen as a model organism being an anaerobic bacterium. Biofilm formation on different materials and corrosion of titanium by SRB were monitored with time using confocal laser scanning microscopy and fluorescent FISH probes were used to authenticate the SRB strain. The thickness of the mono-culture SRB biofilm has ranged from 4 to 24 µm during thed 12–84 hr; however, the maximum biofilm thickness (24 µm) was recorded after 60 hr of growth. Planktonic growth of the SRB strain showed a log phase up to 48 hr and the sulphide production ranged from 2 to 14 mg l−1. For a comparative account, the SRB biofilm formation on copper was chosen as a positive control. Finally, the putative role of extracellular electron transfer by SRB in the biocorrosion process and the plausible mechanism of pitting corrosion of titanium is described in detail. [ABSTRACT FROM AUTHOR]

The chemical etching method has the advantages of high precision and low cost for the preparation of steel surface microchannel, but the composition of the etching solution and the etching process have a great influence on the precision of the microstructure. In this article, the influence of etching solution composition and the etching time on the etching precision of stainless steel using a mixture of HCl and H2O2 as an etching solution is studied. The reactions and passivation processes that occur during the etching process are analyzed. The etching mechanism is revealed. The sample prepared with HCl:H2O2 = 1:2 can obtain better etching precision and high-dimensional stability. The amount of lateral erosion and the depth of etching increases with the increase of etching time, resulting in a decrease in the etching factor and precision. Pitting and intergranular corrosion mainly occur during the etching process, and the loss of metal chloride formed in the process forms holes, which become rapid diffusion channels for corrosive Cl and O elements, and promotes the etching process. The etching reaction forms a passivation film on the surface of the substrate, which reduces the rate of the etching reaction. [ABSTRACT FROM AUTHOR]

To capture the initial corrosion of sintered NdFeB alloys, a quasi-in situ investigation of the localized corrosion behavior was conducted in low-conductive aqueous solutions. It was clearly observed that the corrosion pits were started from the active sites in matrix phase adjacent to the phase boundaries and the oxide rings were simultaneously deposited some distance from the pits. The spatial separation of the anode and cathode areas during the corrosion could be explained by the potential-pH diagram of Fe and the transportation of hydroxide and ferrous ions in the solution. Based on the variation of oxide rings with environmental factors, it was deduced that the ring-shaped deposition of corrosion products was cooperatively determined by the ferrous cations from pits and the hydroxide anion generation at the cathodic regions limited by the diffusion of oxygen from the bulk solution. This observation gives new insights into the galvanic corrosion of alloys in aqueous media. [ABSTRACT FROM AUTHOR]

In the CCUS project, CO2 utilization had achieved remarkable results in oil displacement. But, at present, one of the main reasons that seriously affected the large-scale application of CCUS projects was that the corrosion behavior of underground environment on pipe string or wellbore was not fully evaluated. It was revealed that the wellbore corrosion behavior in the harsh environment in the process of CO2 flooding was the key to ensure the safe production of oil fields. Therefore, this paper took the corrosion environment with temperature of 81.7°C, pressure of 52.3 MPa and high salinity in the well depth of 4517 m as the research object, to study the corrosion behavior of oil casing N80 steel through corrosion rate, corrosion morphology and electrochemical experiments. The results showed that the corrosion rate increased with the increase of experimental time, behaved by the charge transfer resistance decreased. However, when the experiment increased from 800 h to 1000 h, the pitting corrosion rate increased from 1.47 mm/a to 1.782 mm/a, which was consistent with the ratio of anode/cathode Tafel constants and corrosion density. This was mainly because the relatively dense FeCO3 corrosion product layer generated on the N80 steel surface gradually brook down due to synergistic effect of amorphous CrO3, Fe2+/Ca2+ complex salt and Cl– during the experiment, which promoted the initiation and development of the corrosion pits. Compared with the bare N80 steel, the incomplete corrosion product layer aggravated the rapid development of pitting corrosion. [ABSTRACT FROM AUTHOR]

In the present work, the influence of a corrosive environment and temperature on the corrosion resistance properties of duplex stainless steel S31803 was evaluated. The corrosive process was carried out using solutions of 1.5% HCl (m/m) and 6% FeCl3 (m/m), at temperatures of 25 and 50 °C. The microstructure of UNS S31803 duplex stainless steel is composed of two phases, ferrite and austenite, oriented in the rolling direction, containing a ferrite percentage of 46.2% in the rolling direction and 56.1% in the normal direction. Samples, when subjected to corrosive media and temperature, tend to decrease their mechanical property values. It was observed, in both corrosive media, that with increasing test temperature, there is an increase in the corrosion rate, both uniform and pitting. The sample in HCl solution obtained a uniform corrosion rate of 0.85% at 25 °C and 0.92% at 50 °C and pitting rates of 0.77% and 1.47% at the same temperatures, respectively. When tested in FeCl3 solution, it obtained uniform corrosion of 0.0006% and 0.93% and pitting of 0.53% and 18.5%, at the same temperatures. A reduction in dissolution potentials is also noted, thus characterizing greater corrosion in the samples with increasing temperature. [ABSTRACT FROM AUTHOR]

Fe‐0.3C‐15Cr‐1Ni high hardness corrosion‐resistant alloy coating is prepared on the surface of 3Cr13 by laser cladding technology. The effects of scanning speeds on the microstructure, microhardness, and corrosion resistance of the coating are studied. The results show that the microstructure of the cladding layer is mainly composed of intracrystalline martensite and carbides distributed along the grain boundaries. When scanning speed increases from 3 to 5 mm s−1, the grain is obviously fined, and the number of carbides increases, further increasing scanning speed, the grain refinement degree decreases and the carbide quantity decreases gradually. When scanning speed is 5 mm s−1, the microhardness reaches the maximum, the corrosion resistance is significantly improved at 5 and 7 mm s−1, and the pitting potential and passivation zone width increase by 180–219% and 69–78%, respectively, compared with 3 mm s−1 sample, but further increases scanning speed to 9 mm s−1, the hardness and corrosion resistance significantly reduce. This is because scanning rate affects the component undercooling degree of the dynamic molten pool and the temperature gradient at the solidification interface front, which affects the growth of dendrites, the number of carbides, and further affects the alloying elements in the carbide and matrix. [ABSTRACT FROM AUTHOR]

Corrosion rate measurements in the tank enable us to develop a new model for predicting the remaining operating period of the tank. The empirical model for the study of bottom plate thicknesses and corrosion pits is more conservative than the standard linear model, as it considers the autocatalytic nature of the corrosion process. We used the double exponential distribution of maximum values (Gumbel's) to evaluate the maximum depth of pits, and the double exponential distribution of minimum values to evaluate the minimum values of the plate thickness. A comparison of the values of the parameters obtained using linear extrapolation and exponential models indicates the unreliability of linear extrapolation, since disregarding dynamic processes underestimates the actual rate of corrosion. [ABSTRACT FROM AUTHOR]

Pipelines subjected to thermal or mechanical loads may fail due to plastic strain accumulation which leads to ratcheting. In this research, cyclic plastic behavior and shakedown limit are investigated experimentally and numerically for a defected pressurized pipe under cyclic bending moment. In the numerical model, the combined isotropic/kinematic hardening model based on the Chaboche model is adopted to represent the cyclic plastic flow of the material. The hardening parameters are determined experimentally and used in the finite element (FE) model. A four-point bending test rig is manufactured to test a pressurized API 5L steel pipe under cyclic bending. An elliptical defect is created by machining to depict corrosion pits in pipes. The plastic strains are measured experimentally and the results are used to tune the parameters of the FE model. The shakedown limit of the defected pipe is determined numerically by tracking the critical points behavior and the results are verified experimentally. Furthermore, the plastic work dissipated energy (PWD) is estimated within the defective structure to study the behavior of the pipe. By running this compatible model, it is found that the yield and the shakedown limits are lowered by mean values of 55% and 25% respectively due to the presence of metal loss defect occupying almost half of the pipe thickness. [ABSTRACT FROM AUTHOR]

In this study, to investigate the problem of contact fatigue and the damage mechanism of an AD180 high-carbon semi-steel roll, rolling contact fatigue tests were conducted using specimens cut from the periphery of a roll ring. These specimens were characterized under different contact stresses using SEM, a profile system, an optical microscope, and a Vickers hardness tester. The results indicates that the main forms of fatigue damage of an AD180 high-carbon semi-steel roll are peeling, pitting corrosion, and plowing. Moreover, the surface of the roll exhibits delamination and plastic deformation characteristics under high contact stress. Meanwhile, the size and depth of peeling, as well as the amount of pitting corrosion, increase with the contact stress. Peeling is mainly caused by a crack that originates at the edge of the specimen surface and propagates along the pearlite structure and the interface between pearlite and cementite. High contact stress can lead to an increase in the crack propagation depth and angle, resulting in the formation of larger peeling. Under cyclic loading, the near-surface microstructure of the specimen hardens due to grain refinement and dislocation strengthening, and the depth of the hardened layer increases with the increase in contact stress. When the contact stress reaches 1400 MPa, the near surface structure of the specimen changes from pearlite to troostite. [ABSTRACT FROM AUTHOR]

The article provides an assessment of the impact surface defects of rolled stainless steel 08Kh21N6M2Т on its corrosion resistance. To conduct comparative tests for the susceptibility to form pitting corrosion, samples are used with and without jet-abrasive surface machining. It is shown that metal surface defects may indicate structural imperfections in the form of precipitation of chromium carbides and secondary austenite inside δ-ferrite grains. As a result of metallographic and electrochemical studies, it is confirmed that jet-abrasive machining has a negative effect on the rate of general corrosion and resistance to pitting corrosion, while the removal of rolling defects from the stainless steel surface leads to its intense corrosion. [ABSTRACT FROM AUTHOR]

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The influence of chloride ion (Cl−) concentration on the corrosion mechanism of WC–MgO composites has been studied in this work. The results suggest that the corrosion resistance of WC–MgO composite decreases first and then increases with the increase in Cl− concentration. Solution conductivity and dissolved oxygen content are the main influence factors. The solution conductivity determines the charge transfer process, and the dissolved oxygen determines the cathodic oxygen absorption reaction. The corrosion characteristic is typical pitting corrosion. Meanwhile, the corrosion mechanism contains an oxidation process of the WC matrix and the dissolution destruction of the MgO toughening phase. The formation of the WO3 corrosion layer hinders the general corrosion to protect the inner material. However, the dissolution of MgO induces the initiation of pitting. The local alkaline caused by MgO dissolution promotes the dissolution of the WC matrix, which leads to the expansion of pitting. [ABSTRACT FROM AUTHOR]

In this work, corrosion behavior and the concurrent acoustic emission (AE) signals of AZ31 alloy under NaCl and Na2SO4 solution droplets were comparatively investigated in combination with in-situ optical microscopy observations. It was observed that after a short initial corrosion accompanied by the growth and rupture of H2 bubbles, the later corrosion behavior of AZ31 alloy mainly developed into filiform corrosion under NaCl solution droplet and pitting corrosion under Na2SO4 solution droplet. AE signals were detected in both cases. In particular, AE parameters of amplitude and duration were found to well identify filiform and pitting corrosion. AE signals were mainly correlated with the observed evolution of H2 bubbles of different shapes and positions, i.e., regularly round bubbles grew and ruptured at the filament head near the metal surface during filiform corrosion; whereas irregularly-shaped bubbles grew and ruptured at the pit mouth during pitting corrosion. [ABSTRACT FROM AUTHOR]

Friction surfacing (FS) is a solid-state coating technology for metallic materials, where the deposition of a consumable material on a substrate is enabled via friction and plastic deformation. The deposited layer material commonly presents a significantly refined microstructure, where corrosion could be an issue due to this grain refinement within the layer deposited, possibly creating micro galvanic pairs. The present work investigates the corrosion behavior of the FS deposited material as well as stud base material and substrate using cyclic polarization tests and open circuit potential (OCP) monitoring. Comparing the FS deposited material and the respective consumable stud base material (both AA5083), the grain size is correlated with the results from the corrosion tests, where the deposited material shows more equiaxed and refined grains in comparison to the stud base material. The cyclic potentiostatic polarization tests showed that the stud base material is more resistant to pitting nucleation presenting smaller pits and a lower amount of pits compared to deposited material and substrate. As a complement to OCP test, the stud base material is also more stable on a chloride solution compared to the substrate and the deposited material. [ABSTRACT FROM AUTHOR]

Introduction: This work systematically investigates the effect of chloride level, temperature, and the water system's oxidative power on the pitting corrosion performance of stainless steels in pH-neutral environments. Methods: Two test programs were set to a) develop a robust method for constructing the pitting engineering diagrams and b) construct the pitting engineering diagrams based on the obtained method from the first test program. The various electrochemical techniques were selected to assess and understand factors that affect the corrosion behavior of stainless steel. Extensive testing was performed with short-term electrochemical measurements and long-term immersion tests. Results and Discussion: The obtained results demonstrate that the electrochemical methods are sufficient to define pitting diagrams showing the boundaries between pitting and no pitting as a function of chloride concentration, temperature, and the water system's oxidation potential. The laboratory long-term electrochemical test results correspond the best to real applications and clearly underline the importance of an induction time for pit initiation. Accordingly, two sets of pitting engineering diagrams were constructed based on the water system's oxidation potential. Measurements at the applied potential of 150 mV vs. saturated calomel electrode (SCE) correspond to applications in sterile tap water, whereas the applied potential of 400 mV vs. SCE corresponds to slightly chlorinated water or water with some biological activity. Pitting engineering diagrams were proved to be very useful tools to aid material selection in water application. However, it is important to realize that additional factors, such as different surface conditions and the presence of other environmental species, crevice design, or weld will affect the exact position of the boundaries between pitting and no pitting. [ABSTRACT FROM AUTHOR]

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 x 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Among metallic biomaterials, AISI 316L has the cheapest price yet but the lowest mechanical properties and it is prone to corrosion. Bone plate failure is often triggered by dynamics load, crevice or pitting corrosion, or a combination of fatigue and crevice or pitting corrosion attack at the same time. Shot peening and plasma nitriding are surface treatments that enhance material properties. This work examined the shot peening duration effects and plasma nitriding on surface to the depth hardness, roughness, droplet contact angle, and fatigue life in environment containing rich chloride ions. The results revealed that shot peening and plasma nitriding improved both surface layer roughness and hardness. Furthermore, shot peening and plasma nitriding reduced droplet contact angle and enhanced the fatigue life of the material. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper originally investigates the sulfide inclusion-induced micro-scaled pitting corrosion in indoor atmospheric environment on automotive crankshafts manufactured by classical non-quenched and tempered steel using scanning electron microscope using energy-dispersive spectrometer. The crankshafts, which were disassembled from gasoline engines with low mileage after specific tests, were stored in an indoor atmospheric environment with an ambient humidity of approximately 75% for 2 weeks. The experimental results show that the anodic reaction initially took place at the sulfide inclusion/steel matrix interface, which was induced by the sulfide inclusion wherever very small amount of residual neutral chloride medium on the crankshaft surface was activated by moisture in the air. In addition, the reaction products could accelerate the rate of pitting corrosion toward the steel matrix in nearby micro-zones, and tiny rust that could be hardly observed by visual inspection, as a result, appeared in micro-scale on the experimental crankshaft surface even in indoor atmospheric environment. It is concluded that even when the crankshaft is stored indoors, special attention should be pertinently paid to corrosion prevention, for example, to remove all corrosive media on surface carefully by fine cleaning, to implement rust prevention measures, and to control humidity of atmospheric environment at a proper level. [ABSTRACT FROM AUTHOR]

The influence of welding current and nitrogen content in argon shielding gas on the resistance of the welded joint (weld metal and heat‐affected zone [HAZ]) of the stainless steel X5CrNi18‐10 to the formation and growth of pits was investigated. Also, the susceptibility of the welded joint to intergranular corrosion was examined. Pitting corrosion resistance indicators were determined based on anodic potentiodynamic polarization measurements in NaCl + Na2SO4 solution, while susceptibility to intergranular corrosion was determined by the potentiokinetic method with a double loop (DL EPR). SEM/EDS was used to analyze the microstructure. It has been shown that higher nitrogen content in shielding gas leads to an increase in the resistance of welded joints (weld metal and HAZ) to the pit formation. However, an improvement in the resistance to the pit formation leads to a decline in the resistance of the welded joint to pit growth. An explanation of this phenomenon is proposed. Also, it was shown that the increase of the welding current increases the susceptibility of the welded joint to intergranular corrosion, while the higher nitrogen content has no effect. [ABSTRACT FROM AUTHOR]

To improve the performance in service of S32760 duplex stainless steel (DSS) in the marine environment, the influence of cutting parameters of S32760 DSS on the pitting corrosion resistance of the workpiece is studied. Cutting experiments are performed on S32760 DSS by varying the cutting parameters to investigate their effects on the surface morphology. The electrochemical experiments are conducted on the workpiece immersed in the 3.5 wt% sodium chloride solution to investigate how the cutting parameters affect the pitting corrosion resistance of S32760 DSS. The results indicate that the pitting corrosion resistance is influenced by the cutting speed and feed rate, which in turn affects the surface roughness. The cutting depth does not have a significant impact on the surface roughness but significantly affects the pitting resistance. The recommended cutting parameters are as follows: feed rate of 0.1 mm/r, cutting speed of 130 m/min, and cutting depth of 0.4 mm. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V selective dissolution occurs in vivo on orthopedic implants as the leading edge of a pitting corrosion attack. A gap persists in our fundamental understanding of selective dissolution and pre-clinical tests fail to reproduce this damage. While CoCrMo clinical use decreases, Ti-6Al-4V and the crevice geometries where corrosion can occur remain ubiquitous in implant design. Additionally, most additively manufactured devices cleared by the FDA use Ti-6Al-4V. Accelerated preclinical testing, therefore, would aid in the evaluation of new titanium devices and biomaterials. In this study, using temperature, we (1) developed an accelerated pre-clinical methodology to rapidly induce dissolution and (2) investigated the structure-property relationship between the dissolving surface and the oxide layer. We hypothesized that solution temperature and H 2 O 2 concentration would accelerate oxide degradation, increase corrosion kinetics and decrease experimental times. To assess this effect, we selected temperatures above (45 °C), below (24 °C), and at (37 °C) physiological levels. Then, we acquired electrochemical impedance spectra during active β dissolution, showing significant decreases in oxide polarization resistance (R p) both over time (p = 0.000) and as temperature increased (p = 0.000). Next, using the impedance response as a guide, we quantified the extent of selective dissolution in scanning electron micrographs. As the temperature increased, the corrosion rate increased in an Arrhenius-dependent manner. Last, we identified three surface classes as the oxide properties changed: undissolved, transition and dissolved. These results indicate a concentration and temperature dependent structure-property relationship between the solution, the protective oxide film, and the substrate alloy. Additionally, we show how supraphysiological temperatures induce structurally similar dissolution to tests run at 37 °C in less experimental time. Within modular taper junctions of total hip replacement systems, retrieval studies document severe corrosion including Ti-6AL-4V selective dissolution. Current pre-clinical tests and ASTM standards fail to reproduce this damage, preventing accurate screening of titanium-based biomaterials and implant designs. In this study, we induce selective dissolution using accelerated temperatures. Building off previous work, we use electrochemical impedance spectroscopy to rapidly monitor the oxide film during dissolution. We elucidate components of the dissolution mechanism, where oxide degradation precedes pit nucleation within the β phase. Using an Arrhenius approach, we relate these accelerated testing conditions to more physiologically relevant solution concentrations. In total, this study shows the importance of including adverse electrochemical events like cathodic activation and inflammatory species in pre-clinical testing. [Display omitted] [ABSTRACT FROM AUTHOR]

Two mathematical models, which describe the dependence of critical pitting temperatures of 06ХН28МДТ alloy (analogue of AISI904L steel) in model recycled water with pH 4-8 and chloride concentration from 350 up to 600 mg/l on chemical composition and structure, are developed. They are based on multivariate regressions with pairwise combinations of features and a three-layer neural network of direct signal. Applying the developed mathematical models, it is found that the critical pitting temperatures of the 06ХН28МДТ alloy increase with an increase in the pH of model recycled water, the content of Cr, Mo, Cu, the volume of titanium nitrides within it, and a decrease in the medium austenite-grain diameter, the content of nickel within the standard, and chlorides in the media. At the same time, the analysis of the developed mathematical model, which is based on multivariate regressions with paired combinations of features (alloy and media parameters), reveals that the content of Cr and Ni in the alloy in combination with the medium austenite-grain diameter most significantly affect its pitting resistance in model recycled waters, and an effect of the Cr content in combination with pH and chloride concentration in the media is somewhat lower, but much higher than an effect of the Mo and Cu content, and the volume of titanium nitrides in combination with the media parameters. The developed mathematical model, which is based on a three-layer neural network of direct signal propagation, is recommended for predicting the pitting resistance of heat exchangers made of 06ХН28МДТ alloy or AISI904L steel when operating in recycled water. In addition, the developed mathematical model, based on multivariate regressions with paired combinations of features (alloy and media parameters), is recommended for selecting the optimal melts of this alloy or steel, which are most resistant to pitting in recycled water. [ABSTRACT FROM AUTHOR]