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Z3CN20–09M stainless steel, a candidate material for coolant pump shells, experiences cavitation erosion (CE) in nuclear reactor service. Z3CN20–09M steel's CE behavior is studied using scanning electron microscopy, transmission electron microscopy, electron back-scatter diffraction, and optical profilometry. The influence of CE on corrosion resistance is analyzed through potentiodynamic polarization tests and time-of-flight secondary ion mass spectrometry. During the incubation stage, damage occurs primarily in austenite. A higher Taylor factor increases the CE. Slip bands and strain-induced martensite are the main reasons for damage. After the incubation stage, brittle ferrite fracture dominates, which induces large grooves and holes. One hour of exposure improves the corrosion resistance. Slip bands, strain-induced martensite, and stacking faults provide diffusion paths for the Cr and O atoms to form a more compact passive film. Finally, approaches aiming to improve the CE resistance of Z3CN20–09M steel are suggested.

The passivation ability of the coating can be improved by adjusting the elements proportion in the Iron-based Amorphous Coating and the spraying process, but the process is complicated and costly. In this study, it was found for the first time that Iron-based Amorphous Coatings can quickly form passive films in phosphate atmosphere, which simplifies the coating strengthening process. Electrochemical measurements, XPS, AFM, FTIR, and SEM-EDS were used to investigate the inhibition mechanism of eco-friendly phosphates on the dynamic dissolution of passive film of Fe-based amorphous coating. When the coating was soaked in 3.5 wt% NaCl + 0.1 M solution, the iron phosphate compound on the coating surface promoted the repair and growth of the passive film, and the film thickness increased by more than 32.9 %. The increase of Fe2+/Fe3+ and (O2-+H 2 O)/OH- in the passive film means that more insoluble Fe-Cr compound growth significantly reduces the donor density (N d) in the passive film and inhibits the degradation rate of the passive film in the corrosive environment. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the effects of chloride ions, oxygen, and carbon dioxide on the corrosion resistance of passive films formed on 316 L stainless steel were investigated in the aggressive oilfield environment using electrochemical testing and microscopic characterization techniques. The results showed that Cl− accelerated the anodic dissolution of the metal and compromised the structure and densification of the passive film, thus reducing its corrosion resistance. An increase in the partial pressure of carbon dioxide initially promotes pitting, but subsequently inhibited further corrosion development. The presence of oxygen enhanced the cathodic reaction and passive film formation, effectively preventing the invasion of aggressive chloride ions, thus inhibiting further corrosion. These findings provide a significant scientific basis for material selection and protection of oil extraction equipment in oilfield environments. [ABSTRACT FROM AUTHOR]

A novel AlCo 1.2 Cr 0.8 FeNi 2.1 eutectic high entropy alloy (EHEA) was designed and prepared. The microstructure of the as-cast alloy was characterized that a fine lamellar structure composed of FCC (L1 2) phase and B2 phase. The mechanical of the EHEA was studies by the tensile tests, and the corrosion properties of the EHEA in 3.5 wt% NaCl solution at room temperature was investigated. The results shown that the alloy exhibits synergistic effect of strength- plasticity with a high tensile strength of 1048.42 MPa and an excellent elongation of 18.92%. Potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) indicated that the EHEA exhibits spontaneous passivation in 3.5 wt% NaCl solution, forming a protective passive film that exhibits p-type and n-type semiconductor properties, with the main components of Al 2 O 3 , CoO, Cr 2 O 3 , Fe(OH) 3 , and NiO. Furthermore, the corrosion mechanism of EHEA was discussed. • Prepare a novel AlCo 1.2 Cr 0.8 FeNi 2.1 EHEA without Cr-rich precipitates. • Exhibit synergistic effect of strength- plasticity and excellent corrosion resistance. • Study the passive film and corrosion mechanism systematically. [ABSTRACT FROM AUTHOR]

This study investigated the effect of Si content on the corrosion behavior of AlZrNbTiSi x (x=0, 0.3, 0.6, 1.0 at%) lightweight refractory high-entropy alloys in a 1 M HNO 3 solution. The results showed a transformation in the microstructures of AlZrNbTiSi x from a single BCC phase (x=0) to a BCC matrix phase with Zr 5 Al 3 hexagonal precipitated phases (x=0.3, 0.6, 1.0). AlZrNbTiSi 0.6 exhibited the best corrosion resistance, attributed to the addition of Si promoting the growth of continuous and dense oxides. Microgalvanic corrosion affected the formation of the oxide film, triggering an excessive amount of Si worsening the stability of the passive film. • The moderate addition of Si improves the corrosion resistance of AlZrNbTi lightweight refractory high-entropy alloys. • The corrosion resistance mechanism of AlZrNbTiSi x lightweight refractory high-entropy alloys in a 1 M HNO 3 are clarified. • The precipitation of Zr 5 Al 3 phases and Si oxides play a key role on the formation of a continuous protective passive film. [ABSTRACT FROM AUTHOR]

A kind of novel Gd particles-doped Fe-based amorphous metallic coating (Gd-AMC) was designed and produced by thermal spraying technique. The thermal neutron absorption cross-section for the coating containing 4.8 wt% Gd is 14.7 times higher than that of borated stainless steel (BSS) substrate. It is also worth noting that the localized corrosion resistance for Gd-AMCs is considerably superior to that for BSS substrate, which is closely attributed to the rapidly formed protective passive film on amorphous matrix through novel "dissolution-passivation" processes. This work provided a new strategy for the design of corrosion-resistant neutron absorbing materials. [Display omitted] • Novel Gd-AMCs were elaborated and fabricated by thermal spraying technique. • Neutron absorption capability of Gd-AMCs was much higher than that of BSS. • Gd-AMCs exhibited excellent localized corrosion resistance. • Corrosion mechanisms of Gd-AMCs was thoroughly analyzed and proposed. [ABSTRACT FROM AUTHOR]

The corrosion behaviors and underlying mechanisms of laser remelted Zr-Cu-Ni-Al metallic glass matrix composite coatings (MGMCCs) were investigated systematically. The remelted coatings exhibit significantly enhanced corrosion resistance with the lowest corrosion current density of 3.96×10−9 A/cm2 among the reported Zr-Cu-Ni-Al metallic glass (MG) alloy and coatings in 3.5 wt% NaCl solution. The passive film is mainly constituted by ZrO 2 and Al 2 O 3 , and its formation follows the point defect model. Corrosion was preferentially initiated at the crystalline/amorphous interface. By increasing the MG content and suppress the formation of Cu-rich crystalline phase, the corrosion resistance of Zr-Cu-Ni-Al MGMCC can be improved. • Laser remelting can significantly increase the MG content and improve the corrosion resistance of the Zr-Cu-Ni-Al coatings. • The remelted coating exhibits the lowest i corr of 3.74×10−9 A/cm2 within the reported Zr-Cu-Ni-Al MGMC coatings and MGs. • Pitting is preferentially initiated at the MG/crystal interface due to the poor corrosion resistance of Cu-enriched grains. • This work provides an effective method for the corrosion resistance improvement of MGMCCs by laser remelting treatment. [ABSTRACT FROM AUTHOR]

Dilute Mg–Al–Mn–Ca–Gd alloy with extraordinary corrosion resistance (P H = 0.21 mm/year) comparable to that of high-purity Mg was prepared. The Gd addition promoted the second phase transformation from the Al–Mn phase to the Al 8 Mn 4 Gd and Al 2 Gd phases with decreased potential difference with Mg matrix, thus weakening the micro-galvanic corrosion. The homogeneous distribution of nano-sized second phases effectively inhibited localised corrosion, contributing to the integrity of surface film. Furthermore, Gd alloying promoted the formation of compact corrosion products mixed with Gd 2 O 3 and embedded with the nano-sized Al 2 Gd phase, resulting in a stable and protective surface film. [Display omitted] • Dilute Mg alloy with corrosion resistance comparable to high-purity Mg is prepared. • Gd promotes the transformation of Al-Mn phase to less noble Al 8 Mn 4 Gd and Al 2 Gd phase. • The uniform distribution of dense nano-sized phase inhibits localised corrosion. • The surface film containing Gd 2 O 3 and nano-sized Al 2 Gd is more protective to matrix. [ABSTRACT FROM AUTHOR]

The influence of the potential for film formation and immersion time on the corrosion resistance of the passive film formed on Fe-based amorphous coating was thoroughly investigated. The semiconducting properties and chemical composition of the passive films were analyzed employing Mott-Schottky and XPS techniques. Results indicate that the stability of the film diminished as the potentials and immersion periods increased. The structural properties and chemical composition of film played a crucial role in the corrosion resistance of the coating in a chloride electrolyte. The accumulation of cation vacancies and the formation of metal chlorides increased the likelihood of film rupture, ultimately leading to pitting. • Reveal the effect external environmental conditions on the characteristics of the passive film. • The corrosion resistance of passive film is independent of the thickness. • Reveal the effect of passive film structure and composition on the coating's corrosion resistance. • The formation of a cation vacancy condensate and solid metal chloride lead to failure of the passive film. [ABSTRACT FROM AUTHOR]

Laser shock peening induced smaller grain size than ultrasonic severe surface rolling for 316L stainless steel. Furthermore, laser shock peening processing facilitated to induce more strain induced α′-martensites. Therefore, the refined grains and α′-martensite enhanced significantly the hardness of 316L stainless steel. Moreover, laser shock peened sample exhibited better corrosion resistance than ultrasonic severe surface rolled one in a medium containing chloride ions. Although α′-martensite would decrease passivation and anti-corrosion ability of 316L stainless steel, the grain refinement promoted the diffusion activity of chromium element, which accelerated surface passivation process. • Laser shock peening promoted to form smaller grains in 316L stainless steel than ultrasonic severe surface rolling. • Laser shock peening induced more strain induced α′-martensites in 316L stainless steel. • Laser shock peening induced protective passive films and enhanced corrosion resistance. [ABSTRACT FROM AUTHOR]

A passive film serves as a first defense of any material against the attack of a corrosive environment for any material. So, it is essential to understand the parameters affecting the characteristics of the passive film. The present work focused on investigating the effect of tensile load during stress corrosion cracking (SCC) condition on the characteristics of the passive film developed on a TRIP Fe 39 Mn 20 Co 20 Cr 15 Si 5 Al 1 high entropy alloy (HEA) in a 3.5 wt.% NaCl solution at room temperature. A constant load of ∼25% of the yield strength was applied to a flat dog-bone-shaped tensile specimen for 24 h in a 3.5 wt.% NaCl salt environment. For comparison purposes, a specimen with no-load was kept in a salt solution under similar conditions. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) techniques were used for passive film characterization. EIS results revealed that the passive film deposited on the no-load and load conditions exhibited a dense and stable structure. However, the passive film deposited on the no-load specimen showed relatively better resistance to corrosion ions. XPS results indicated that the passive film deposited on the no-load and load specimens consisted of Cr rich oxide and hydroxide, forming a monolayer type of passivation film. Nonetheless, the passive film on the no-load specimen exhibited higher concentrations of Cr than the passive film on the loaded specimen. XPS depth profile results showed that the film thickness was relatively greater for the no-load specimen than for the loaded specimen. This study underscores the critical influence of tensile load on the degradation of passive film properties of the HEA. [ABSTRACT FROM AUTHOR]

Long-term corrosion evolution of boron-containing stainless-steel (BSS) in simulated environment of spent nuclear fuel wet storage is investigated. Corrosion evolution goes through three phases of rising, stabilization and declining, which corresponds to five electrochemical processes. As B content increases, the initiation and stable growth of pits are promoted by decreased Cr ox 3+ and increased inhomogeneity of passive film and enhanced micro-galvanic effect, resulting in reduced |Z| 10mHz value and the duration of the second stage. Due to reduced grain sizes, the corrosion resistance of hot-rolled BSS is substantially improved with homogeneous passive film, higher Cr ox 3+ in it and weaker micro-galvanic effect. • Long-term corrosion of BSSs in SNF wet storage environment was investigated. • Corrosion evolution for BSS exhibited three distinct stages based on in-situ EIS. • Long-term corrosion resistance of the BSSs was significantly improved by hot-rolling treatment. [ABSTRACT FROM AUTHOR]

In tests of typical iron-based materials, it has been found that the dissolution efficiency at low temperature is greater than that at ambient temperature. By utilizing sputtering X-ray photoelectron spectroscopy (sputtering XPS) and focused ion beam scanning electron microscopy (FIB-SEM), it was found that this abnormal phenomenon is rooted in a thinner passive film and lower valence oxides formed on the surface at low temperature. Transmission electron microscopy (TEM) analysis supported these conclusions at the microscopic level. First-principles calculations further revealed that lower valence oxides of iron are more conductive than higher valence oxides. • This study found an anomalous increase in the dissolution efficiency of iron-based materials at low temperatures. • This study intuitively demonstrates the incomplete formation of passive films on the surface at low temperatures. • This study characterized the structure of surface products during the active dissolution stage. • This study explained the reason for the anomalous efficiency improvement through DFT and theoretical calculations. • This new discovery is of significant importance for the future development of electrochemical machining. [ABSTRACT FROM AUTHOR]

• ·The self-corrosion current density of Zr 55 Cu 35 Al 10 BMG is 1.59 × 10−7 A·cm−2, which is two times higher than that of Zr 56 Co 28 Al 16 BMG. • ·The impedance value of Zr 56 Co 28 Al 16 BMG is 1.96 × 106 Ω·cm2, which is 2.7 times higher than that of Zr 55 Cu 35 Al 10 BMG. • ·The enrichment of Cu elements within corrosion pits leads to uneven distribution of elements, which accelerates the corrosion rate. • ·The replacement of Cu elements with CO elements increases the content of ZrO 2 , thereby improving the stability of the passive film. In this paper, the corrosion mechanisms of Zr 55 Cu 35 Al 10 and Zr 56 Co 28 Al 16 bulk metallic glasses (BMGs) in 3.5 wt.% NaBr solution was systematically investigated by the kinetic potential polarization and electrochemical impedance spectroscopy. Both Zr 55 Cu 35 Al 10 and Zr 56 Co 28 Al 16 BMGs were subjected to pitting damage during the polarization process in NaBr solution due to the presence of Br− ions. However, Zr 56 Co 28 Al 16 BMG exhibits better corrosion resistance compared to Zr 55 Cu 35 Al 10 BMG. Zr 55 Cu 35 Al 10 BMG experiences selective dissolution of alloying elements under the attack of Br−, and Cu element was enriched in the corrosion pit. The surface of Zr 56 Co 28 Al 16 BMG shows a more uniform distribution of elements after corrosion. Simultaneously, the substitution of Cu by Co changes the composition of the passive films and increases the relative content of ZrO 2 , which is a principal factor contributing to the enhanced stability of Zr 56 Co 28 Al 16 BMG's passive film. [ABSTRACT FROM AUTHOR]

Exploring the failure mode of passive film is the most fundamental issue for corrosion research and prevention of metals. In the actual service of reinforced concrete structures, steel rebars are typically exposed to a complex solution environment, characterized by electric fields, chloride ions, and fluctuating temperatures. Using scanning electron microscope, scanning electrochemical microscope, and a series of electrochemical tests, we present the damage mode of steel passive film in a simulated alkaline environment of concrete; and then establish a deductive diagram to illustrate it. Additionally, we use atomic force microscope, X-ray photoelectron spectroscopy and transmission electron microscope to explore the structural characteristics of passive film on an atomic scale, and confirm that specific ion channels serve as the pathway for chloride invasion. This study can enable a deeper understanding of the micro-mechanisms involved in steel depassivation and the initiation of corrosion electrochemical reaction. [Display omitted] • The failure mode of passive film under coupled electric field was found. • The sensitivity of passive film to multi factors was discussed. • The microstructure of passive film was explored on the nano scale. • Putting forward special ion channel is the way that chloride invade passive film. [ABSTRACT FROM AUTHOR]

Due to the growing shortage of fresh water resources worldwide, it is necessary to explore the feasibility of using seawater to produce concrete. However, the passivation and pitting corrosion resistance of reinforcing steel will inevitably be impaired by the chlorides contained in seawater. Therefore, it is particularly important to develop a corrosion-resistant steel that could be employed in seawater-mixed concrete. One option being considered is using duplex stainless steel (DSS). To evaluate the feasibility of application in seawater-mixed concrete, the passive films of 2304 DSS were both generated by cyclic voltammetry and naturally formed in alkaline solutions with and without admixed chlorides, which was further compared with those of the conventional low-carbon steel (HRB400E steel). Unlike 2304 DSS, HRB400E steel failed to be passivated with admixed chlorides. Furthermore, the passive film of 2304 DSS was investigated by EIS, AFM and XPS measurements. Although the passivation ability was slightly reduced by admixed chlorides, and the morphology and composition of passive film were also modified, the high pitting corrosion resistance of 2304 DSS guaranteed its application in seawater-mixed concrete. • A protective passive film with reduced passivation ability was formed for 2304 DSS in seawater-mixed concrete. • Morphology and composition of passive film of 2304 DSS were modified by admixed chlorides. • 2304 DSS has the potential for application in seawater-mixed concrete. [ABSTRACT FROM AUTHOR]

The electrochemical behavior and passive film properties of the selective laser melted (SLM) and wrought Ti-6.5Al-2Zr-1Mo-1 V (TA15) alloys were examined in H 2 SO 4 solutions through various electrochemical measurements. The results demonstrated that the SLM TA15 alloy exhibited better corrosion resistance than the wrought alloy in different concentrations of H 2 SO 4 solutions. However, the advantageous performance of the SLM TA15 alloy gradually diminished as the H 2 SO 4 concentration increased. In-depth analysis indicated that the chemical and structural characteristics of the passive films formed on the surface of SLM TA15 alloy contributed to effectively protect the alloy and improve its corrosion resistance in H 2 SO 4 solutions. • Electrochemical and surface film properties of the SLM Ti-6.5Al-2Zr-1Mo-1 V alloy are studied for the first time. • The SLM TA15 alloy shows better corrosion resistance than the wrought TA15 alloy in H 2 SO 4 solutions. • The SLM TA15 alloy has a dense and thick surface film, with few carrier densities and a high content of TiO 2. • The good microstructure of the SLM TA15 alloy reduces microgalvanic corrosion and improves corrosion resistance. [ABSTRACT FROM AUTHOR]

Ce doped α-Fe 2 O 3 nanorods with rich oxygen vacancies (CeFeO x) were prepared using low-temperature oxalate precipitation method and added to epoxy resin as active anti-corrosion filler. In an oxygen rich high-temperature and high-pressure environment (HPHT-O 2), the impedance modulus of coatings containing CeFeO x fillers is still close to 1010 Ω·cm2, which is more than 104 times that of pure epoxy coatings. It is attributed to the preferential permeability of CeFeO x fillers to O 2 , which promotes the formation of a dense passive film on the substrate surface, further hinder corrosion, and ensure that the coating does not peel off from the substrate surface. [Display omitted] • Preparation of an α-Fe 2 O 3 nanorods with a "thousand-layer" morphology. • Ce element is doped in α-Fe 2 O 3 nanorods to generate generous oxygen vacancies. • CeFeO x filler can transport oxygen to substrate surface during the coating curing. • O 2 has reached the substrate surface to form a passive film after the coating is cured. • The passive film prevents the rust formation and maintains the coating adhesion. [ABSTRACT FROM AUTHOR]

Duplex stainless steel (DSS) hydraulic control pipelines readily form sigma phase during the heat treatment process, reducing corrosion resistance and leading to pipeline leakage and failure. This study employs various analysis methods to investigate the effect of sigma phase on the corrosion behavior of 2205 hydraulic control pipeline steel, focusing on the electronic characterization of passive film and pitting corrosion behavior. Results revealed that the sigma phase content reaches a maximum value of 13 % at 850 °C within the heat treatment temperature range of 750–950 °C. The voltaic potential of the sigma phase is approximately 47 mV higher than the matrix, but the Cr-depleted zone around the sigma phase is about 85 mV lower than the matrix. The passive film of specimens containing sigma phase exhibits higher carrier densities and lower content of Cr(OH) 3 and Cr 2 O 3 compared to as-received specimens. The morphologies of the film show obvious groove defects, which provide a corrosion channel to the matrix. Moreover, specimens containing sigma phase exhibit higher intergranular corrosion susceptibility and lower pitting corrosion resistance. Pits preferentially nucleate and develop in the Cr-depleted zone around the sigma phase, with their quantity and size positively correlated with the sigma phase content. • The volta potential of sigma phase is approximately 47 mV higher than matrix, but the chromium depleted region is about 85 mV lower than matrix. • The relationship between sigma phase quantitative analysis and passive film property is clarified. • Sigma phase affects the morphology and composition of passive film on 2205 DSS, reducing its corrosion resistance. • The specimen containing sigma phase shows higher sensitivity to intergranular corrosion and lower pitting corrosion resistance. [ABSTRACT FROM AUTHOR]

The AlNiZrYCo high-entropy metallic glass (HEMG) coating with an amorphous content of 60 % was prepared by supersonic plasma spraying, and its multiphase coupling corrosion mechanism was investigated. Due to the presence of amorphous phase and passivation elements, the formation of a passive film that was abundant in Co elements on the surface of the coating efficiently inhibited Cl- erosion. The existence of crystalline and oxide phases in the coating led to galvanic corrosion, accelerating the corrosion process of the coating. • A novel AlNiZrYCo high-entropy metallic glass coating was designed and prepared. • The amorphous content of the AlNiZrYCo high-entropy metallic glass coating can be up to 60 %. • Passive film of the AlNiZrYCo coating efficiently inhibited Cl- erosion. • The existence of crystalline and oxide phases in the coating lead to galvanic corrosion. [ABSTRACT FROM AUTHOR]

This work investigated the effects of L1 2 nanoprecipitates on the electrochemical corrosion behavior and passive film characteristics of CoCrNiAlTi-type high-entropy alloys (HEAs) in chloride-containing solutions. Compared with the single-phase recrystallized alloys, the precipitation of the L1 2 phase destabilized surface passive films, thus deteriorating the localized corrosion resistance and increasing the metastable pitting activities of the L1 2 -strengthened HEA. Influenced by the L1 2 -induced chemical inhomogeneities, the increase of Cr(OH) 3 content in passive films together with the high galvanic corrosion tendency between the two phases was considered as the main reason for the increased susceptibility of the L1 2 -strengthened alloys to localized corrosion attacks. [Display omitted] • A heterogeneous precipitation behavior characterizing the spherical L1 2 nanoparticles and lamellar L1 2 nanorods was observed. • L1 2 -induced chemical inhomogeneities increased the localized corrosion susceptibility of the aged alloy. • The nanoscale passive film with an amorphous structure was directly visualized by STEM. • The increased Cr(OH) 3 content combined with the high galvanic corrosion weakened the aged alloy passive film stability. [ABSTRACT FROM AUTHOR]

The passivity and corrosion behavior of 254SMo stainless steel in aggressive oilfield environments containing both carbon dioxide (CO 2) and hydrogen sulfide (H 2 S) were investigated using weight-loss and surface analyses. The results indicated that the corrosion rate increased with the increase in temperature, CO 2 /H 2 S partial pressures, tensile stress and flow rate. Compressive stress led to a reduction in sulfide compound contents and promoted the formation of protective oxide films, while tensile stress had an opposite effect. Furthermore, a synergistic effect of stress and flow was observed. • The corrosion rate of 254SMo SS increased with the temperature, CO 2 /H 2 S pressures, tensile stress and flow rate. • Cr 2 O 3 were mainly distributed in inner layer, and outer layer was dominated by FeS or MoS 2. • Tensile stress and flow coupling have a promoting effect on the corrosion of 254SMo SS. • The synergistic effect of the compressive stress and flow on the corrosion of 254SMo SS could be neglected. • Significant inhibition of corrosion of 254SMo SS under compressive stress and flow coupling. [ABSTRACT FROM AUTHOR]

In this paper, the structural and compositional evolution of the passive films formed on the Mo-containing stainless steels induced by chloride ions in 0.1 mol L−1 NaOH solution has been studied by means of aberration-corrected transmission electron microscopy and X-ray photoelectron spectroscopy. Mo is enriched at the outer layer of the passive film, which is attributed to the induction of Cl-. Moreover, MoO 4 2- is formed due to the alkaline solution, which impedes the film formation process and inhibits the thickening of the film. Consequently, the positive effect of Mo in the passive film on the corrosion resistance is strongly suppressed. [Display omitted] • The evolution of passive film induced by Cl- in NaOH solution is observed. • The passive film is homogeneous in element distribution in alkaline solutions. • The direct experimental evidence for the formation of NiFe 2 O 4 spinel is observed. • Mo incorporated in passive films is induced by Cl- is directly visualized. • The positive effect of Mo is suppressed due to the formation of MoO 4 2-. [ABSTRACT FROM AUTHOR]

The effect of cold deformation levels on the corrosion behavior of ZrTiNb alloys in an anodic environment of proton exchange membrane water electrolysis was investigated. The findings revealed that cold deformation facilitated the formation of α " martensite and the accumulation of dislocations near deformation bands. The protective quality of the passive film decreased up to 50 % deformation but improved at 75 %. Nb 2 O 5 plays a major role in the protectiveness of passive film. Additionally, crystal orientation selective corrosion was observed, with higher deformation intensifying the corrosion rate. Annealing improved corrosion resistance by producing smaller recrystallization grains. [Display omitted] • The corrosion behavior of ZrTiNb alloys induced by cold deformation was studied. • Low-Σ boundaries and Σ3 boundaries decreased with cold deformation level. • A 50 % deformation rate results in the most defective passive film. • Crystal orientation selective corrosion intensified with increased deformation. [ABSTRACT FROM AUTHOR]

This research explores the effect of the magnetic fields on the passive film of 5083 aluminum alloy. After the application of a 0.3 T magnetic field, 5083 aluminum alloy exhibits an improvement in passivation performance. These improvements manifest as a reduction in passivation current density and an increase in impedance, passive film thickness, and carrier concentration. Additionally, there is an augmentation in the content of the Al 2 O 3 phase within the passive film. The magnetic field facilitates the movement of metal ions during the corrosion process of 5083 aluminum alloy through microscale magnetohydrodynamics, facilitating passive film growth and improving corrosion resistance. [Display omitted] • Effect of magnetic field on passivation performance of 5083 alloy was revealed. • XPS results of Al element in aluminum alloy were analyzed exactly. • The composition of the passive film was analyzed using TOF-SIMS. • Explained 5083 alloy corrosion resistance in magnetic field via passive film. [ABSTRACT FROM AUTHOR]

The superior corrosion resistance of high-entropy alloys (HEA) has attracted much attention from researchers in recent years. In this study, with minor additions of passivation elements into a CoCrFeNi matrix, a (CoCrFeNi)94Ti1.5Al4.5 HEA coating was prepared by a plasma cladding method. This coating has a single FCC phase structure and uniform microstructure, which is expected to form a uniform and compact passive film on the corrosion surface. After adding Ti and Al elements, the passive film became more compact due to the decrease in the proportion of porous hydroxide, which increased the impedance of the passive film, thereby improving the corrosion resistance of the whole HEA coating. After potentiostatic polarization for 4 h, a stable passive film was formed on the (CoCrFeNi)94Ti1.5Al4.5 coating surface in a 0.5-M H2SO4 solution. The corrosion current density was only 175 nA/cm2, which was much lower than that of 304 stainless steel and pure titanium. This indicated that minor additions of Ti and Al can promote the formation of corrosion-resistant high-performance passive films without forming deleterious second phases, and that this phenomenon is more obvious in sulfuric acid solution than in hydrochloric acid solution. [ABSTRACT FROM AUTHOR]

Electrochemical characteristics and semiconducting behavior of additively manufactured electron beam melted (EBM) and wrought (WR) Ti–6Al–4V (Ti-G5) are compared in Ringer's physiological solution. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) confirmed the α + β structure of the tested materials, with two different microstructure types of "bimodal" and "basket-weave" for WR and EBM, respectively. Potentiodynamic polarization (PDP) revealed that the corrosion current density for EBM (icorr = 0.27 ± 0.06 μA cm−2) is less than the WR (icorr = 0.70 ± 0.05 μA cm−2). Moreover, potentiostatic polarization (PS) that was employed to form the passive layers at three different potentials of 300, 500, and 700 mVAg/AgCl, showed that the passive films on the EBM sample are thinner. This finding was confirmed by electrochemical impedance spectroscopy (EIS). Furthermore, through Mott–Schottky (M–S) analysis, donor densities on WR passive films were found to be ~ 1.5 times larger than EBM. Although PS and EIS confirmed that the passive layer on EBM is thinner, it provides higher corrosion resistance than WR. The passive layer on both samples were found to have n-type characteristics with a duplex structure. [ABSTRACT FROM AUTHOR]

In the present work, a low-pressure chemical vapor deposition (LPCVD) Ti0.17Al0.83N and state-of-the-art arc ion plating PVD-Ti1−xAlxN (x = 0.25, 0.55, 0.60, 0.67) coatings were deposited on cemented carbide substrate. The morphological, structural, and electrochemical properties of LPCVD-Ti0.17Al0.83N and PVD-Ti1−xAlxN coatings were compared. The X-ray diffraction (XRD) results and scanning electron microscopy (SEM) images revealed that the LPCVD-Ti0.17Al0.83N coating had a face-centered cubic (fcc) structure, while presenting a crack-free surface morphology and a compressive residual stress of −131.9 MPa. The PVD coatings with a composition of x ≤ 0.60 had an fcc structure, while the PVD-Ti0.33Al0.67N coating consisted of fcc and w-AlN phases. The results of the electrochemical corrosion test showed that the LPCVD-Ti0.17Al0.83N coating had the lowest corrosion current density in a 3.5 wt.% NaCl solution. After a 20-day immersion corrosion test in a 5 mol/L HCl solution, the LPCVD-Ti0.17Al0.83N coating displayed higher stability than the PVD-Ti1−xAlxN coating. The results of electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) analysis revealed that more uniform and denser passivation film, as well as higher Al2O3 proportion in the Al2O3/TiO2 composite passive layer, led to the outstanding corrosion resistance of the LPCVD-Ti0.17Al0.83N coating. [ABSTRACT FROM AUTHOR]

The influences of the rust layer on the passivation and corrosion of Q235b carbon steel in simulated concrete pore solution were studied. The differences between the inner and outer rust layer were characterized. Results show that the pre-rusted samples could still reach passive state at high pH condition free of chloride ions. However, the quality of the passive film formed on the pre-rusted steel were dramatically lower than that formed on the fine polished steel. The pitting corrosion resistance of the pre-rusted steel was significantly higher than that of the fine polished steel in the chloride-containing pore solution. The pitting corrosion potential would be further promoted after the elimination of the outer rust layer. The reaction between the hydrogen ions and the rust layer could inhibit the pitting initiation. Furthermore, the consumption of the corrosive agents induced by the rust layer could further retard the area expansion of the pits. [ABSTRACT FROM AUTHOR]

To compare the corrosion inhibition behaviors of rust inhibitors with different mechanisms on steel bars, the rust resistance effect of sodium molybdate (Na2MoO4), sodium chromate (Na2CrO4), benzotriazole (BTA), N-N dimethyl ethanolamine, sodium molybdate (Na2MoO4) + benzotriazole (BTA), and sodium chromate (Na2CrO4) + benzotriazole (BTA) on steel bars in a simulated chloride concrete pore solution was studied. The rust resistance effects of different types of rust inhibitors were assessed by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effects of different types of rust inhibitors on the film formation characteristics of a passive film on a steel bar surface were expounded. The results show that: When sodium molybdate (Na2MoO4) and benzotriazole (BTA) acted together, the impedance value and the capacitive reactance arc radius were the largest, and the density of the passive film and the inhibition efficiency were the highest. The composition of the passive film was primarily composed of iron compounds, and it also contained oxide and adsorption films that were formed on the steel bar surface by the rust inhibitors. The rust resistance effect was proportional to the compactness of the passive film. [ABSTRACT FROM AUTHOR]

Metallic elemental powder mixture and pre-alloyed metallic powder are both frequently used powder feedstock in the additive manufacturing process. However, little research has been conducted to compare the corrosion behavior of selective laser melting (SLM) alloys, fabricated by pre-alloyed metallic powder and mixed metallic powder. Hence, it is important to investigate the corrosion behavior of SLMed alloys, as well as the corresponding cast ingot, with the aim to better understand the feasibility of designing new materials. In this work, the SLM-produced Ti6Al4V3Cu alloys were manufactured using a metallic elemental powder mixture and pre-alloyed metallic powder, respectively. The corrosion behavior of the different Ti6Al4V3Cu alloys was investigated in following electrochemical tests and ion release measurements. The results showed that the Ti6Al4V3Cu alloy prepared by pre-alloyed metallic powder showed better corrosion resistance than that produced from mixed metallic powder. Moreover, the SLM-produced Ti6Al4V3Cu alloys performed significantly better in corrosion resistance than the cast Ti6Al4V3Cu. The results are expected to achieve a better understanding of the feasibility of designing new materials using mixed powders, contributing to reducing development costs and cycles. [ABSTRACT FROM AUTHOR]

The passivation behaviour of passive films on the surface of reinforcing steels exposed to alkaline solutions was investigated. Two types of reinforcing steels (low-carbon steel and low-alloy steel) with different surface conditions (polished steel with uniform surface and as-received ribbed surface with mill scale) were chosen to compare their passivation capability. Moreover, steels were exposed to high-alkaline simulated concrete pore solution and low-alkaline saturated Ca(OH)2 solution for 10 d to form passive films spontaneously. The results reveal that the passivation capability of steels was significantly affected by the surface condition, whereas the influence of steel type and alkaline solution was relatively less pronounced. [ABSTRACT FROM AUTHOR]

[Display omitted] The deposition of the CaCO 3 scale in circulating cooling water is a common and serious concern in the industry, which hinders the heat transfer, reduces water flow and blocks membrane filters. This paper aims at studying the effect of the γ-Fe 2 O 3 , Fe 2 (MoO 4) 3 ·γ-Fe 2 O 3 and FePO 4 ·γ-Fe 2 O 3 passive films on CaCO 3 scale deposition on Q235 steel by electrochemical methods, including linear sweep voltammetry (LSV), chronoamperometry and electrochemical impedance spectroscopy (EIS) tests. The scale and corrosion inhibition performance of the passive films was evaluated by the residual current density (i r) and charge transfer resistance (R ct) values. Electrochemical results suggested that the passive films could inhibit corrosion and reduce the CaCO 3 scale deposition on Q235 steel and the FePO 4 ·γ-Fe 2 O 3 complex passive film showed the best anti-scaling effect. Scanning electron microscope (SEM) and X-ray diffractometer (XRD) tests showed that the passive films could lead to a decrease in the proportion of aragonite to calcite under cathodic water reduction conditions and the composition of the FePO 4 ·γ-Fe 2 O 3 complex passive film could deform the CaCO 3 crystal. [ABSTRACT FROM AUTHOR]

The electrochemical behavior and passive film properties of Hastelloy C22 alloy, laser-cladding C22 coating, and Ti–6Al–4V alloy in sulfuric acid dew-point corrosion environment were investigated through a combination of electrochemical measurements and surface analyses. The C22 alloy and laser-cladding C22 coating exhibited similar passivation and repassivation behavior without pitting corrosion, resulting from a similar passive film with a bilayer structure consisting of a Cr2O3-dominated compact inner layer and a porous outer layer containing oxides of Mo and hydroxides of Ni and Cr. The slightly poorer corrosion resistance and higher sensitivity to localized corrosion exhibited by the C22 coating were attributed to the microscale heterogeneity of the passive film resulting from the element segregation in the microstructure introduced by the laser-cladding process. The corrosion of the TC4 alloy performed as the preference dissolution of the β phase. Compared to the C22 alloy and C22 coating, the TC4 alloy exhibited more stable passivation behavior but poorer corrosion resistance, which is attributed to a compact but less protective single-layer passive film consisting of oxides of Ti and Al. An increase in temperature degrades passive film stability and accelerates the charge transfer process. [ABSTRACT FROM AUTHOR]

Passive alloys are commonly considered to exhibit a current that is essentially independent of potential over the passive range in neutral chloride solutions. However, the current‐potential dependence of Ti and its alloys, CoCr alloys, and 316L stainless steel in buffered, simulated physiological solutions containing phosphate differs from that usually reported for the alloys in chloride‐only solutions. An analysis of potentiodynamic polarization data from previous studies showed that these alloys typically exhibit an exponential dependence of current on potential—as reflected by Tafel‐type behavior—over the initial part of the passive range in buffered solutions. This behavior is consistent with that predicted by the Generalized Growth Model for film growth and dissolution in the case of thin films where cation migration through the film is the rate‐controlling step and where the anodic current is associated predominantly with dissolution. Film growth is thought to be impeded in the buffered solutions, allowing the rate of migration and hence dissolution to remain relatively high over a wider potential range. Analysis of the apparent Tafel slopes indicated that the Ti and CoCr alloys exhibit a similar corrosion mechanism, with a small difference in the slopes for the two groups of alloys being attributable to the difference in the type of oxide. Stainless steel 316L exhibits a distinctly higher apparent Tafel slope, which is likely associated in large part with the duplex nature of the oxide. [ABSTRACT FROM AUTHOR]

Ni-Cr-Mo alloy coatings with different content of Cr element were produced on carbon structural steel by laser cladding. Coatings exhibited similar phase composition containing γ-Ni solid solution and similar microstructure composed of primary grains and eutectics with segregated Mo. Corrosion behavior of coatings in a sulfuric acid dew point corrosion environment were investigated through the combination of immersion test, electrochemical measurements, and surface analysis. Coatings exhibited similar passive behavior and passive film with a bilayer structure consisting of a compact inner layer and a porous outer layer. An increase in Cr resulted in a more protective passive film with thicker and more compacting inner layer. However, the corrosion resistance was firstly degraded as the content of Cr increased from 18 wt.% to 22 wt.%, and then improved as the content of Cr increased from 22 wt.% to 26 wt.%. This phenomenon was attributed to the competition effect between the increase in Cr and relative decrease in Ni. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of titanium (Ti) was investigated before and after anodic polarization at different potentials in simulated seawater solutions. The results showed that the Ti anodically polarized at 3.2 VSCE was much more stable than those at 0.5 VSCE and the open-circuit potential (OCP), and the passive film formed at the low potentials could be transformed to a more protective film after polarization at the high potential. The polarization at the high anodic potential could effectively enhance the long-term durability of Ti under natural immersion conditions. Nitzschia closterium f. minutissima could only slightly influence the electrochemical behavior of Ti. The film formed at the 3.2 VSCE on Ti appeared to have very limitedly better antifouling performance than those formed at the 0.5 VSCE and OCP. [ABSTRACT FROM AUTHOR]

This study presents microstructural, electrochemical, and mechanical characterizations on pure copper fabricated using constrained groove pressing (CGP) in quiescent phosphate buffer solution (pH = 11.73). We tested the effect of surface modifications on electrochemical features using electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. A three-dimensional simulation via finite element modeling evaluates the CGP effects on the maximum principal stress and the plastic strain distribution. The transmission electron microscopy (TEM) micrographs confirm that the increasing CGP cycles result in a nano/ultrafine grain microstructure. Our electrochemical study showed that the CGP process can positively impact the passive behavior of pure copper. Mott–Schottky analyses illustrated that the point defect densities decline in the p-type semiconducting passive layer upon receiving CGP. Besides, increasing the CGP cycles lowers the corrosion current density and produces less defective passive films.

The composition and characteristics of the passive film formed in the simulated carbonation solution with the concentration of 1.0% and 2.0% rust inhibitor were studied by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The formation mechanism of steel passive film under the action of rust inhibitor was expounded. The results showed that the anticorrosion performance was the best and stable passive film was formed on the steel surface when the content of rust inhibitor was 2.0%; under the action of rust inhibitor, the main compositions of passive film on the steel surface were Fe2O3 and FeOOH. Among anodic rust inhibitors, Na2MoO4 was more effective than Na2CrO4. Between cathodic rust inhibitors, the anticorrosion performance of benzotriazole (BTA) was better than N-N dimethyl ethanolamine (DMEA). Among the composite rust inhibitors, the corrosion resistance of Na2MoO4 + BTA group was superior, and the corrosion resistance of Na2MoO4 + DMEA group was the worst. The composite rust inhibitor was better than the single rust inhibitor, and the inhibition efficiency was the highest when Na2MoO4 and BTA were mixed together.

The passive film growth process, the composition of passive films, and the electrochemical behavior of ferrite and austenite individual phases on the unbroken surface of 2205 duplex stainless steel (DSS) were investigated by scanning electron microscopy, energy dispersive spectrometry, Kelvin probe force microscopy, magnetic force microscopy, in situ electrochemical atomic force microscopy, and Auger electron spectroscopy depth analysis. The electrochemical characteristics of the α/γ individual phases on the unbroken 2205 DSS surface were similar. The distribution of elements resulted in an element gradient at α/γ phase boundaries with a 2–6-μm width. Three stages of passive film formation were defined: nucleation, rapid growth, and stable growth. An even distribution of alloying elements with a difference in the concentration of Fe and Cr in the barrier layer was observed in the two-layer passive film of α/γ individual phases on the intact 2205 DSS surface. The preferential dissolution occurring on DSS was also discussed.

The presence of hydrogen sulfide and chloride in oil and gas production environments can induce deterioration of the passive film, leading to pitting corrosion of stainless steel. In this research, localized behavior of stainless‐steel type 316 L was studied in highly hydrogen sulfide and chloride environment. The environmental condition was setting up using NACE TM0177 Solution A at different partial pressures of 0 bar, 3 bar and 15 bar of hydrogen sulfide, respectively. The results indicated that the presence of sulfides and chloride ions in test solution can decrease its corrosion resistance due to pitting corrosion attacking and promoting passive layer break down. Deterioration of passive film was analyzed using weight loss calculation, pit penetration analyses was done by infinite focus microscopy and surface morphology with the corrosion products were investigated by scanning electron microscope after 7 days immersion in test solution. Energy‐dispersive x‐ray results shows the presence of sulfur on the passive oxide layer at 3 bar and 15 bar conditions. Thus, the protection for these steels is undermined by hydrogen sulfide corrosion that affects on the passive films and altered its structure. [ABSTRACT FROM AUTHOR]

This study extensively compares the corrosion behavior of austenitic 316L and Duplex 2205 stainless-steels at different partial pressures of H2S gases. The results showed that the corrosion rate of both steels at 3 bar H2S showed the highest rate among those parameter setups. 316L steel is dominated by both uniform and pitting corrosion under H2S-containing conditions due to the dissolution of Cr present on the alloy surface. According to the cross-sectional analysis, a Cr enrichment layer formed at 0 bar H2S in both steels. After depletion of the Cr compound in the passive film of both steels, Ni was enriched in the outer layer at 3 bar H2S, forming Ni oxide/sulphide compounds within the passive layer. At 15 bar H2S, Mo was enriched in 316L steel, while Fe and Cr were enriched on the 2205 steel surface. Thus, a kinetic study of the chemical composition of both steels was discussed. [ABSTRACT FROM AUTHOR]

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The electrochemical corrosion behavior of an aged Fe-18Cr-15Mn-0.66 N high-nitrogen austenitic stainless steel in 3.5 wt.% NaCl solution was studied using the measurements of polarization curves and electrochemical impedance spectroscopy, and the composition of the passive films formed on the HNSS was investigated using x-ray photoelectron spectroscopy (XPS). XPS analyses results showed that the passive films formed in this solution were composed of Cr oxide/hydroxide (mainly) and iron oxides (partially). The XPS depth profile suggested that near the passive film /HNSS interface, both Cr and Fe contents increased, but the Cr and Fe oxide/hydroxide contents decreased. [ABSTRACT FROM AUTHOR]

In the present work, the electronic properties of the passive films formed on equiatomic CoCrFeNi and CoCrFeNiAl high-entropy alloys were investigated in sodium chloride solution. The point defect model (PDM) was employed to study the effect of aluminum addition on the transport of p-type or n-type dopants through the passive films. The crystalline structure of the alloys was determined by X-ray diffraction. CoCrFeNi alloy was comprised of one single face-centered cubic crystalline phase. Aluminum addition promoted the formation of a mixed B2 and BCC structure. X-ray photoelectron spectroscopy (XPS) analysis allowed the examination of the correlation between passive film composition and their electronic properties. The major species in the passive film of the CoCrFeNi alloy were Cr2O3 and Cr(OH)3 while Al2O3 and Al(OH)3 were the predominant species in that of the Al-containing alloy. Electrochemical impedance spectroscopy (EIS) was employed to evaluate the corrosion resistance of the alloys. Aluminum addition promoted the formation of a thicker and more defective passive film. The pitting corrosion susceptibility of the HEAs was dependent on the passive film composition and increased with Al addition. The predominance of n-type defects in the passive film of the CoCrFeNiAl alloy was enhanced upon Al addition. Interaction between passive film composition and the electronic properties of the film played a central role in the corrosion resistance of the high entropy alloys.