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The microstructures and corrosion properties of selective laser-melted (SLM) 304L stainless steel (SS) were investigated after vacuum heat treatment. The electrochemical analysis showed that heat treatment was able to improve the pitting resistance of SLM 304L SS, which was even better than that of wrought 316L SS after vacuum heat treatment at 1100 °C for 2 hours. The microstructure analysis showed that the 1100 °C heat treatment eliminated the melt pool boundaries, reduced the defect density, optimized the micro-interfaces of the material, and weakened the agglomeration of nano-oxide particles. In addition, the heat treatment increased the content of Cr2O3 in the passive film, which enhanced the stability of the passive film. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy, potentiodynamic polarization curves, and the Mott–Schottky method were used to study the corrosion behaviors of vermicular graphite cast iron and gray cast iron and the characteristics of the passive films on the surfaces of vermicular graphite cast iron and gray cast iron in engine coolant. The results showed that the passive film formed on the surface of vermicular graphite cast iron exhibited a low density of defects and had a higher protective property compared to that on gray cast iron under the same conditions. Flake graphite was conducive to the formation of the passive film on the surface of cast iron, but the dissolution rate of the passive film on the surface of gray cast iron was higher than that of vermicular graphite cast iron. Vermicular graphite cast iron showed better corrosion resistance than gray cast iron in engine coolant. The charge transfer resistance of the anodic reaction of vermicular graphite cast iron and gray cast iron in engine coolant was much greater than that of the cathodic reaction, and the control step of the corrosion process in the system was the anodic reaction process. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are special type of alloy suitably developed for use in petroleum exploration, energy storage devices, medical implants, etc. This is because they possess excellent corrosion, thermal, and mechanical properties. Corrosion characteristic of HEAs prepared via spark plasma sintering is a top notch as the technique generates corrosion resistant phases and homogenous microstructure. This study was aimed at reviewing recent publications on corrosion characteristics of HEAs processed by SPS in order to develop ways of improving their anti-corrosion properties. The resource materials were obtained from Scopus-indexed journals and Google Scholar websites of peer-reviewed articles published within the last 5 years. From the study, it was revealed that incorporation of some elements (Al, Cr, Ti) into HEAs can improve their corrosion resistance, while addition of some others can reduce their brittleness and enhance their stability and formability. It was recommended that optimization of SPS parameters was one of the strategies of generating better corrosion characteristics in HEAs. [ABSTRACT FROM AUTHOR]

The corrosion behavior of 6082 aluminum alloy in deicing salt was investigated by electrochemical impedance spectra combined with an X‐ray diffractometer, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscope. The experiment results showed that the corrosion tendency of 6082 aluminum alloy in deicing salt strongly depends on its different matrix and grain boundary precipitates, which also show the characteristics of transformation during the corrosion process. The Nyquist plot exhibits the characteristics of double capacitive resistance arcs, and the capacitive resistance arcs were affected by corrosion characteristics and corrosion products on aluminum alloy surface. The nucleation and development of pitting and the formation of a passive film were closely related to the Si phase in the 6082 aluminum alloy. [ABSTRACT FROM AUTHOR]

Metastable Ti–Nb alloys are promising bone-implant materials due to improved mechanical biofunctionality and biocompatibility. To overcome increasing bacterial infection risk, alloying with antibacterial elements is a promising strategy. This study investigates the effect of minor gallium (Ga) additions (4, 8 wt% Ga) to as-cast and solution-treated β-type Ti–45Nb-based alloy (96(Ti–45Nb)-4Ga, 92(Ti–45Nb)-8Ga (wt.%)) on corrosion and passive film properties, as well as cytocompatibility and antibacterial activity. The electrochemical properties were evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analyses in phosphate-buffered saline (PBS). X-ray photoelectron spectroscopy (XPS) was performed to analyze the chemical composition of passive films. Early adhesion and viability of macrophages and Staphylococcus aureus were assessed by nucleocounting and colony-forming unit counting, respectively. The results showed that high corrosion resistance and passive film properties of Ti–45Nb are retained and even slightly improved with Ga. EIS results revealed that Ga addition improves the passive film resistance. XPS measurements of 92(Ti–45Nb)-8Ga show that the passive film contains Ti-, Nb- and Ga-based oxides, implying the formation of mixed (Ti–Nb-Ga) oxides. In addition, marginal Ga ion release rate was detected under free corrosion conditions. Therefore, it can be assumed that Ga species may contribute to passive film formation on Ga-containing alloys. The 92(Ti–45Nb)-8Ga elicited an antibacterial effect against S. aureus compared to cp-Ti at 4 h. Moreover, Ga-containing alloys showed good cytocompatibility with THP-1 macrophages at 24 h. In conclusion, it was demonstrated that Ga additions to Ti–45Nb are beneficial to corrosion resistance and showed promising initial host and bacterial interactions.

In the proton exchange membrane water electrolysis (PEMWE), the titanium bipolar plate coated with noble metals is usually used, which puts forward higher requirements for costs. This study investigates the cathode plasma electrolytic deposition (CPED) for the titanium and obtains TiN and TiN/CrN coatings. The TiN coating exhibits the diffusion resistance in the anode PEMWE environment, resulting in an increase in the interfacial contact resistance (ICR). The denser TiN/CrN coating eliminates the diffusion resistance and increases the polarization resistance (R p) value from 3873 Ω cm2 of TiN coating to 12,320 Ω cm2 of TiN/CrN. After long-term potentiostatic polarization, the ICR of TiN/CrN coating is 8.5 mΩ cm2, which is 3.5 times lower than that of TiN coating. Therefore, the low-cost TiN/CrN coating obtained by CPED has brought a good application prospect for bipolar plates in PEMWE. • The TiN and TiN/CrN coatings improve electrical conductivity after long-time service. • The dense TiN/CrN coating avoids the diffusion resistance of the TiN coating. • The corrosion mechanism of TiN/CrN coating in PEMWE environment was revealed. • The passive film properties of TiN and TiN/CrN coatings on TA1 were studied. [ABSTRACT FROM AUTHOR]

The corrosion resistance of two cast CoCr-based alloys with different amounts of chromium and with different alloying elements in the bulk composition of the alloy was assessed. In this study, we investigated the corrosion behavior of Co21Cr8Mo7W and Co29Cr7W by open-circuit potential (OCP), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) in 0.1 M phosphate buffer solution (PBS) at 37 °C with long immersion times. After 1000 h of immersion, the corrosion current density (icor), estimated from anodic polarization tests, was lower for the Co21Cr8Mo7W (i.e., 49 nA cm−2) alloy compared to the Co29Cr7W alloy (180 nA cm−2). As regards the corrosion potential (Ecor), a greater value was observed for Co21Cr8Mo7W (i.e., −59 mV vs. Ag/AgCl) compared to Co29Cr7W (i.e., −114 mV vs. Ag/AgCl). Microstructure analysis before and after immersion revealed the formation of a more compact passive film on the Co21Cr8Mo7W alloy, suggesting superior corrosion resistance compared to Co29Cr7W. These findings suggest better corrosion resistance for the film formed on the alloy containing lower amounts of Cr and two alloying elements, Mo and W. These results are promising in terms of medical applications because they open the door to new strategies for obtaining alloys with lower chromium content and with more protective anti-corrosion properties. [ABSTRACT FROM AUTHOR]

In this study, an Al–Mn–Zr alloy was designed and its microstructure and corrosion behavior compared after laser welding to that of AA3003. As the results of immersion and electrochemical tests showed, both alloys had a faster corrosion rate in the fusion zone than in the base metal. Laser welding caused interdendritic segregation, and spread the intermetallic compounds (IMCs) evenly throughout in the fusion zone. This increased the micro-galvanic corrosion sites and destabilized the passive film, thus increasing the corrosion rate of the fusion zone. However, Zr in the Al–Mn alloy reduced the size and number of IMCs, and minimized the micro-galvanic corrosion effect. Consequently, Al–Mn–Zr alloy has higher corrosion resistance than AA3003 even after laser welding. [ABSTRACT FROM AUTHOR]

To reveal the influence of passive film on the tribocorrosion behaviour of stainless steel, SUS430 was loaded at 2.0 N or 10.0 N in aqueous solutions with various pH from 1.0 to 10.0. The pure wear behaviour was investigated in the air for comparison. The polarization behaviour, the morphology of the worn or tribocorroded surface, and the depth profiles of the formed groove were measured to discuss the mechanism. The passive state was confirmed at pH = 7.0 and 10.0, but vanished at pH = 1.0 and 2.0. The pure wear in air depended on the applied loads, rather than the sliding time. On the other hand, the tribocorrosion in deionised water was much smaller than the pure wear in air. Under a load of 2.0 N, the tribocorrosion at pH = 1.0 was weaker than pH = 2.0. However, the situation reversed when increasing the load to 10.0 N. The tribocorrosion in neutral and alkaline solutions is considerably smaller than in acid solutions. [ABSTRACT FROM AUTHOR]

The corrosion behavior and surface conductivity of type 446 stainless steel were investigated in the simulated cathode environment of proton exchange membrane fuel cell with 0.0005 M H2SO4 + 0.1 ppm F− solution at 80 °C under different polarization potentials by using electrochemical measurement methods, X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The 446 stainless steel passivates spontaneously in the simulated environment. The current density and interface contact resistance (ICR) enlarge slightly with increasing the anodic polarization potential in the passive region. As the potential changes from 0.7 to 1.5 V vs. SCE, the current density and ICR increase markedly due to the occurrence of transpassivation, secondary passivation, and oxygen evolution. The ICR values are larger by about 24 mΩ cm2 after the polarization above 0.7 V vs. SCE. The polarization potential shifts from the passive region to oxygen evolution region, resulting in higher oxidized Fe and Mo contents in the product film on specimen surface and relatively more release of alloying constituents (especially Cr and Mo) into the solution. These are mainly responsible for the degradation of corrosion and surface conductivity properties. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are emerging as a new family of alloys with equal/near-equal amounts of constituting elements and outstanding properties. In particular, eutectic high-entropy alloys (EHEAs) with alternate lamella phases possess both high strength and ductility, offering the advantage of conquering the strength–ductility trade-off that could hardly be achieved by conventional alloys. While the mechanical behavior of EHEAs has been widely studied, the corrosion behavior is still not fully understood. Furthermore, the environment-induced degradation could largely decide the service life of EHEA as engineering alloys, and the eutectic structure may have a special influence on the corrosion process. This article systematically reviews the corrosion studies of EHEAs by pointing out the structural features of EHEAs, summarizing the general corrosion issues for EHEAs and identifying the specific corrosion performance of different EHEA systems. It is found that EHEAs feature micro-galvanic corrosion due to their eutectic crystal structure, and such a corrosion mode is further affected by testing time, heat treatment, temperature, and applied potential. All the corrosion-affecting factors are summarized, and future research directions are suggested, aiming at ensuring the wide engineering application of EHEAs with both high strength–ductility and corrosion resistance. [ABSTRACT FROM AUTHOR]

Among various materials available for alleviating the corrosion-related degradation, thermal sprayed Fe-based metallic glass coatings (MGCs) have received huge attention from the scientific community due to the exceptional combination of mechanical and corrosion properties, along with commercially attractive low material cost of this particular alloy system. Emerging reports on the thermal sprayed Fe-based MGCs outperforming conventional corrosion-resistant materials and coatings have accelerated further exploration of this domain, resulting in an immense increase of research activities over the last few decades producing fascinating results. This review takes a holistic approach encompassing an in-depth assessment of all the relevant salient work till date, including corrosion properties, corresponding degradation mechanisms, metallurgical and environmental factors with reference to passive film dynamics and/or formation of corrosion products. Moreover, various strategies for improved corrosion properties and recent research progress have been reviewed with an attempt to identify the present knowledge gaps and the future research directions. [ABSTRACT FROM AUTHOR]

Using Cr-bearing low-alloy steel is an effective preventive measure for marine structures, as it offers superior corrosion resistance when compared to plain carbon steel. However, it remains unclear how quenching and tempering heat treatment, which is commonly applied to steel reinforcement in some specific environments to improve its mechanical properties, affects its corrosion resistance. In the present work, the impact of heat treatment on the passive film and depassivation behavior of the 0.2C-1.4Mn-0.6Si-5Cr steel are studied. The results reveal that quenching and tempering result in grain refinement of the Cr-bearing steel, which increases its hardness. However, this refinement causes significant degradation in its corrosion resistance. The critical [Cl−]/[OH−] ratio after quenching and tempering is determined to be approximately 6.6 times lower than that after normalization, and the corrosion rate is 1.6 times higher. After quenching and tempering, the passive film predominantly comprises iron oxides and hydroxides, with relatively high water content and defect density. Additionally, the FeII/FeIII ratio and film resistance are relatively low. In comparison, after normalization, the steel exhibits high corrosion resistance, with the passive film formed offering the highest level of protection. [ABSTRACT FROM AUTHOR]

The corrosion performance of high-strength FeNiCrAl medium-entropy alloy compared with that of 304 stainless steel was investigated in 1 mol/L KOH solution. The electrochemical results indicated that the FeNiCrAl medium-entropy alloy has a better corrosion resistance and lower corrosion rate. The immersion tests confirmed that the degree of corrosion of the FeNiCrAl medium-entropy alloy was less severe than that of 304 stainless steel. X-ray photoelectron spectroscopy results revealed that the higher corrosion resistance of the FeNiCrAl medium-entropy alloy results from the difference in composition of the passive films. The FeNiCrAl medium-entropy alloy promotes the enrichment of Al and Ni with an oxidation state on the surface, and it suppresses the formation of iron oxidation, inducing effective passive films with increased compactness, higher charge transfer resistance, and lower defect density. Our results are meaningful for designing and applying medium-entropy alloys with excellent corrosion resistance in alkaline media. [Display omitted] • FeNiCrAl medium-entropy alloy has a higher corrosion resistance in KOH media. • Passive films on MEA are compact with a higher impedance and lower defect density. • Al and Ni with an oxidation state are enriched in passive films of MEA. • The formation of less protective iron oxides is suppressed in passive films of MEA. [ABSTRACT FROM AUTHOR]

The effect of electrochemical hydrogen charging on the corrosion behavior of the AlNbTiZr high entropy alloy in a 0.5 M H 2 SO 4 solution was investigated. The results revealed localized corrosion and cracks occurring after 120 h of charging, with failure analysis indicating transgranular cracking. Moreover, both the corrosion and passive current densities exhibited an increase with prolonged charging time from 0 h to 120 h. XPS analysis showed that the ratio of OH − to O 2 − within the passive film increased from 0.379 to 0.854 as the time extended to 120 h. This observation suggested that hydrogenation diminished the alloys' corrosion resistance. • Electrochemical hydrogen charging reduces the corrosion resistance of AlNbTiZr. • Electrochemical hydrogen charging results in hydrogen-induced cracking. • The mechanism of corrosion resistance deterioration caused by electrochemical hydrogen charging is explained. • Element segregation induces local corrosion during electrochemical hydrogen charging. [ABSTRACT FROM AUTHOR]

The corrosion resistance of two cast CoCr-based alloys with different amounts of chromium and with different alloying elements in the bulk composition of the alloy was assessed. In this study, we investigated the corrosion behavior of Co21Cr8Mo7W and Co29Cr7W by open-circuit potential (OCP), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) in 0.1 M phosphate buffer solution (PBS) at 37 °C with long immersion times. After 1000 h of immersion, the corrosion current density (icor), estimated from anodic polarization tests, was lower for the Co21Cr8Mo7W (i.e., 49 nA cm−2) alloy compared to the Co29Cr7W alloy (180 nA cm−2). As regards the corrosion potential (Ecor), a greater value was observed for Co21Cr8Mo7W (i.e., −59 mV vs. Ag/AgCl) compared to Co29Cr7W (i.e., −114 mV vs. Ag/AgCl). Microstructure analysis before and after immersion revealed the formation of a more compact passive film on the Co21Cr8Mo7W alloy, suggesting superior corrosion resistance compared to Co29Cr7W. These findings suggest better corrosion resistance for the film formed on the alloy containing lower amounts of Cr and two alloying elements, Mo and W. These results are promising in terms of medical applications because they open the door to new strategies for obtaining alloys with lower chromium content and with more protective anti-corrosion properties.

Metallic glasses are promising materials for microdevices, although corrosion and friction limit their effectiveness and durability. We investigated nanoscale friction on a metallic glass in corrosive solutions after different periods of immersion time using atomic force microscopy to elucidate the influence of corrosion on nanoscale friction. The evolution of friction upon repeated scanning cycles on the corroded surfaces reveals a bilayer surface oxide film, of which the outer layer is removed by the scanning tip. The measurement of friction and adhesion allows one to compare the physicochemical processes of surface dissolution at the interface of the two layers. The findings contribute to the understanding of mechanical contacts with metallic glasses under corrosive conditions by exploring the interrelation of microscopic corrosion mechanisms and nanoscale friction.

High-entropy alloys (HEAs) are emerging as a new family of alloys with equal/near-equal amounts of constituting elements and outstanding properties. In particular, eutectic high-entropy alloys (EHEAs) with alternate lamella phases possess both high strength and ductility, offering the advantage of conquering the strength–ductility trade-off that could hardly be achieved by conventional alloys. While the mechanical behavior of EHEAs has been widely studied, the corrosion behavior is still not fully understood. Furthermore, the environment-induced degradation could largely decide the service life of EHEA as engineering alloys, and the eutectic structure may have a special influence on the corrosion process. This article systematically reviews the corrosion studies of EHEAs by pointing out the structural features of EHEAs, summarizing the general corrosion issues for EHEAs and identifying the specific corrosion performance of different EHEA systems. It is found that EHEAs feature micro-galvanic corrosion due to their eutectic crystal structure, and such a corrosion mode is further affected by testing time, heat treatment, temperature, and applied potential. All the corrosion-affecting factors are summarized, and future research directions are suggested, aiming at ensuring the wide engineering application of EHEAs with both high strength–ductility and corrosion resistance.

With the continuous tightening of marine exhaust emission standards, removing nitric oxide (NO) by Fe(II)EDTA solution complex adsorption is regarded as a promising method. In order to evaluate the feasibility and risk of the corrosion failure for candidate metal in the Fe(II)EDTA-based liquid-phase denitrification system, the corrosion behavior of 316L stainless steel (SS) in Fe(II)EDTA, Fe(III)EDTA, and Fe(II)EDTA-NO was investigated using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, Mott-Schottky method, and X-ray photoelectron spectroscopy (XPS). The experimental results reveal that 316L SS is applicable to the liquid-phase denitrification environment, because of a passive film produced on the 316L SS surface which can protect effectively itself from further corrosion. Thereinto, the homogeneity and thickness of the passive film formed in the Fe(III)EDTA secure the maximum value. Beyond all doubt, the corrosion rate of 316L SS in Fe(III)EDTA is minimum only 0.001 mm·year−1. Meanwhile, the passive film was found to have semiconductive characteristics. The XPS results provide strong evidences for the above electrochemical measurements that the different electrochemical properties including variation of n/p-type semiconductor behavior are attributed to its chemical component. The passive film mainly consists of Cr2O3, Fe3O4, and MoOx, and FeO, CrO3, NiO, and MoO2 are not detected in the passive film formed in Fe(III)EDTA. These phenomena reasonably explain why the Mott-Schottky plot in Fe(III)EDTA only showed one n/p-type transformation rather than two in Fe(II)EDTA and Fe(II)EDTA-NO. [ABSTRACT FROM AUTHOR]

In this work, the influence of temperature on the corrosion behavior of AlCoCrFeNi2.1 eutectic high-entropy alloy in a chloride-containing sulfuric acid solution was investigated using electrochemical measurement, X-ray photoelectron spectroscopy, and scanning electron microscopy. Results show that the passive film of AlCoCrFeNi2.1 is stable in chloride-containing sulfuric acid solutions at low temperatures, while an unstable film forms on the alloy at high temperatures. Furthermore, temperature changes the proportion of hydroxide and oxide in Fe and Cr, but it has no noticeable effect on Al and Ni, which is a significant factor on the passive behavior. L12 phase exhibits good corrosion resistance at different temperatures. Pitting occurred on B2 phase in the chloride-containing sulfuric acid solution at a low temperature of 5 °C, while pitting and dissolution take place on AlCoCrFeNi2.1 in the acid solution at room temperature and above. [ABSTRACT FROM AUTHOR]

This research work shows the contribution of supplementary cementitious materials (SCMs) in reducing the corrosion phenomenon in steel embedded in ternary concrete. Ternary steel-concrete systems were developed, consisting of AISI 1018 (AC) steel embedded in ternary concrete with a water/cement ratio of 0.45. Partial substitutions were made with respect to the mass of ordinary portland cement (OPC) by sugarcane bagasse ash (SCBA) and fly ash (FA) at 10, 20 and 30 %, the value of these percentages corresponds to 50 % CBCA and 50 % CV. The systems were evaluated with the electrochemical polarization resistance (Rp) technique, where corrosion current density (icorr) and corrosion velocity (Vcorr) were analyzed as indicators to evaluate corrosion phenomenon. The steel-concrete system with 20 % substitution (AC-CT20), decreased the Vcorr by 89 % with respect to the reference system (AC-REF). This result was attributed to the AC being in a passive state, which was associated with the passive film formation that was confirmed by the value of the mean icorr of 0.09 µA/cm² . [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 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]

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]

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]

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]

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]

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 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]

The corrosion behavior of an Inconel 718 alloy fabricated using the selective laser melting (SLM) technique in a 3.5 wt.% NaCl solution is determined. The corrosive effect of the NaCl solution on the Inconel 718 alloy is investigated using potentiodynamic polarization curve measurements, Mott-Schottky plots, electrochemical impedance spectroscopy, atomic force microscopy, and x-ray photoelectron spectroscopy (XPS) and is compared with that on a commercially rolled Inconel 718 alloy (R 718). Electrochemical results suggest that the application of SLM to the Inconel 718 alloy lowers its corrosion resistance. The passive films formed on both alloys show p-type and n-type semiconductor behaviors. However, the concentrations of the defects in the passive films formed on the surface of the SLM Inconel 718 alloy are higher than those on the surface of the commercially rolled R 718. XPS shows that the passive film formed on the SLM Inconel 718 alloy has a higher NiO content, leading to the deterioration of its protective properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adding 0.5 wt% TiB 2 nanoparticles, the grain refinement effect of 7055 alloy is significant. • Adding 0.5 wt% TiB 2 nanoparticles, the 7055 alloy reduces the pitting diameter and the pitting area fractions. • Adding 0.5 wt% TiB 2 nanoparticles, the passivation layer resistance, charge transfer resistance, and polarization resistance of 7055 alloy increase significantly. In this study, 7055 alloy inoculated by a minor addition of TiB 2 nanoparticles was prepared and subjected to passivation treatment. The microstructures, pitting behaviors, and electrochemical properties of the 7055-0.5TiB 2 composite were comparatively investigated with respect to the base alloy. The results show that the incorporation of 0.5 wt% TiB 2 nanoparticles refines the grain size (from 142.4 μm to 44.1 μm) and reduces the volume fractions of the residual intermediates from 0.59 % to 0.49 %, leading to an increased thickness (from 4.05 nm to 5.95 nm) and improved homogeneity of the passivation film. Both the pitting diameter and the pitting area fractions are reduced upon immersing in 3.5 % NaCl for 24 h. Electrochemical test results show that the values of passivation layer resistance, charge transfer resistance, and polarization resistance are significantly increased, while the corrosion current is reduced after the incorporation of TiB 2 nanoparticles, confirming the formation of a more effective barrier layer, i.e., the passivation film. The improved corrosion resistance of 7055 alloy with the incorporation of TiB 2 nanoparticles is attributed to the reduced active dissolution rate in the grain boundary region and a more uniform and thicker passivation film with a lower corrosion rate. [ABSTRACT FROM AUTHOR]

In this study, the relationship between the microstructural evolution, electrochemical behavior, and passivation capability in Fe 68 Ni 10 Mn 10 Co 10 Ti 1.5 Si 0.5 medium entropy alloy (MEA) with different microstructure is investigated. The passive film formed on the selectively corroded dual-phase microstructure was characterized by an inner thin discontinuous Fe-, Mn-, Ni-, and Co-based oxides and hydroxides layer with a thinner pure Si-oxide layer partially grown on the TiO 2 /SiO 2 layer. By contrast, a continuous oxide/hydroxide layer accompanied by a dense TiO 2 /SiO 2 monolayer in the uniformly corroded austenitic microstructure exhibited the highest protective effect owning to the prevention of galvanic corrosion resulting in the best corrosion resistance. [Display omitted] • Enhanced corrosion resistance by reversion treatment of Fe 68 Ni 10 Mn 10 Co 10 Ti 1.5 Si 0.5 MEA. • Localized corrosion was surpassed by designing the lower strain level of the second phase. • Formation of a dense TiO 2 /SiO 2 monolayer reduced the current density to 4.668×10–8A/cm2. • Microstructural engineering: A promising direction in designing corrosion-resistant H/MEAs. [ABSTRACT FROM AUTHOR]

In this study, the passivation of coarse-grained and ultrafine-grained steels was investigated through electrochemical measurements and potentiostatic polarization at 0 V SCE , 0.3 V SCE , 0.5 V SCE , and 0.8 V SCE in 0.1 M NaHCO 3 solutions. Then Mott-Schottky, Raman spectra, X-ray photoelectron spectroscopy, and atomic force microscopy were adopted to characterize the compositions, topographic structure and semiconductor performance of the passive film. The findings indicate a positive correlation between grain refinement and enhanced corrosion resistance of the passive films. Specifically, grain refinement leads to an increase in the ratio of Fe3+/Fe2+ and average surface roughness, while the trends of donor concentration and the content of Fe0 demonstrate a decrease. These findings elucidate the impact of grain refinement on the enhanced corrosion resistance of the passive film. Moreover, it is observed that the corrosion resistance of the passive films initially increases and subsequently diminishes with rising passive potentials. [Display omitted] • Grain refinement improve the corrosion resistance of the passive film. • Grain refinement elevates Fe3+/Fe2+ ratio, enhancing film's corrosion resistance. • Grain refinement improves the integrity of the passive film. [ABSTRACT FROM AUTHOR]

Localized plastic deformation has been observed to render nuclear reactor components more susceptible to stress corrosion cracking (SCC). However, it is not fully clear how localized strain impacts corrosion (oxidation) behavior. Herein, the surface reactivity and corrosion behavior of 304 L stainless steel specimens, deformed to different strain levels, was analyzed using advanced multimodal and multiscale methods. For the first time, we observed that localized deformation regions, e.g., deformation bands and α’-martensite featured smaller Volta potentials than the parent austenite matrix. This resulted in the establishment of localized corrosion potential gradients and the emergence of accelerated microscale galvanic corrosion. Particularly, regions that featured higher dislocation concentrations were more reactive on account of the reduction in the activation energy of corrosion due to the stored energy. The superposition of surface reactivity and strain distributions reveals that, SCC cracking is expected to initiate in regions of strain localization wherein micro-galvanic corrosion is favored.

In this work, the characteristics of passive films formed on as-cast Ti-6Al-4V before and after transpassivation by electrochemical methods will be studied. A simulated body fluid of Hank’s solution was used as the electrolyte in this work. According to the potentiodynamic polarization test, the passivation range, transpassive range, and repassivation range of as-cast Ti-6Al-4V were obtained. Afterward, the potentiostatic polarization was employed to passivate the Ti-6Al-4V in both passivation and repassivation ranges. Electrochemical impedance spectroscopy (EIS) was used to analyze the characteristics of formed passive films. Different electrochemical behavior of as-cast Ti–6Al-4V is found in passivation and repassivation ranges. The passivation current density of the sample in the repassivation range is significantly larger than that in the passivation range. Meanwhile, the growth rate of passive film in the repassivation range is also greater than that in the passivation range. Although the sample shows a higher charge transfer impedance in the repassivation range, metastable pitting corrosion is also observed, indicating the formation of the unstable passive film. Such results advance the understanding of as-cast Ti-6Al-4V polarized under different potentials for potential biomedical applications.

Citric acid passivation is an attractive alternative to increase the corrosion resistance of stainless steels. In this work, the correlation of passive film composition and the corrosion properties of citric acid‐passivated AISI 316L stainless steel samples was assessed. The concentration of citric acid in the passivating solution was varied from 10 to 30 wt.%. Passive film composition was examined by X‐ray photoelectron spectroscopy. The corrosion behavior was investigated by potentiodynamic polarization curves. The citric acid passivation treatment led to Cr2O3 enrichment of the passive film, especially for the 20‐wt.% concentration. By increasing the citric acid concentration to 30 wt.%, the corrosion resistance decreased. In addition to chromium compounds, the passivation treatment also affected the relative concentrations of Fe, Mo, and Ni compounds in the passive films. The formation of Mo oxides was triggered at citric acid concentrations of 10 and 20 wt.%, contributing to slower anodic dissolution rate. The corrosion resistance of the passivated samples was favored as the relative concentration of Fe oxides (FeO and Fe2O3) increased with respect to FeOOH. [ABSTRACT FROM AUTHOR]