Search

The study simulated copper corrosion in a bentonite/groundwater solution, analyzing the kinetics of metal passivation through potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy experiments. Morphological characterization provided insights into corrosion development patterns, and the mechanisms by which bentonite affects copper corrosion were comprehensively elucidated based on the point defect model. The findings revealed that bentonite affects copper corrosion resistance through Donnan exclusion, cation adsorption, and hydrolysis salt effects. At lower potentials, bentonite aids in inhibiting anodic dissolution, reducing the polarization current by approximately 75 % under certain conditions. With increasing bentonite content, the induction time for stable pitting corrosion shortens significantly, down to 10 %, the current surge before breakdown intensifies, and the breakdown potential decreases. When the bentonite volume ratio exceeds 0.5/0.1, the breakdown potential of OFP-Cu/OF-Cu markedly decreases and stabilizes at 0.1/0 V SCE. The microscopic mechanism of pitting corrosion induced by bentonite hydrolysis salts was elucidated using the point defect model, calculating the polarizability of the passive layer/outer layer interface as α = 0.1. The reliability of the cation adsorption and adsorption-desorption mechanisms was confirmed through experimental data fitting, point defect model fitting, and theoretical analysis. [ABSTRACT FROM AUTHOR]

A multi-principal element alloy consisting of equi-atomic concentrations of Cr, Ni, Ti, and V, was produced by arc melting. The CrNiTiV alloy was characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and scanning transmission electron spectroscopy (STEM), revealing a complex microstructure containing five phases. The corrosion performance of the alloy was evaluated with cyclic potentiodynamic polarization tests, indicating a low corrosion current density, a high breakdown potential and high repassivation potential. X-ray photoelectron spectroscopy and STEM were carried out after constant immersion in 0.6 M NaCl solution, revealing the passive (surface) film for each of the five phases. The Cr and V dominant phase consisted of an oxidized Cr/V-rich surface film, while the remaining four Ti-containing phases were predominantly TiO 2 -rich surface films. Ni enrichment and Ti deficiency were observed at the metal/oxide interface in certain Ti-containing phases. [ABSTRACT FROM AUTHOR]

Unlike conventional alloys, where carbon content typically promotes carbide compound formation and reduces localized corrosion resistance, the impact of carbon in additively manufactured materials remains largely unexplored due to rapid cooling rates inhibiting carbide formation. This study addresses the novel question of whether reducing carbon content benefits corrosion performance and its underlying mechanisms in Ni-Fe-Cr-based alloy 718. Employing high-resolution techniques and microcapillary electrochemical methods, it was revealed that higher carbon content increases dislocation density at cell boundaries. This increased dislocation density facilitates the enhanced ejection of nickel and iron from the protective chromium oxide layer on the surface, leading to the formation of a defective outer Ni-Fe oxide layer. This compromised layer subsequently diminishes the alloy's corrosion resistance, particularly under tensile stress conditions. [ABSTRACT FROM AUTHOR]

• Long-term assessment of EDM bath influence on Ti6Al4V corrosion in simulated body fluid. • EDM in water and HA bath significantly enhanced long-term corrosion resistance of Ti6Al4V. • Long-term temporal evaluation of corrosion mechanisms in EDMed Ti6Al4V in simulated body fluid. • EDM in HA bath shows potential for enhancing Ti6Al4V biointegration. Ti-6Al-4V (Ti64) alloy is a widely used bioimplant material due to its excellent properties. However, long-term exposure to body fluids can lead to corrosion, a concern given increasing lifespans. Electrical discharge machining (EDM) can improve Ti64 corrosion resistance at long term. This study investigates the long-term corrosion behaviour of Ti64 in simulated body fluid (SBF) after EDM treatment using different bath compositions (oil, water, and hydroxyapatite dissolution (HA)). Electrochemical and microscopy techniques were used to analyse corrosion mechanisms over immersion periods ranging from 2 h to 3 months. Results show that EDM-treated samples in water exhibited the highest corrosion resistance, while those processed in oil possessed the lowest. Especially, the corrosion resistance of samples treated in water and HA remained constant over time, unlike the non-EDMed and oil-treated samples. Furthermore, all samples exhibited evolving corrosion mechanisms over time, with faster deposition of SBF elements observed on oil and HA-treated samples, suggesting enhanced biointegration potential. The thicker deposited SBF layer on these samples further supports the potential of these EDM treatments to improve the biointegration of Ti64 implants. [ABSTRACT FROM AUTHOR]

The effect of formic acid (H C O O H or shortly H F r) on corrosion mechanisms of X65 steel was systematically investigated in pH controlled, N 2 -sparged and C O 2 -sparged solutions using potentiodynamic polarization and linear polarization resistance (LPR) techniques. The results from the electrochemical experiments conducted in 1 wt.% N a C l solutions at 1 bar (total pressure) confirm that H F r is not significantly electroactive and therefore is not directly reduced on the steel surface under the conditions studied here. Experiments at various H F r concentration, temperature, pH, and flow rate also confirm that the main role of H F r on the corrosion of X65 steel is through the "buffering effect" mechanism. According to this mechanism, weak acids such as H F r increase the cathodic limiting current by providing hydrogen ions (H +) through their chemical dissociation similarly as is seen with acetic acid (C H 3 C O O H or H A c). A comparison between H F r and H A c shows that these two organic acids have some differences in their behavior. First, H A c seems to retard the anodic reaction and decrease the corrosion rate, especially at lower temperatures and higher concentrations, while H F r does not. Second, the influence of these two acids on increasing the limiting current density seems to be similar at 30 °C, but at higher temperatures (50 °C, 80 °C), the cathodic limiting current density in the presence of H A c is greater than that with H F r at the same molar concentration. Under similar experimental conditions, H A c was observed to be less corrosive at lower temperature (30 °C), and more corrosive at higher temperatures (50 °C and 80 °C) compared to H F r at the same molar concentration. Experimental data collected in this study were used to validate a newly developed mechanistic model. According to our investigations this model shows an accurate fit to the experimental data at different H F r concentrations and pH at 30 °C. However, the model deviates from the experimental limiting current density value at higher temperatures (50 °C and 80 °C). It is speculated that this deviation results from a potential inaccuracy in the available temperature function for equilibrium constant of H F r dissociation reaction, which requires further investigations. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of vanadium on microstructural characteristics and corrosion properties of the AlCoCrFeNi HEA. Two alloys: AlCoCrFeNiV and AlCo 0.5 CrFeNiV 0.5 , were designed via thermodynamical calculations using Thermo-Calc software and synthesized by arc melting. Structural analysis was conducted using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Both alloys exhibited a two-phase microstructure, consisting of a continuous matrix and dispersed precipitates. The evaluation of corrosion behaviour through electrochemical tests showed that the equimolar alloy has excellent corrosion resistance, which is attributed to its refined microstructure and formation of a stable passive film. Conversely, the AlCo 0.5 CrFeNiV 0.5 alloy demonstrate a broader passive region, due to its higher relative Cr content. Impedance spectroscopy tests suggested that a more uniform oxide film with fewer defects was formed on the AlCoCrFeNiV alloy. [ABSTRACT FROM AUTHOR]

• The effect of 11 phosphonium–based ILs on the corrosion of Al and Cu using potentiodynamic polarization was investigated. • Corrosion parameters: corrosion potential, corrosion current density, and corrosion rate were determined. • A discussion of the influence of ILs structure elements on the obtained parameters was carried out. • A discussion in the context of potential application of ILs in absorption refrigeration technology was performed. The effect of phosphonium—based ionic liquids (ILs): 1,3-dimethyl-imidazolium dimethyl phosphate, [C 1 C 1 IM][DMP], 1-ethyl-1-methylpyrrolidinium dimethyl phosphate, [C 1 C 2 PYR][DMP], 1-hydroxyethyl-1-methylpyrrolidinium dimethyl phosphate, [C 1 C 2OH PYR][DMP], 1-methylpyridinium dimethyl phosphate, [C 1 Py][DMP], 1-ethyl-1-methylmorpholinium dimethyl phosphate, [C 1 C 2 MOR][DMP], 1-ethyl-1-methylpiperidinium dimethyl phosphate, [C 1 C 2 PIP][DMP], N,N,N -trimethyl- N -methylammonium dimethyl phosphate, [N 1,2,2,2 ][DMP], 1-ethyl-3-methylimidazolium diethyl phosphate, [C 1 C 2 IM][DEP], 1-ethyl-1-methylpyrrolidinium diethyl phosphate, [C 1 C 2 PYR][DEP], 1-ethyl-1-methyl-morpholinium diethyl phosphate, [C 1 C 2 MOR][DEP] and tri(butyl)ethylphosphonium diethyl phosphate, [P 2,4,4,4 ][DEP] on the corrosion of aluminium and copper were investigated using potentiodynamic polarization. All tested ionic liquids formed a passivation layer on the surface of the tested metals and due to their low affinity to promote corrosion of Cu and Al, can be used in refrigeration technology. [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]

• The Au-bearing PLA accelerated the corrosion of Zn and Fe in Hanks' solution. • PLA accelerates corrosion by acidifying the metal interface and reducing Ca/P. • Au NPs induced micro-galvanic corrosion manifesting as corrosion pits. • Certain features of the PLA coating (thickness, mixed MW, structure) affect corrosion acceleration. The commercial application of biodegradable metals (BMs), such as iron (Fe) and zinc (Zn), is hampered by their slow degradation rate. Polylactide (PLA) coatings on BMs have been proven to accelerate the corrosion of Fe and Zn but with limited success. This is the first study exploring the use of gold nanoparticles (Au NPs) to enhance and control the corrosion of polylactide (PLA)-coated Fe and Zn. The Au NPs enhanced the corrosion rate of Fe and Zn by promoting micro-galvanic corrosion after nanoparticle agglomeration. The optimal corrosion acceleration depended on the polymer's molecular weight, coating thickness, and coating structure. The results suggest that the Au-reinforced PLA-based coatings can be used to control Fe and Zn corrosion rates in the physiological environment. [Display omitted] [ABSTRACT FROM AUTHOR]

• Corrosion area at acid pH shifts to higher pHs with increasing LiBr concentration. • Immunity area of iron and chromium decreases with increasing LiBr concentration. • Passivation area decreases with increasing LiBr concentration. • Alkaline corrosion area shifts to higher pHs with increasing LiBr concentration. • Corrosion area at high potentials decreases with increasing LiBr concentration. The influence of lithium bromide concentration on the Pourbaix diagrams for iron-chromium alloys is evaluated in this work, which allows for predicting the corrosion to stainless steels exposed to the aggressive operating conditions of lithium bromide absorption machines (concentrations ranging from: 400–992 g/L). The novelty of this work is found in the development of Pourbaix diagrams for the Fe-Cr-Br–-H 2 O quaternary system in aqueous solutions with a high concentration of lithium bromide, a topic which has not yet been studied. Results show that the corrosion region at acid pH corresponding to the aqueous species FeBr 2 (aq), FeBr 3 (aq), Cr+2, CrOH+2, Cr+3 or CrBr+2 shifts to higher pHs with increasing lithium bromide concentration, which decreases the immunity region of iron and chromium and decreases the passivation region of the solid species FeCr 2 O 4 , Fe 2 O 3 and Cr 2 O 3. [Display omitted] [ABSTRACT FROM AUTHOR]

Zn–air batteries are a promising route that might be used in a range of energy sectors. Significant disadvantages, such as passive film and hydrogen gas evolution (HGE) in alkaline corrosive medium; restrict the possible usage of Zn–air batteries. To address these problems and increase the performance of zinc-air batteries, an ionic liquid (tris(2hydroxyethyl) hydroxymethylammonium methyl sulfate [IL]+[MS]-) has been used in this study. The usage of [IL]+[MS]- in 7.0 M KOH solution has a considerable effect on suppressing hydrogen gas creation, with an effectiveness of 86.2 %. Increasing the depth of the Bode-phase angle and the charge transfer resistance by adding [IL]+[MS]- also indicates a slower hydrogen gas production rate. The application of the [IL]+[MS]- additive improves the zinc-air battery's specific discharge capacity and capacity retention. To support these findings, SEM/EDX has been used to analyze the morphological features of Zn anodes in various electrolytes. [ABSTRACT FROM AUTHOR]

• Corrosion of M300-CuCr1Zr by single-step multi-material PBF-LB was studied. • Printing configuration influences the interface microstructure and corrosion rate. • Galvanic corrosion occurred merely in the interface region of bimetallic parts. • Base materials beyond the interface region underwent localized pitting. • Intergranular corrosion in Cu is governed by sub-surface defects from printing. Additive manufactured parts of thermally-conductive CuCr1Zr and high-hardness M300 tool steel were fabricated via a single step multi-material Laser-based Powder Bed Fusion (PBF-LB). The corrosion properties of two interface configurations , CuCr1Zr built on M300 and M300 on CuCr1Zr, were evaluated using the electrochemical polarization resistance measurement, weight loss method and galvanic corrosion current measurement via a Zero Resistance Ammeter. The interface microstructure of the dissimilar bi-metallic parts fabricated by multi-material PBF-LB is tunable. The printing configuration influences the defect size and density and interface microstructure, which affect the global corrosion rate of the fabricated parts. Electrochemical measurements were performed on the fabricated parts in oxygen-saturated and chloride-containing water at elevated temperature, complimented by post-mortem characterizations. The interface configuration with M300 on CuCr1Zr has a slightly lower corrosion rate than that of CuCr1Zr on M300. Unexpectedly, galvanic corrosion occurred only locally in the interface region between M300 and CuCr1Zr materials. Beyond the interface regions, there is no clear sign of galvanic corrosion. Pitting and intergranular corrosion in CuCr1Zr material is the dominant corrosion mechanism. Both base materials beyond the interface region underwent localized pitting, particular in CuCr1Zr. Intergranular corrosion in CuCr1Zr is governed by sub-surface defects like pores and microcracks formed during printing. [ABSTRACT FROM AUTHOR]

Controlling the concentrations of Zr4+ and F − in traditional Zirconium (Zr)-based film-formation solution is challenging due to their dependence on the hydrolytic equilibrium of H 2 ZrF 6. In this study, Zr-based films were prepared on cold rolled steel surface through the film-formation solution prepared by mixing Zr(NO 3) 4 and different amount of HF. The electrochemical results demonstrated that the Zr-based film prepared by Zr(NO 3) 4 and HF exhibited superior corrosion resistance compared to H 2 ZrF 6. Under optimal film formation conditions, the protective efficiency of the prepared film reached 74.4 % which was higher than that of film fabricated in H 2 ZrF 6. The electrochemical results concurrently demonstrated the self-reinforcing anti-corrosion performance of the prepared films. Scanning electron microscopy revealed that the Zr film, prepared in Zr(NO 3) 4 and HF, exhibited excellent corrosion resistance attributed to its high film density. The X-ray photoelectron spectroscopy and energy dispersive spectroscopic results indicated the presence of a fluoride layer on the surface of the Zr film. The F − ions can chelate with the corrosion products and selectively deposit onto the damaged areas of the film, thereby effectively contributing to the repair of the film layer. The results of density functional theory calculations demonstrated that Zr4+ readily forms Zr(OH) 4 rather than ZrF 6 2−. The present study offers an enhanced approach for regulating the properties of films prepared via H 2 ZrF 6 by separately providing zirconium and fluorine ions. [ABSTRACT FROM AUTHOR]

• LDI treatment increases surface geometric and energy inhomogeneity. • Increased surface inhomogeneity alters the structure of the EDL and reduces cross time scale ion hopping from the compact layer to the diffusion layer. • LDI treatment accelerates the electrochemical corrosion rate. • The effect of droplet velocity on surface inhomogeneity and corrosion rate has been studied. The electrochemical corrosion behavior of Q345C carbon steel under liquid droplet impingement (LDI) treatment with different velocities has been investigated. The results showed that the LDI treatment increased the surface inhomogeneity (geometric and energetic inhomogeneity) and accelerated the corrosion of the samples. After LDI treatment with droplet at velocities ≥ 100 m/s, the surface of the samples showed material shedding and increased roughness. The LDI treatment with a droplet velocity of 200 m/s resulted in the fragmentation of the Q345C surface grains and the formation of small grains and subgrains with different orientations. The EIS response was analyzed by means of the theoretical model of dynamics of electric double layer, and it was found that an increase in the surface inhomogeneity changed the structure of the electric double layer and reduced the crossing time scale of the ions jump from the compact layer to the diffusion layer (τ H), which may be the main reason for the accelerated electrochemical corrosion of Q345C after LDI treatment. [ABSTRACT FROM AUTHOR]

• ZIF-67 polyhedral particles are in-situ coated on the surface of TiO 2 nanorods. • The mechanism of inhibition of 316 L SS pitting by ZIF-67/TiO 2 Z-scheme heterojunction is described. • The charge transfer mechanism of photoanode protection 316 L SS is analyzed by impedance spectroscopy. Photocathodic protection (PCP) anticorrosion using sunlight is a green and sustainable technology. However, the ease of carriers compounding and the low light utilization are still the main restraints to its development. To develop an effective photoanode, a metal-organic framework (MOF, i.e., ZIF-67) material is electrodeposited and grown in-situ on TiO 2 nanorods. The morphological structure, light absorption properties, photoelectrochemical properties and cathodic protection principle of ZIF-67/TiO 2 photoanode are analysed by SEM, PL, I-V and EIS. The material characterization and light absorption characteristics show that the photoanode has good light absorption performance and higher electron hole separation efficiency. Photoelectrochemical test shows that ZIF-67/TiO 2 photoanode has excellent photocathodic protection for 316L stainless steel (316L SS). ZTRs-60 has the optimal protection effect. Under simulated sunlight, the OCP of 316L SS coupled ZTRs-60 is -0.41 V vs. Ag/AgCl, and the current density of the I-t curve can reach 20 μA/cm2. EIS and Tafel tests show that the photogenerated electrons transfer to the stainless steel surface, which promotes the cathode polarization process and alleviates the metal corrosion. [Display omitted] [ABSTRACT FROM AUTHOR]

• This paper innovatively introduced low temperature into ECM of DD6. • Low temperature suppresses the formation of passive film. • Low temperature reduces the self-corrosion potential difference between the two phases of DD6. • TaC on the surface is removed by peeling. • The processing surface quality is better in the cryogenic environment. Electrochemical machining (ECM) is a highly effective method for processing nickel-based single crystal (NBSC) superalloys. However, the influence of temperature on the electrochemical corrosion of NBSC remains underexplored. This study investigates the temperature dependence of the corrosion characteristics on the growth surface and its isomorphous perpendicular surface of NBSC DD6 were investigated. Results indicate that temperature significantly impacts the passivation and dissolution processes of the material: at low temperatures, the passivation effect weakens, and the differences in self-corrosion potential between phases decrease, leading to smaller variations in corrosion. Additionally, a mechanism is proposed to elucidate the temperature-dependent corrosion behaviors on different surfaces. [ABSTRACT FROM AUTHOR]

• Sn-14wt% Bi electrodeposited at various current densities (5,12,25, and 40mA/cm2). • Sn25 and Sn40 coating offered highest and least corrosion resistance, respectively. • Sn25 coating formed Sn-1.2at% Bi solid solution, low energy (301) oriented grains. • Sn40 coating exhibited unstable porous film and higher energy (110) grain orientation. • Bi nanoclusters within β-Sn matrix decreased corrosion resistance of Sn40 coating. The electrochemical Corrosion behaviour of Sn−14wt% Bi coatings, electrodeposited at four different cathodic current densities (5, 12, 25, and 40 mA/cm2), were studied in aqueous 3.5 wt% NaCl (0.6M) electrolyte and was correlated with the coating's micro-texture and solute Bi distribution in the β−Sn matrix. Lower energy (301) grain orientation, Sn−1.2at% Bi solid solution, and SnO 2 oxide passive layer yielded highest corrosion resistance (R p = 17518 Ω·cm2) for coating electrodeposited at 25mA/cm2. Higher energy (110) grain orientation, Bi-enriched nanoclusters in β−Sn matrix, and unstable passive layer consisting of SnO and Sn(OH) 2 oxides produced lowest corrosion resistance (R p = 3911 Ω·cm2) for coating electrodeposited at 40 mA/cm2. [Display omitted] [ABSTRACT FROM AUTHOR]

• Hf 12 Nb 16 Ta 35 Ti 29 Zr 8 with improved corrosion behavior was designed using machine learning. • The amount of Ti oxide forming in SBF exceeded that forming in air. • The experimentally determined e corr of −404 mV validates the predicted e corr of -409 ± 35 mV. • Samples with homogeneous microstructure revealed novel electrochemical parameters. This study demonstrates the use of machine learning as a potential tool to efficiently develop new biomedical alloys with improved corrosion resistance by exploring the whole compositional space in the HfNbTaTiZr system. Owing to the small volume and inherited uncertainty of available corrosion data in the literature, k-fold cross-validation and bootstrapping were used to quantify the uncertainty of models and select a robust one. Potentiodynamic polarization experiments were performed on the predicted composition in simulated body fluid at 37 ± 1 °C for validation, demonstrating the new alloy's superior corrosion properties with a homogeneous microstructure as opposed to the dendritic structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding the corrosion behavior of biomedical materials in the human body is an essential step for the development of improved materials and clinical procedures in arthroplasty. In this work, the corrosion behavior of Ti and CoCrMo alloys in human synovial fluids directly extracted from patients was investigated through an electrochemical experimental protocol, including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results show that the corrosion behavior of both materials largely depends on patients. The obtained corrosion rates of both materials correspond well to the metal ion release rate detected in patients with joint implants revealing the adequateness of the electrochemical experimental protocol for quantifying in-vivo corrosion of biomedical implants. Based on the results, no significant risk of galvanic corrosion of Ti/CoCrMo coupling is anticipated. The rates of wear-accelerated corrosion (one of the main degradation mechanisms of metallic artificial hip joints) were theoretically extracted from the present electrochemical measurements using an established tribocorrosion model. Those material loss rates are patient-dependent and can be up to two orders of magnitude higher than the static corrosion rates, indicating that the nature of the patient can critically affect the degradation rate of the joint implant. [ABSTRACT FROM AUTHOR]

Ti is used as a construction material in many applications including electrodes in various electrochemical technologies due to its high corrosion stability provided by the stable oxide layer on the surface. However, this oxide layer is also the reason for its resistivity causing high interfacial resistance between components and energy losses. This problem can be solved by various surface modifications such as acid etching or coating with a layer of precious metals. In this study, we present a novel method for controlled hydridation of Ti materials based on a combination of acid etching and cathodic hydridation aimed primarily for surface modification of Ti components for proton exchange membrane water electrolyser. Cathodic polarisation represents the means to increase the amount of Ti hydride and to tune its properties to obtain a Ti surface with low interfacial resistance and preserved corrosion stability. The study investigated the effects of concentration, temperature, time, and current density on cathodic polarization in H 2 SO 4 electrolytes. The resulting samples were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, Kelvin probe and temperature-programmed desorption. This allowed finding interesting correlations between the surface composition of the Ti samples and their electrochemical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

• Effect of surface finish on corrosion and metal release from Ti6Al4V studied. • Ti6Al4V was produced by laser powder bed fusion using biomedical protocols. • Nitric acid passivation had a negligible effect on metal release and corrosion. • Effect of surface finish (sandblasted, polished) explained by true surface area. • More proteins were adsorbed on rough (sandblasted) surfaces. The biomedical titanium alloy Ti6Al4V has excellent corrosion resistance and biocompatibility and is, therefore, widely used in orthopedic and orthodontic implants. Biomedical implants are increasingly fabricated by additive manufacturing, such as laser powder bed fusion (LPBF). These manufacturing protocols often include sandblasting, surface finish, and passivation. This study aims to investigate the effect of different surface finishes and the commonly used ASTM F86–13 nitric acid passivation for LPBF Ti6Al4V on its corrosion resistance, metal release, and surface changes in benign (bovine serum albumin in a pH 7.4 buffer) and harsh (hydrochloric acid at pH 1.5) solutions using various electrochemical and spectroscopic techniques. Electrochemical, solution and surface analysis showed an insignificant effect of passivation. Smooth surfaces exhibited a slightly better corrosion resistance than rough surfaces due to a 10–20 % smaller true surface area and lower protein adsorption. Implanted ceramic beads from the sandblasting procedure remained on the surface even after the mirror-polishing and passivation procedures. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, high-strength 7075 and 7050 aluminum alloys were processed by the laser powder bed fusion (LPBF) technique. Titanium and boron carbide particles were added to base 7050 and 7075 alloy feedstocks. These reacted in the melt to form inoculants in situ, resulting in a crack-free, refined, and textureless microstructure. X-ray diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectroscopy (EDS) techniques were used to characterize the process-induced microstructure of the alloys. Reactive Additive manufactured (RAM) alloys showed precipitation of various sub-micron to nanoscale phases such as Zn-Cu, Cu-Fe, Mg-Cu, Mg-Zn, and pure Zn. The corrosion response of RAM alloys was analyzed and compared with respective wrought alloys by various electrochemical measurements such as potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and atomic spectroelectrochemistry (ASEC) techniques. A reduction in corrosion resistance was observed in RAM alloys as compared to wrought counterparts due to thepresence of unreacted Ti and B 4 C particles and a higher cathodic activation attributed to the underlying microstructure. Time evolution surface imaging and post-corrosion microstructures were analyzed to support the understanding of underlying corrosion mechanisms. [Display omitted] [ABSTRACT FROM AUTHOR]

Additive manufacturing technologies are quickly gaining success in several industries. However, a complete understating of how the unique macro- and microstructures obtainable influence the corrosion behavior is still far from being achieved. In this work, potentiodynamic and potentiostatic polarization tests were performed in an aerated chloride solution on laser powder bed fusion (LPBF)-produced AlSi10Mg specimens, built adopting different baseplate temperatures. Potentiodynamic polarization tests evidenced two separate breakdown potentials. The first was associated with the initiation of corrosion localized at the edge of the melt pool, while the second with the break of the passive film of the matrix. This phenomenon highlighted that potentiodynamic curves can overestimate the critical potentials required to trigger the selective corrosion. Potentiostatic polarization tests were performed at an intermediate potential value with respect to the ones highlighted in the previous test. All the specimens achieved the dissolution of the passive layer after a certain immersion time. This period was lower for the specimens built using higher baseplate temperatures, due to the coarsening of the microstructure and disruption of the Si-rich network. A similar behavior was encountered by the heat-treated samples. These required significantly less time to trigger corrosion, due to the complete disappearance of the melt pool macrostructure and formation of Si particles. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of microporous nickel-chromium systems was studied by means of conventional electrochemical techniques and localized ones using two chloride based electrolytes with and without cupric ions in their composition. The conscious combination of different methodologies using these techniques has provided valuable information about the corrosion process. Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) measurements were performed in bulk solution, whilst Scanning Kelvin Probe (SKP) measurement were carried out using two methodologies: i) electrolyte droplets monitoring (measuring simultaneously potential and droplet height with time), and ii) potential maps of dried surfaces that previously were exposed to droplets. Further characterization was done based on the morphology of the attack and composition on the surface by Optical Microscopy (OM), Field Emission- Scanning Electron Microscope (FE-SEM) and X-ray Photoelectron Spectroscopy (XPS) together with the analysis of electrolyte composition with time by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Results have shown the harmful effect of Cu2+ cations in the corrosion resistance and a different morphological impact on the surface. Such negative effect has revealed a new time constant at high frequency in the impedance diagrams as well as an abrupt potential decrease (due to a change in the cathodic reaction involved: Cu2+ + e− ↔ Cu+ takes place) using SKP droplet test. Apparently, Cu+ species were stabilized in bulk solution by the formation of chloride complexes, as was confirmed by the precipitation of a white CuCl compound during droplet evaporation, pointing out the key role of Cu+ in the corrosion process. [ABSTRACT FROM AUTHOR]

Modern Ti-based materials such as nanocrystalline α Ti and metastable β alloy Ti-29Nb-13Ta-4.6Zr (TNTZ) offers unique mechanical properties which are essential in case of dental implants. However, successful permanent implantation is governed also by material's functional properties such as corrosion behaviour in body fluids. Although both of this materials demonstrated high corrosion resistance in standard physiological solutions, the effect of simulated inflammatory conditions, which are more realistic following the implantation, is still unknown. Hence, in this work the influence of simulated inflammation on the corrosion response of nanocrystalline α Ti and metastable β TNTZ alloy was investigated and compared with the widely used microcrystalline α Ti. This study provides an insight how the presence of non-toxic β phase stabilizers and grain refinement to the nanoscale affect Ti corrosion behaviour in the simulated inflammatory conditions. [ABSTRACT FROM AUTHOR]

Concretes with fly ash, slag, limestone calcined clay, etc. exhibiting high resistivity are being used to enhance the chloride resistance of structures – to achieve durability. Prior to use, the engineers need to determine the chloride threshold (Cl th) of such highly resistive steel cementitious (S-C) systems (a key parameter to estimate service life). Most Cl th tests involve repeated measurements of polarization resistance (R p) and detection of corrosion initiation of steel embedded in hardened cementitious system (a sol-gel structure with partially filled pores). The high resistivity of such systems should be considered while interpreting the electrochemical response to determine R p. This paper experimentally evaluates the suitability of LPR and EIS techniques for assessing R p of steel embedded in highly resistive systems. Experiments were conducted with lollipop type specimens (steel reinforcement embedded in mortar cylinders). The following three types of mortar having various resistivities were prepared: (i) ordinary portland cement (OPC), (ii) OPC + fly ash, and (iii) limestone calcined clay cement. Experimental observations on how the following three factors affect the electrochemical response in highly resistive S-C systems are provided: (i) resistivity of concrete covering the embedded steel, (ii) electrode configuration, and (iii) electrochemical test parameters. It was found that electrochemical impedance spectroscopy (EIS) can detect corrosion initiation in highly resistive systems at earlier stages than the linear polarization resistance (LPR) technique. Also, the guidelines on how to use EIS technique to determine the R p of steel embedded in highly resistive S-C systems are provided. [ABSTRACT FROM AUTHOR]

Abstract Laser powder bed fusion (LPBF) is one of the most widespread additive manufacturing (AM) technologies for metals, in which the components are built additively layer upon layer along the z-axis (the building direction) perpendicular to the building platform (xy-plane). Here, we evaluated the effect of post-processing heat treatments at 200, 300, and 400 °C on the corrosion resistance of AlSi10Mg alloy manufactured by LPBF for two orientations in the building chamber (XY – parallel to the building plane or XZ – perpendicular to the building plane). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were conducted at the constant chloride ion concentration of 0.02 M and 23 °C for the as-built and heat-treated specimens. All specimens were polished on the surface and displayed similar behaviors in the EIS tests. The pitting potential results were widely scattered and therefore analyzed using a statistical approach. Statistical data analysis based on analysis of variance technique (ANOVA) was performed. The results confirmed that the population significantly differs only by considering the heat treatments and the building direction plays only minor role. The cumulative distribution curves of pitting potentials showed a decrease in pitting resistance as the temperature of heat treatment increases. Graphical abstract Effect of heat treatment temperature on the pitting potentials of AlSi10Mg obtained by means of laser powder bed fusion. Image 1 Highlights • Pitting potentials of AlSi10Mg present a wide experimental variability. • Cumulative frequency of pitting potentials shows a deleterious effect of the temperature of post-processing heat treatment. • Corrosion attack take place at the edge of melt pool up to 300 °C of heat treatment temperature. [ABSTRACT FROM AUTHOR]

Abstract The electrochemical behaviour of a metal-rubber composite is studied in NaCl-based solutions. The metallic reinforcement is brass-coated pearlitic steel. Electrochemical investigations were performed in 0.01 M NaCl and in a solution containing 0.01 M NaCl with species released from the rubber during immersion. These species were identified using gas chromatography coupled with mass spectrometry. The role as inhibitors of some species (released from the rubber or added in the solution) was evaluated by determining polarisation curves and electrochemical impedance diagrams. In the cathodic domain, no synergistic effect was noticed between 2-aminobenzothiazole (added in the solution) and benzothiazole (released from the rubber in the solution). It was found from EIS diagrams that inhibition is caused by specific adsorption at the specimen surface. In the anodic domain, it was proposed that there is a synergistic effect between 2-aminobenzothiazole and benzothiazole. [ABSTRACT FROM AUTHOR]

Abstract The corrosion process of iron in 1M LiPF 6 solution using an ethylene carbonate/diethyl carbonate (EC/DEC) mixture solvent is studied using gravimetric and electrochemical methods. The electrochemical technique employed is electrochemical impedance spectroscopy, EIS, and a special electrode arrangement is used in a pouch cell. The electrochemical and gravimetrical data match reasonably well, indicating a decreasing corrosion rate with time of exposure. The EIS data are analysed using a transmission line model that accounts for the shifts observed in the high frequency limit of the impedance. The data presented suggest that PF 6 − corrodes Fe to Fe2+ that further evolves to Fe3+, forming porous structures based on FeF 3. The formation of Fe3+ has also been confirmed by X-ray photoelectron spectroscopy, XPS analysis. In the presence of non-oxidising salts (e.g., LiBOB, LiBF 4), the Fe corrosion rate decreases. Graphical abstract Image 1 Highlights • Iron as an active material and current collector for LiBs. • LiPF 6 in typical LiBs electrolyte is corrosive to iron. • The corrosion products layer is porous and reducible to Fe. • EIS allows following the film-forming process. [ABSTRACT FROM AUTHOR]

Abstract Understanding the kinetics of passive oxide formation and breakdown has been an ongoing problem for corrosion scientists for several decades. Here, we present a model for the formation of a passive oxide film on a metal that is an extension of the Point Defect Model (PDM) by Macdonald and coworkers. We replace the potential description of the PDM with a boundary value problem and ensure that Gauss's law is satisfied at the oxide-solution interface by considering the presence of the Helmholtz layer in solution. Our model predicts the observed linear variation of the steady-state film thickness with anode potential, and an increasing film thickness with increasing pH. We perform a linear stability analysis of the model and show that, depending on the parameters, the passive film may be unstable to morphological perturbations of the film interfaces, leading to nonplanar films and potentially the formation of a pit in the oxide. This also implies that one-dimensional models, which assume planar interfaces, can be inapplicable in broad classes of corrosion processes. The analysis shows that a morphological instability exists if the oxide dissolution mechanism is such that an increasing Helmholtz layer potential drop leads to an increasing dissolution rate. The instability behavior is consistent with the literature on breakdown of passivity in the presence of chloride ions. The theory provides insights on the initiation of passivity breakdown leading to pitting corrosion and the role that interfacial energy plays in determining stability. [ABSTRACT FROM AUTHOR]

Abstract A proteinaceous biopolymer, mussel adhesive protein #5 (MeFP-5), isolated from the common blue mussel (Mytilus edulis L) has been investigated as a model for designing an aqueously soluble candidate corrosion inhibitor system that is non-toxic and environmentally friendly and is capable of inhibiting the flash rusting of exposed high strength low alloy (HSLA) steel surfaces during the paint removal process. In a previous study it was found that a significant amount of corrosion inhibition is possible (nearly 100% inhibition after 7 days) on HY80 steel in a 100% relative humidity environment at 40 °C. In an attempt to determine the possible mechanisms of corrosion inhibition, surface characterization of HY80 steel treated with various solutions containing the MeFP-5 biopolymer were performed. Fourier transform infrared (FT-IR) spectroscopy using attenuated total reflectance (ATR) of the protein adsorbed onto glass and metal surfaces indicated that complexation of the iron atoms on the oxyhydroxide covered metal surface involved the amino acid l -dopa and the primary amine of lysine. The involvement of these amino acids in the adsorption of the protein onto glass were much less evident. When the adsorbed protein was treated with a catechol oxidase enzyme, vibration bands consistent with metal complex formation involving l -dopa were not observed, indicating that the treatment with enzyme resulted in mess metal chelation at the surface oxide-protein film interface. Energy dispersive x-ray spectroscopy (EDS) findings indicate that iron content is highest where the MeFP-5 biopolymer is adsorbed onto the steel substrate at pH 5.5, 50% higher than the content of the iron on the steel surface alone. When the biopolymer is enzymatically cross-linked on the steel surface at pH 5.5, the iron content is decreased by 15% of that of the adsorbed biopolymer, suggesting that the iron at the steel surface is undergoing complexation and possible metal-mediated cross-linking, whereas the enzyme cross-linked protein on the steel surface complexes less of the iron. Three-dimensional modeling efforts of MeFP-5 suggest that specific domains of MeFP-5 where two amino acids, l -Dopa and lysine, are concentrated may be involved in adsorption to a metal oxyhydroxide film. These results indicate that it is possible to utilize the biochemistry of a naturally occurring biopolymer isolated from the marine mussel, Mytilus edulis (L), to develop a non-toxic and environmentally friendly corrosion inhibitor. [ABSTRACT FROM AUTHOR]

Abstract The development of the single substrate technique presents a realistic possibility of utilising electrochemical noise measurement for on-site evaluations of corrosion behaviour. A theoretical model was developed to further understand the effects of reference electrodes on the acquired data to increase confidence in the technique. The model demonstrates that the reference electrodes can have a significant impact on the measurements, resulting in erroneous values if the reference electrodes are not selected carefully. Furthermore, the derived equations elucidate how to limit/remove such influence, facilitating accurate application of the single substrate technique on bare metal and coated substrates both in laboratories and in the field. [ABSTRACT FROM AUTHOR]

Abstract The increasing demand for high-performance lightweight metallic materials is driving an interest in Plasma Electrolytic Oxidation (PEO) as one of the most promising techniques for surface engineering of Mg. In order to enable smart and multifunctional performance, it can be beneficial to incorporate into ceramic PEO coatings nanocontainers to carry appropriate active and functionalising agents. In situ incorporation of nanocontainers is challenging since their integrity may be compromised by plasma discharge assisting coating formation. We studied incorporation of halloysite nanotubes (HNTs) as potential nanocontainers into forsterite, Mg 2 SiO 4 , formed during PEO processing of AM50 alloy at the frequency range of 100–5000 Hz. Detailed analysis of the coating microstructure, chemical and phase composition carried out by Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy, Transmission Kikuchi Diffraction and X-ray Diffraction enabled evaluation of a pattern of surface temperature evolution during current pulses underpinning the PEO process. Transient analysis revealed that at pulses longer than 10−4 s, the surface heating becomes affected by the metal substrate acting as a heat sink. As the pulse duration approaches 10−3 s, raising surface temperature and increasing thermal gradients across the coating cause crystallisation of forsterite and grain growth towards the surface; this triggers thermally induced degradation and decomposition of HNTs adsorbed on the surface. In contrast, at short pulse durations (2 × 10−5 s), the energy released is insufficient to induce forsterite crystallisation and incorporated HNTs are retained in their original tubular structure. Due to the fine porosity and good structural integrity, such coatings show enhanced corrosion resistance in saline solution. Strong correlations between surface thermodynamic conditions and evolution of coating microstructure disambiguate the fundamental mechanisms underlying incorporation of nanoparticles into growing PEO coatings, thus creating the basis for efficient design of PEO processes and development of novel smart and multifunctional coatings with potential applications in many industrial sectors. [ABSTRACT FROM AUTHOR]

Abstract The corrosion behavior of Ni Co Cu nanocrystalline coatings in neutral salt environments was systematically investigated by potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, and long-term salt spray tests. The electrodeposited ternary coatings were Ni-based solid solution alloys that contained markedly different contents of Co and Cu. Greater Co and Cu contents strongly reduced the polarization and charge-transfer resistance of the coatings, thus decreasing their corrosion resistance in neutral NaCl solutions. In salt spray tests, the initial porous corrosion product film on the Co-/Cu-poor coating evolved into a compact film that finally grew to cover the coating surface, while such morphological transition was absent on the Co-/Cu-rich coating, where the formed film showed a continuous deterioration in its initial porous structure. Abundant Co-/Cu-substituted α-Ni(OH) 2 might grow to form the primary compact films that could coalesce and thicken as corrosion was suppressed. A large amount of Cu(OH) 2 together with high corrosion rates might be detrimental to the formation of compact films. A mechanism of the formation of the corrosion product films was proposed based on the corrosion characteristics of the ternary system and detailed corrosion product film analysis. Highlights • Greater Co and Cu contents reduced the polarization and charge-transfer resistance. • The porous corrosion product film on Ni-rich coatings evolved into a compact film. • A large amount of α-(Ni,Co,Cu) (OH) 2 promoted the formation of compact films. • Films with abundant Cu(OH) 2 showed a continuous deterioration in porous structures. [ABSTRACT FROM AUTHOR]

Abstract The development of tools that can probe corrosion related phenomena at the (sub)microscale is recognized to be increasingly important in order to understand the surface structural factors (grain orientation, inclusions etc.) that control the (electro)chemical stability (corrosion susceptibility, pitting, passivity etc.) of metal surfaces. Herein we consider the application of scanning electrochemical cell microscopy (SECCM), a relatively new member of the electrochemical droplet cell (EDC) family, for corrosion research and demonstrate the power of this technique for resolving structure and activity at the (sub)microscale. Hundreds of spatially-resolved (2 μm droplet size) potentiodynamic polarization experiments have been carried out on the several hours timescale and correlated to complementary structural information from electron backscatter diffraction (EBSD) and energy dispersive x-ray spectroscopy (EDS) in order to determine the effect of grain orientation and inclusions on electrochemical processes at low carbon steel in neutral solution (10 mM KNO 3). Through this approach, it has been shown unequivocally that for the low index planes, anodic currents in the passive region (an indicator of corrosion susceptibility) are greatest on (101) planes compared to (100) and (111) planes. Furthermore, individual sub-micron MnS inclusions have been probed and shown to undergo active dissolution followed by rapid repassivation. This study demonstrates the high versatility of SECCM and the considerable potential of this technique for addressing structure-activity problems in corrosion and electromaterials science. [ABSTRACT FROM AUTHOR]

Abstract In the context of H 2 S corrosion of mild steel, the direct electrochemical reduction of H 2 S is currently believed to be the main contribution of this species to cathodic currents. That is perhaps due to the distinct behavior of the cathodic polarization curves observed in the presence of H 2 S, as compared to those obtained in strong acids solutions or in the presence of other weak acids such as carboxylic acids and carbonic acid. In the presence of aqueous H 2 S, the cathodic polarization curves show a "double wave" shape, that is widely considered to be the result of the direct reduction of H 2 S. In the present study, the mechanism of H 2 S corrosion of mild steel is theoretically investigated with the focus on the buffering ability of H 2 S. It is shown that all characteristic behaviors of cathodic currents that were previously associated with the direct reduction of H 2 S, including the "double wave", can be fully explained in terms of the H 2 S dissociation reaction and its buffering effect. In order to further evaluate this mechanistic argument, a comprehensive mathematical model for the H 2 S system was developed and the calculated cathodic polarization curves were compared with the existing experimental data in the open literature. The results showed that the model, built with H+ reduction as the sole cathodic reaction, is able to reasonably capture all characteristic behavior of cathodic currents, further supporting this mechanistic argument. [ABSTRACT FROM AUTHOR]

Abstract A cellular automaton model is used for 3D simulations of metal corrosion in electrolyte solutions in potentiostatic conditions. The focus of this research is the formation of the passive layer on the metal surface. A general, mesoscopic-scale model is used. It contains only the elements necessary to reproduce the most important features of passivation. It is a 3D version of the 2D model presented in our previous papers. The simulations are run on graphics processing units which allow an effective operation on large 3D lattices. We consider the influence of three factors: the rate of corrosion (related to the electric potential), solubility of the corrosion products and their adhesion or absence of adhesion to the metal surface. For each set of the parameters we wait in the simulation run for the system to attain the steady state. Then we collect data characterizing steady-state properties such as electric current density, passive layer thickness, its roughness and overall morphology. The qualitative properties of passivation are reproduced in our 3D simulations confirming the conclusions based on earlier, 2D simulations. [ABSTRACT FROM AUTHOR]

• An ion-conductive copolymer film containing Zn salt is coated onto Zn foil electrode. • The surface-coated Zn electrode is free of dendrite growth and hydrogen gas evolution. • Long cycle life of the Zn anode is enabled by the copolymer coating. • Full cells using the surface modified Zn anode show much longer cycle life and higher capacity. The Zn metal anode endows aqueous zinc-ion batteries (ZIBs) with merits in terms of low cost, high safety, and bivalent ions as charge carriers. Yet the current ZIB technology is immature due to some issues arising from the Zn anode, including the dendrite growth, formation of compound byproducts, and hydrogen gas evolution. Here, a nanoporous and ion-conductive polyvinylidene fluoride-hexafluoro propylene copolymer containing zinc trifluoromethanesulfonate (Zn2+-PVDF-HFP coating) is applied onto the Zn foil to improve its anode performance. The Zn anode covered with Zn2+-containing PVDF-HFP coating (Zn@Zn2+-PVDF-HEP) shows good anti-corrosion performance and much longer cycle life, compared to the bare Zn anode. Also, the byproduct growth and hydrogen gas evolution can be efficiently suppressed due to the Zn2+-conductive copolymer coating. For symmetric cells using Zn@Zn2+-PVDF-HFP, a long lifespan of 2200 cycles is achieved when tested at 1 mA cm−2 and 1 mAh cm−2. Even cycled at 10 mA cm−2 and 5 mAh cm−2, this cell can sustain for over 1800 h. The efficacies of Zn2+-PVDF-HFP coating in prolonging cycle life and enhancing areal capacity of the Zn anode are further verified in MnO 2 - or V 2 O 5 -based full cells, for which the mechanisms are discussed in detail. [ABSTRACT FROM AUTHOR]

• EIS results of Mg-based materials strongly influenced by non-stationarity. • Internal non-stationarity is originated from the Mg-electrolyte system. • External non-stationarity is induced by the perturbation of EIS measurement. • Impacts of non-stationarity get more pronounced with the decrease of frequency. • Non-stationarity in EIS measurement is one of plausible origins of inductive loop. For most bare Mg-based materials in aqueous media, an inductive behavior can be detected at the low frequencies electrochemical impedance spectroscopy (LF-EIS) measurement, which potentially can be associated with the non-stationarity of the system. The non-stationarity in EIS measurement leads to inaccurate acquisition of experimental data and, thus, misunderstanding of the electrochemical behavior of tested samples. To investigate the non-stationarity of EIS measurements on Mg-based materials in aqueous media, conventional EIS measurements are performed on pure Mg and several representative Mg alloys (AZ31, AZ91, AM50) in NaCl and Na 2 SO 4 solutions. The results indicate that the impedance spectra of Mg-based materials in aqueous media is influenced by the internal non-stationarity of the Mg-electrolyte system and the external non-stationarity induced by EIS measurement. Multisine odd random phase EIS (ORP-EIS) measurements were performed to visualize the non-stationarity and non-linearity of the system. Moreover, the comparison of conventional and ORP-EIS results exhibits the difference between pseudo and real inductive behavior for the AZ31-NaCl system. Accordingly, the origin of the inductive behavior of Mg-based materials is discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) are an attractive option for different energy storage applications due to their cost-effectiveness, safety benefits, and high capacity. Nevertheless, their development is constrained by challenges such as hydrogen evolution reaction (HER), significantly affecting the battery lifespan. This work presents a promising solution to this problem using a hybrid electrolyte, consisting of water and tetra ethylene glycol dimethyl ether (TEGDME) containing Zn(OTf) 2. Results demonstrate that this hybrid electrolyte can suppress HER and can lessen zinc corrosion by reorienting hydrogen bonds with water and actively participating in the solvation structure of Zn2+ ions. Such reorientation reduces water activity and weakens the interactions between water molecules and between water and Zn2+ ions. By employing an optimal TEGDME/H 2 O ratio of 2:1 in the hybrid electrolyte, hydrogen evolution overpotential increased by 0.26 V. As a result, in the Zn//Zn symmetrical cells, the developed hybrid electrolyte is seen to enable the Zn electrode to exhibit excellent cycle durability, lasting over 4300 h with coulombic efficiency (CE) of 99.68% at 0.5 mA cm−2 and 0.5 mAh cm−2, surpassing the 92.79% achieved by the base electrolyte (1 M Zn(OTf) 2 aqueous solution) cells. Moreover, when implemented in Zn/δ-MnO 2 batteries, the hybrid electrolyte maintained its performance for over 1800 cycles at a discharge rate of 100 mA g−1. This cost-effective and adaptable strategy highlights its wide-ranging potential, offering vital insights for the enhancement of AZIB technology. [ABSTRACT FROM AUTHOR]

In the face of aggressive environment, cathodic protection shows promise as a solution to reducing the risk associated with corrosion initiation and propagation of prestressed concrete structures. This can be achieved by applying an impressed current to the system that brings the electrical potential of steel members to such a level where localized corrosion does not occur. However, atomic hydrogen that evolves at negative potential can cause hydrogen embrittlement of ASTM A416 steel wires used in prestressed concrete, leading to system failure without warning. To reduce the risks of brittle failures, nickel–cobalt alloy was applied to steel wires. The corrosion properties of the coated specimens were studied in simulated concrete and corrosive environments. The steel wires were also placed in an aggressive environment to predict the time to failure of the samples due to hydrogen embrittlement. A brittle crack developed in wires tested in the as-received condition, but samples coated with the proposed coating passed the embrittlement test. Nickel–cobalt coated specimens not only showed corrosion properties similar to as-received samples, but also did not fail the embrittlement test. [ABSTRACT FROM AUTHOR]

• The presence of LOF pores in L-PBF specimen increases its susceptibility to pitting. • LOF pores and Cr element ablation can lead to loss of the passive region. • High Cr/C content causes corrosion in LOF-free region generating pitting nucleation. • Pitting nucleation is initiated by M 7 C 3 carbides around 100 nm in size. In this study, 420 stainless steel (SS) was fabricated by L-PBF with specific processing parameters: 140 W laser power, 550 mm/s scanning speed, 80 μm spot size, and 50 μm layer thickness. The resulting specimens exhibited 0.42% porosity and an average size of 18 μm for Lack-of-fusion (LOF) pores, with elemental C and Cr ablation at approximately 35.9% and 18.0%, respectively. A comparative analysis between the corrosion resistance of L-PBF specimens and cast 420 SS was conducted. Despite exhibiting extraordinary mechanical properties, L-PBF specimen displayed lower corrosion resistance and failed to produce a passive region. LOF pores and elemental ablation from intrinsic laser additive manufacturing process were the primary reasons for this outcome. Two distinct corrosion mechanisms were observed in the study. The LOF pores exhibited a higher susceptibility to pitting corrosion, leading to the formation of larger pitting pits with an approximate size of 100 μm. Conversely, the LOF-free areas displayed the presence of smaller pitting nucleation, measuring < 2 μm. This observation was attributed to the ablation of C element, leading to a 28% increase in the Cr/C content. The higher Cr/C in the LOF-free areas offered enhanced protection, thus preventing the formation of larger pitting pits in these regions. [ABSTRACT FROM AUTHOR]

Post implantation, a thin TiO 2 film protects Ti-6Al-4V in vivo. Mechanically and chemically destructive conditions may disrupt this oxide film and promote corrosion at the device interface. While tribocorrosion has been explored in vitro , pre-clinical tests fail to fully reproduce the damage documented on retrievals. A gap persists in our fundamental knowledge of the oxide film and its response to adverse electrochemical events. In this study, we first characterized the TiO 2 oxide film structure after inducing β phase selective dissolution. Next, we used electrochemical impedance spectroscopy and Mott-Schottky analysis to investigate the oxide film on freshly prepared surfaces following negative potential excursions. We systematically increased electrode potential from -1 V vs. Ag/AgCl in 0.1 V steps to +0.5 V. Various H 2 O 2 concentrations (0.1 M to 0.001 M) in phosphate buffered saline and temperatures ranging from 24 °C to 55 °C were investigated. Atomic force microscopy showed morphological changes to oxide domes over the α phase following β phase selective dissolution. Below the Ti-6Al-4V open circuit potential (ca. -0.3 V), we identified systematic variations in polarization resistance (R p) and capacitance (C) with potential, solution chemistry, and temperature. The combined effect of cathodic activation and H 2 O 2 solution concentration synergistically and systematically decreased R p by orders of magnitude (p = 0.000). Increased solution temperatures decreased R p (p = 0.000). At high concentrations of ROS (0.1 M), we documented changes in constant phase element capacitance, from n-type to p-type. Finally, we developed empirical equations to predict R p for a given concentration, temperature, and potential. In totality, these experiments help to further elucidate the complex interactions at the oxide-biology interface in vivo and provide guidance for in vitro testing methods development. In vivo , the Ti-6Al-4V oxide film is subject to destructive conditions including inflammation and tribocorrosion. In this study, we investigated the dynamic remodeling of the oxide film, using H 2 O 2 as a proxy for inflammatory species and cathodic activation to simulate negative potential drops at the interface. We identify a synergistic effect of cathodic potential and H 2 O 2 on oxide polarization resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Laboratory and numerical corrosion experiments impose an electric potential on the metal surface, differing from natural corrosion conditions, where corrosion typically occurs in the absence of external current sources. In this work, we present a new computational model that enables predicting corrosion under charge-conservation conditions. The metal potential, an output of the model, is allowed to change, capturing how the corrosion and cathodic reactions must produce/consume electrons at the same rates, as in natural conditions. Finite element simulations are performed over a large range of concentrations and geometric parameters. The results highlight the notable influence of the charge-conservation assumption and pioneeringly quantify corrosion rates under realistic conditions. They further show: (i) the strong coupling between the corrosion rate and the hydrogen and oxygen evolution reactions, (ii) under which circumstances corrosion pits acidify, and (iii) when corrosion is able to become self-sustained lacking oxygen. • A numerical model for corrosion in absence of external current sources is presented. • The model requires corrosion currents to be counteracted by cathodic reactions. • We simulate pencil-electrodes under varying geometric and environmental conditions. • We show strong influence of available oxygen and external surface area on corrosion. • Oxygen is required to develop acidic pits, but pits can sustain corrosion lacking oxygen. [ABSTRACT FROM AUTHOR]

Fe-P, Ni-P and Ni-Fe-P alloys were prepared by galvanostatic electrodeposition over copper electrodes in aqueous media in order to obtain a corrosion resistant layer. All electrodeposits were prepared in optimized conditions at acidic medium (pH < 2.0), using 80 mA cm −2 for Fe-P and Ni-P alloys and 60 mA cm −2 for Ni-Fe-P alloy at 55 °C. The morphology of the electrodeposits was evaluated by scanning electron microscopy, which revealed a nodular, hemispheric grains in Ni-P and Ni-Fe-P alloys and the same grains with cracks in Fe-P alloy. X-ray diffraction (XRD) measurements showed characteristic peaks for Fe and Ni, and P incorporation was observed due to characteristic peak at 2θ ≈ 50°, which means that P atoms amorphized the structure of the electrodeposits. Energy Dispersive X-Ray Spectroscopy (EDS) measurements showed the following composition for all alloys (mass percentage): Fe 91.1% -P 4.3% , Ni 88.5% -P 9.7% , Ni 46.5% -Fe 39.4% -P 12.6% . Linear potentiodynamic polarization showed the following order for crescent nobility corrosion potential: E corr (Fe-P) < E corr (Ni-P) < E corr (Ni-Fe-P). Although Ni-P presented lower anodic current values than Ni-Fe-P in polarization curves, the analysis of E-E corr polarization curves in these studies showed that Ni-Fe-P and Fe-P coatings had the lowest and highest anodic current values, respectively, among the three electrodeposits. The same trend was observed in electrochemical impedance spectroscopy when a nested circuit for two capacitance events was applied, having Ni-Fe-P layer the highest polarization resistance value among the three and Fe-P the lowest polarization resistance, showing the viability of anticorrosion properties of Ni-Fe-P layers. [ABSTRACT FROM AUTHOR]

The effects of feeding sequence of reactants on the properties of a MgAl layered double hydroxide (LDH) coating on Mg alloy are reported herein for the first time. Based on the X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra, MgAl-LDH coatings were successfully obtained with different feeding sequences. However, characterizations of scanning electron microscopy (SEM) and electrochemical methods show that the surface morphologies and corrosion resistance of the MgAl-LDH coatings are dependent upon the feeding sequence. Furthermore, the MgAl-LDH coatings were modified in an 8-quinolinol (8HQ) solution by a facile soaking measurement. Energy dispersive X-ray spectroscopy (EDS) maps and X-ray photoelectron spectroscopy (XPS) spectra demonstrate the effective adsorption of 8HQ layer on the MgAl-LDH primer. The high-resolution N 1s XPS spectra manifest the existence of chemisorption owing to formation of a complex chelate, (bis (8-hydroxyquinolinato) magnesium, Mg(HQ) 2 ), between 8HQ anions and dissolved Mg 2+ . The modified MgAl-LDH coatings, which are named as 8HQ@MgAl-LDH coatings in the body text, show significant enhancement in corrosion resistance and remains excellent corrosion protection even exposure to a NaCl aqueous solution for one month. The mechanism of corrosion inhibition for the 8HQ@MgAl-LDH coatings is proposed finally, which mainly includes the increase in water contact angles, Cl − and CO 3 2− anion-exchangeability, and redeposition of Mg(HQ) 2 precipitation. These findings of this study provide some valuable insights into the corrosion protection mechanism of the MgAl-LDH coatings and the designment of a highly corrosion resistant coating on Mg alloy and other lightweight alloys. [ABSTRACT FROM AUTHOR]

The effect of bulk cargo materials - iron ore and coal – on the corrosion of cargo hulls in carriers was investigated using electrochemical noise. Two reference corrosion systems were set up with the steel samples in contact with moist silica sand and immersed in NaCl solution, which generated localised corrosion and general corrosion, respectively. The electrochemical noise was measured and recurrence quantification analysis was used to extract feature variables. A random forest model using these feature variables as predictors was able to discriminate between the two reference corrosion systems. This model was successfully applied to the assessment of carbon steel corrosion in iron ore and coal. The results predicted by the model were in agreement with visual and microscopic observations of the relevant corroded steel samples. This work provides a novel analytical approach to future on-line monitoring of carrier structures in contact with bulk cargoes. [ABSTRACT FROM AUTHOR]

Corrosion of iron exposed to H 2 S saturated solution at pH 4 was studied by electrochemical impedance spectroscopy, weight loss coupons and surface analysis. Hydrogen permeation was also used as indirect means of evaluating the intensity of the proton reduction reaction leading to hydrogen entry into the metal. Since corrosion in this type of test solution results in the rapid build-up of a conductive and highly porous iron sulfide scale, a specific contribution of the film has to be considered. An impedance model was thus proposed. The faradaic anodic impedance consists of a two-step reaction with charge transfer and adsorption – desorption. An additional contribution, associated with the conductive and highly porous iron sulfide film was added in parallel. This contribution, mostly visible in the low frequency domain, presents a 45° tail associated with a porous electrode behavior. This model was well adapted to describe impedance diagrams measured at various exposure times, up to 620 h. Charge transfer resistance determined from impedance analysis allowed calculating the evolution with time of the corrosion current density. A very good correlation was found between this corrosion current density and the hydrogen permeation current density. As expected in our experimental conditions, a permeation efficiency close to 100% is demonstrated. Corrosion rate of 490 μm/year was measured by weight-loss specimens, confirming the validity of the impedance analysis, which resulted in a calculated corrosion rate of 530 μm/year. [ABSTRACT FROM AUTHOR]

We describe the interfacial characteristics of a Ti-6Al-4V alloy fabricated using laser powder-bed fusion (L-PBF) upon exposure to a corrosive environment and tribocorrosion conditions. Electrochemical techniques in both the time and frequency domains demonstrated a correlation between the manufacturing process parameters and corrosion properties, and a titanium oxide passive layer produced specific semiconductor n-type properties. The influence of the microstructure on the titanium oxide passive layer was revealed by comparing L-PBF parts with a traditionally manufactured Ti-6Al-4V alloy in Ringer's simulated body solution. Tribocorrosion characterization reflected the endurance of the surface oxide when the process parameters were adjusted. In addition, wearing simultaneously reflected the mechanical condition as the surface repassivate. The production of fragmentation film during wear caused accumulation of the corrosion product and demonstrated the effect of aggressive ions on the chemical and mechanical properties of the passivation film. [ABSTRACT FROM AUTHOR]

In this work, the study of the time-dependent behaviour of lithium carbonate based inhibitor technology for the active corrosion protection of aluminium alloy 2024-T3 is presented. Odd random phase electrochemical impedance spectroscopy (ORP-EIS) is selected as the electrochemical tool to study the corrosion protective properties of a model organic coating with and without lithium carbonate as a function of immersion time, by examination of the non-linearities and non-stationarities in the system. A dedicated qualitative and quantitative analysis allows linking the presence of non-stationarities in a certain frequency range with the (un)stable behaviour of different electrochemical processes. Monitoring of the system with and without lithium corrosion inhibitors during the first 12 h after immersion in a 0.05 M NaCl aqueous solution and modelling the ORP-EIS data with equivalent electrical circuit (EEC) models revealed a relation between the trends in the parameter evolution and the (un)stable behaviour of the morphological changes taking place. This paper shows that the ORP-EIS based methodology allows us to study the behaviour of corrosion inhibitors in an alternative way; the time-dependent behaviour of corrosion inhibitor containing electrochemical systems is highlighted, proving that this a useful approach for further corrosion inhibitor and active protective coating research. [ABSTRACT FROM AUTHOR]