Formation Of Passive Film Research Articles

Modulation of Al-Zn-0.5Sn-0.5Mn anode properties by trace Sb

In aluminum-air batteries, hydrogen precipitation corrosion is a difficult problem for aluminum anodes in alkaline electrolytes, which causes a decrease in the efficiency and shortens the service life of aluminum anodes. Under the condition of 4 mol·L-1 NaOH alkaline solution, the addition of trace Sb (0.04 wt%) to Al-Zn-0.5Sn-0.5Mn resulted in an increase of 88.64% in energy density and 74.03% in the specific capacity of the aluminum anode, and a constant current discharge at a current density of 10 mA·cm-2, with a discharge voltage as high as 1.43 V and the discharge process is stable, the anode efficiency reaches 90.90% and the energy density reaches 2526 Wh·kg-1. The improvement in the performance of the aluminum anode is mainly due to the precipitation of the AlSb phase, which activates the grain boundaries, improves the electrochemical activity of the aluminum anode, and forms Sb-containing membranes to inhibit the formation of surface passivation films. Efficient discharge in alkaline solution and long battery life.

A novel multicomponent micro-alloyed magnesium for orthopaedic applications: a microstructural, mechanical, degradation and bioactivity study

ABSTRACT The current study focuses on development of magnesium based micro-alloy with the composition of Mg–0.5Zn–0.15Ca–0.1Mn–0.1Sn–0.1Ag–0.2Ce–0.2Sr using casting method. Microstructural examinations conducted using optical microscopy and scanning electron microscopy (SEM) unveiled a uniform grain distribution in the alloy with minimal intermetallic content, corroborated by X-ray diffraction (XRD) analysis matching the magnesium peak precisely. Tensile testing indicated that the solution strengthening process boosted the alloy’s required yield strength and stiffness, while enhancing magnesium’s ductility up to 19.07% elongation. Electrochemical tests demonstrated an outstanding corrosion resistance rate of 0.91 mm/year, supported by Nyquist plots indicating passivation behaviour and film formation. The pH variations revealed an initial spike to 8.13 within the first 24 hours, gradually declining thereafter. The bioactivity assessment of the developed alloy showcased the formation of near-stoichiometric apatite layers on the alloy surface, confirming its potential as a suitable orthopaedic implant material.

Effect of neodymium on microstructure, mechanical properties, and corrosion behavior of Mg-2Si-xNd alloys fabricated by powder metallurgy

In the present work, the effects of neodymium (Nd) on microstructure, mechanical performance, and corrosion behavior of powder metallurgy Mg-2Si-xNd (x = 0.05 wt%, 0.15 wt%, and 0.20 wt%) alloys were investigated. Microstructures were examined by optical and scanning electron microscopes combined with an energy-dispersive spectrometer. Hardness and compressive tests were used to study the mechanical properties of alloys. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis, and the hydrogen evolution test were applied to characterize the corrosion behavior of alloys in Hanks’ solution. The microstructure of Mg-2Si-xNd alloys mainly consists of α-Mg matrix, Mg2Si, and MgNd phases. The increase in Nd content tends to decrease the aspect ratio of α-Mg grains, which leads to the enhancement of the ultimate-compressive strengths and hardness of the alloys. Potentiodynamic polarization shows that increasing Nd content leads to a lower corrosion current density in the Mg-2Si-xNd alloys. The EIS results confirm that a higher addition of Nd suppresses the dissolution kinetics of the alloys due to the increasing charge transfer resistance. Mott-Schottky analysis reveals the formation of an n-type semiconductive passive film on the alloy surfaces, where the interstitial and oxygen vacancies predominate over the metal vacancies. The X-ray photoelectron spectroscopy (XPS) reveals that a mixture of Mg(OH)2, MgO, MgCO3, and Nd2O3 has formed as the corrosion products on the Mg-2Si-xNd alloy surfaces after a longer immersion time in Hanks’ solution.

Stabilizing the Bilateral Interfaces by a PVDF-Based Double-Layer Solid Composite Electrolyte with a Relieved Dehydrofluorination Effect for Solid-State Lithium Metal Batteries.

The dehydrofluorination effect of poly(vinylidene fluoride) (PVDF) induced by ceramic fillers with an alkaline surface compromises the comprehensive properties of the solid composite electrolyte (SCE) and leads to the deficient performance of the solid-state lithium metal batteries (SLMBs). In this work, a unique PVDF-based double-layer solid electrolyte was fabricated, which consisted of a Li6.4La3Zr1.4Ta0.6O12 (LLZTO)-filled SCE with poly(acrylic acid) (PAA) as an alkalinity-scavenging agent in contact with the Li anode, and another SCE with lithium difluoro(oxalato)borate (LiDFOB) as a film-formation additive facing the cathode. It is found that a moderate amount of PAA relieves the dehydrofluorination degree of the PVDF matrix and improves the Li plating/stripping reversibility, and the addition of LiDFOB is involved in the formation of a stable passivation film on the cathode. Consequently, the resultant double-layer SCE holds favorable overall properties, especially being well-compatible with both electrodes, endowing the SLMBs with superior cycle and rate performance at room temperature.

Titanium Alloy Ti-6Al-4V Electrochemical Dissolution Behavior in NaNO3 and NaCl Solutions at Low Current Density

Jet electrochemical micromilling (JEMM) exhibits significant potential for high-efficiency and high-quality machining of titanium alloy microstructures. However, during the JEMM process, the machined surface of the workpiece inevitably experiences stray current attacks at low current levels. Due to the formation of a dense passive film on the surface of the titanium alloy under electrochemical action, stray corrosion occurs on the machined surface. Hence, the electrochemical dissolution behavior of titanium alloys at low current densities directly impacts both machining efficiency and quality. This study first analyzed the effects of electrolyte composition and current density on the transpassive potential, breakdown of the passive film, current efficiency, and the dissolved surface on Ti-6Al-4V. The transpassive potential and electrochemical impedance of Ti-6Al-4V were found to be lower in NaCl solution than in NaNO3 solution. In addition, lower current densities enabled higher current efficiency and resulted in a more uniform and flat dissolution surface. Subsequent experiments used these two solutions for JEMM of complex-shaped microstructures on Ti-6Al-4V. The findings demonstrated that, compared to the NaNO3 solution, the use of NaCl solution increases the material removal rate by approximately 30%, enhances the aspect ratio by about 26%, and reduces surface roughness by roughly 58%. This indicates that employing NaCl solution can lead to superior machining efficiency and quality.

Passivation and depassivation of reinforcement steel in alkali-activated materials—A review

This paper reviews the formation and breakdown of passive film on the surface of reinforcement steel in alkali-activated materials (AAMs) considering the characteristics of reaction product and pore solution chemistry. The literature review shows that the pore solution of AAMs has higher concentrations of OH−, Na+, silica and aluminium compared to Portland cement (PC). This relatively high alkalinity contributes to the generation of a passive film, which has positive effects on the corrosion resistance of reinforcement steel embedded in AAMs. The silica-aluminium zeolite layer present on the surface of passive film adsorbs chloride ions and effectively inhibits chloride-induced depassivation. Generally, lower ratios of [Cl−]/[SO42−] and [Cl−]/[S2O32−] potentially inhibit the depassivation of reinforcement steel. The high pH value and the elevated concentrations of HS− of AAMs contribute to the increase of critical chloride content (Ccrit). However, the higher content of reduced sulfide mainly dissolved from slag results in the consumption of dissolved oxygen, which is necessary for the formation of passive film. Generally, the presence of reduced sulfide forms Fe-S complexes on the surface of reinforcement steel in AAMs. Even so, higher corrosion resistance for AAMs is mostly expected with longer depassivation time due to finer microstructure and lower chloride penetration rates compared to PC-based materials. The decrease in pH value in the pore solution of the AAMs is the main factor affecting carbonation-induced depassivation of reinforcement steel, while high concentrations of bicarbonate and carbonate ions inhibit depassivation.

Effects of varying pH on the passive film formation in high-strength anti-seismic rebar

ABSTRACT In this paper, electrochemical measurements (CV, PDP, M-S and EIS) and surface characterisation techniques (SEM, EDS, AFM, TEM and XPS) were used to study the passivation phenomenon in high-strength anti-seismic rebar under varying pH conditions. The results show that a passive film with a polycrystalline structure with a certain roughness is formed on the surface of the rebar. The passive film is mainly composed of Fe oxides and hydroxides, and there are also oxides of Nb, Mn, Si and Cr. The existence of these oxides builds a dense and stable passive film. The passive film is basically stable at 7d, but the early growth of the passive film at higher alkalinity show instability. After 10 days of passivation, with the decrease of pH, the passive film gradually densifies, the pitting potential increased by about 0.03–0.14 V, the carrier density decreased by 30% on average, the phase angle increased slightly, and the ratios of Fe2+/Fe3+ and O2−/OH− increased, resulting in a passive film thickness of 6.2 nm.

On corrosion and passivity of Inconel alloy 625 in HNO3 solution

Exploring the passivity and electrochemical behavior of Inconel alloy 625 in nitric acid solution could open up possibilities for potential applications, either in bulk form or as claddings. Hence, this research investigates corrosion behavior and passivity of Inconel alloy 625 in nitric acid solutions of varying concentrations (0.01–1.00 mol/L) using a range of analytical techniques, including potentiodynamic polarization testing, chronoamperometry measurement, Mott-Schottky (MS) analysis, X-ray diffraction (XRD) approaches, and point defect modeling (PDM). Results demonstrate that corrosion current density does not necessarily decrease with increasing electrolyte concentration (Please check it out). Additionally, the alloy exhibits higher passive film transpassive potentials in more concentrated solutions. Potentiostatic polarization tests reveal an increase in steady-state current densities attributed to the passive films formed in more concentrated solutions. Lower electrolyte concentrations lead to the formation of more intact bilayered passive films. In this context, the formation of passive films is elucidated by examining the generation and annihilation of point defects. The semiconducting behavior of passive layers is further examined through XRD patterns and electrochemical properties. According to PDM, the diffusivity of point defects within the passive films and their respective donor densities can be closely correlated.

Towards electrochemical machining of powder superalloy René 88DT with high surface integrity in different solvent-based electrolytes

Electrochemical machining (ECM) presents numerous applications in the production of aero-engine components. The effects of current density on surface quality during ECM of René 88DT in NaCl-ethylene glycol and NaNO3-aqueous solutions was investigated here. The results indicated that the René 88DT surface has lower sensitivity to current density and more homogeneous electrochemical dissolution in NaCl-glycol solution than in NaNO3-aqueous solution, which results in the suppression of stray corrosion and consistently high surface quality regardless of current density. These strengths are attributed that C2H5O2- and Cl- ions replace OH– ions and combine with alloy ions to form solubles and complexes, which prevent the formation of obstructive passive film, oxide layer, and insoluble electrolytic products. The electrochemical dissolution model in two solutions was established. Furthermore, the high tensile strength and precision machinability of René 88DT in NaCl-glycol solution were also demonstrated.

Electrochemical corrosion behavior and passive film properties of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy coating prepared by laser cladding

The phase composition, microstructure morphology, and corrosion behavior of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy (EHEA) coatings produced via laser cladding were investigated. The research delved into discerning the phase structures and microstructural variations of the EHEA coatings concerning differing Nb compositions. The findings highlighted a direct correlation between Nb content and the volume fraction of the eutectic structure, specifically the FCC/Laves phases. Electrochemical evaluations, including diverse tests such as potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic polarization, Mott-Schottky measurements, and X-ray photoelectron spectroscopy, revealed distinct corrosion behaviors among the EHEA variants. Notably, the Fe2Ni2CrV0.5Nb0.2 coating exhibited relatively superior corrosion resistance compared with Fe2Ni2CrV0.5Nbx (x=0.4,0.6,0.8) coatings, attributed to its lower corrosion current density (Icorr) and the formation of a thicker passive film with prolonged passivation duration. Conversely, the Fe2Ni2CrV0.5Nb0.8 coating, characterized by increased eutectic structures and grain boundary density, yielded a thicker yet non-uniform passive film with higher vacancy defects. This comprehensive exploration into the corrosion behavior and passive film properties of these EHEA coatings provides a reference for designing materials that hold promising implications for future corrosion-resistant material development in industrial parts repair applications.

Excellent combinations of strength-ductility and corrosion resistance in SAF 2205 duplex stainless steel with multi-scale grain distribution

In this work, a multi-scale grain structure was obtained in SAF 2205 duplex stainless steel (DSS) by severe deformation and short-term annealing process. The influence of th is structure on the mechanical properties and electrochemical behavior is systematically investigated. Experimental results indicate that the sample subjected to short-term annealing at 1000 °C (SA-1000 °C) exhibits the best comprehensive properties, with a yield strength (YS) of 652.6 MPa and an elongation (EL) of 39.9 %. Both strength and ductility surpass those of the original sample and long-term annealed (LA-1000 °C) samples. The strength-ductility product is increased by 32 % compared to the original sample and by 18 % compared to the LA-1000 °C sample. The increase in YS is predominantly attributed to dislocation strengthening and grain refinement strengthening, and the heterogeneous microstructure leads to good ductility. Moreover, the multi-scale distribution of the grain structure exhibits enhanced corrosion resistance due to the increased low-Σ grain boundaries and the promotion of stable passivation film formation by a limited number of defects, thereby mitigating the corrosion rate.

Corrosion resistance enhancement for 6Mo austenitic stainless steel through B alloying coupled with a simple pre-aging method

The effect of boron (B) addition coupled with 500 ℃ pre-aging on the corrosion resistance of S31254 was systematically investigated. The results suggested that the diffusion of Mo to grain boundaries (GBs) played a crucial role in enhancing intergranular corrosion resistance. Additionally, the addition of B further promoted the uniform distribution of Mo during the pre-aging process by suppressing Mo segregation at GB. Ultimate, the B microalloying coupled with the pre-aging strategy optimized the composition of passive film through promoting the formation of Mo-rich passivation film, which significantly enhanced the corrosion resistance of Mo-containing stainless steel.

Role of intermediate phases on microstructures, wear and corrosion resistance in new-developed (α + β) titanium alloy

A new (α + β) Ti alloy has been designed and prepared in this work, and the results show that three intermediate phases will be transformed including α′′ martensite, O′ and ω. Upon continuous heating, the α′′ martensite decomposes gradually and disappears before α precipitation. The ω and O′ domains are generated continuously upon aging, and such two intermediate phases co-exist when α phase nucleation occurs. It has been proved that the ω and O′ domains play a direct role in promoting α phase formation. Through the ω and O′ domains assisting α nucleation mechanism, a uniform distribution of fine α precipitates can be obtained after aging. Under the treatment of pre-aging at 300 °C plus aging at 600 °C, the α phase having smallest size and largest number density is obtained, resulting in highest wear resistance and corrosion resistance. For this sample, its average friction coefficient and wear ratio are 0.174 and 3.75×10−4 mm3/(N·m), respectively. During friction tests, the mixture of abrasive wear, adhesive wear and oxidation wear should be activated. Due to the formation of passivation films on the alloy surface, this alloy has exhibited better anti-corrosion properties than Ti-6Al-4 V alloy, and its corrosion current density in 3.5 wt% NaCl solution can be reduced to 1.79×10−8 A·cm−2. Compared with the samples under duplex aging treatments, the direct aged sample also presents outstanding anti-corrosion properties.

Challenges and Progress in Rechargeable Magnesium‐Ion Batteries: Materials, Interfaces, and Devices

AbstractRechargeable magnesium‐ion batteries (RMBs) have garnered increasing research interest in the field of post‐lithium‐ion battery technologies owing to their potential for high energy density, enhanced safety, cost‐effectiveness, and material resourcefulness. Despite substantial advancements in RMB research, a number of intrinsic challenges remain unresolved, such as the strong Coulombic interaction between Mg2+ and the host crystal structure of cathode materials, sluggish Mg2+ diffusion kinetic, poor electrolyte compatibility, and the formation of passivation films on the Mg anode interface. These issues hinder the commercial applications of RMBs. This review provides a comprehensive overview of the progress in key areas of RMB research, including representative magnesium‐ion storage cathode/anode materials and magnesium‐ion conducting electrolytes. Additionally, recent developments in electrode‐electrolyte interface regulations and pouch‐cell fabrication are outlined, highlighting current challenges and the implementation of effective solutions. Finally, future research directions are proposed to guide the development of high‐performance RMBs with practical applications.

Preparation of high-performance electroplated zinc coatings using modified DESs method

This study suggests a new process for zinc recycling in the iron and steel industry, that is, using RHF zinc-containing refined dust as the raw material and ChCl-urea DES (Reline) as the medium. The solid waste from the bottom-turning furnace is leached out, and the resulting zinc is plated directly onto automobile plates. This paper focuses on the utilization of EDTA as an additive to improve the overall performance of the zinc coatings. The results demonstrated that the addition of EDTA realized the modulation of the morphology of the coatings, which made the surface milky white and uniformly bright. The coating consists of hexagonal lamellar grains, dominated by (002) crystalline surfaces that grow at small angles, and the surface flatness is dramatically improved. Most importantly, the hardness of the modified coatings was increased by 70.0% and the coefficient of friction was reduced by about 29.2% compared with the coatings obtained in the pure solution. The addition of EDTA led to the formation of a surface passivation film during the corrosion process, which significantly improved the corrosion resistance of the material surface and the corrosion rate was reduced by 0.355 mm.A−1.

Mechanism of Improving Etching Selectivity for E-Beam Resist AR-N 7520 in the Formation of Photonic Silicon Structures

The selectivity of the reactive ion etching of silicon using a negative electron resist AR-N 7520 mask was investigated. The selectivity dependencies on the fraction of SF6 in the feeding gas and bias voltage were obtained. To understand the kinetics of passivation film formation and etching, the type and concentration of neutral particles were evaluated and identified using plasma optical emission spectroscopy. Electron temperature and electron density were measured by the Langmuir probe method to interpret the optical emission spectroscopy data. A high etching selectivity of 8.0 ± 1.8 was obtained for the etching process. The optimum electron beam exposure dose for defining the mask was 8200 pC/m at 30 keV.

Tailoring surface properties and corrosion resistance of laser shock peened Ti6Al4V alloy by low-temperature annealing

The present study examined the effects of laser shock peening (LSP) and low-temperature annealing after LSP (LSPA) on the corrosion resistance of the Ti6Al4V alloy. The high density of dislocations in the LSP samples contributes to the rapid formation of a TiO₂ passive film during the electrochemical corrosion process. In this study, low temperature annealing was employed to further improve the corrosion resistance. The results indicated that the corrosion resistance of the LSPA samples was significantly improved compared to that of the LSP-treated samples. The LSPA treatment facilitated the pre-generation of a dense TiO2 passive film on the alloy surface via oxidation, reduced corrosion rate, inhibited the penetration of dissolved oxygen and ions present in the sodium chloride solution into the alloy surface. Meanwhile, low-temperature annealing could rearrange and annihilate dislocations, creating subgrains and relaxing non-equilibrium grain boundaries induced by deformation. This process reduced active sites and grain boundary energy, ultimately improving the corrosion resistance of the Ti6Al4V alloy.

Design, microstructure, wear and corrosion behaviors of laser clad FeNiCoCrMo0.3Nbx hypoeutectic high entropy alloys coatings

FeNiCoCrMo0.3Nbx (x = 0.15, 0.40 and 0.55 in molar ratio) hypoeutectic high entropy alloys (HEAs) coatings are prepared by laser cladding (LC) designed by binary eutectic composition strategy. Nbx HEAs coatings present FCC + Laves duplex. Under the joint action of various strengthening mechanisms, the average microhardness of Nb0.15, Nb0.40 and Nb0.55 coatings is as high as 480.5 ± 7, 510.2 ± 6 and 540.6 ± 5 HV0.2, respectively. The unique fluctuating oxide film of the HEAs coatings plays a role in reducing wear, with the specific wear rates of 0.37 × 10−4, 0.22 × 10−4 and 0.18 × 10−4 mm3/Nm for Nb0.15, Nb0.40, and Nb0.55 cladding layers, respectively. The Nbx HEAs coatings displayed excellent corrosion resistance in 0.5 M H2SO4 solution. For Nb0.15 and Nb0.40 HEAs coatings, the increase of Nb promotes the formation of passivation film and improves corrosion resistance. However, the higher dislocation density intensifies the chemical inhomogeneity of the alloy due to excessive addition of Nb, which is not conducive to the corrosion resistance of Nb0.55 HEAs coating. The Nb0.40 cladding layer exhibits better corrosion resistance, and the Icorr is only 1.24 ± 0.6 μA/cm2. Combined with Mott-Schottky (M-S) test, the carrier densities (ND) of three HEAs coatings are increased in the order of Nb0.40 (1.09 × 1021 cm−3) < Nb0.15 (1.83 × 1021 cm−3) < Nb0.55 (3.57 × 1021 cm−3), indicating that the strong protective passivation film is also a key factor to achieve better corrosion resistance.

Improved passivation performance of selective laser melted Inconel 718 alloy via tempering treatment

The passivation performance of the selective laser melted Inconel 718 alloy after tempering treatments was investigated, and the underlying mechanism for the improved passivation film protectiveness was explored. The dislocation reversion and the mitigated segregation of Nb, Mo and Ti at Laves and δ phases decreased the storage energy of lattice distortion were critical factors for the formation of more protective passivation film in chloride-containing solutions. The film formation rate increased after tempering, presenting the increased electric field strength and the decreased dissolution rate accordingly, as well as for the point defect diffusion coefficient and the oxygen vacancy flux therein.

Tribocorrosion behaviour of CoCrMo in simulated body fluid under anaerobic conditions

CoCrMo has been used as an implant material for a long time due to its excellent combination of strength, corrosion resistance and biocompatibility. The formation of a thin passive oxide film on the surface of the material plays a crucial role in its performance. This passive film can be ruptured during contact between two surfaces, but usually reforms in short timescales. However, the reformation of the film depends on the availability of oxygen in the surrounding fluid. The oxygen level in human tissue, cartilage and synovial fluid, around which the implant is situated, is much lower than that in laboratory testing under open-air conditions. Moreover, the local oxygen concentration and pH values in the body vary from patient to patient, depending on the patient's health condition and other factors, which leads to variation in the corrosion resistance of metallic implants. Therefore, an implant that performs well at one time may still experience an undesirable level of corrosion at another. Thus, evaluation of the tribocorrosion of implant materials carried out in open-air conditions does not reflect the actual process the implants undergo once in the body, particularly if there is irritation due to injury or surgery. In this study, we investigate the tribocorrosion behaviour of CoCrMo in bioactive solutions under fully aerobic to anaerobic conditions with varying loads/contact pressures. The anaerobic condition leads to a reduction in wear rate and a reduction in the extent of tribofilm formation but does not have an appreciable effect on friction. The mechanisms are discussed in detail.