Stability Of Passive Film Research Articles

Influence of oxygen partial pressure on the passivation and depassivation of super 13Cr stainless steel in high temperature and CO2 rich environment.

The passivation and depassivation characteristics of Super 13Cr stainless steel were examined under a range of oxygen partial pressures within a high-temperature (120 ℃) and high-pressure (3MPa) CO2 atmosphere. We performed comprehensive electrochemical assessments, encompassing open-circuit potential monitoring, electrochemical impedance spectroscopy, and linear polarization resistance analysis, to evaluate the corrosion resistance and passive film stability. The results demonstrate that the addition of low O2 partial pressures enhanced the stability of the passive film, while higher O2 levels led to the loss of the passivation properties of Super 13Cr stainless steel. The study elucidates the pivotal role of oxygen in the corrosion mechanisms affecting Super 13Cr stainless steel, presenting valuable data to enhance for integrity management in severe environmental conditions.

Optimizing the corrosion resistance of additive manufacturing TC4 titanium alloy in proton exchange membrane water electrolysis anodic environment

Titanium alloys are commonly used as the bipolar plate material in proton exchange membrane water electrolysis (PEMWE). However, traditional machining methods are difficult to process titanium alloy parts, which further increases the cost of bipolar plates. The wire-arc directed energy deposition (WA-DED) additive manufacturing (AM) technology is low cost and high utilization of material. However, the undesirable microstructure always restricts the performance improvement. In this work, the electrochemical corrosion and passive characteristics of wrought TC4 and WA-DED AM TC4 alloys in the simulated PEMWE anode environment were investigated. The microstructure of AM TC4 alloy was optimized and the corrosion resistance was enhanced by heat treatment. The results indicate that the corrosion resistance of AM TC4 alloy is better than wrought TC4 alloy, and appropriate heat treatment can further improve the stability of passive film. Compared to wrought TC4, Ti −β phase fraction of AM TC4 decreased from 9.6 % to 1.3 %, and the heat treatment further reduced Ti −β phase fraction of AM TC4-850 and AM TC4-1050 alloys to 0.8 % and 0.1 %. The passive film thickness of wrought TC4, AM TC4, AM TC4-850, and AM TC4-1050 alloys calculated with the Power-Law model were 0.5 nm, 1.76 nm, 1.94 nm, and 2.02 nm, respectively. After heat treatment of 1050 °C, AM TC4-1050 alloy exhibited the best corrosion resistance, showing the lowest corrosion current density of 54 μA/cm2 and the lowest passive current density of 19.5 μA/cm2. Moreover, Ti oxide contributed most to the composition of passive film. In AM TC4-1050 alloy, the percentage of Ti oxides was 80.9 %, showing the best corrosion resistance.

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.

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.

A novel BCC-L21-BCC hierarchical heterostructure high entropy alloy with excellent corrosion resistance and mechanical properties in as-cast state

In this paper, a novel as-cast CrFeNiAl0.35Si0.1Ti0.1 high entropy alloy (HEA) with micron-to-nano hierarchical heterostructure was designed, and its microstructure, mechanical properties and corrosion resistance have been systematically investigated. It is found that, this novel HEA exhibits well-dispersed L21 phases with various sizes from micron-scale to nano-scale in the BCC matrix, while nano-sized BCC lamellas could also emerge in the L21 phase with large diameter. Moreover, this HEA exhibits not only excellent corrosion resistance in 3.5 wt.% NaCl solution that close to super-stainless steels, but also high mechanical properties combining yield strength of 1712±56 MPa, compressive plasticity of 21.2%±0.5% and hardness of ∼560 Hv. Such outstanding comprehensive properties for this HEA are possibly resulted from the complex hierarchical BCC-L21-BCC heterostructure with stable passive film and low diversity in work function between different phases. This work provides a novel route in the development of high-performance corrosion-resistant HEAs for structural and coating 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.

Effects of Ti and Y on resistance to corrosion in Fe–Cr-X Alloys

The effect of Ti and Y on the corrosion behavior of the FeCr alloy was investigated in a 3.5% NaCl solution. Ti was found to inhibit the formation of the σ phase, significantly reducing the presence of pitting in the material. In addition, Ti acted indirectly on the oxide layer, increasing the concentrations of Cr and Fe, consequently generating a probable enrichment of Cr2O3 and FeOOH, which enabled the formation of a more stable passive film resistant to attack by chloride ions. On the other hand, Y caused the precipitation of a phase identified as Fe17Y2, which was accompanied by an elongated σ phase, both located at the grain boundaries, besides the formation of Cr23C6 and Y2O3. Its addition resulted in an improvement in the corrosion resistance of the FeCr alloy by reducing the precipitation of the σ phase. However, its effect was much less important than that of Ti, since the results showed that the FeCrY alloy was still highly susceptible to localized forms of corrosion.

Microstructures and corrosion behaviors under sodium chloride aqueous conditions of Co-free non-equiatomic Al0.32CrFeTi0.73(Ni1.50-xMox) (x=0, 0.23) high entropy alloys

High entropy alloys (HEAs) were prepared using a vacuum arc melting method. The effect of Mo partially substituting Ni on the crystal structure and corrosion behaviors was studied. The results show that the HEAs exhibited a multiphase complex crystal structure which was composed of a BCC matrix and several intermetallic phases. The HEAs showed good corrosion resistance despite multiphase heterogeneity. But cyclic polarization showed that the HEAs were susceptible to pitting corrosion. Selective corrosion of Cr-depleted phases after polarization tests was attributed to the galvanic corrosion between Cr-depleted and Cr-rich phases. The spontaneous passive films on the HEAs surface were characterized by p-type semiconductor. Existence of Mo element of the HEAs accelerated passivation reaction kinetics, improved the stability of passive film, accordingly, acquired better general and pitting corrosion resistance.

Effect of combination of ultraviolet radiation and biocide on fungal-induced corrosion of high-strength 7075 aluminum alloy

The effect of ultraviolet (UV) radiation and biocide benzalkonium chloride (BKC) on fungal-induced corrosion of AA7075 induced by Aspergillus terreus (A. terreus) was deeply studied using analysis of biological activity, surface analysis, and electrochemical measurements. Results demonstrated that the planktonic and sessile spore concentrations decline by more than two orders of magnitude when UV radiation and BKC are combinedly used compared with the control. UV radiation can inhibit the biological activity of A. terreus and influence the stability of passive film of AA7075. Except for direct disinfection, the physical adsorption of BKC on the specimen can effectively inhibit the attachment of A. terreus. The combination of UV radiation and BKC can much more effectively inhibit the corrosion of AA, especially pitting corrosion, due to their synergistic effect. The combined application of UV radiation and BKC can be a good method to effectively inhibit fungal-induced corrosion.

On electrochemical corrosion of mechano-activated and thermally processed AlxCryNiz 2D decagonal quasicrystalline structures and crystalline approximants

This article represents a pioneering study centered on the corrosion kinetics of untreated and thermally processed mechano-synthesized AlxCryNiz two-dimensional decagonal quasicrystalline structure and crystalline approximants. It sheds light on the distinguished corrosion behavior of untreated and heat-treated mechano-synthesized Al72Cr15Ni13 and Al86Cr12Ni2 alloys, including a wide diversity of miscellaneous intermetallic phases. A comprehensive characterization was performed to analyze crystallographic structure and thermal characteristics of AlxCryNiz powder particles. Electrochemical evaluations of the mechano-synthesized Al72Cr15Ni13 and Al86Cr12Ni2 specimens and their heat-treated counterparts were conducted under cyclic potentiodynamic polarization tests with 0.1 mol/L Na2SO4 (pH=2) and 3.5% NaCl (pH=8.5) electrolytes at room temperature, respectively. Al72Cr15Ni13 two-dimensional decagonal quasicrystalline phase was attained following 6 h mechano-synthesis and subsequent annealing treatment at 1035°C. There is no evidence of quasicrystal formation in the Al86Cr12Ni2 alloy system after 6 h mechano-synthesis and successive thermal processing at 445 and 570°C. In this study, we conducted the first investigation into electrochemical performance of both Al72Cr15Ni13 and Al86Cr12Ni2 intermetallics. Both Al72Cr15Ni13 and Al86Cr12Ni2 alloys develop a protective passive film in 0.1 mol/L Na2SO4 electrolyte. It was determined that 6 h mechano-synthesized Al72Cr15Ni13 sample, subjected to annealing at 1035°C, stands out in the Al-Cr-Ni alloy systems for applications necessitating exceptional corrosion resistance, passivation behavior, and minimal susceptibility to pitting corrosion when compared to other tested counterparts. This alloy is characterized by a corrosion current density of 3.73 µA/cm2 and a corrosion potential of -0.16 V(vs. Ag/AgCl), revealing a remarkably stable passive film up to a current density of 0.02 A/cm2 and a potential of 2.41 V(vs. Ag/AgCl) within 0.1 mol/L Na2SO4 medium. Likewise, it exhibited a drastically diminished corrosion current density of 11.65 µA/cm2 and a reduced corrosion potential of -0.27 V(vs. Ag/AgCl) within 3.5% NaCl electrolyte, attributed to the formation of two-dimensional decagonal quasicrystalline phase and hexagonal δ-Al3Ni2 crystalline approximant at 1035°C. It also encompassed a re-passivation current density and potential of 50.35 µA/cm2 and -0.04 V(vs. Ag/AgCl), respectively, within the latter solution. Its corrosion mechanism may be ascribed to a two-step surface precipitation process: initially, Al dissolves into a hydroxide, succeeded by the formation and precipitation of Al oxides, such as NaAlO2 and Al2O3∙xH2O.

Corrosion resistance and passive film stability of laser direct energy deposited TiVZrNbAl lightweight multi-principal element alloy

This work reports the corrosion behaviour of a novel laser direct energy deposited Ti45V30Zr12Nb12Al1 lightweight multi-principal element alloy (MPEA) in a 0.6 M NaCl solution. The MPEA exhibits superior corrosion resistance to typical titanium alloys, including Ti80. Its excellent corrosion resistance is attributed to a passive film with bipolar semiconducting behaviour and an amorphous structure. This unique feature inhibits anion permeation from the electrolyte and cation dissolution from the passive film. Further analyses revealed that Nb alloying effectively reduces the point defect density in the passive film, enhancing its ability to resist attacks by chloride ions.

Role of sodium citrate in electrochemical behavior of reinforcing steel exposed to carbonated alkali-activated fly ash contaminated with chloride ions

Alkali-activated fly ash (AAFA) is considered as a promising alternative to ordinary Portland cement (OPC). However, the lack of calcium hydroxide in AAFA leads to an increased susceptibility to carbonation, thereby resulting in a decreased alkalinity of pore solutions in AAFA and significantly impacting the stability of steel passive films. To improve the corrosion resistance of steel in carbonated AAFA environments, sodium citrate was used as an environmentally-friendly corrosion inhibitor with three carboxylate groups. In this context, the corresponding electrochemical behavior of steel exposed to carbonated AAFA solutions with different concentrations of citrate was studied. In spite of the detrimental effect on the initial passivation behavior, sodium citrate was found to effectively improve the corrosion resistance to chloride attack for steel owing to a synergistic inhibition effect of adsorption film and precipitates on the steel surface. In addition, the correlation of citrate concentration and inhibition mechanism in carbonated AAFA solutions was revealed.

Corrosion and corrosion-friction effects induced by cutting fluid on binderless WC matrix composite and cemented carbide

The corrosion behavior of WC-4.3 wt%MgO-2wt.%ZrO2 composite in alkaline solution with 5 % oil-based cutting fluid as medium was studied by electrochemical and microstructure analysis methods. The results showed that WM2Z composite has better corrosion resistance than YG3 and YG6 in alkaline environment. A stable passivation film was formed inside the WC phase after dissolution on the surface, which was the key reason for its high corrosion resistance. However, large areas of WC phase fell off in cemented carbide. In the process of corrosion-friction coupling experiment, due to the more excellent corrosion resistance and mechanical properties of WM2Z composites, the corrosion resistance and friction properties of WM2Z composites are better than that of YG3 cemented carbide. The corrosion-friction coupling effect on WM2Z was low, and the degree of damage to the topography after the experiment was relatively light.

Comparison of microstructure, mechanical properties and corrosion resistance of Ti6321 alloy by wire-arc directed energy deposition versus rolling

Ti-6Al-3Nb-2Zr-1Mo (Ti6321) alloy, as a new type of marine metal, has excellent corrosion resistance and mechanical properties, but its application is restricted by the traditional manufacturing processes. Wire-arc directed energy deposition (DED) has some incomparable advantages in the efficient and customized fabrication of large/extra-large components, which makes it become a potential manufacturing process for the fabrication of Ti6321 alloy components. However, the formability and corresponding performance evaluation of wire-arc DEDed Ti6321 alloy remains unknown. Here, for the first time, the microstructure, mechanical properties and corrosion resistance of wire-arc DEDed Ti6321 alloy was characterized and compared with rolling, and the relationship between process-microstructure-properties was established. Results show that the full lamellar α+β structure of the DEDed specimens demonstrated better corrosion resistance than the near equiaxed αp + lamellar αs/β structure of rolled specimens. This is owed to the higher grain boundary density, more content of β phase and slighter element segregation of the DEDed specimens, resulting in a more uniform and stable passivation film on its surface. Meanwhile, the grain morphology and low dislocation density of the DEDed specimens causing in lower tensile strength (decrease by ∼15.6 %) but higher elongation (increase by ∼41.5 %) than the rolled specimens. Due to the presence of coarse prior-β grains, the DEDed specimens show expected anisotropy in building direction and traveling direction, but overall exhibits sufficient mechanical properties, which exceed the execution standard. This study verified the feasibility of fabricating Ti6321 alloy with idea properties by wire-arc DED, and provides a potential strategy for the production and practical application of large-size Ti6321 alloy components.

Synergistic improvement of pitting and wear resistance of laser powder bed fusion 420 stainless steel reinforced by size-controlled spherical cast tungsten carbides

The spherical cast WC/W2C is selected to produce a martensitic stainless steel-based composite using the laser powder bed fusion technique. W and C reacted with Fe and Cr, creating a strong bond between the particles and the matrix, reducing the wear rate by over 98 %. W and C diffuse to the matrix, increasing the hardness over 100 HV0.5. The interface between cast WC/W2C and matrix is sensitive to pitting corrosion through galvanic effects. However, the formation of austenite and WO3 from spherical cast WC/W2C decomposition improves the critical pitting potential and passive film stability.

The corrosion properties of ferritic stainless steel with varying Cr and Mo contents in the early stages of a simulated proton exchange membrane fuel cell environment investigated using experimental and joint calculation method HKD

The initial corrosion resistance of ferritic stainless steels with various Cr and Mo levels in simulated fuel cell environments is evaluated using the HKD calculation method and electrochemical tests. HKD utilizes high-throughput DFT, KMC, and AIMD statistical coverage calculations to study passivation film development and ion/molecule adsorption behaviors, like O2-, F-, H2O, and OH-. Super-high Cr-containing Mo steel shows reliable corrosion resistance due to their stable structure and effective passivation film integrity at various F- concentrations and pH values. Furthermore, the impact of F- competes with O2-, influencing film formation as pH lowers and concentration rises.

Optimization of surface oxide chemistry for enhanced corrosion resistance of AlMnFeCoNi – Carbon nanotube composite coatings

AlMnFeCoNi high entropy alloy (HEA) composite coatings with different volume fractions of carbon nanotubes (CNTs) (from electrolyte bath with 2.5, 4, 5, 15, 17.5, 20 mg/L of CNT) were electrodeposited onto mild steel. Corrosion rate of HEA-CNT coatings exhibited non-monotonic variation with increasing CNT volume fraction. Corrosion resistance initially increased and then decreased with increasing CNT addition. Highest corrosion resistance exhibited by coating produced from 5 mg/L of CNT was due to higher surface uniformity, least surface roughness (732 ± 2.92 nm), induced hydrophobicity (115.44 ± 0.29˚) and presence of stable passive oxide films (Al3+, Co2+, Fe3+).

Stability of passive film and pitting susceptibility of 316 L stainless steel in the aggressive oilfield environment containing Cl−-CO2-O2

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.

Superior corrosion-resistant Zr-Ti-Ag thin film metallic glasses as potential biomaterials

Low-cost and non-cytotoxic ternary Zr-Ti-Ag thin film metallic glasses (TFMGs) were synthesized by DC magnetron sputtering. Results revealed that Ag addition enhanced the crystallization resistance and thermal stability of TFMGs. An appropriate Ag addition favored the mechanical property and corrosion resistance of TFMGs, while the excessive Ag addition had the opposite effect. Moreover, Ag did not directly form the passive film but altered the passive film stability and anti-corrosion capacity of TFMGs by inducing the disordered atomic arrangement, forming a dense microstructure, and tuning the corrosion-resistant Zr and Ti components. With low Young’s modulus of 116.2 GPa and passive current density of 0.45 × 10−7 A/cm2, the TFMG with an Ag target sputtering power of 11 W exhibited superior corrosion resistance, suggesting its application potential as biomaterials.

Effect of Temperature on the Corrosion Behavior of a Al2Cr5Cu5Fe53Ni35 Multi-Principal Element Alloy (MPEA) in Simulated Soil Environments

The effect of varying temperatures (15, 35, and 45 °C) on the corrosion behavior of a new single-phase distorted face-centered cubic (fcc) Al2Cr5Cu5Fe53Ni35 multi-principal element alloy (MPEA) was studied in simulated soil environments (NS4 solution). X-ray diffraction and electron backscattered diffraction were used to confirm the presence of a single phase throughout the microstructure. Electrochemical tests such as electrochemical impedance spectroscopy and linear polarization resistance were performed to evaluate the interfacial behavior and corrosion rate at various test conditions. Additionally, cyclic potentiodynamic polarization (CPP) tests were also carried out at the selected temperatures to study the pitting behavior of the MPEA. Surface characterization techniques such as X-ray photoelectron spectroscopy and scanning electron microscopy were used to identify the nature of the passive film formed in such complex materials as well as study the pitting characteristics after CPP testing. A stable passive film was found to be present all tested temperatures with the absence of preferential sites for pitting due to homogenous element distribution.