Composition Of Passive Film Research Articles

How does the pore solution chemistry influence the passivation of reinforced alkali‐ and salt‐activated slag materials?

AbstractService life predictions of reinforced concrete structures are underpinned by the passivation film chemistry, structure, and thickness. In this work, we present how the formation of passive films at the steel–concrete interface of reinforced alkali‐ and salt‐activated slag materials can be affected by the pore solution chemistry, namely, pH, Eh, and chemical composition. Thermodynamic simulations are used to illustrate the time‐dependent changes to the pore solution chemistry, where estimated electrical conductivities of the pore solution are used as a single‐value parameter to understand the solution complexity and capacity for charge transfer. A set of passivation reactions are proposed to understand the effects of OH− and HS− (reduced sulfur species) competition on the passivation pathways. These passivation reactions become more complex considering that a reducing pore solution might not establish until 3 days into the curing process—a crucial factor explaining the significant differences in the phase composition of passive films of activated slag materials (FeOOH, FeS). This study sheds light on recent progress in understanding these initial passivation reactions, emphasizing the essential role of material design and, therefore, the pore solution chemistry of these cements, along with significant insights for vital research and development concerning the corrosion durability of activated slag materials.

Passive film and surface characterization of Alx(CoCrFeNi)100-x (x = 0, 5, 10, 15, 20) high entropy alloys

The current research on the corrosion resistance of high entropy alloys (HEAs), mainly focuses on the influence of element composition and percentage difference. Considering the almost consistent passivation range with different corrosion resistance contributed by element addition, it inevitably exists obvious differences the passive film properties. The effect of passive film on corrosion behavior of HEA is worthy to be investigated in detail. Considering the microstructure transformation detected by electron probe X-ray microanalysis (EPMA) and surface feedback effect measured by approach curve of scanning electrochemical microscopy (SECM), the passivity of Alx(CoCrFeNi)100-x (x = 0–20) HEAs in 0.5 M H2SO4 solution has been investigated by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the passive film is thick and dense at low Al content (5%), which shows excellent corrosion resistance. However, with the increase of Al content, the corrosion resistance of passive film deteriorates gradually. XPS are adopted to detect film composition to explain the reason of film property change. The results suggest that there are more oxidized states of Al and less oxidized states of Cr in the passive film of HEAs with Al addition. The dominate semiconductor characteristics of Alx(CoCrFeNi)100-x with Al addition change from p-type to n-type. All results indicate that the addition of Al has a significantly influence on the composition and properties of passive film on the Alx(CoCrFeNi)100-x alloys surface.

Effect of minor gallium addition on corrosion, passivity, and antibacterial behaviour of novel β-type Ti–Nb alloys

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

Cooperative effect of Cr and Al elements on passivation enhancement of eutectic high-entropy alloy AlCoCrFeNi2.1 with precipitates

In conventional corrosion-resistant alloys, precipitation usually reduces corrosion resistance severely by weakening passive films locally. In this work, we found that the aging-treated AlCoCrFeNi 2.1 samples, which have abundant nanosized L 12 and body-centered cubic (BCC) precipitates in the lamellar face-centered cubic (FCC) and B2 phases, displayed better corrosion resistance than solution-treated AlCoCrFeNi 2.1 samples without precipitates. In the AlCoCrFeNi 2.1 alloy, the FCC phase with L1 2 precipitates and the B2 phase with BCC precipitates were protected by passive films enriched with Cr and Al elements, respectively. Moreover, the Al-rich passive film of the B2 phase was less stable than the Cr-rich passive film of the FCC phase, so B2 phase dissolved preferentially. The Cr-rich passive film of the FCC phase remained stable with the formation of Al-rich L1 2 precipitates inside the phase because those precipitates with the size of ∼5 nm were too small to affect the composition of the Cr-rich passive film. The formation of Cr-rich BCC precipitates within the B2 phase increased the content of the Al element inside the phase, improving the stability of Al-rich passive film on the B2 phase. Furthermore, BCC precipitates with the size of ∼30 nm were protected by Cr-rich passive film, which could inhibit the expansion of corrosion pits. Thus, the corrosion resistance of eutectic high-entropy alloy AlCoCrFeN 2.1 was unprecedentedly enhanced by the precipitation of BCC precipitates. Our study could provide an attractive strategy for designing high-entropy alloys with excellent corrosion resistance and high strength.

Synchrotron XPS and Electrochemical Study of Aging Effect on Passive Film of Ni Alloys

To investigate aging effect on the passive film of Ni23Cr15Mo and Ni22Cr9Mo3Nb, synchrotron-based X-ray photoelectron spectroscopy (XPS) was used to analyze the structure and composition of the air-formed passive film on the alloys. The corrosion resistance of the two Ni alloys in 1 M NaCl solution was evaluated with electrochemical cyclic polarization measurement. The synchrotron XPS measurement provided detailed information about chemical states of alloying elements in the passive film, showing that the passive film consists of an inner oxide layer and an outer hydroxide layer. The XPS data allowed precise determination of the chemical composition and the thickness of the outer hydroxide layer, the inner oxide layer, and the underlying subsurface alloy layer. The Cr-oxide in the inner layer grows thicker with aging time, leading to Cr-depletion in the subsurface region. Mo and Nb in the alloy form mixed oxides and hydroxides, and aging in air leads to transformation of the lower valence oxides into higher valence oxides. The freshly formed oxide film exhibits similar barrier properties as the aged oxide film. The stability of the passive film formed on Ni22Cr9Mo3Nb seems to be better than that on Ni23Cr15Mo.

Passivation of Ni-Cr and Ni-Cr-Mo Alloys in Low and High pH Sulfate Solutions

The kinetics of passive oxide film formation, its thickening, and composition on Ni-22Cr and Ni-22Cr-6Mo wt% alloys were investigated at selected anodic potentials. Experiments were performed in acidic and alkaline sulfate environments using a number of characterization techniques including a combination of potentiodynamic polarization, on-line atomic emission spectro-electrochemistry (AESEC), in situ potentiostatic passive film growth, along with in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS). The roles of solution pH and Mo on the passivation behavior were discussed in terms of thermodynamic and kinetic factors governing passivation. The pH was found to have an impact on the relative chemical compositions of passive film of the Ni-22Cr alloy but not noticeably for the Ni-22Cr-6Mo alloy. Ni-rich films formed early during the passivation process while Cr(III) enrichment was observed at longer times, albeit less extensively than observed previously in Cl− solutions. The fraction of Cr(III) cations also increased with alloying of Mo at low and high pH demonstrating a strong effect of Mo on Cr(III) content during aqueous passivation in Ni based superalloys, however, a larger effect is seen in Cl−. This is a noteworthy finding as Mo is usually assumed to mainly influence pit and crevice stabilization.

Corrosion Behavior of Hastelloy C-276 in Hydrochloric and Sulfuric Acid

This research was conducted to determine the corrosion rate by varying the concentration of the solution against hydrochloric acid and sulfuric acid. The method used is open circuit potential (OCP) and Tafel plot. Based on the research conducted, Hastelloy C-276 was more prone to get oxidized in sulfuric acid rather than hydrochloric acid. It can be seen from the OCP value of sulfuric acid was much more negative than that of hydrochloric acid as of-1.5 V for 0.5 M sulfuric acid and-0.2 V for hydrochloric acid. The corrosion rate of Hastelloy C-276 in sulfuric acid was also higher compared to same alloy in hydrochloric acid. At the most concentrated solution, 0.5 M, the corrosion rate of sulfuric acid reached 0.39 mmpy and as for corrosion cate in hydrochloric acid, only at 0.16 mmpy. It is thought that there was a difference of passive film composition for both solutions. Keywords: Hastelloy C-276, Corrosion, Hydrochloric acid, Sulfuric acid.

Effect of chloride concentration on the properties of passive film formed on Q235 steel in simulated concrete pore solutions

PurposeThis paper aims to study the effect of chloride concentration on the properties of passive film formed on Q235 steel in simulated concrete pore solutions.Design/methodology/approachMott–Schottky analysis and electrochemical impedance spectroscopy were used to study the passive film of Q235 steel in simulated concrete pore solution. X-ray photoelectron spectroscopy was used to analyze the composition of passive film on Q235 steel.FindingsWhen the chloride concentration is below the chloride threshold value, open circuit potential (OCP) and Rct gradually increases and donor concentration (ND) remains unchanged with the increasing immersion time. When the chloride concentration exceeds chloride threshold value, OCP and Rct decreases after a temporary increase and ND increases. The linear region of the Mott–Schottky curve lost its linearity. The electrochemical process control step is changed from charge transfer control to oxygen diffusion control. As the chloride concentration increases, the FeO content in the passive film increases and the Fe2O3 content decreases. Chloride can destroy the outer layer of passive film and introduce impurities.Originality/valueThe effects of chloride and immersion time on the change process of passive films on Q235 steel in simulated concrete pore solution were studied using electrochemical methods. The mechanism of chloride destroying passive film was analyzed.

Mechanism of surface corrosion resistance of 304 stainless steel processed by nanosecond laser pulses

AbstractA nanosecond pulsed fiber laser was used to modify the surface of 304 stainless steel. The compactness, microstructure, chemical composition, and corrosion resistance of the stainless steel passive film were observed by the blue dot detection method, scanning electron microscopy, x‐ray photoelectron spectroscopy, and electrochemical methods. The influence of different laser fluences on the stability and corrosion resistance of the stainless steel passive film was studied. The results show that with increasing laser fluence, the discoloration reaction time of the stainless steel surface increases first and then decreases, while the surface roughness decreases first and then increases. When the laser fluence is lower than 11.19 J/cm2, a compact and uniform passive film is formed. When the laser fluence is larger than this value, the stainless steel substrate is prone to secondary corrosion. Chromium oxides are enriched in the passive film, and the anodic dissolution rate decreases, which promotes a positive shift in the corrosion potential of the stainless steel, decreases the corrosion current density and increases the polarization resistance and the corrosion resistance. The surface corrosion resistance is thus significantly improved.

Passive Film Structure and Corrosion Initiation in Al Alloys with Far-from-Equilibrium Compositions and Microstructures

Al alloys with far-from-equilibrium compositions and microstructures are reported to possess high corrosion resistance and strength. These alloys produced are by non-equilibrium processing techniques such as high-energy ball milling, sputtering, and ion implantation. Depending on the processing techniques and conditions, the microstructure of the alloys could be heterogeneous. For example, alloys produced by high-energy ball milling and subsequent consolidation comprise a matrix with high solid solubility of the solute and uniformly distributed secondary phases. Such a heterogeneous microstructure is expected to influence the passive film composition and localized corrosion mechanisms. In the present study, passive film composition on the ball-milled alloys was studied using a combination of scanning transmission electron microscope, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry (SIMS). Additionally, pits and regions near pits were investigated which helped in understanding factors causing pit initiation and repassivation.

Enhanced Passivity and Resistance to Pitting of New Cr-Fe-Co-Ni-Mo Multi-Principal Element Single-Phase Alloys

Extensive thermodynamic calculations exploring the large composition space of the Cr-Fe-Co-Ni-Mo system were performed in order to design new multi-principal element single-phase fcc alloys with enhanced passivity and resistance to localised corrosion.This presentation will cover several aspects from design to production, passivation, surface analysis and pitting resistance of alloys with up to 15 at.% Mo . The newly designed and produced quinary alloys, Cr25Fe25Co5Ni40Mo5 and Cr15Fe10Co5Ni60Mo10 (at.%) show superior resistance to localised corrosion in chloride solution. The chemical states, composition and stratification of passive films were investigated by X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The resistance to pitting was measured after pre-passivation of the alloy surfaces in Cl--free acidic solution.Stratification of the passive films was observed, with Cr, Fe, Ni,Mo oxides and hydroxides in the outer layer and Cr oxide in the inner layer.The amounts and distribution of chloride ions that penetrated into the passive films were also investigated. In-depth profiles show that, on the Mo-bearing alloys, chloride ions do not penetrate the Mo-enriched outer layer of the oxide film.A direct link between the structural and chemical nature of passive films and the resistance to pitting in chloride solution was observed. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (advanced grant agreement # 741123)

Different passivation behavior between α and β phases of Ti-6Al-4V in HCl solutions under oxygenated/deoxygenated conditions

The passivation behavior of the α and β phases in a Ti-6Al-4V alloy under different oxygen conditions was investigated. The α and β phases exhibit a stronger tendency toward galvanic corrosion under deoxygenated conditions, but not under oxygenated conditions. From in situ scanning Kelvin probe force microscopy (SKPFM) method we find the α oxidation rate is higher. Meanwhile, the passive film composition and structure of α's and β's were compared by using FIB-STEM. The α phase has a lower Al/V element concentration and more atoms in the matrix to participate in the annihilation reaction of metal vacancies. Furthermore, based on first principles and statistical mechanics, the alloying element Al/V alters the Ti atoms coordination environment and reduces the Ti atoms adsorption potential.

Consequences of mobile and trapped hydrogen on the dissolution kinetics and pitting processes of an austenitic stainless steel

The effect of cathodic hydrogen charging on corrosion behaviour of an AISI 316 L austenitic stainless steel in acidified sodium chloride is studied. A large set of electrochemical and physico-chemical methods allows to demonstrate that the oxide initial growth steps are little affected while the dissolution kinetics increase drastically in relation to hydrogen oxidation. This effect is mainly reversible with hydrogen desorption, highlighting the role of mobile hydrogen. Defects induced by hydrogen could be responsible for a small irreversibility. Hydrogen promotes the pitting processes, but seems to have few impacts on the passive film composition and thickness.

Structure and Composition of the Passive Film Studied Using a Combination of X-Ray Photoelectron Spectroscopy, Secondary Ion Mass Spectrometry, and Scanning Transmission Electron Microscopy

Characteristics of the passive film and the ability of an alloy to repassivate in any event of passive film breakdown control the corrosion. Studying the passive film has been of great interest since late 1836 when first-time iron was called altered iron. Significant progress in understanding the passive film composition and factors causing breakdown, pit growth and repassivation has been made over the past several decades. However, the role of metallurgical parameters on the passive film structure, composition, crystallinity, chloride ion interaction needs further research attention. The composition and structure of the passive film in Al alloys and stainless steels have been studied using advanced analytical techniques with high depth and spatial resolution have been presented herein. We have used a combination of time of flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron microscopy (XPS), and scanning transmission electron microscopy to study the passive film and pits. The surface film was studied after potentiostatic polarization as well as immersion tests in NaCl solution with immersion time varying from 30 minutes to four weeks. The crystallinity of the passive film was dependent on the composition and microstructure of the alloy. The incorporation of chloride and its distribution in the passive film was dependent on the material and conditions used to produce the passive film. The thickness of the passive film was found to depend on the microstructure of the underlying substrate. The role of the microstructure on passive film structure, breakdown, and repassivation or pit growth will be discussed.

Understanding the passivation behavior and film chemistry of four corrosion-resistant alloys in the simulated flue gas condensates

The passivation behavior and passive film composition of 254SMO, 316 L, 310 S stainless steels, and C276 nickel-based alloy in simulated desulfurization flue gas condensates at 60 °C were studied. The four alloys exhibited similar passivation behavior and capacitive properties in simulated flue gas condensate at 60 °C. Mott-Schottky analysis is performed to obtain semiconductor properties such as semiconductor type, carrier density, flat-band potential of the passive film. Electrochemical experiments show that four alloys form protective passive films in simulated flue gas condensate, among which 310 S has the best corrosion resistance, while C276 has the worst corrosion resistance, and the other two stainless steels have similar corrosion resistance. The passive film of the three stainless steels is mainly composed of Cr and Fe. The film generated on 254SMO and 316 L have similar compositions, while that of C276 is mainly composed of Cr, Fe, Ni, and a small amount of Co and W. Compared with the passive film formed by natural immersion, the electrochemically formed passive film promotes the enrichment of Cr in 254SMO and 310 S and the enrichment of Fe in C276.

Real-time evolution and characterization of passive films on individual ferrite and austenite phases of duplex stainless steel

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

Unravelling the Role of Nitrogen in Surface Chemistry and Oxidation Evolution of Deep Cryogenic Treated High-Alloyed Ferrous Alloy

The role of nitrogen, introduced by deep cryogenic treatment (DCT), has been investigated and unraveled in relation to induced surface chemistry changes and improved corrosion resistance of high-alloyed ferrous alloy AISI M35. The assumptions and observations of the role of nitrogen were investigated and confirmed by using a multitude of complementary investigation techniques with a strong emphasis on ToF-SIMS. DCT samples display modified thickness, composition and layering structure of the corrosion products and passive film compared to a conventionally heat-treated sample under the same environmental conditions. The changes in the passive film composition of a DCT sample is correlated to the presence of the so-called ghost layer, which has higher concentration of nitrogen. This layer acts as a precursor for the formation of green rust on which magnetite is formed. This specific layer combination acts as an effective protective barrier against material degradation. The dynamics of oxide layer build-up is also changed by DCT, which is elucidated by the detection of different metallic ions and their modified distribution over surface thickness compared to its CHT counterpart. Newly observed passive film induced by DCT successfully overcomes the testing conditions in more extreme environments such as high temperature and vibrations, which additionally confirms the improved corrosion resistance of DCT treated high-alloyed ferrous alloys.

Anodic Dissolution Behavior of Al-Y Alloy in LiCl-KCl Eutectic and Its Passivation Inhibited Aided by LiF

The anodic dissolution behaviors of solid Al-Y alloy were investigated in LiCl-KCl eutectic without and with LiF by electrochemical techniques. The passivation phenomenon was observed in LiCl-KCl eutectic and disappeared when LiF concentration higher than 3% by weight. The results of XRD and SEM-EDS indicated the composition of passive film was Al2O3. Meanwhile, the dissolution rate and current efficiency were also calculated using ICP-AES. Furthermore, the mechanism of LiF inhibiting passivation was explored and found the addition of LiF could increase alumina solubility. The kinetic properties were compared in LiCl-KCl and LiCl-KCl-LiF melts. The transfer resistance decreased obviously in LiCl-KCl-LiF melts.

Effect of rust inhibitor on the composition of steel passive film in carbonized concrete

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

Influence of Homogenization and Annealing Temperatures on the Microstructure, Mechanical Properties, and Passive Properties of Cold Rolled 2205 Duplex Stainless Steel

The effects of homogenization, cold working, and subsequent annealing treatment were studied on the microstructural evolution, mechanical properties, and passive properties of duplex stainless steel (DSS). A hot-rolled 2205 DSS was subjected to two processing routes. In one, the DSS goes through an extra homogenization step at 1100 °C for 1800 s before cold rolling. After cold deformation (~75%) the specimens were isothermally annealed at 900, 1000, and 1100 °C for 180 s. The microstructure evolution was studied by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XDR). Mechanical properties were evaluated by microhardness and tensile tests. The electrochemical behaviors were investigated by potentiodynamic measurements, electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis (MS). Chemical composition of the lowest corrosion resistant passive film was assessed by X-ray photoelectron spectroscopy (XPS). Homogenization before cold rolling lowered strain hardening, slowing the microstructural transformation process. The thermomechanical process did not change the semiconductor type of the passive films. However, grain refinement after annealing improved the corrosion resistance in borate buffer solution. Cold rolling significantly decreased the corrosion resistance. The passive film of the specimen homogenized before cold rolling had the lowest corrosion resistance and high amounts of Cr(OH)3 and FeO.