Structure Of Passive Film Research Articles

Super-impermeable polyurethane coating constructing inspired by passive film structure

Super-impermeable polyurethane coating constructing inspired by passive film structure

Passive behavior of TNB intermetallic and Inconel 625 in electrochemical machining

The TNB alloy, a novel lightweight material, shows great potential for application in crucial aero-engine parts. This paper reveals the passive behavior of TNB alloy in electrochemical machining (ECM), Inconel 625 alloy was used for comparison. The polarization curve shows that TNB and Inconel 625 alloys have obvious passivation phenomenon at the passivation potential. Research reveals that the passive film structure of TNB alloy comprises a compact layer (about 7 nm) and a loose layer (about 13 nm), with significantly higher corrosion resistance in the compact layer compared to the loose layer. In contrast, the passive film structure of Inconel 625 alloy is a single layer with a thickness of approximately 11 nm. It was also found that the passive film composition for TNB alloy is TiO2, Al2O3, and Nb2O5. The composition of passive film for Inconel 625 alloy is NiO, Ni(OH)2, Cr2O3, MoO3, Nb2O5, FeO, and Fe2O3, and the content of Ni and Cr is high. TNB alloys exhibit uneven and loose lamellar morphology at low current densities, but can reach Ra 0.15 μm at greater than 15 A/cm2. There are always some disordered carbides rich in Nb and Mo on the surface of Inconel 625 alloy. Quantitative models were developed for both alloys to describe their electrochemical dissolution behavior.

Detecting structure and composition of passive film on Mo-containing stainless steel formed in alkaline environment by aberration-corrected TEM

In this paper, the structural and compositional evolution of the passive films formed on the Mo-containing stainless steels induced by chloride ions in 0.1 mol L−1 NaOH solution has been studied by means of aberration-corrected transmission electron microscopy and X-ray photoelectron spectroscopy. Mo is enriched at the outer layer of the passive film, which is attributed to the induction of Cl-. Moreover, MoO42- is formed due to the alkaline solution, which impedes the film formation process and inhibits the thickening of the film. Consequently, the positive effect of Mo in the passive film on the corrosion resistance is strongly suppressed.

Inhibition efficiency and mechanism of nitrilo-tris(methylenephosphonato)zinc on mild steel corrosion in neutral fluoride-containing aqueous media

Abstract Corrosion-electrochemical behaviour of steel E 235 in borate buffer solution (pH = 7.4) containing F− ions with and with no added ZnNTP as an inhibitor, where NTP = N(CH2PO3)3, was studied by the potentiodynamic polarization and depth-profiling XPS analysis of specimens polarized at different potentials applied. Depending on the potential applied, F− ion was shown to influence differently on the formation, composition and structure of passive film. At E < 0.1–0.2 V/SSCE, F− ion promotes the passivation via forming sparingly soluble FeF2, and the resulting film is comprised of mainly iron(II) oxides and hydroxides, as well as sparingly soluble FeF2 and FeZnNTP. At E > 0.1–0.2 V/SSCE, F− ion works for the destruction of the passive film by forming soluble compounds with Fe3+ ions, which leads to its thinning. ZnNTP inhibitor forms FeZnNTP heterometallic complex with iron ions, which is the most stable constituent of the passive film. When F− ion concentration does not exceed 1.4 mmol/L, ZnNTP inhibitor is optimal to be added in amount of 0.5–1.0 g/L, whereas concentrations of 5.6 mmol/L F− ion and higher require 5 g/L ZnNTP or even more to be added.

Enhanced scale inhibition and anti-wax capacities of passive materials via ultrasonic rolling processing

Scale damage and wax formation on pipelines surface have become prevalent issues in the development and production of the oil and gas industry throughout the world. The utilization of the ultrasonic surface rolling process (USRP) on pipeline surfaces is a promising protective approach and its universal verification for the enhancement of the scale inhibition and anti-wax capacities of passive materials is presented in this work. The effect of USRP on surface integrity (including roughness, cross-sectional microstructure, residual stress and water contact angle), scaling and wax deposition behavior, passive film structure and characteristics are experimentally analyzed by comparing three passive materials (13Cr stainless steel, 825 nickel-base alloy and Ti6Al4V alloy) with 3Cr carbon steel. The results indicate that USRP can effectively reduce the surface roughness and contribute to the growth of passive film due to the enriched passive elements on the metal surface, which consequently endow the passive materials with reduced surface free energy and enhanced anti-scaling/anti-wax capacities. Furthermore, benefitting from the surface passivation, the enhancement in the corrosion resistance of the film helps to provide good chemical stability. The main reason for why USRP has a protective effect on the scale inhibition and anti-wax capacities of the passive materials is also elucidated. The input energy of USRP not only achieves chip-free polishing and triggers structural response changes in the surface and subsurface plastic deformation but also produces a unique passivation response that can alter the chemical composition, thickness, compactness and defect density of the passive film. This in turn leads to significant changes in its corrosion resistance, which is related to the semiconductor characteristics of the materials, surface energy, and hydrophilic–hydrophobic physical and chemical properties. This results in a significant inhibitory effect on the deposition of scaling ions or wax crystals at the passive film/solution interface.

Effect of nitrogen content on corrosion behavior of high-nitrogen austenitic stainless steel

A series of electrochemical tests combined with the techniques of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and X-ray photoelectron spectroscopy (XPS) were used to study the effect of nitrogen content on the composition, structure and protectiveness of passive films, which were formed on the surfaces of high-nitrogen austenitic stainless steels (HNSS) in 0.5 mol/L NaCl solution. The results showed that the HNSS with higher nitrogen content had a larger proportion of low-angle grain boundaries, and it also had a lower corrosion current density in 0.5 mol/L NaCl solution and thus a lower corrosion rate. The existence of a larger proportion of stable oxides (e.g., Cr2O3) in the passive films facilitates the passivation/repassivation process and contributes to the high corrosion resistance of HNSS.

Study of the passivation and repassivation behavior of pure titanium in 3.5 wt% NaCl solution and 6 M HNO3 solution

We reveal differences in composition and structure of passive films and repassivation rate of titanium in 3.5 wt% NaCl and in 6 M HNO3. Titanium in 6 M HNO3 shows worse corrosion resistance than in 3.5 wt% NaCl due to higher defect concentration and lower TiO2 content despite the thicker passive film, which is the result of accelerated cathodic process and promoted dissolution/formation dynamic equilibrium of passive film in 6 M HNO3. Repassivation rate in 3.5 wt% NaCl is higher although film growth rate is lower, as the film exhibits good barrier effect when it is thin. Our results provide insights needed to guide application of titanium in SNFR plants.

Effect of Passive Oxide Film Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

Effect of Passive Oxide Film Structure and Surface Temperature on the Rate of Anodic Dissolution of Chromium-Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 2. Anodic Dissolution of Titanium Alloys in Nitrate and Chloride Solutions

Time-Dependent Passivation Performance of Plasma Sprayed FeCrMoCBY Amorphous Coating

The relationship between passive film growth behavior and passivation time for plasma-sprayed Fe48Cr15Mo14C15B6Y2 amorphous coating in borate buffer solution has been thoroughly studied. The morphological characteristic and structural feature of as-spayed amorphous coating were estimated by scanning electron spectroscopy (SEM), X-ray diffraction (XRD) and transmission electron spectroscopy (TEM). The influence of passivation time on the film evolution properties was measured by electrochemical impedance spectra (EIS), Mott–Schottky curves, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The results revealed that both corrosion resistance and self-repairing capacity of passive film greatly increased with time based on high electric field assumption. Reductions in donor density and flat band potential were accountable for a lower conductivity of passive film. An increment in Cr2O3 oxide as the inner barrier layer derived from the dehydration reaction of Cr(OH)3 contributed to the gradually densified structure of passive film. The extracted passive film thickness d increment with passivation time t conformed to the logarithm law on the basis of effective capacitance hypothesis: d=0.43lnt+52.06−2.18 (nm). Passivation mechanism within 600 s was ascribed to the adsorption of mechanical mixtures between metal ions and electrolytes, possibly leading to mechanical stress and rupture of passive film in the later growth procedure. The cation vacancy condensation process at the interface of coating/film was propitious in stabilizing the growth rate of passive film.

Broken passive film and subsequent pitting corrosion behavior of 2205 duplex stainless steel induced by marine fungus Aspergillus terreus in artificial seawater

Studies of fungal corrosion for duplex stainless steels (DSS) in marine environments are poor. In this work, effects of fungus Aspergillus terreus on the structure of passive film and the subsequent corrosion behavior of 2205 DSS in artificial seawater were deeply investigated. Results indicated that A. terreus promoted local deterioration of 2205 DSS passive film by changing its structure and components compared to the abiotic control, and then significantly accelerated the corrosion of 2205 DSS especially pitting corrosion. The nucleation and growth of metastable pitting corrosion were accelerated by A. terreus. Furthermore, A. terreus could preferentially corrode the austenitic phase.

Effect of the Structure of Passive Oxide Films and Surface Temperature on the Rate of Anodic Dissolution of Chromium–Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 1. Anodic Dissolution of Chromium–Nickel Steel in a Nitrate Solution

Effect of the Structure of Passive Oxide Films and Surface Temperature on the Rate of Anodic Dissolution of Chromium–Nickel and Titanium Alloys in Electrolytes for Electrochemical Machining: Part 1. Anodic Dissolution of Chromium–Nickel Steel in a Nitrate Solution

Corrosion Susceptibility of Passive Films on 1060, 2024, and 5083 Aluminum Alloys: Experimental Study and First-Principles Calculations

The corrosion characteristics of passive films on 1060, 2024 and 5083 aluminum alloys formed in citric acid solution are studied in Cl–-containing solutions by combining scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The passive film on 1060 pure Al exhibits the best corrosion resistance while the presence of alloying elements (Cu and Mg) in the passive films reduce the corrosion resistance of the passive films on 2024 and 5083 Al alloys. According to first-principles calculations, Cu/Mg doping γ-Al2O3 surfaces are looser and more reactive than pure γ-Al2O3 (110) surface, and Cl adsorption behavior is changed in Cu/Mg doping γ-Al2O3 surfaces. This illuminates the difference of corrosion resistances of 1060, 2024 and 5083 aluminum alloys from the aspects of the passive film structure and interaction of chlorine ions with the passive films.

Synthesis and corrosion behavior of Mo15Nb20Ta10Ti35V20 refractory high entropy alloy

The Mo15Nb20Ta10Ti35V20 refractory high entropy alloy with BCC structure was prepared by vacuum arc melting. The synthesized Mo15Nb20Ta10Ti35V20 demonstrated better corrosion resistance compared to 316 stainless steel in chloride corrosion environment, whose better corrosion resistance is attributed to the complex passive film structure and shows the characteristics of passivation-transpassivation-secondary passivation on the polarization curve. Mott-Schottky curves analysis and XPS results show that the primary and secondary passive films have different P-N junctions which were composed of different oxides showing bilayer structure characteristics. Through the thermodynamic calculation, the relationship between the competitive growth of multiple principal elements in RHEA were analyzed. The dynamic changes of TiO2 and Ti2O3 contents were responsible for the secondary passivation phenomenon.

Age-hardening behavior, corrosion mechanisms, and passive film structure of nanocrystalline Al-V supersaturated solid solution

• Synthesis of a nanocrystalline Al-5at.%V alloy with high solid solubility of V by high-energy ball milling • Study on the age hardening behavior of the ball milled Al-V alloy • Corrosion behavior as a function of age hardening time and temperature • Study of the passive film and pits using transmission electron microscope • Microstructural features causing passive film breakdown and subsequent pit growth or repassivation The effect of age-hardening on microstructure, hardness, and corrosion of an Al-5at.%V alloy, produced using high-energy ball milling and subsequent cold compaction, has been investigated. The alloy exhibited a grain size below 100 nm and extremely high solid solubility of V in Al (3.1 at.%). The age-hardening was carried out at 150, 200, and 250 ℃. The peak-aged condition of 150 ℃ demonstrated the highest hardness—transpired from grain refinement, precipitation, and solid solution hardening. The corrosion resistance of the Al-5at.%V alloy was studied as a function of aging conditions. The peak-aged condition retained the corrosion resistance while it deteriorated in the over-aged condition. Nonetheless, the corrosion resistance of the ball-milled Al alloys in all the aging conditions was superior to that of pure Al. The passive film structure and origin of corrosion were studied using scanning/transmission electron microscopy (S/TEM). The high corrosion resistance of the alloy was attributed to the V enrichment at the film/metal interface and deposition of V on the cathodic phases, which suppresses the dissolution of Al within the pit and therefore promotes repassivation in the early stages of corrosion.

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.

Influence of Ru on structure and corrosion behavior of passive film on Ti-6Al-4V alloy in oil and gas exploration conditions

In order to investigate the influence of minor Ru on the electrochemical behaviour and structural characteristics of passive films on the surface of Ti-6Al-4V alloys under various oil and gas exploration conditions, electrochemical techniques, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and corrosion simulation tests were carried out. The results revealed that the oil and gas exploration conditions had a serious impact on the electrochemical behaviour and corrosion resistance of the tested alloys. The passivation film resistance and corrosion potential of the tested titanium alloys were significantly reduced with increasing acidity and temperature. With the addition of minor ruthenium, the potential of the passive film on the Ti-6Al-4V-0.11Ru alloy surface increased because of the high surface potential of the ruthenium element. The contents of metallic ruthenium and tetravalent titanium oxide TiO2 in the surface film of the Ti-6Al-4V-0.11Ru alloy both increased with increasing temperature, which led to increase the thickness, stability, corrosion resistance and repairability of the passive film on the surface of the Ti-6Al-4V-0.11Ru alloy being better than those qualities of Ti-6Al-4V. These results were also confirmed by corrosion simulation tests.

Effect of temperature on the passive film structure and corrosion performance of CoCrFeMoNi high-entropy alloy

The effect of temperature on the passive film structure and corrosion performance of CoCrFeMoNi HEA was studied. The results indicated that the passive films exhibited a bilayer structure, where Co and Mo were segregated in the outer film, while Cr was enriched in the inner layer. The content of Fe and Mo species in the passive films decreased with rising temperature, leading to the passive film degradation. The CPT of the HEA was 50–60 ℃. The HEA suffered from selective dissolution of FCC phase below 50 ℃ during the potentiodynamic polarization tests, while pitting corrosion occurred above 60 ℃.

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.

Structural characteristics and chloride intrusion mechanism of passive film

Passive film is a natural barrier against corrosion, which forms spontaneously in alkaline solution. But as a key problem for corrosion resistance, the growth and failure process of passive film has not been clearly confirmed. In this paper, the fine structure of passive film is explored on the atomic scale, and the growth mode of crystals is demonstrated; ion channels are found in inner passive film, which explains the appearance of defect zones and concentrated attack of chloride ions in corrosion. This study will help to judge the corrosion initiation from the perspective of micro damage of passive film.

Mechanism of enhancing corrosion inhibition of carbon steel by nitrilo-tris(methylenephosphonato)zinc in neutral chloride-containing environments: electrochemical and XPS studies

The formation and structure of passive films on steel in a borate buffer environment pH= 7.4 containing Chloride ions have been thoroughly investigated. The effect of the inhibitor Na4[ZnNTP]·13H2O with a certain molecular structure have been studied, including the mechanism of its action. The lowest anodic dissolution current is reached at the ZnNTP concentration of about 0.6 g/L. At the initial stage of its formation, the passive film is composed of iron oxides, which may further approach the structure of magnetite. Under conditions of counter-diffusion of ZnNTP and Fe2+ ions, the heteropolynuclear complex Zn1/2Fe1/2(H2O)3µ-H4NTP]n is formed. As for the character of the formed chemical bonds, steel passivation in the presence of ZnNTP differs significantly from both oxide and salt passivation, and thus should be considered as a specific case, called by “coordination passivation”.