Composition Of Passive Film Research Articles

Effect of martensite transformation on chemical composition, semiconductor property and corrosion resistance of passive film on SAE 304 stainless steel

Effect of martensite transformation on chemical composition, semiconductor property and corrosion resistance of passive film on SAE 304 stainless steel

Passive film on 2205 duplex stainless steel studied by photo-electrochemistry and ARXPS methods

The passive film formed on 2205 duplex stainless steel in pH 8.59 borate buffer solutions was studied by photo-electrochemical techniques and Mott-Schottky analysis. The passive film displays both n-type and p-type semiconductor character in different potential regions of the passive state. The band gap energy of barrier layer of the passive film was 2.4∼2.75 eV. Additionally, the composition of passive film was analyzed by AR-XPS; at -400∼100 mVSCE and above 600 mVSCE Fe2O3, Fe3O4, FeOOH and CrO3 dominate the passive film, showing n-type semi-conductivity; while at 100∼600 mVSCE the passive film comprises FeO, Cr2O3 and Cr(OH)3, exhibiting p-type semi-conductivity.

Electrochemical behaviour of passive film formed on the surface of Ti-6Al-4V alloys fabricated by electron beam melting

The microstructure, composition, semiconductive properties and electrochemical performance of passive film formed on the surface of Ti-6Al-4 V alloy produced by electron beam melting (Abbreviated as ET) were compared with conventional wrought counterpart (WT) in phosphate buffered saline at 37 °C. The results demonstrated a thinner and more compact passive film formed on ET, which was attributed to the small grain size and high density of grain boundaries in ET, these active sites increased the growth rate at the initial stage in the manner of 3D progressive nucleation mechanism of passive film, leading to superior corrosion resistance than WT.

Effect of pH on the Electrochemical Behaviour and Passive Film Composition of 316L Stainless Steel

The effect of pH on the electrochemical behaviour and passive film composition of 316L stainless steel in alkaline solutions was studied using electrochemical measurements and a surface analysis method. The critical pH of 12.5 was found for the conversion from pitting corrosion to the oxygen evolution reaction (OER). OER was kinetically faster than pitting corrosion when both reactions could occur, and OER could postpone pitting corrosion. This resulted in pitting being initiated during the reversing scan in the cyclic polarization at the critical pH. According to the X-ray photoelectron spectroscopy analysis, the content of Cr and Mo decreased with pH, while Fe content increased. This induced the degradation of the passive film, which resulted in the higher passive current densities under more alkaline conditions. The selective dissolution of Mo at high pH was found, which demonstrated that the addition of Mo in austenitic stainless steels might not be beneficial to the corrosion resistance of 316L in strong alkaline solutions.

Influence of yttrium on surface chemistry and stability of passive film in Al-based binary metallic glasses

The effect of yttrium on the electrochemical polarization behavior, composition and semiconductor property of passive film in Al-Y glasses have been studied. It was found that the corrosion potential and passive current density are sensitive to the minor variation of yttrium content. The high Y-containing samples possess a homogeneous single layer passive film rich in yttrium. The passive film exhibits a p-type semiconducting behavior and the carrier density tends to be reduced with increasing yttrium due to the formation of YAlO3. Higher yttrium content makes the passive film inert to electron transfer and the metastable pitting are inhibited.

Enhanced passivation of alloy corrosion-resistant steel Cr10Mo1 under carbonation — Passive film formation, the kinetics and mechanism analysis

It has been repeatedly reported that Cr-series alloy steels have enhancing passivation under carbonation (within alkalinity range), which is diametrically opposed to plain carbon steel. This work investigated the composition and structure depth profiles of passive film formed on alloy corrosion-resistant steel Cr10Mo1 in simulating concrete pore solutions of different pH (13.3, 12.0, 10.5 and 9.0) by X-ray photoelectron spectroscopy (XPS), and analyzed the kinetics of the passive film growth and formation influenced by the pH through current transient analysis. The results stated that the growth and formation process of passive film on the steel could be explained using dissolution-precipitation reaction mechanism. When exposed to an alkaline medium, the metal first incurs rapid anodic dissolution and releases metallic cations into the electrolyte before the passive oxides/hydroxides precipitation. Decreasing pH promotes excessive anodic dissolution of the metal and more metallic cations are released into the solution, resulting more Cr species enriched in the film layer for their high stability insensitive to lower pH although Fe species become soluble under carbonation. This contributes to the formation of a thicker passive film with higher corrosion resistance, providing the steel enhanced passivity in less alkaline environments.

Surface characterisation of electroplated tinplate with different coating mass

ABSTRACTIn this paper, electrodeposited tinplates with different coating mass have been characterised by SEM, XRD, XPS, and EDS. The results indicate that a much lower coating mass may lead to an ununiformly distributed tin coating layer. To obtain a qualified tin coating with lower tin mass, the roughness of the base steel surface should be strictly controlled to gain a flat surface with lower roughness and defects. Cr2O3 and Cr(OH)3 were found as the main composition of passivation film with Cr2O3 locating at the outermost film surface, and the amount of Sn element increases and Cr element decreases as a function of depth from the surface of tin coating. In addition, the amount of Fe impurity in the plating bath should be strictly controlled as its presence in tin coating is harmful to coating corrosion resistance.

Effects of Ti addition on corrosion behavior of Zr-based metallic glass in chloride medium

The effects of Ti element on the corrosion resistance of the metallic glass Zr51.3Al10Ni6Cu31.8Ag0.1Y0.8 in aqueous solution with various chloride concentrations were investigated, and the effect mechanism was discussed. X-ray diffraction confirmed that Ti-added Zr51.3Al10Ni6Cu31.8Ag0.1Y0.8 metallic glasses with diameter of 3 mm were all metallic glasses. Weight loss and electrochemical method were introduced to characterize their corrosion resistance, and X-ray photoelectron spectroscopy study was used to characterize the passive film composition. The results show that the corrosion resistance of metallic glass is significantly improved with Ti addition, and Zr dioxides dominate in passive film during corrosion when Ti content is low. High Ti addition can lead to an obvious accumulation of Ti dioxides, which results in a thicker, Ti-enriched protective passive film.

Corrosion properties of phase reversion induced nano/ultrafine grained AISI 304 metastable austenite stainless steel

AISI 304 metastable austenite stainless steel was cold rolled under cryogenic temperature and transformed into martensite completely, after reverse transformation by annealing, bulk nano/ultrafine grained material was obtained. The material’s microstructure was observed by TEM, and the corrosion resistance was studied by polarization curve, EIS, and Mott-Schottky plot. Results showed that samples cold rolled at −120 °C had an equiaxed microstructure and displayed the best corrosion performance. The distinctive polarization curve shape indicated that its passive film had a peculiar feature, and the M-S plot showed its abnormal semiconductor character. XPS measurements are used to directly characterize the composition of passive film formed on specimens. Heterogeneous microstructures might help with the improvement on corrosion resistance of the nano/ultrafine grained stainless steel.

A Contribution to explain the Mechanisms of Adhesive Wear in Plastics Processing by example of Polycarbonate

In the plastics industry, adhesive wear resulting from hot melt flow is one of the main damage mechanisms affecting extrusion tools. Such damages strongly influence the economic efficiency and the product quality. Due to their beneficial properties, Cr-based nitride hard coatings deposited by physical vapor deposition (PVD) are applied as protective coatings. These coatings can prevent the formation of iron oxides, which have an influence on the wetting of plastic melt on the tool surface. In the present work, four different CrAl-based nitride and oxynitride monolayer coatings were synthesized onto the tool steel substrate AISI 420 (X42Cr13, 1.2083) by means of a hybrid direct current and a high power pulsed magnetron sputtering (dcMS/HPPMS) process. Various Cr/Al metal ratios led to different chemical compositions of the nitride and oxynitride coatings. All coatings as well as one uncoated steel substrate were analyzed prior to and after long-term heat treatment as well as before contact angle measurements and after shear tests in order to investigate the influence of the respective processes on the chemical composition of the native passive film at the surface; analyses were run using X-ray photoelectron spectroscopy (XPS). Furthermore, the influence on the wetting behavior of polycarbonate melt was studied by means of high temperature contact angle measurements; the influence on the shear energy necessary for removing the solidified plastic droplet was investigated using shear tests. It could be shown that the heat treatment leads to a significant increase of polycarbonate wetting on the uncoated steel compared to the coated samples. Additionally, the coatings with an increased Al content exhibit a lower wetting rate compared to the other coatings and the uncoated steel. A beneficial effect of an oxidative post-treatment after deposition has been demonstrated.

The passivation mechanism of Fe in the acidic AlCl3-EMIC ionic liquid

The passivation behavior of Fe in the acidic AlCl3-1-ethyl-3-methyl-imidazolium chloride (AlCl3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to characterize the composition and morphology of passive film formed on the Fe electrode, such as scanning electron microscopy (SEM), Raman spectra and X-ray Photoelectron Spectroscopy (XPS). The results showed that the critical passivation potential of Fe shifted to more negative when the molar ratio of AlCl3:EMIC changing from 2 to 1.3. A film with a light yellow color was observed on the surface of the Fe electrode after passivation. The composition of the passive film was demonstrated to be FeCl2. The passive film was composed of particulate FeCl2 with average diameter of about 500 nm. The formation of FeCl2 film was attributed to the variation of the electrolyte Lewis acidity from acidic to neutral at the interface during the dissolution process of Fe. The reason caused the variation of the electrolyte acidity was discussed.

A comparative study of primary and secondary passive films formed on AM355 stainless steel in 0.1 M NaOH

Abstracts In this study, the structure and composition of primary and secondary passive films formed on AM355 martensitic stainless steel were characterized and compared. The film composition analysis revealed that the Fe/Cr ratio in the secondary passive film is significantly lower than that in the metal matrix. Both the primary and secondary passive films are composed of nanoscale particles, and some pores are present in the secondary passive film. Compared to the secondary passive film, the primary passive film exhibits reduced donor density, with a more positive formation potential.

Effect of hydrogen on semiconductive properties of passive film on ferrite and austenite phases in a duplex stainless steel

Hydrogen effect on semiconductivity and compositions of passive films formed on ferrite and austenite phases in a duplex stainless steel were investigated by current sensing atomic force microscopy and X-ray photoelectron spectroscopy. It is demonstrated that hydrogen significantly increases the conductivity of passive film due to the increase of OH−/O2− ratio. The passive film on austenite has higher conductivity than that on ferrite after hydrogen charging due to more hydrogen in austenite. The presence of hydrogen causes an inversion of conductivity type of passive film from p-type to n-type, attributed to the chemical composition change.

Surface morphology and passive film composition after pickling and electropolishing

In this work, a novel method of selecting the most favourable electropolishing (EP) conditions is presented as a compromise between the processing time and obtaining the lowest possible roughness value of Sa or Sq (commonly used parameters) as well as the gradual increase of parameters highlighted in this work Ssk and Sku. The results showed that the most appropriate EP charge input should be higher than 1.2 Amin cm−2 and lower than 2.3 Amin cm−2. XPS high-resolution spectra revealed that pickling and EP of the samples results in a decrease of the ratio of the iron oxides amount (at.-%) to the total amount of chromium oxides and hydroxides (at.-%) in the passive film. This ratio gradually decreases reaching the values 1.2, 1.0 and 0.7 for as-received, pickled and electropolished samples, respectively. This result demonstrates iron dissolution of the outer surface layer by pickling and EP.

Critical Review—Photocurrent Spectroscopy in Corrosion and Passivity Studies: A Critical Assessment of the Use of Band Gap Value to Estimate the Oxide Film Composition

A critical assessment of the Photocurrent Spectroscopy (PCS) Technique for the semi-quantitative characterization of passive film and corrosion layers composition is carried out. We take into account more than three decades of PCS usage as “in-situ” analytical technique and related results as well as the criticism of the underlying semi-empirical correlation relating the measured optical bandgap (Eg) to the passive film composition. The discrepancies between the experimental data, gathered by PCS measurements, and Eg estimates originating from recently developed Density Functional Theory based modeling of solid state properties are stressed with particular emphasis on the case of anodic passive film grown on technologically important alloys (Fe-Cr and stainless steels). The extension of this correlation to mixed oxides and its use for relating the oxide composition to the bandgap values is critically reviewed by comparing the predicted Eg of mixed oxides with the experimental values. Suggestions on how to account for different bandgap values of oxide polymorphs and how to correlate the Eg values to the composition of mixed s,p-d-metal oxides are presented and discussed on the basis of experimental results reported in the literature. On the basis of this assessment, the ability of PCS in providing quantitative information on the composition of passive film and corrosion layer is generally confirmed.

Microstructure, Surface Characterization, and Electrochemical Behavior of New Ti-Zr-Ta-Ag Alloy in Simulated Human Electrolyte

A new Ti-20Zr-5Ta-2Ag alloy was elaborated and characterized regarding its microstructure, its native passive film composition and thickness, its surface wettability, its electrochemical behavior in Ringer solution of different pH values, and its ion release. The new alloy has a bi-phase, α + β, acicular, homogeneous microstructure (scanning electron microscopy (SEM)). Its native passive film (12-nm thicknesses) consists of the protective TiO2, ZrO2, and Ta2O5 oxides, Ti and Ta suboxides, and metallic Ag (X-ray photoelectron spectroscopy (XPS) data). The alloy possesses high hydrophilic properties. The main electrochemical parameters of the new alloy are superior to those of Ti as a result of the beneficial influence of Zr, Ta, and Ag alloying elements, which reinforce its native passive film. Electrochemical impedance spectroscopy (EIS) spectra in Ringer solutions for the new alloy displayed better values of impedances and phase angles, proving a more insulate passive film than that on the Ti surface. The main corrosion parameters for the new Ti-20Zr-5Ta-2Ag alloy are more favorable by about 25 to 38 times than those of Ti, confirming extremely resistant passive film. The new Ti-20Zr-5Ta-2Ag alloy releases into Ringer solution low quantities of Ti4+, Zr4+ metallic ions (inductively coupled plasma–mass spectroscopy (ICP-MS)). The Ag+ ions are released in low quantity, conferring to this alloy’s low antibacterial activity. All experimental results show that the new Ti-20Zr-5Ta-2Ag alloy fulfills the requirements for biocompatibility, corrosion resistance, and antibacterial protection.

Microstructure, surface characterization and long-term stability of new quaternary Ti-Zr-Ta-Ag alloy for implant use

The novel Ti-20Zr-5Ta-2Ag alloy was characterised concerning its microstructure, morphology, mechanical properties, its passive film composition and thickness, its long-term electrochemical stability, corrosion resistance, ion release rate in Ringer solution of acid, neutral and alkaline pH values and antibacterial activity. The new alloy has a crystalline α microstructure (by XRD). Long-term XPS and SEM analyses show the thickening of the passive film and the deposition of hydroxyapatite in neutral and alkaline Ringer solution. The values of the electrochemical parameters confirm the over time stability of the new alloy passive film. All corrosion parameters have very favourable values in time which attest a high resistance to corrosion. Impedance spectra evinced a bi-layered passive film formed by the barrier, insulating layer and the porous layer. The monitoring of the open circuit potentials indicated the stability of the protective layers and their thickening in time. The new alloy releases (by ICP-MS measurements) very low quantities of Ti, Zr, Ag ions and no Ta ions. The new alloy exhibits a low antibacterial activity.

Electrochemical Corrosion Behavior of Ta₂N Nanoceramic Coating in Simulated Body Fluid.

In order to improve the corrosion and wear resistance of biomedical Ti-6Al-4V implants, a Ta2N nanoceramic coating was synthesized on a Ti-6Al-4V substrate by the double glow discharge plasma process. The Ta2N coating, composed of fine nanocrystals, with an average grain size of 12.8 nm, improved the surface hardness of Ti-6Al-4V and showed good contact damage tolerance and good adhesion strength to the substrate. The corrosion resistance of the Ta2N coating in Ringer’s physiological solution at 37 °C was evaluated by different electrochemical techniques: potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and capacitance measurements (Mott-Schottky approach). The evolution of the surface composition of the passive films at different applied potentials was determined by X-ray photoelectron spectroscopy (XPS). The results indicated that the Ta2N coating showed higher corrosion resistance than both commercially pure Ta and uncoated Ti-6Al-4V in this solution, because of the formed oxide film on the Ta2N coating having a smaller carrier density (Nd) and diffusivity (Do) of point defects. The composition of the surface passive film formed on the Ta2N coating changed with the applied potential. At low applied potentials, the oxidation of the Ta2N coating led to the formation of tantalum oxynitride (TaOxNy) but, subsequently, the tantalum oxynitride (TaOxNy) could be chemically converted to Ta2O5 at higher applied potentials.

Passivation Characteristics of Alloy Corrosion-Resistant Steel Cr10Mo1 in Simulating Concrete Pore Solutions: Combination Effects of pH and Chloride.

The electrochemical behaviour for passivation of new alloy corrosion-resistant steel Cr10Mo1 immersed in alkaline solutions with different pH values (13.3, 12.0, 10.5, and 9.0) and chloride contents (0.2 M and 1.0 M), was investigated by various electrochemical techniques: linear polarization resistance, electrochemical impedance spectroscopy and capacitance measurements. The chemical composition and structure of passive films were determined by XPS. The morphological features and surface composition of the immersed steel were evaluated by SEM together with EDS chemical analysis. The results evidence that pH plays an important role in the passivation of the corrosion-resistant steel and the effect is highly dependent upon the chloride contents. In solutions with low chloride (0.2 M), the corrosion-resistant steel has notably enhanced passivity with pH falling from 13.3 to 9.0, but does conversely when in presence of high chloride (1.0 M). The passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer enriched in Fe oxides and hydroxides, and an inner layer, rich in Cr species. The film composition varies with pH values and chloride contents. As the pH drops, more Cr oxides are enriched in the film while Fe oxides gradually decompose. Increasing chloride promotes Cr oxides and Fe oxides to transform into their hydroxides with little protection, and this is more significant at lower pH (10.5 and 9.0). These changes annotate passivation characteristics of the corrosion-resistant steel in the solutions of different electrolyte.

Passivation and Potential Fluctuation of Mg-Alloy AZ31B in Alkaline Environments

The pH effect on the passivation and corrosion behavior of Mg alloy AZ31B was investigated in chloride-free NaOH solutions in the range of 10 to 14. The electrochemical behavior of α-Mg matrix, secondary (β-phase) Mg17Al12, and constituent intermetallic particles (AlxMny) were compared in these solutions using various techniques such as open circuit potential (OCP) monitoring, potentiodynamic and potentiostatic polarization, scanning vibration electrode technique (SVET), microcapillary cell technique as well as electrochemical atomic force microscope (EC-AFM) technique. Optical microscope (both in-situ and ex-situ) was utilized to characterize corrosion morphology of AZ 31B alloy in different pH NaOH solutions and yield information on the cathodic and anodic behavior of different phases and particles. Microscopic examination of the passive film formation and composition on different phases/particles was carried out via field emission scanning electron microscope (FE-SEM) equipped with energy dispersive spectroscopy (EDS). Gallium focused ion beam (FIB) was used to examine the cross section of different phases after exposure. The results indicate that significant potential fluctuations (from -1.6 VSCE to -0.4 VSCE) occurred to AZ31B in high pH (≥ 13) NaOH solutions with the presence of oxygen. Removal of oxygen by argon sparging diminished the fluctuation range (from -1.6 VSCE to -1.3 VSCE). Oxide nodules and associated cracks were found at the interface between α-matrix and β-phase. Thick oxide film was found to form on the α-matrix and the thickness decreased as the distance increased from the α/β interface (~1500 nm) into the α-matrix (~700 nm). In contrast, oxide film thickness of <100 nm was determined on β-phase. AlxMny particles were found to preferentially dissolve in high pH NaOH solutions and crevice was identified at the interface between Mn oxide layer and α-matrix. In relatively low pH (≤ 11) NaOH solution, OCP remained constant at -1.4 VSCE during long term exposure with the presence of oxygen. No significant potential fluctuation was observed. SEM/FIB examination indicated that corrosion occurred on the α-matrix in these NaOH only environment. In comparison, β-phase remained intact with thin passive film. Mg(OH)2 dome formed on AlxMny particles suggesting cathodic nature of the intermetallic particles. This was also corroborated by the in-situ microscopic examination of the gas formation on the AlxMny particles. OCP and polarization experiments suggest that hydrogen evolution reaction is the dominant cathodic reaction at these pH levels and the bubbles were found to initiate and grow preferentially on the AlxMny particles. At pH 12, thin oxide film (<100 nm) formed across the entire sample surface without any preferential corrosion and/or passivation on different phases/particles. The OCP remained constant at -1.3 VSCE during long term exposure. This was approximately 0.1 V higher than the value observed in pH 11 solution and no significant potential rise and drop was observed. Both potentiodynamic and potentiostatic polarization indicated that anodic current density decreased with increasing pH from 10 to 12 but increased with increasing pH from 12 to 14. Lowest passivation current density was identified at pH 12, which agrees with SEM/FIB and optical microscopic examinations. It is hypothesized that below pH 12, microgalvanic effect exists between α-matrix (anode) and AlxMny particles (cathode), which leads to the preferential dissolution of α-matrix. This was verified by SVET technique and AlxMny particles were found to be the cathode compared to α-matrix. At pH 13 and above, better passive film formation on β-phase may lead to the significant increase in OCP where the dominant cathodic reaction switched to oxygen reduction reaction, which in turn caused significant oxidation of α-matrix by microgalvanic coupling. AlxMny particles were anodic compared to the α-matrix and preferential dissolution of Al is suggested by SEM/EDS.