Properties Of Passive Films Research Articles

Effect of tartrate on the electrochemical behaviour and semiconductive properties of passive film on steel in saturated calcium hydroxide

This paper presents results of the basic study on the inhibitive action of tartrate toward chloride‐induced corrosion on carbon steel rebar in alkaline environment. Modification of the electrochemical behaviour and semiconductive properties of passive film formed on steel surface in the presence of tartrate were characterised by a range of electrochemical techniques in saturated calcium hydroxide. In the presence of tartrate in saturated calcium hydroxide with addition of 0.14 M sodium chloride pitting corrosion initiation was postponed for 622 mV up to potentials of oxygen evolution reaction. The hypothesis on the competitive adsorption between the chloride ions and tartrate anion through the surface complex formation was applied on the studied system.

Modeling Electronic Properties of the Passive Films on Carbon Steel in Simulated Concrete Pore Solutions

The performance of five existing models for predicting the electronic properties of passive oxide films on carbon steel that are exposed to synthetic alkaline media representing concrete pore solutions was investigated. It was found that the two donor band model, which is based on the presence of two discrete donor bands each with a Gaussian distribution of energy states for an n-type semiconductor, most accurately predicts experimental measurements. The model supports the experimental data that show an increase in the deep donor density and width of the deep donor band with increasing passivation time. A comparison of films formed in different passivating solutions revealed the potential of this model to predict the passive film electronic properties in environments not yet studied experimentally.

Effect of Hydrogen Sulfide Ions on the Passive Behavior of Type 316L Stainless Steel

The effect of hydrogen sulfide ions (HS−) on the passivity of type 316L stainless steel was investigated in pH 8.4 boric acid-borate buffer solution. Galvanostatic polarization of a silver microelectrode covered with Ag2S generated both OH− and HS− above the stainless steel surface. During potentiostatic polarization of the stainless steel, the passivity-maintaining current density increased with increase in the concentration of HS− in the vicinity of the surface. The impedance of the stainless steel at a constant frequency decreased during polarization in the presence of HS−, while it was sustained after dilution of HS−. Electrochemical impedance spectroscopy (EIS), Mott-Schottky (M-S) analysis and scanning electrochemical microscopy (SECM) showed that a defective and n-type semiconductive passive film was formed in the solution containing HS−. Auger electron spectroscopy (AES) revealed that metal cations and oxygen vacancies in the passive film on the stainless steel increased when it was formed in a HS−-containing solution. The series of changes in passive film properties is thought to be due to adsorption of HS– on the film surface during the polarization.

Electrochemical Characterization of Passive Films on Ni-Based Alloys in Acidic and Neutral Solutions

The present work reports the structure, chemical composition and electronic properties of passive films formed on Alloy 600 and Alloy 690 in borate buffer and sulfuric acid solutions. Photoelectrochemical response from passive films varied depending on the alloy substrates and the solutions. XPS analysis revealed that the passive films formed on Alloy 600 and Alloy 690 consisted of an outer hydroxide layer and an inner oxide layer in the borate buffer solution as well as the sulfuric acid solution. The chemical composition of the layers was relatively different depending on the solutions, that is, more Fe was incorporated into the passive films formed in the borate buffer solution. [doi:10.2320/matertrans.M2014384]

Corrosion Inhibition of Carbon Steel in Acidic Mediaby Using <i>Actinidia deliciosa</i> (Kiwifruit) Extract

The corrosion inhibition of 1018 carbon steel in 0.5 M H2SO4 by using Actinidia deliciosa (Kiwifruit) peel extract has been investigated by using potentiodynamic polarization curves and electro-chemical impedance spectroscopy. Two kinds of extracts are investigated, one from the tender, and another one from ripe Actinidia deliciosa. Concentrations include 0, 25, 50, 75, and 100 ppm at room temperature. Results indicate that both kind of extracts acted as good corrosion inhibitors, is more efficient in the ripe extract. Corrosion inhibition efficiency increases with increasing its concentration for ripe extract, whereas for the tender Actinidia deliciosa, the higest inhibitor efficiency is obtained by adding 25 ppm and decresaing with a further increase in its concentration. Both extracts improve the passive film properties by decreasing the passive current density values. It is found that the corrosion inhibition is due to the presence of heteroatoms present in Actinidia deliciosa, mainly quercitine, which is physically adsorbed in the steel following a Frumkin type of adsorption isotherm which forms a protective film.

Passive film properties and corrosion behavior of Ni–Nb and Ni–Nb–Ta amorphous ribbons in nitric acid and fluorinated nitric acid environments

Potentiodynamic polarization and electrochemical impedance studies revealed the passivation ability and corrosion resistance of Ni60Nb40 and Ni60Nb30Ta10 amorphous ribbons in 11.5 M HNO3 and 11.5 M HNO3 + 0.05 M NaF media at room temperature. Mott–Schottky analysis indicated the formation of n-type semiconducting passive film on these amorphous ribbon samples. Electrochemical parameters such as corrosion current density, passivation current density and donor density confirmed the passive film property of Ni60Nb30Ta10 amorphous ribbon to be superior to that of Ni60Nb40 amorphous ribbon. Weight loss was insignificant in Ni60Nb30Ta10 ribbon exposed to boiling 11.5 M HNO3 for 240 h. XPS analysis revealed that the origin of passivity of Ni60Nb40 and Ni60Nb30Ta10 amorphous ribbons in boiling 11.5 M HNO3 was due to the formation of a relatively thick passive film of ≈3 nm enriched with Nb2O5 and a thin passive film of ≈1.5 nm enriched with both Nb2O5 and Ta2O5 on the respective ribbon's surface. In boiling fluorinated nitric acid, Ni60Nb40 ribbon underwent severe dissolution owing to the instability of Nb-oxide passive film and the oxide/metal interface.

Improved Power Performance of Activated Carbon Anode by Fe<sub>2</sub>O<sub>3</sub> Addition in Microbial Fuel Cells

Poor energy output and high cost are the key factors to inhibit the development and application of microbial fuel cells (MFCs). Different types of modification techniques for anode material are suggested to improve power performance in MFCs. nanoFe2O3 is characteristics of no toxicity, biocompatibility and low cost. In this work, stainless steel mesh (SSM), ultracapacitor activated carbon with SSM (AcM), Fe2O3 added AcM (AMF) anodes are investigated to improve MFCs performance. The highest maximum power density (806 ± 26 mW·m-2) is obtained in AMF anode, which is 11 % higher than that of AcM (730 ± 27 mW·m-2), and 57 folds higher than that of SSM anode (12 ± 0.7 mW·m-2). The semi-conducting properties of passive film on the anode surface play a rather important role in anodic reaction by Mott-Schottky analysis. Tafel test demonstrates that the exchange current density (8.36×10-4 A·m-2) is improved by 20 % for AMF compared with AcM control (6.93×10-4 A·m-2). These results show AcM is suitable as MFCs anode, and further addition of Fe2O3 can increase the extracellular electron transfer in that way increase power production in MFCs.

The effect of plasma nitriding temperature on the electrochemical and semiconducting properties of thin passive films formed on 316 L stainless steel implant material in SBF solution

In this study, 316L stainless steel samples were nitrided plasma at temperatures of 350, 400 and 450°C for 2h under a gas mixture of 50% N2–50% H2. The effect of plasma nitriding temperature on the corrosion performance and semiconductor properties of the passive film on the 316L stainless steel was evaluated in simulated body fluid (SBF) using electrochemical test and Mott–Schottky analysis. In literature study, the effect of plasma nitriding temperature on corrosion behavior of 316L stainless steel was evaluated in solutions of NaCl, H2SO4 and acidic for biomedical applications. However, corrosion studies are more suitable to test in simulated body solution. Also, there are no enough studies on the effects of plasma nitriding temperature on semiconductor properties of the passive film obtained on film 316L stainless steels in SBF solution. So, in this study the effects of plasma nitriding temperature on the electrochemical and semiconducting properties of thin passive films formed on 316L stainless steel implant material in SBF solution at 37°C were investigated. The effects of microstructure and phase structure on corrosion properties of samples were determined. The results showed that the phase composition and microstructure of the treated samples were affected from the nitriding temperatures. It was obtained that s-phase formed at the lower temperature than 400°C. According to electrochemical test results, the plasma nitriding process at 350°C was the most suitable process condition for improving the corrosion resistance in SBF. All oxide films showed p-type (acceptor) semiconductor behavior at low potentials and n-type (donor) behavior at high potentials.

Time-dependent variation of the electrochemical impedance for thermo-mechanically treated versus plain low alloy steel rebars in contact with simulated concrete pore solution

Electrochemical studies (AC impedance and DC polarization) have been used to study the protective properties of passive films that form on reinforced steel embedded in concrete as a function of time and space. Experiments have been performed on passive/oxide films grown on the surface of steel reinforcement bars exposed to chloride-contaminated simulated concrete pore solution (SPS) prepared by dissolving a representative amount of sodium hydroxide and potassium hydroxide in distilled water and saturated with lime. A common type of locally available concrete reinforcement TMT (thermo-mechanically treated) mild steel with TM (tempered martensitic) and PF (pearlite ferrite) rings (source “A”) was investigated in comparison to a type of hot rolled low-alloy steel without thermo-mechanical treatment (source “B”). The results of the elemental analysis and metallographic microstructure coupled with electrochemical studies indicate that the coupled surface and sub-surface composition of TMT rebar has a time-dependent reversing effect on the protective properties of the passive oxide films that provide durability and protection to the steel rebars against corrosion in concrete. Steel with TM–PF rings has a better initial corrosion resistance in comparison to low alloyed steel. However, with the passage of time, its corrosion resistance decreases, and alloyed steel finally dominates over the TMT rebar.

Effects of passive films on corrosion resistance of uncoated SS316L bipolar plates for proton exchange membrane fuel cell application

The effects of passive films on the corrosion behaviors of uncoated SS316L in anode and cathode environments of proton exchange membrane fuel cells (PEMFCs) are studied. Potentiodynamic and potentiostatic polarizations are employed to study the corrosion behavior; Mott-Schottky measurements are used to characterize the semiconductor properties of passive films; X-ray photoelectron spectroscopy (XPS) analyses are used to identify the compositions and the depth profiles of passive films. The passive films formed in the PEMFC anode and cathode environments under corresponding conditions both behave as n-type semiconductor. The passive film formed in the anode environment has a single-layer structure, Cr is the major element (Cr/Fe atomic ratio>1), and the Cr/Fe atomic ratio decreases from the surface to the bulk; while the passive film formed in the PEMFC cathode environment has a bi-layer structure, Fe is the major element (Cr/Fe atomic ratio<0.5), and in the external layer of the bi-layer structure Fe content increases rapidly and gradually in the internal layer. SS316L shows better corrosion resistance owing to both the high content of Cr oxide in the passive film and low band bending in normal PEMFC anode environments.

Effect of ferrite on pitting corrosion of Fe20Cr9Ni cast austenite stainless steel for nuclear power plant pipe

The ferrite content and grain size in a Fe20Cr9Ni (wt-%) cast austenite stainless steel which has been widely used in primary coolant pipes of nuclear power plants were found to vary due to non-uniform solidification of the large pipe with a thickness of 95 mm. The pitting corrosion of Fe20Cr9Ni cast austenite stainless steel with five ferrite contents, i.e. 13, 11, 10, 9·5 and 8 vol.-% and different ferrite grain sizes was investigated in a 0·5 mol L−1 NaCl solution by means of potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Both pitting potential and charge transfer resistance value of specimens increased with the decreasing ferrite content and grain size, indicating that few and small ferrite grains were beneficial for improving pitting resistance. The passive film properties studied by EIS correlated well with the polarisation results. Electron probe microanalysis results showed that the difference in the Cr concentration between ferrite and austenite decreased with a decreasing amount of ferrite phase. Accordingly, the composition microsegregation was reduced, and passive film homogeneity of the specimens was improved.

Correlation Between Properties of Passive Film and Stress Corrosion Cracking of α -Ti in Methanol Solution

Correlation Between Properties of Passive Film and Stress Corrosion Cracking of α -Ti in Methanol Solution

Gold oxide films grown in the confined aqueous layer between gold and organic solvents

The properties of anodic passive films potentiostatically formed on polycrystalline gold in aqueous phosphate solutions were studied using voltammetry, electrochemical impedance spectroscopy, and contact angle measurements. The nature of the gold oxide layer was analyzed as a function of a potential holding in the aqueous double layer charge region at the interface between gold and the aqueous layer confined by insoluble organic solvents (hexane, chloroform, anisole, butyl acetate, xylene, and isopropyl ether). Different growth conditions change the homogeneity of the oxide layer leading to different passive properties. A synergetic effect on the gold oxidation of hydrogen dissolved in both the bulk metal and the confined aqueous layer is discussed.

Properties of passive nano films on zircaloy-4 affected by defects induced by hydrogen permeation

In this work, hydrogen absorption and the permeation behavior of the passive layer formed on zircaloy-4 are investigated. Potentiodynamic polarization, Mott—Schottky analysis, electrochemical impedance spectroscopy, and Raman scattering spectroscopy are employed to characterize the passive defects before and after hydrogen permeation. It is found that the nanoscale passive ZrO2 films play an important role in the resistance against corrosion; hydrogen impingement, however, reduces the passive impedance towards hydrothermal oxidation. The increase of defects (vacancies) in passive film is probably attributed to the degradation. We believe that this finding will provide valuable insight into the understanding of the corrosion mechanism of zircaloys used in light water reactors.

Corrosion Resistance and Semiconducting Properties of Passive Films Formed on 00Cr13Ni5Mo2 Supermartensitic Stainless Steel in Cl− Environment

The semiconducting properties of passive films grown on 00Cr13Ni5Mo2 supermartensitic stainless steel were investigated in comparison with conventional 2Cr13 martensitic stainless steel. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used for the studies. 00Cr13Ni5Mo2 steel exhibited a good corrosion resistance performance, attributing to its passive capability. The results of Mott-Schottky analysis demonstrated n-type semiconductors for the passive films with doping densities of about 1O20 − 1021 cm−3, and the thickness of spacecharge layers was also calculated. The experimental results confirmed that Mo plays an important role in improving the corrosion resistance of 00Cr13Ni5Mo2 steel due to its impact on the doping density.

Characterization of electrochemical and passive behaviour of Alloy 59 in acid solution

The electrochemical behaviour and passive film properties of the Alloy 59 in sulfuric acid solution was evaluated by the potentiodynamic electrochemical measurements, electrochemical impedance spectroscopy, Mott-Schottky approach, and ex situ surface analytical technique as X-ray photoelectron spectroscopy (XPS) and Auger Electronic Spectrometer (AES). The results confirmed that the Alloy 59 exhibits well passive behaviour. A considerably thinner n-type passive film is observed on this type alloy. Based on the evaluations of surface composition analysis, the primary constituents of passive film formed in the air and acid solution are different, with the (Cr, Ni)-oxides and (Cr, Ni) hydroxides, respectively.

Electronic and transport properties of passive films grown on different Ni-Cr binary alloys in relation to the pitting susceptibility

In the presence of chloride ions, passive films grown on Nickel-Chromium alloys may be sensitive to chemically induced breakdown. As chloride ion adsorption on the passive film/electrolyte interface and their penetration through the film are the main reasons for passivity breakdown, their mechanisms need to be assessed and understood. In the present study, the passivity of pure Ni, pure Cr and different Ni-Cr alloys (with 16, 20, 24 and 28 wt% Cr) was characterized for two film growth conditions by electrochemical impedance spectroscopy (EIS) and the Mott-Schottky analysis. EIS spectra, obtained after the immersions, were analyzed from an Equivalent Electrical Circuit taking into account migration phenomena through the passive film (transport resistance, apparent diffusivity). Mott-Schottky analyses were performed to obtain the semiconductor properties of the passive films, such as semiconducting type, charge carrier density and flat band potential. All of these results were compared as a function of substrate composition and film-forming conditions. The relation between chloride anions adsorption or penetration and the electronic and transport properties of the passive films is then discussed. Particular attention is paid to the migration parameters, the flat band potential and the charge carrier density.

Effect of alloying elements on the electronic properties of thin passive films formed on carbon steel, ferritic and austenitic stainless steels in a highly concentrated LiBr solution

The influence of alloying elements on the electrochemical and semiconducting properties of thin passive films formed on several steels (carbon steel, ferritic and austenitic stainless steels) has been studied in a highly concentrated lithium bromide (LiBr) solution at 25°C, by means of potentiodynamic tests and Mott–Schottky analysis. The addition of Cr to carbon steel promoted the formation of a p-type semiconducting region in the passive film. A high Ni content modified the electronic behaviour of highly alloyed austenitic stainless steels. Mo did not modify the electronic structure of the passive films, but reduced the concentration of defects.

Water molecules effect on pure Ti passive film structure in methanol solution

To understand the role of water on titanium SCC properties in methanol solutions, composition and structure of the passive film were studied using X-ray photoelectron and electrochemical impedance spectroscopies. The passive film consists of the inner compact layer and a porous outer layer. The inner layer thickness is less than 4nm and decreases with the increasing water content. Water improves the passive film properties, thus changes SCC susceptibility by altering the hydrogen bonding of methanol and reacting with titanium preferentially.

Borate 완충용액에서 니켈 산화피막의 생성 과정과 전기적 성질

Borate 완충용액에서 Ni의 부동화 피막의 생성과정(growth kinetics)과 부동화 피막의 전기적 성질을 변전위법, 대 시간 전류법 그리고 단일 주파수 또는 다중 주파수 전기화학적 임피던스 측정법으로 조사하였다. 이때 생성되는 산화피막은 Mott-Schottky 식이 적용되는 p-형 반도체 성질을 보였으며, 낮은 전극전위에서 생성되는 Ni의 부동화 피막 <TEX>$Ni(OH)_2$</TEX>는 전극 전위가 증가하면서 NiO, NiO(OH)로 변화되는 것을 알 수 있었다. In a borate buffer solution, the growth kinetics and the electronic properties of passive film on nickel were investigated, using the potentiodynamic method, chronoamperometry, and single- or multi-frequency electrochemical impedance spectroscopy. The oxide film formed during the passivation process of nickel has showed the electronic properties of p-type semiconductor, which follow from the Mott-Schottky equation. It was found out that the passive film (<TEX>$Ni(OH)_2$</TEX>) of Ni formed in the low electrode potential changes to NiO and NiO(OH) while the electrode potential increases.