Steel Passive Film Research Articles

Study on the passivation properties of austenitic stainless steel 316LN based on the point defect model

The Point Defect Model was successfully developed to study the passivation of 316LN. Steel's passive film exhibits n-type semi-conductivity with interstitial cations as the dominant point defect. The transfer coefficients αi and rate constants ki are independent of the applied potential but vary with temperature. The electronic structure of the barrier layer (bl) is discussed as a degenerate defect semiconductor in which the bl comprises essentially the depletion zone with the electronic charge and the electron-hole charge being concentrated at the metal/bl and the bl/solution interfaces, respectively. The closest classical analog is postulated to be a tunnel diode.

Failure mode of passive film under electric field and chloride environment in concrete

Exploring the failure mode of passive film is the most fundamental issue for corrosion research and prevention of metals. In the actual service of reinforced concrete structures, steel rebars are typically exposed to a complex solution environment, characterized by electric fields, chloride ions, and fluctuating temperatures. Using scanning electron microscope, scanning electrochemical microscope, and a series of electrochemical tests, we present the damage mode of steel passive film in a simulated alkaline environment of concrete; and then establish a deductive diagram to illustrate it. Additionally, we use atomic force microscope, X-ray photoelectron spectroscopy and transmission electron microscope to explore the structural characteristics of passive film on an atomic scale, and confirm that specific ion channels serve as the pathway for chloride invasion. This study can enable a deeper understanding of the micro-mechanisms involved in steel depassivation and the initiation of corrosion electrochemical reaction.

The effect of chloride, sulfate, and ammonium ions on the semiconducting behavior and corrosion resistance of AISI 304 stainless steel passive film

The effect of chloride, sulfate, and ammonium ions on the semiconducting behavior and corrosion resistance of AISI 304 stainless steel passive film

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.

Effect of Hydrogen on Corrosion Behavior of 321 Stainless Steel in NH4Cl Solution.

For a hydrogenation heat exchanger operating under severe working conditions such as high temperature, high pressure and a hydrogen environment, perforation accidents caused by NH4Cl corrosion occur frequently. However, few reports on the effect of hydrogen on the corrosion behavior of metal materials in NH4Cl aqueous solution have been published. In this paper, X-ray photoelectron spectroscopy (XPS), electrochemical dynamic potential polarization, electrochemical impedance spectroscopy (EIS), Mott–Schottky (M-S) curves and scanning electron microscopy (SEM) were used to study the effect of electrochemical hydrogen charging (EHC) on the corrosion behavior of 321 stainless steel in an NH4Cl solution environment. The results show that: (1) hydrogen can change the structure and chemical composition of 321 stainless steel passive film and promote the conversion of metal oxide to hydroxide. At the same time, it can reduce the stability of the passive film. (2) Hydrogen can increase the thermodynamic and kinetic tendency of corrosion reaction and cooperate with Cl− to promote the occurrence of pitting corrosion.

The adsorption of two organic inhibitors on stainless steel passive film: A reactive force field study

Reactive molecular dynamics (MD) simulations were performed to investigate the adsorption of water and the organic corrosion inhibitors vitamin C (VC) and 2-vinylsuccinic acid (VSA) on Cr2O3 (001) surface. Adsorption of the inhibitors is accompanied by the formation of Cr-O covalent bonds and O…H hydrogen bonds. The superior corrosion inhibition performance of VC than VSA and their preferential parallel adsorption geometry can be attributed to more bonds to the surface. The adsorption of water on the Cr2O3 surface leads to the formation of a multilayered structure with a higher atomic intensity than bulk water in which the first two layers interact directly with the metal oxide surface. When an inhibitor layer and water are both present, the inhibitor effectively blocks Cr2O3-water interactions but water significantly weakens the inhibitor’s adsorption. These findings shed new light on the mechanism of corrosion inhibition in stainless steel.

Influence of Rust Inhibitors on the Microstructure of a Steel Passive Film in Chloride Concrete

To compare the corrosion inhibition behaviors of rust inhibitors with different mechanisms on steel bars, the rust resistance effect of sodium molybdate (Na2MoO4), sodium chromate (Na2CrO4), benzotriazole (BTA), N-N dimethyl ethanolamine, sodium molybdate (Na2MoO4) + benzotriazole (BTA), and sodium chromate (Na2CrO4) + benzotriazole (BTA) on steel bars in a simulated chloride concrete pore solution was studied. The rust resistance effects of different types of rust inhibitors were assessed by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effects of different types of rust inhibitors on the film formation characteristics of a passive film on a steel bar surface were expounded. The results show that: When sodium molybdate (Na2MoO4) and benzotriazole (BTA) acted together, the impedance value and the capacitive reactance arc radius were the largest, and the density of the passive film and the inhibition efficiency were the highest. The composition of the passive film was primarily composed of iron compounds, and it also contained oxide and adsorption films that were formed on the steel bar surface by the rust inhibitors. The rust resistance effect was proportional to the compactness of the passive film.

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.

Effects of stray current and silicate ions on electrochemical behavior of a high-strength prestressing steel in simulated concrete pore solutions

This work aims to shed new light on the evolution of passivation and chloride-induced corrosion behavior of a high-strength prestressing steel affected by stray current and silicate ions in alkaline solutions simulating the concrete interstitial electrolyte. A thinner and less stable steel passive film was formed due to the stray current interference, and this degradation effect was much more pronounced in the presence of chloride ions. Despite the negative impact on the natural formation of passive films, silicate ions were proven to be an eco-friendly corrosion inhibitor for steels subjected to coupling effects of stray current interference and chloride attack.

Electrochemical studies and molecular simulations on the use of molybdic acid for stabilization of AISI 304 stainless steel passive film in sulfuric acid medium

In this work, the corrosion of AISI 304 stainless steel (SS) in the absence and presence of different concentrations of molybdic acid was investigated using potentiodynamic polarization, open circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis (MS) and theoretical simulations including molecular dynamics (MD), Monte Carlo (MC), and density functional theory (DFT). Although it is obvious that the use of molybdate ions can improve the anti-corrosion properties of austenitic SS, there are fewer comprehensive reports which has been devoted to “investigation of electrochemical properties of passive film” and/or “theoretical studies using molecular-scale simulations”. Therefore, the present study focused on examining these two issues. The results of potentiodynamic polarization showed that molybdic acid not only can reduce the corrosion rate but also decrease the critical current density (icrit) for passive film formation. MS analysis revealed the donor density in the passive film was increased up to 6.6 × 1020 cm−3 by increasing the molybdic acid concentration to 0.02 mM. The computational studies associated with MD and MC simulations showed that the adsorption energy of molybdic acid, as an inhibitor on steel surface, is −35.4 and −98.3 kcal mol−1, respectively. Moreover, the HOMO and LUMO energies and the energy difference between them were calculated by DFT simulation.

Study on the Effect of F− and Cl− on the Differentiation of 904L Stainless Steel Passive Film in acid Environment

Study on the Effect of F− and Cl− on the Differentiation of 904L Stainless Steel Passive Film in acid Environment

Compatibility of Imidazolium-Based Ionic Liquids for CO2 Capture with Steel Alloys: a Corrosion Perspective

Ionic Liquids (ILs) could find applications in CO2 stripping, where their use could reduce energy consumptions compared to current technologies based on amine absorption. Although preliminary studies showed potential compatibility between metallic alloys and a limited number ILs, their corrosiveness still needs to be fully assessed. This work analyzes the corrosion behavior of steel alloys in contact with several imidazolium-based ILs, changing alternatively cation and anion to highlight possible dependences of corrosion behavior on relevant groups. Potentiodynamic polarization tests were performed in all ILs considered and in water as reference. Different ILs preparation conditions were considered: after purging in nitrogen, i.e., with reduced content of oxygen and water, and after exposure to the atmosphere to restore their natural humidity and oxygen content. Results showed a reduction in the protective character of stainless steel passive film, with no clear trend related to anion composition or cation chain length. Conversely, carbon steel corrosion rate decreased compared to aqueous solutions, and a passivation effect was observed in presence of long chain cations, which was ascribed to a steric effect of adsorbed molecules.

Characterization of corrosion scale formed on stainless steel delivery pipe for reclaimed water treatment

To reveal corrosion behavior of stainless steel delivery pipe used in reclaimed water treatment, this research focused on the morphological, mineralogical and chemical characteristics of stainless steel corrosion scale and corroded passive film. Corrosion scale and coupon samples were taken from a type 304 pipe delivering reclaimed water to a clear well in service for more than 12 years. Stainless steel corrosion scales and four representative pipe coupons were investigated using mineralogy and material science research methods. The results showed corrosion scale was predominantly composed of goethite, lepidocrocite, hematite, magnetite, ferrous oxide, siderite, chrome green and chromite, the same as that of corroded pipe coupons. Hence, corrosion scale can be identified as podiform chromite deposit. The loss of chromium in passive film is a critical phenomenon when stainless steel passive film is damaged by localized corrosion. This may provide key insights toward improving a better comprehension of the formation of stainless steel corrosion scale and the process of localized corrosion. The localized corrosion behavior of stainless steel is directly connected with reclaimed water quality parameters such as residual chlorine, DO, Cl− and SO42−. In particular, when a certain amount of residual chlorine in reclaimed water is present as an oxidant, ferric iron is the main chemical state of iron minerals.

Surface preparation effect on duplex stainless steel passive film electrical properties studied by in situ CSAFM

Abstract

Electrochemical Behavior and Nonlinear Mott-Schottky Characterization of a Stainless Steel Passive Film

The electrochemical behavior of 304-stainless steel in solutions with different pH values and chloride concentrations was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and a nonlinear Mott-Schottky analysis method. The results showed that the corrosion behavior of 304-stainless steel was affected by various factors, such as pH, chloride ion concentration, and dissolved oxygen. The pit initiation and propagation stage were observed in EIS plots through the addition of sodium chloride. In addition, the effect of pH on the passive film dominated one of the film growth kinetic reactions. The effect of chloride ion concentration was caused by the generation of more cation vacancies, leading the passive film more susceptible to pitting, which was also demonstrated by X-ray Photoelectron Spectroscopy. The results are consistent with the point defect model.

Duplex stainless steel passive film electrical properties studied by in situ current sensing atomic force microscopy

The duplex stainless steel passive film electrical properties before and after passivation were investigated by current sensing atomic force microscopy and X-ray photoelectron spectroscopy (XPS). The current maps and band gap energies extracted from I–V curves show that the conductivity of passive film covering austenite and ferrite is different and decreases with increasing film formation potential due to the changes in the passive film thickness and composition, confirmed by XPS analysis. I–V curves reveal that the passive films exhibit p-type or n-type semiconducting properties depending on the film formation potential, attributed to different film chemical composition, supported by XPS results.

EIS evaluation of steady-state characteristic of 316L stainless steel passive film grown in acidic solution

The EIS is a useful tool to characterize corrosion behavior of stainless steel, especially when it comes to the properties of the passive film. A specific electrical equivalent circuit was therefore developed to investigate the diffusion/migration of vacancies occurring within this oxide as described in the point defect model. This circuit was used at 20°C, 60°C and 80°C. The vacancy diffusion coefficient calculated was found to be close to 10−14cm2s−1.

Biomolecule−Biomaterial Interaction: A DFT-D Study of Glycine Adsorption and Self-Assembly on Hydroxylated Cr2O3 Surfaces

The adsorption of glycine, the building block of amino acids, on hydroxylated (0001)-Cr2O3 model surfaces, representing the stainless steel passive film surface, was modeled by means of the GGA + U method. The roles of glycine coverage and surface termination (hydroxylated Cr- and O-terminated surfaces) on the adsorption mode and self-assembly properties were explored. The hydroxylated Cr-terminated Cr2O3 surface, which presents two types of (H)OH groups exhibiting different acidic character, is more reactive than the hydroxylated O-terminated surface, where one single type of OH group is present, for all adsorption modes and coverages considered. Outer sphere adsorption occurs in the zwitterion form, stabilized at low coverage through H-bond formation with coadsorbed water molecules, and at the monolayer coverage by glycine self-assembling. The OH substitution by glycinate is favored on the hydroxylated Cr-terminated surface and not on the O-terminated one. The inclusion of dispersion forces does not change the observed tendencies. An atomistic thermodynamics approach suggests that outer sphere adsorption is thermodynamically favored over inner sphere adsorption in the whole domain of glycine concentration. The obtained SAM's free energies of formation are rationalized in a model considering the balance between sublimation and solvation free energies, and extrapolated to other amino acids, to predict the SAMs formation above hydroxylated surfaces. It is found that hydrophobic AA tend to self-assemble at the surface, whereas hydrophilic ones do not.

Making reinforced concrete immune from chloride corrosion

Chloride-induced corrosion is a major factor affecting the durability of reinforced-concrete structures. However, a high tolerance to chloride contamination has often been achieved under laboratory conditions. A significant factor affecting the chloride threshold level for corrosion initiation in concrete is the presence of defects, such as air voids, in the cement paste at the steel–concrete interface. To explain this observation it is noted that corrosion initiation and propagation involve the local production of acid at sites where the steel passive film breaks down in the otherwise highly alkaline concrete environment. Thus, solids with pH-dependent dissolution behaviour affect the corrosion process. Solid phase corrosion inhibitors would release hydroxyl ions to prevent this local reduction in pH. By reducing the entrapped air-void content at the steel to values below 0·2% it was possible to increase the chloride threshold level from 0·2% to above 2% chloride by weight of cement as the voids no longer dilute the inhibitive solid phases. A high tolerance to chloride contamination may also be achieved by reducing the electrolyte content of voids and by using electrochemical treatments to generate a reservoir of hydroxide-containing salts at the steel–concrete interface. Chloride contamination at levels above 2% chloride by weight of cement at a reasonable steel cover depth may not be possible in concrete exposed to many environments when the concentrating effects of evaporation are minimised. Thus, a chloride threshold level of 2% may effectively render steel immune to chloride-induced corrosion.

Atomic Force Microscopy and X-Ray Photoelectron Spectroscopy Study on the Passive Film for Type 316L Stainless Steel

Abstract The surface of Type 316L (UNS S31603) stainless steel (SS) passive film formed in nitric acid (HNO3) solution was studied by x-ray photoelectron spectroscopy (XPS) and atomic force microsc...