Formation Of Protective Oxide Film Research Articles

Effect of Temperature on Thermal Oxidation Behavior of Ti-6Al-4V ELI Alloy.

In this paper, the morphological, micromechanical and tribological characteristics of the Ti-6Al-4V ELI alloy after thermal oxidation (TO) were identified. TO was carried out at temperatures of 848 K, 898 K and 948 K over a period of 50 h. Microscopic examination revealed that an increase in temperature resulted in an improved uniformity of coverage and an increased oxide grain size. Micromechanical tests showed that TO of the Ti-6Al-4V ELI alloy led to an increase in hardness and deformation resistance. Following oxidation, a decrease (by approximately 10-22%) was observed in the total mechanical work of indentation, Wtotal, compared to the as-received material. The formation of protective oxide films on the Ti-6Al-4V ELI alloy also led to the improvement of tribological characteristics, both when tested under dry friction conditions and in Ringer's solution. The sliding wear resistance increased with an increase in the oxidation temperature. However, a greater degree of wear reduction (by approximately 30-50%) was found for the lubricated contact in comparison with the dry friction tests. Surface roughness also increased with the increase in temperature.

Impact of multi-factor coupling on the corrosion behavior of 254SMo stainless steel in an aggressive oilfield environment containing CO2 and H2S

The passivity and corrosion behavior of 254SMo stainless steel in aggressive oilfield environments containing both carbon dioxide (CO2) and hydrogen sulfide (H2S) were investigated using weight-loss and surface analyses. The results indicated that the corrosion rate increased with the increase in temperature, CO2/H2S partial pressures, tensile stress and flow rate. Compressive stress led to a reduction in sulfide compound contents and promoted the formation of protective oxide films, while tensile stress had an opposite effect. Furthermore, a synergistic effect of stress and flow was observed.

Four-dimensional electrochemical impedance spectroscopy: Role of microstructure on corrosion behaviour of Al-Si alloys additive-manufactured by laser powder bed fusion

Four-dimensional (4D) electrochemical impedance spectroscopy was applied to clarify the role of microstructures on the corrosion behaviour of Al-Si alloys additively manufactured by laser powder bed fusion in the immersion of NaCl solution. 3D complex impedance plots, comprising real, imaginary, and time axes, indicate that the impedance increases gradually at initial stage and then does not show apparent time variation. These behaviours, following surface morphology analysis, are strongly related to the remaining fine silicon particles on the surface due to the preferential Al dissolution, which suppress the further dissolution from underlying along with the protective oxide film formation.

Development of targeted chloride-responsive Ag/Ca-MoO4-LDH for synergistic corrosion resistance

Layered double hydroxides (LDHs), as novel corrosion inhibitor in reinforced concrete, face instability in chloride consolidation due to sensitivity to environmental anions. This study explored the use of nano-Ag loaded on MoO4-intercalated CaAl-LDH (Ag/Ca-MoO4-LDH), based on isomorphic substitutes for cement hydration products (AFm), to target and stabilize chloride ion fixation in alkaline environments, thereby enhancing steel corrosion resistance. The mechanism of targeting and the enhancement of corrosion resistance were explored through comprehensive experimental and theoretical analyses. Results showed that Ag/Ca-MoO4-LDH enhanced chloride ion consolidation stability, increased the threshold of chlorides needed to trigger corrosion in simulated chloride-contaminated concrete pore (SCCP) solutions, and boosted steel’s anti-corrosion effectiveness. Unlike direct application methods, Ag/Ca-MoO4-LDH released MoO42− in response to chloride presence, providing superior corrosion prevention. The study elaborated on the stability of Ag+ and Cl− interactions in SCCP solutions, the spontaneous exchange reactions between LDH-MoO4 and both LDH-OH and LDH-Cl, and various anti-corrosion mechanisms, including the formation of protective oxide films on steel surfaces and the precipitation of CaMoO4.

Effect of Mo on the high-temperature oxidation behavior of Cr-Ni-Mo hot-work die steels

To investigate the effect of molybdenum (Mo) on the high-temperature oxidation behavior of low-carbon hot-work die steels in a Cr-Ni-Mo system, five 3Cr3MoxNiW steels were prepared. The addition of Mo resulted in a decrease in the grain size of the 3Cr3MoxNiW steel, as well as an improvement in its oxidation resistance. The addition of Mo to 3Cr3MoxNiW steel reduces the inward diffusion of oxygen and the outward diffusion of iron, which accelerates the formation of chromium oxide. The oxide of Mo can then also participate in the process of protective oxide film formation, thus improving its oxidation resistance.

Enhanced corrosion resistance in accident-tolerant FeCrAl alloy by water-assisted laser surface modification

FeCrAl alloys have been widely developed as an alternative accident-tolerant cladding material in light water reactors since the Fukushima nuclear accident in 2011. A large thermal neutron cross-section is the most severe challenge for FeCrAl alloys in the final commercial use, and a thinner cladding was necessary to overcome this, which led to higher corrosion resistance requirements. To address this issue, a surface treatment process is described here to enhance the corrosion resistance of the FeCrAl alloy via a water-assisted laser modification. By varying the laser power and laser scanning speed, the relationship between corrosion and processing parameters was investigated to better understand the mechanism with various characterizations. A heat-transfer model with boiling heat transfer boundary conditions was built and simulated using a finite element method to reveal the change in temperature field during processing. A corrosion test was performed with a simulated light water reactor (LWR) hydro-thermal environment for 120 h. The corrosion rate and oxide film thickness of the water-assisted laser modified FeCrAl alloy sample decreased by 83 % and 50 %, respectively, compared to the as-received one, and this was ascribed to the formation of protective oxide film during laser processing, along with grain refinement and elimination of holes and scratches.

Electrochemical corrosion performance of Si-doped Al-based automotive alloy in 0.1 M NaCl solution

The aim of this study is to investigate the electrochemical corrosion behavior of Al-Si automotive alloys with different levels of Si doping in 0.1 M NaCl solution at room temperature. The study was performed by electrochemical method, using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The condition of surfaces was characterized by both optical and scanning electron microscopy. Both the EIS and Tafel analyses revealed that the corrosion resistance was improved with the addition of Si up to the eutectic point due to the formation of protective oxide films. The higher Si added alloys showed lower values of current density, while the corrosion potential was shifted to a more positive direction. For higher Si added alloys, a higher amount of Mg2Si was formed as precipitates, which tend to form oxides such as SiO2 and MgO, further protecting the surfaces from corrosion. It can be observed from the micrographs that the scratches from polishing are removed after corrosion. Additionally, the SEM images reveal that corroded surfaces appear to have pits that are less noticeable in alloys with a greater Si content, suggesting thus the formation of a protective layer of oxides.

Effects of Al, Zn, and rare earth elements on flammability of magnesium alloys subjected to sonic burner–generated flame by Federal Aviation Administration standards

Mg alloys are promising structural materials in aerospace industry due to high strength to weight ratio. However, most Mg alloys are limited in aircraft cabins due to their susceptibility to ignition and burning. To improve fire resistance, adding alloying elements is a strategy. Thus, the goal of this study is to explore the effects of alloying elements Al, Zn, and rare earths on Mg-alloy flammability by experiment, using the system and procedures in compliance with the Federal Aviation Administration (FAA) standards for Mg-alloy flammability test. Six commercial Mg alloys with different alloying elements (AZ91E, ZK61A, ZE63A, EZ33A, WE43B, and EV31A) were tested. Results indicate that Mg alloys with Al or Zn elements were of short ignition time and high weight loss. With rare earths, Mg-alloy flammability was suppressed obviously. It appears that this suppression effect with rare earth addition was attributed to the formation of protective oxide film on the surface of molten alloy. Further, a heat transfer model was established to analyze the temperature evolution of the test specimen subjected to the sonic burner–generated flame by FAA standards, and ignition temperatures of all testing Mg alloys were predicted based on the experimental ignition time. The predicted results confirm that with rare earths addition, ignition was delayed after melting by the protective oxide film formed on the surface of the molten alloy.

Enhancing oxidation resistance of Cu during repeated melting by the in-situ formation of protective oxide films

Copper is readily oxidizable in the air, especially at high temperatures. The existing anti-oxidation methods are mainly based on coatings that cannot survive in the harsh environment of repeated melting. This work introduces the in-situ formation of protective films along grain boundaries to improve the oxidation resistance under repeated melting. The Pb is more favorable oxidized than Cu and applied as the protective materials. Under repeated melting, the Pb dissolves in liquid Cu, then precipitates a reticular structure that wrapping up Cu grains and absorbing local oxygens. The formed PbO acts as a diffusion barrier to oxygen. The low-voltage contact test showed the Cu-Pb composite provides better oxidation resistance with a decreased contact resistance and temperature rise compared with pure Cu samples after 5,000 times arcing.

Basic models and approximation for the engineering description of the kinetics of the oxide layer of steel in a flow of heavy liquid metal coolant under various oxygen conditions

The article presents the results of corrosion processes, kinetics and changes in the oxide layer modeling using MASKA-LM software complex. The complex is intended for a numerical simulation of three-dimensional non-stationary processes of mass transfer and interaction of impurity components in a heavy liquid metal coolant (HLMC: lead, lead-bismuth). The software complex is based on the numerical solution of coupled three-dimensional equations of hydrodynamics, heat transfer, formation and convective-diffusive transport of chemically interacting components of impurities. Examples of calculations of mass transfer processes and interaction of impurity components in HLMC, formation of protective oxide films on the surfaces of steels are given to justify the coolant technology.

Adsorption and dissociation of water on halogen pre-adsorbed Ni(111) and Ni–Cr(111) surfaces: A DFT study

Theoretical study of the adsorption and dissociation of water on halogen pre-adsorbed Ni(111) and Ni–Cr(111) surfaces has been investigated systematically. The stable co-adsorption configurations and corresponding adsorption energies for H2O molecule and halogen atom were obtained. It was found that the halogen atom strengthens the interaction of H2O with Ni surfaces. The corresponding activation barriers and reaction energies of complete water dissociation were determined. The results show that the pre-adsorbed halogen changes the rate-determining step from the dissociation of OH group to the first step dissociation of H2O molecule. The activation barrier for H2O dissociation step increases significantly by halogen atom, together with lower exothermicity. These phenomena indicate that pre-adsorbed halogen can hinder the dissociation of H2O further retard the formation of protective oxide film.

Comparative study on the adsorption behaviors of O and Cl on Fe(110) surfaces with different Cr content

Joint density functional theory calculations have been performed to investigate the interactions of atomic oxygen and chlorine with the Fe(110) and Cr-doped Fe(110) surfaces both in vacuum and in aqueous solution. The results show that Cr doping on the top of surface makes the atomic oxygen adsorption more thermodynamically favorable but slightly decreases the absorbability of chlorine. Subsurface doping atom makes little contribution to the adsorption characteristics of the cases considered in this study, which indicates that doping on the first layer is a reasonable and simplified approach for studying adsorption properties on iron surfaces. The adsorption strength of O decreases on Cl pre-adsorbed surfaces, demonstrating a competition relationship between the two species. This result is consistent with the adsorption theory of passivation, which attributes Cl-induced corrosion to its inhibition of oxygen adsorption. Cr surface doping can significantly decreases the negative effects caused by chloride ion, resulting in the formation of protective oxide film.

The effect of nickel on corrosion behaviour of high-strength low alloy steel rebar in simulated concrete pore solution

The effect of nickel on the corrosion behaviour of high-strength low alloy steel reinforcement was investigated by electrochemical measurement techniques, X-ray photoelectron spectroscopy, and auger electron spectroscopy. The results demonstrate that 3 wt% of nickel addition reduced the corrosion rate to 17 nA/cm2 compared to 730 nA/cm2 of carbon steel in the contaminated concrete condition. The enhancement of corrosion resistance for nickel-bearing steel was attributed to the formation of protective oxide film. The oxide film exhibited n-type semiconductivity in which oxygen vacancy was the main defect. The involvement of nickel in the formation process of oxide film changed its structure and composition. Nickel was enriched in the oxide film, simultaneously decreasing the defects density and the whole thickness of oxide film, and together with the increase of the Fe2+/Fe3+ ratio and the inner barrier oxide film thickness. The protective inner barrier layer of oxide film on the nickel-bearing steel can strongly inhibited the corrosive attack.

Electrochemical Inhibitory Effects of Non-edible Vegetable Oils on Low-Alloyed Low Carbon Steel in H2SO4

Corrosion inhibition mechanisms of Rubber, Neem and Jatropha seeds oils on low-alloyed low-carbon steel in 0.5 M·H2SO4 environment have been investigated herein. Potentiodynamic polarization, electrochemical impedance spectroscopy and scanning electron spectroscopy techniques were employed for the experimental process. The results obtained showed that inhibition efficiencies for Rubber, Neem and Jatropha seeds oils reached values of 99.957, 99.275 and 99.998%, respectively. The most shifts in corrosion potentials were > 85 and < 85 in positive directions for Rubber and Neem seeds oils, respectively, while Gibbs free energy of adsorption had values − 29.29 and − 15.06 and − 11.90 kJ/mol for Rubber, Neem and Jatropha seeds oils, respectively. Addition of oil inhibitors initiated formation of protective oxide films on substrate which contributed to increased inhibition efficiencies. The porosity of formed oxide film directly had impact on corrosion inhibition process as it led to localized reactions on substrate. Morphological examination of corroded substrates revealed that RSO was less prone to local corrosive attack. Inhibition efficiencies under the two electrochemical techniques employed corroborated, and corrosion inhibition occurred by retarding charge transfer reactions.

Surface Characterization and Corrosion Behavior of 90/10 Copper-Nickel Alloy in Marine Environment.

Surface characterization and corrosion behavior of 90/10 copper-nickel alloy in seawater from Xiamen bay at 30 °C for 56 days were investigated in this study. The results indicated that the corrosion product layer was mainly a mixture of CuO, Cu2O, and Cu(OH)2, with a transition to CuCl, CuCl2, and Cu2(OH)3Cl during the corrosion process. However, as corrosion proceeds, the resistance of the product film was reduced due to its heterogeneous and fairly porous structures, which led to local corrosion of the alloy. The corrosion potentials (Ecorr) increase while corrosion current densities (Icorr) decrease with time because of the formation of protective oxide film.

Effect of microstructure on electrochemical dissolution characteristics of titanium alloys in electrochemical micromachining

Titanium alloys exhibits high corrosion resistance owing to the spontaneous formation of protective oxide film when exposed to oxygen environment. Ti6Al4V is an (α+β) titanium alloy and its dissolution depends on the microstructure i.e., distribution of α and β phases and the formation of the oxide layer. In this work, the electrochemical characteristics of Ti6Al4V alloy under different heat treatment conditions were investigated using 1M NaBr solution as an electrolyte. It was found that with the heat treatment condition of 1050FC (i.e. heat treatment temperature above β transus temperature and furnace cooling), a less passive oxide film is formed as compared to the other heat treatment conditions. The electrochemical dissolution behaviour is further verified by electrochemical micromachining (ECMM) of the alloy via fabricating micro-dimples. It was concluded from electrochemical dissolution study and ECMM that the 1050FC alloy dissolves quickly compared to the other heat treated alloys.

SCC susceptibility of solution-annealed 316L SS in hydrogenated hot water below 288 °C

Stress corrosion cracking (SCC) susceptibility of solution-annealed 316L stainless steel was evaluated by slow strain rate test in oxygenated, deaerated and hydrogenated water below 288 °C. At 288 °C, no SCC was found in the specimens tested in oxygenated water, while in hydrogenated water, SCC occurred irrespective of dissolved-hydrogen (DH) content in the late stage of deformation where cold-working was followed by necking. The SCC susceptibility diminishes as temperature decreased from 288 °C to RT, which was accompanied by a reduction of oxide film thickness. At 220 °C, SCC occurred at the highest DH content only, which suggests a combined effect of DH content and test temperature on the SCC susceptibility. The combined effect can be explained by anodic reaction rate, hydrogen diffusion rate and hydrogen trapping ability. The SCC susceptibility appeared to increase with DH content, which was reasonably explained by suppression of the protective oxide film formation on specimen surface and increasing hydrogen content in the specimen. Based on an SCC model that hydrogen reduces cohesive force in austenitic stainless steel lattice, the SCC behavior can be interpreted in terms of hydrogen-assisted SCC (HASCC) where corrosion-induced hydrogen production, suppression of the formation of protective oxide film caused by hydrogen, work-hardening, and hydrogen-induced reduction of cohesive force of the lattice atoms are necessary.

Corrosion resistance of 310S and 316L austenitic stainless steel in a quaternary molten salt for concentrating solar power

This paper evaluates the corrosion of 310S and 316L austenitic stainless steel in a quaternary molten salt KNO3-NaNO2-NaNO3-KCl (wt%, 50.35:38:6.65:5) at 500℃. The corrosion rates were determined using gravimetric analysis, which measures the weight loss over 1848h in order to identify the corrosion products with field-emission scanning electron microscope (FESEM) and X-ray diffraction (XRD).The results showed that the corrosion rate of these two austenitic stainless steels has the highest value at the initial stage, and then decrease followed by a constant value, which is due to the formation of protective oxide film on the interface to prevent further corrosion. Compared to 316L, 310S has better corrosion-resistance in the salt, since it contains more Cr and Ni element. The corrosion layer thickness of the 310S and 316L is 1.613μm and 2.903μm based on the cross-section micrographs, which is equal to 0.499μm/year and 1.460μm/year, respectively.

Performance of Corrosion-Resistant Alloys in Concentrated Acids

Nickel alloys containing optimum amounts of chromium (Cr), molybdenum (Mo) and tungsten (W) are widely used in the chemical processing industries due to their tolerance to both oxidizing and reducing conditions. Unlike stainless steel (SS), Ni–Cr–Mo (W) alloys exhibit remarkably high uniform corrosion resistance in major concentrated acids, like hydrochloric acid (HCl) and sulfuric acid (H2SO4). A higher uniform corrosion resistance of Ni–Cr–Mo (W) alloys, compared to other alloys, in concentrated acids can be attributed to the formation of protective oxide film of Mo and W in reducing acids, and Cr oxide film in oxidizing solutions. The localized corrosion resistance of Ni–Cr–Mo (W) alloys, containing high amount Cr as well as Mo (or Mo + W), is also significantly higher than that of other commercially available alloys. The present study investigates the role of alloying elements, in nickel alloys, to uniform corrosion resistance in concentrated acids (HCl, HCl + oxidizing impurities and H2SO4) and localized corrosion performance in chloride-rich environments using ASTM G-48 test methodology. The corrosion tests were conducted on various alloys, and the results were analyzed using weight loss technique and electrochemical techniques, in conjunction with surface characterization tools.

Development of Stand for Testing Electrochemical Permeation (STEP) of Hydrogen through Metal Foils

Experimental Stand for Testing Electrochemical Permeation (STEP) of hydrogen through metal foils was constructed and described in this paper. Hydrogen diffusion coefficients in different metal foils at room temperature can be determined by using STEP. Influence of pulsed electron beam irradiation on hydrogen diffusion coefficient in zirconium alloy E110 was investigated. It was established that treatment by pulsed electron beam with the energy density of 18 J/cm2, by three impulses with duration 50 μs leads to a decrease in the diffusion coefficient of hydrogen on the order of one. This is due to the fact that structure with more branched crystals’ boundary formed after irradiation and such structure is effective trap for hydrogen. Also there is formation of protective oxide film after irradiation.