Electrochemical Polarization Analysis Research Articles

Prolonged and Enhanced Protection Against Corrosion Over Titanium Oxide-Coated 304L Stainless Steels Having Been Irradiated With Ultraviolet

Austenitic stainless steels are commonly used as the base material for dry storage canisters in nuclear power plants because of their excellent corrosion resistance and mechanical properties. Dry storage canisters are often exposed to chloride-containing atmosphere near seashores that could induce localized stress corrosion cracking in these stainless steels near the welded regions. Titanium dioxide (TiO2) coatings applied on stainless steel substrates (i.e. Type 304 L stainless steels) along with ultraviolet irradiation have been proposed as a mitigation measure against corrosion in canister materials. In this study, TiO2 coatings were applied on stainless steel samples using a dip-coating method. The coated samples were then thermally treated under different annealing temperatures. Corrosion behavior and photocatalytic responses of the coated samples with and without UV illumination were evaluated by electrochemical polarization analyses and open circuit potential measurements. Surface morphologies of the samples and the crystal structures were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). It was found that the TiO2 coating not only showed markedly enhanced photocathodic protection on Type 304 L stainless steels during UV illumination but also maintain more active open circuit potentials for several hours after the cutoff of UV illumination. Results from electrochemical polarization analyses further supported the superior corrosion resistance of the coated samples under UV illumination conditions. In addition, the specifically processed TiO2 coatings once irradiated with UV could lead to a prolonged corrosion resistance of the samples even hours without UV illumination.

Mechanisms investigation of cathodic-anodic coupling reaction of Zr-H2O at 360 °C by long-term in-situ electrochemical polarization analyses

Long-term on-line monitoring of in-situ electrochemical polarization curves were conducted on two zirconium claddings during corrosion in 360 °C water. Results suggest that cathodic reaction is activation-controlled, while anodic reaction is diffusion-controlled. Cathodic Tafel constants match well with the value predicted by Tafel kinetics and different hydrogen evolution reaction mechanisms of alloys with corrosion time are observed. Generally, recombination of hydrogen atoms becomes harder with time and is even harder in one of the alloys, which is proposed to increase the diffusion probability of hydrogen atoms into zirconium matrix. This proposal is in good agreement with experimental data.

Ferrocene fortified multifunctional hybrid polyurethane coatings: Synthesis, characterization and properties evaluation

The present work delineates the development of ferrocene (Fc) fortified, multifunctional, hybrid polyurethane coating films. Initially ferrocene containing polyol (Fc-PL) was successfully synthesized with the assistance of catalyst free azide-alkyne click chemistry and each step of the synthesis was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), Ultraviolet-visible spectroscopy (UV/Vis) spectroscopy and Electrospray ionization mass (ESI-mass) spectrometry. Polyurethane coatings of varying concentrations of Fc-PL, polypropylene glycol (PPG), trimethylol propane (TMP) were prepared in such a way that to maintain Fc concentrations in 0, 5, 10, 15 weight percentages with respect to polyol mixture and mixed with polymeric diphenylmethane diisocyanate (PMDI) at a OH: NCO ratio of 1:1.05 and cured under atmospheric moisture to obtain corresponding polyurethane coatings and labeled as Fc-0, Fc-5, Fc-10, Fc-15. Successful incorporation of Fc into PU coatings was confirmed by energy-dispersive X-ray spectroscopy (EDS) analysis. Effect of ferrocene on thermal stability and thermo-mechanical properties was assessed by thermo-gravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) respectively and TGA suggests that onset decomposition temperature, 30 % weight loss temperature, 50 % weight loss temperature and weight % remaining at 500°C increased as Fc wt% increases from 0 to 15 wt%, which implies that thermal stability enhanced with increasing the ferrocene concentration. DMTA demonstrated that mechanical properties i.e., storage modulus enhanced and glass transition temperature (Tg) declined with increasing the ferrocene concentration, on account of redistribution of intermolecular hydrogen bonds and metal-polymer complex formation. Ferrocene effect on corrosion resistant property, water contact angle and anti-fungal susceptibility was studied by electrochemical polarization analysis, contact angle measurements and disk diffusion test respectively. Electrochemical polarization analysis revealed that corrosion resistant property improved as the ferrocene content increases from Fc-0 to Fc-15. Ferrocene additionally imparted hydrophobicity to synthesized PU coatings. Fc-5 PU coating sample showed better hydrophobicity than other samples i.e, Fc-0, Fc-10 and Fc-15. These PU coatings are anti-fungal in nature due to the presence of hydrogen bonded triazole ring formed by click chemistry.

Electrochemical polarization analysis for optimization of external operation parameters in zinc fuel cells.

Zinc–air flow fuel cells utilizing zinc particles as fuel possess the potential to evolve as efficient distributed grid generators. In this research study, electrochemical impedance analysis was employed to determine the optimum design and operational parameters for the feasible maneuver and enhanced energy generation from zinc fuel cells. Polarization resistance (Rp), ohmic resistance (Rs), and mass transfer resistance (Rm) were used as the indicators for determination of the optimum parameters of fuel cell performance. Experimental conditions optimized from previous studies like potassium hydroxide electrolyte with temperature of 25 °C and concentration of 40 wt% zinc powder quantity of 20 g, electrode reaction surface area of 48 cm2 were followed in the fuel cells used in the present study. Parameters like collector plate material, air flow velocity and cell operating temperature were augmented and finally were all implemented in the fuel cell and operated. Plain nickel or nickel-plated copper were both advantageous as collector plate materials whereas an air flow velocity ranging from 1–3 m s−1 and a cell operating temperature of 25 °C to 45 °C were beneficial for the stability and performance of the zinc fuel cells. Finally, based on the optimized parameters obtained from the above experiments, performance tests of zinc fuel cells were investigated. The maximum power produced was 16.5 W, along with a corresponding voltage of 0.8 V, maximum current density of 430 mA cm−2 and peak power density of 364.6 mW cm−2. Thus it can be concluded that the fuel cells designed and operated in this study were capable for feasible and efficient future applications.

Fabrication of porous NiTi biomedical alloy by SHS method.

Having similar properties with natural bone, has made porous NiTi shape memory alloy (SMA) a promising material for biomedical applications. In this study porous NiTi SMA has synthesized with 30 and 40 vol.% green porosity by self propagating high temperature synthesis (SHS) from elemental Ni and Ti powders. After synthesizing, the average porosity of specimens reached to 36.8 and 49.8% for green compacts with 30 and 40 vol.% of green porosity, respectively. Combustion products were characterized by XRD, SEM, EDS and electrochemical polarization test. Although desired B2 (NiTi) phase was the dominant phase, other phases like Ti2Ni, Ni3Ti and Ni4Ti3 are found. Electrochemical polarization analysis in simulated body fluids (SBF) shows that, synthesized porous NiTi has better corrosion resistance than solid one and hydroxy apatite coating on porous NiTi worsen electrochemical corrosion resistance which is because of bioactive behavior of hydroxy apatite.

Enhanced Corrosion Mitigation of TiO2 coated Stainless Steels Under UV Illumination

Austenitic stainless steels are commonly used as the structural material for dry-storage canisters in nuclear power plants because of their excellent corrosion resistance and mechanical properties. Dry-storage canisters are often exposed to chloride containing atmosphere near seashores, which could induce localised stress corrosion cracking in these stainless steels near the welded regions. TiO2 coatings applied on stainless steel substrates (i.e. Type 304 stainless steels) along with ultraviolet (UV) irradiation have been proposed as a mitigation measures against the corrosion in canister materials. In this study, TiO2 coatings were applied on stainless steel samples using a sol-gel dip-coating method. The corrosion characteristics of the coated samples were studied under the conditions of different coating treatments, annealing temperatures, annealing atmospheres and UV illumination durations. The corrosion mitigation performance of the coated samples with and without UV illumination was evaluated by electrochemical polarization analyses and open-circuit potential measurements. The surface morphologies of the samples were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and laser Raman spectroscopy. In addition, the photocatalytic responses of these coatings exposed to various acidic and alkaline aqueous solutions under aerated and deaerated conditions were also studied. The results indicated that the TiO2 coating not only could lead to low electrochemical potentials of the stainless steel samples during UV illumination, but could also maintain the low electrochemical potentials even after the cut off of UV illumination. Results from Electrochemical polarization analyses further support the superior corrosion resistance under UV-illumination conditions. Keywords: Stainless steel, TiO2 coating, ultraviolet illumination.

Enhanced Corrosion Mitigation of TiO2 Coated Stainless Steels Under UV Illumination

Austenitic stainless steels are commonly used as the structural material for dry-storage canisters in nuclear power plants because of their excellent corrosion resistance and mechanical properties. Dry-storage canisters are often exposed to chloride containing atmosphere near seashores, which could induce localised stress corrosion cracking in these stainless steels near the welded regions. TiO2coatings applied on stainless steel substrates (i.e. Type 304 stainless steels) along with ultraviolet (UV) irradiation have been proposed as a mitigation measures against the corrosion in canister materials. In this study, TiO2 coatings were applied on stainless steel samples using a sol-gel dip-coating method. The corrosion characteristics of the coated samples were studied under the conditions of different coating treatments, annealing temperatures, annealing atmospheres and UV illumination durations. The corrosion mitigation performance of the coated samples with and without UV illumination was evaluated by electrochemical polarization analyses and open-circuit potential measurements. The surface morphologies of the samples were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and laser Raman spectroscopy. In addition, the photocatalytic responses of these coatings exposed to various acidic and alkaline aqueous solutions under aerated and deaerated conditions were also studied. The results indicated that the TiO2coating not only could lead to low electrochemical potentials of the stainless steel samples during UV illumination, but could also maintain the low electrochemical potentials even after the cut off of UV illumination. Results from Electrochemical polarization analyses further support the superior corrosion resistance under UV-illumination conditions. Keywords: Stainless steel, TiO2 coating, ultraviolet illumination.

Laser-treated austenitic steel and nickel alloy for human implants

ABSTRACTThe recent research in biocompatible materials has been useful in replacing and supporting the fractured natural human bones/joints. Under some condition, negative reaction like release of ions from the bare metal toward the human body fluid leads to corrosion. In this proposed research paper, the biocompatibility of the laser surface-modified austenitic stainless steel (SS316L) and nickel-based superalloy (Inconel 718) was studied. The investigation on laser-modified surfaces is evaluated through electrochemical polarization analysis using simulated body fluid (SBF). The samples subjected to electrochemical polarization analysis were characterized by optical image analysis, SEM, EDS, and XRD analysis. It was inferred that laser surface-modified materials provided enhanced corrosion resistance and bare nickel alloy is more susceptible to corrosion by SBF.

Corrosion behavior of TiO2-treated type 304 stainless steels in high temperature water containing with hydrogen peroxide

ABSTRACTTitanium dioxide (TiO2) treatment coupled with ultraviolet irradiation was selected as a corrosion mitigation technique for Type 304 stainless steel (SS) in high-temperature pure water with the presence of hydrogen peroxide (H2O2). Type 304 SS specimens were pre-oxidized in oxygenated pure water at 288 °C and then coated with TiO2 nanoparticles by hydrothermal deposition. Electrochemical polarization analyses were conducted to investigate the corrosion behavior of both TiO2-treated and pre-oxidized specimens in 288 °C pure water with 300 ppb H2O2. Ultraviolet (UV) irradiation was then imposed upon the TiO2-treated specimens to examine if there was any distinct photoelectric effect on the corrosion behavior of the treated samples. It was found that the electrochemical corrosion potentials of the TiO2 treated specimens under UV irradiation were 10–20 mV lower than those without UV. In addition, the corrosion current densities of the treated specimens were also lower in the presence of UV radiation. Without UV radiation, however, no significant differences were observed between the TiO2 treated and untreated specimens. These results indicate that the TiO2 treatment in combination with UV radiation would reduce the corrosion rate of Type 304 SS in H2O2-rich, high-temperature pure water.

Effect of laser remelting on the microstructure and corrosion resistance of plasma sprayed Fe-based coating

Fe-based amorphous and nanocrystalline coatings were fabricated by air plasma spraying. The coatings were further treated by laser remelting process to improve their microstructure and properties. The corrosion resistance of the as-sprayed and laser-remelted coatings in 3.5wt% NaCl and 1 mol/L HCl solutions was evaluated by electrochemical polarization analysis. It was found that laser-remelted coating appeared much denser than the as-sprayed coating. However, laser-remelted coating contains much more nanocrystalline grains than the as-sprayed coatings, resulting from the lower cooling rate in laser remelting process compared with plasma spraying process. Electrochemical polarization results indicated that the laser-remelted coating has great corrosion resistance than the as-sprayed coating because of its dense structure.

Effect of Heat Treatment on Corrosion Behaviour of Amorphous Metal Fibers

Amorphous metal fiber has high corrosion resistance and excellent mechanical properties, making it a kind of good material for reinforcing concrete matrix. The effect of heat treatment on the corrosion behaviour of Fe73-Cr6C9Si1P11 amorphous metal fibers in 0.5 mol/L H2SO4 solution was investigated by electrochemical polarization analysis. Differential scanning calorimetry (DSC) was used to measure the thermal properties. The evolution of the crystallization process after heat treatment was identified by X-ray diffraction (XRD). The results show that the a-Fe. Fe2 P and Fe3 P crystalline phases individually precipitate in the amorphous matrix with increasing annealing temperature. The as prepared amorphous sample shows high corrosion resistance with a lower passivation current density and a wider passive region. The corrosion resistance dramatically decreases after the annealing temperature is higher than 400 °C.

Corrosion performance and metal ion release of amorphous and nanocrystalline Fe-based alloys under simulated body fluid conditions

The corrosion performance of Fe55−xCr18Mo7B16C4Nbx (x=0 and 3at%) amorphous and nanocrystalline ribbons in Ringer and 0.9% NaCl+HCl solutions open to air at 37°C, was investigated by electrochemical polarization analysis, aiming to estimate the feasibility of alloys as potential biomaterials. It was indicated that the both Fe52Cr18Mo7B16C4Nb3 amorphous and nanocrystalline ribbons have higher corrosion resistance value than that of 316L stainless steel. Besides, the results showed that the amorphous ribbons have larger polarization resistance value than that of nanocrystalline alloys under the same condition. Interestingly, the results of the inductively coupled plasma apparatus showed that all the samples do not release any significant ions into the Ringer’s solution, while there are very few ions releasing into the aqueous 0.9% NaCl+HCl solution for amorphous alloys compared to nanocrystalline alloys and 316L stainless steel.

Hydrothermal treatments of TiO2 on Type 304 stainless steels for corrosion mitigation in high temperature pure water

Incidents of intergranular stress corrosion cracking (IGSCC) have occurred in boiling water reactors (BWRs) for decades. The electrochemical corrosion potential (ECP) is currently a major indicator for the IGSCC susceptibility of stainless steel (SS) components in BWR environments. This study proposes a novel technique of titanium dioxide (TiO2) treatment to mitigate the IGSCC problems in BWRs that could eventually lead to a lower demand of dissolved hydrogen for hydrogen water chemistry (HWC). Electrochemical polarization analyses and ECP measurements were conducted to investigate the impact of ultraviolet (UV) radiation on the electrochemical behavior of oxygen and TiO2 treated specimens in 288°C pure water. Prior to the electrochemical tests, all specimens were thermally sensitized and pre-oxidized in high temperature pure water containing 300ppb dissolved O2. Afterwards, 38nm TiO2 nanoparticles were deposited on the specimens by hydrothermal deposition at 150°C for 96h. The surface morphologies of the specimens were examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and laser Raman spectra (LRS). SEM and EDX results showed that the distribution of TiO2 deposited on the oxides with both hematite (α-Fe2O3) and magnetite (Fe3O4) structures were not uniform and continuous. LRS results showed that the TiO2 particles on the treated specimens had an anatase-type structure. In addition, the ECPs of the TiO2 treated specimens with UV radiation were 100mV lower than those without UV in high temperature water containing various levels of dissolved O2. The results of electrochemical potentiodynamic polarization analysis revealed that the corrosion current densities of the treated specimens and the exchange current densities of the O2 reduction reactions were comparatively lower in the presence of UV radiation. Without UV radiation, however, no significant differences were observed between the TiO2 treated and untreated specimens. These results indicate that the TiO2 treatment in combination with UV radiation would effectively reduce the corrosion rate of Type 304 stainless steels in high temperature oxygenated environments.

Electrochemical characteristics of zirconium oxide treated Type 304 stainless steels of different surface oxide structures in high temperature water

Electrochemical polarization analyses were conducted to investigate the impact of different oxide structures on corrosion resistance of ZrO 2-treated Type 304 stainless steel specimens in high temperature water. All specimens were pre-oxidized in high temperature water containing either 300 ppb dissolved oxygen or 50 ppb dissolved hydrogen, followed by a hydrothermal deposition treatment with ZrO 2 nanoparticles. Experimental results revealed that the corrosion potentials and corrosion current densities on the ZrO 2-treated specimens were lower than those on the untreated ones, and the decreases in these parameters were more distinct on the ZrO 2-treated specimens with oxides developed under dissolved oxygen condition.

The Influence of Various Treating Parameters on the Corrosion of ZrO2-Treated Type 304 Stainless Steels in High-Temperature Water

Corrosion mitigation techniques specifically developed for the vessel internals of boiling water reactors (BWRs) such as hydrogen water chemistry (HWC), catalytic coatings, and inhibitive coatings have been studied and/or adopted worldwide in the past decade. The common goal of these techniques is to mitigate intergranular stress corrosion cracking in the vessel internal components of BWRs. For enhancing the effectiveness of HWC through a more effective reduction in electrochemical corrosion potential accompanied by a lower hydrogen consumption rate or even without any added hydrogen, the technique of inhibitive treatment on structural component surfaces was brought into consideration. In the current study, surfaces of preoxidized square-disk specimens made of Type 304 stainless steel (SS) were treated with zirconium oxide (ZrO2) (particle sizes of 0.7 μm and 0.1 μm) via hydrothermal deposition at either 90 or 150°C for 7 or 14 d, while some preoxidized specimens remained untreated. The concentration of the treating solution was maintained at either 10 parts per million (ppm) or 122 ppm (1mM) during the ZrO2 deposition processes. Electrochemical polarization analyses at 288°C were conducted to characterize the electrochemical properties of the treated and untreated SS specimens in pure water with either dissolved oxygen or dissolved hydrogen. It was found that a smaller particle size, a longer treating time, a lower treating temperature, as well as a higher treating solution concentration seemed to improve the corrosion resistance of the treated specimens in oxygenated environments and to moderately deter the hydrogen oxidation rate on the specimens.

The Influence of Various Treating Parameters on the Corrosion of ZrO2-Treated Type 304 Stainless Steels in High-Temperature Water

Corrosion mitigation techniques specifically developed for the vessel internals of boiling water reactors (BWRs) such as hydrogen water chemistry (HWC), catalytic coatings, and inhibitive coatings have been studied and/or adopted worldwide in the past decade. The common goal of these techniques is to mitigate intergranular stress corrosion cracking in the vessel internal components of BWRs. For enhancing the effectiveness of HWC through a more effective reduction in electrochemical corrosion potential accompanied by a lower hydrogen consumption rate or even without any added hydrogen, the technique of inhibitive treatment on structural component surfaces was brought into consideration. In the current study, surfaces of preoxidized square-disk specimens made of Type 304 stainless steel (SS) were treated with zirconium oxide (ZrO2) (particle sizes of 0.7 μm and 0.1 μm) via hydrothermal deposition at either 90 or 150°C for 7 or 14 d, while some preoxidized specimens remained untreated. The concentration of the treating solution was maintained at either 10 parts per million (ppm) or 122 ppm (1mM) during the ZrO2 deposition processes. Electrochemical polarization analyses at 288°C were conducted to characterize the electrochemical properties of the treated and untreated SS specimens in pure water with either dissolved oxygen or dissolved hydrogen. It was found that a smaller particle size, a longer treating time, a lower treating temperature, as well as a higher treating solution concentration seemed to improve the corrosion resistance of the treated specimens in oxygenated environments and to moderately deter the hydrogen oxidation rate on the specimens.

The Influence of ZrO2 Treatment on the Electrochemical Behavior of Oxygen and Hydrogen on Type 304 Stainless Steels in High Temperature Water

For enhancing the effectiveness of hydrogen water chemistry (HWC) in boiling water reactors (BWRs) in the aspects of lower hydrogen consumption and of a more effective reduction in electrochemical corrosion potential (ECP), the technique of inhibitive protective coating on structural materials was brought into consideration. The application of inhibitive treatment is aimed at deterring the reduction reactions of oxidizing species occurring on metal surfaces and the oxidation reaction of metals. In the current study, electrochemical polarization analyses at 288°C were conducted to characterize the electrochemical properties of ZrO2 treated and untreated 304 stainless steel specimens in pure water with dissolved oxygen or hydrogen. The polarization results showed that the treated specimens exhibited lower corrosion potentials, corrosion current densities, exchange current densities, and cathodic current densities than the untreated one in high temperature pure water with dissolved oxygen. For the environment with dissolved hydrogen only, reductions in anodic current density and exchange current density were observed, indicating that the ZrO2 treatment also deterred the oxidation reaction of hydrogen. However, in comparison with the data obtained, the ZrO2 treatment seemed to be relatively more effective in inhibiting the oxygen reduction reaction than inhibiting the hydrogen oxidation reaction. One additional beneficial outcome was that the anodic current density of the metal was also decreased, leading to a much lower overall corrosion current density of the ZrO2 treated specimen.

Intergranular Stress Corrosion Cracking of Platinum Treated Type 304 Stainless Steels in High Temperature Water

Electrochemical polarization analyses, slow strain rate tensile (SSRT) tests and crack growth tests were conducted to investigate the intergranular stress corrosion cracking (IGSCC) characteristics of platinum treated Type 304 stainless steels in 288°C pure water. All specimens were thermally sensitized and pre-oxidized before the tests, and some of them were additionally treated with platinum via hydrothermal deposition. Test environments were specifically designed in a circulation loop to create water chemistry conditions of hydrogen to oxygen molar ratios (MH/O)of 0, 0.5, and 2.7 in the coolant. Test results showed that the corrosion current densities of the specimens treated with platinum were higher than those of the pre-oxidized ones under oxygenated conditions, but the corrosion potentials of the treated specimens could be either lower or higher than those of the untreated ones. In addition, IGSCC was not observed on all specimens (treated or untreated) when the MH/O in the test coolant was 0.5 or 2.7. However, the platinum treated specimens actually showed severer IGSCC after the SSRT tests conducted under the coolant condition of MH/O=0. Crack growth test results indicate a similar but worse trend to that in the SSRT tests. It was therefore suggested that one must exercise extra caution to use corrosion potential as a sole indicator in evaluating the influence of noble metal treatment on the IGSCC susceptibility of Type 304 stainless steels, especially when the MH/O in the coolant is relatively low or the dissolved oxygen concentration remains comparatively high.

Effect of Halide Ions on Electrochemical Behavior and Stress Corrosion Cracking of 67/33 α-Brass in Aqueous Environments

Abstract The slow strain rate tension (SSRT) technique was used to study the effect of strain rate on susceptibility to stress corrosion cracking (SCC) and crack velocity of 67/33 α-brass (UNS C26800) in 0.1 M sodium halide solutions (pH = 6.8) at 25°C. The effect of halide ions on electrochemical behavior of α-brass also was investigated using cyclic polarization techniques. Results indicated fluoride ions (F−) induced a significant susceptibility to intergranular stress corrosion cracking (IGSCC). Susceptibility increased with decreasing strain rate. Crack velocity also increased with strain rate in a double logarithmic relationship. The entire fracture surface was characteristic of IGSCC at a critical strain rate of 2 × 10−6/s. The open-circuit potential (OCP) was within the potential range where cuprous oxide (Cu2O) is stable. Electrochemical polarization analysis confirmed that 67/33 α-brass can form a passive Cu2O film in 0.1 M sodium fluoride (NaF) solution and that this passive film can break down...