共查询到20条相似文献,搜索用时 15 毫秒
1.
Alina-Crina Ciubotariu Lidia Benea Magda Lakatos-Varsanyi Viorel Dragan 《Electrochimica acta》2008,53(13):4557-4563
In this paper, the results on the electrochemical impedance spectroscopy and corrosion properties of electrodeposited nanostructured Al2O3-Ni composite coatings are presented. The nanocomposite coatings were obtained by codeposition of alumina nanoparticles (13 nm) with nickel during plating process. The coating thickness was 50 μm on steel support and an average of nano Al2O3 particles inside of coatings at 15 vol.% was present. The structure of the coatings was investigated by scanning electron microscopy (SEM). It has been found that the codeposition of Al2O3 particles with nickel disturbs the nickel coating's regular surface structure. The electrochemical behavior of the coatings in the corrosive solutions was investigated by polarization potentiodynamic and electrochemical impedance spectroscopy methods. As electrochemical test solutions 0.5 M sodium chloride and 0.5 M potassium sulphate were used in a three electrode open cell. The corrosion potential is shifted to more negative values for nanostructured coatings in 0.5 M sodium chloride. The polarization resistance in 0.5 M sodium chloride decreases in 24 h, but after that increases slowly. In 0.5 M potassium sulphate solution the polarization resistance decreases after 2 h and after 30 h of immersion the polarization resistance is higher than that of the beginning value. The corrosion rate calculated by polarization potentiodynamic curves obtained after 30 min from immersion in solution is smaller for nanostructured coatings in 0.5 M potassium sulphate (4.74 μm/year) and a little bit bigger in 0.5 M sodium chloride (5.03 μm/year). 相似文献
2.
Gang Liu Huamin Zhang Hexiang Zhong Jingwei Hu Dongyan Xu 《Electrochimica acta》2006,51(26):5710-5714
A novel Pt4ZrO2/C catalyst was prepared and compared with 20 wt.% Pt/C in terms of the sintering resistance and corrosion resistance. To evaluate their sintering resistance and corrosion resistance properties, an accelerated ageing test (AAT) was performed. The catalysts before and after AAT were characterized by cyclic voltammetry (CV), rotating disk electrode (RDE) and X-ray diffraction (XRD). After AAT, the dissolution rate of Pt and Zr in H3PO4 media (105 wt.%, 204 °C) was characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The electrochemical area (ECA) changes of thin film electrodes based on Pt4ZrO2/C and Pt/C catalysts were also evaluated using continuous CV sweep technique. All the results showed that Pt4ZrO2/C has higher sintering resistance and corrosion resistance than Pt/C. ‘Anchor effect’ is proposed to explain the enhanced effect of ZrO2 in Pt4ZrO2/C binary catalyst compared with Pt/C that contain platinum alone. 相似文献
3.
Hyeoung Ho Park Kyeong Seon Kim Byeung Kyeun Park Tae Sung Bae 《Electrochimica acta》2010,55(20):6109-4667
The selection of bioactive and electrochemically stable materials for implants having effective corrosion resistance during long-term use in the body is essential. In this study, the bioactive and electrochemical properties of titanium implant materials with a nanotube surface treatment and various types of post-treatments were examined. Two types of amorphous TiO2 nanotubes were grown homogeneously on the surface: one with a larger diameter (approximately 85 nm) and one with a smaller diameter (approximately 50 nm). Amorphous TiO2 nanotubes were partially crystallized to anatase and rutile by heat treatment at 500 °C for 2 h. The corrosion potential (Ecorr) of the heat-treated sample (HT) had a novel value of 0.102 V due to the stable TiO2 crystal phase compared to the −0.106 V observed in the anodic oxidation sample (AN). The corrosion current density (Icorr) ranged from 0.20 to 0.64 μA/cm2 according to the post-treatment conditions. However, at 0.6 V, where a passive layer had formed, the corrosion resistance of the HT was approximately ten times that of the AN and untreated (UT) samples. After evaluating the hydroxyapatite (HA)-forming ability by immersion in a simulated body fluid (SBF) solution, the CP process induced the adsorption of Ca and P onto HT. A comparison of the time-dependent amount of Ca and P adsorption showed that Ca adsorption plays a role in determining the rate at which hydroxyapatite (HA) is formed. For the induction of HA formation, a level of Ca adsorption above a critical level is required. 相似文献
4.
The mechanism of inhibition of carbon dioxide (CO2) corrosion of high purity iron by cetyl trimethyl ammonium bromide (CTAB) was investigated by contact angle, polarization resistance and X-ray photoelectron spectroscopy (XPS). The wetting properties, corrosion inhibitor performance and the adsorption of the inhibitor on a high purity iron surface were investigated. Test conditions during corrosion testing were 25 °C, 3 wt% NaCl brine, initial pH 3.9 and 1 bar CO2 partial pressure. The samples were precorroded for 5 h before inhibitor was added.The inhibitor performance data showed that addition of CTAB significantly reduced the corrosion rate of high purity iron. The decreased corrosion rate seems to be caused by a blocking effect, where the CTAB forms a surface structure on the iron surface. Chemisorption of the CTAB molecules, which could lead to gradually increasing inhibitor efficiency, might be the reason for the slowly decreasing corrosion rate. The XPS data confirmed a gradual accumulation of inhibitor on the surface but did not show any distinct change between different mechanisms at different exposure times. The contact angle measurements showed that the iron was water wet, with a contact angle higher than 160°, at all CTAB concentrations. 相似文献
5.
The Cr2O3 nanoparticles were modified with 3-amino propyl trimethoxy silane in order to obtain proper dispersion and increment compatibility with the polyurethane coating matrix. The nanocomposites prepared were applied on the St-37 steel substrates. The existence of 3-amino propyl trimethoxy silane on the surface of the nanoparticles was investigated by Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Dispersion of the surface modified particles in the polyurethane coating matrix was studied by a field emission-scanning electron microscope (FE-SEM). The electrochemical impedance spectroscopy (EIS) and salt spray tests were employed in order to evaluate the corrosion resistance of the polyurethane coatings. Polarization test was done in order to investigate the corrosion inhibition properties of the Cr2O3 nanoparticle on the steel surface in 3.5 wt.% NaCl solution. The adhesion strengths of the coatings were evaluated by pull-off adhesion tester before and after 120 days immersion in 3.5 wt.% NaCl solution. FT-IR and TGA analyses revealed that surface modification of the nanoparticles with 0.43 silane/5 g pigment resulted in the greatest amount of silane grafting on the surface of particles. Results obtained from FE-SEM analysis showed that the surface modified nanoparticles dispersed in the coating matrix properly. Results obtained from EIS and salt spray analyses revealed that the surface modified particles enhanced the corrosion protection performance of the polyurethane coating considerably. The improvement was more pronounced for the coating reinforced with 0.43 g silane/5 g pigment. Moreover, the adhesion loss decreased in the presence of surface modified nanoparticles with 0.43 silane/5 g pigment. 相似文献
6.
For thermal barrier coating (TBC) applications, yttria stabilized zirconia (YSZ) is susceptible to hot corrosion. This paper examines the hot corrosion performance of ZrO2/Ta2O5 compounds. Different compositions of ZrO2–Ta2O5 samples in the presence of molten mixture of Na2SO4+V2O5 at 1100 °C were tested. The compositions were selected to form tetragonal and orthorhombic phases of zirconium-tantalum oxides. Results show that orthorhombic zirconium-tantalum oxide is more stable, both thermally and chemically in Na2SO4+V2O5 media at 1100 °C, and shows a better hot corrosion resistance than the tetragonal phase. 相似文献
7.
Hot corrosion behaviors of gas tunnel type plasma sprayed La2Zr2O7 thermal barrier coatings 总被引:1,自引:0,他引:1
Subramaniam YugeswaranAkira Kobayashi P.V. Ananthapadmanabhan 《Journal of the European Ceramic Society》2012,32(4):823-834
Gas tunnel type plasma sprayed free-standing La2Zr2O7 coating specimens with a thickness of 300-400 μm were prepared under optimized operating conditions and were subjected to hot corrosion test in the presence of corrosive impurities such as V2O5, Na2SO4, and Na2SO4 + V2O5 mixtures (60:40 wt%) at two different temperatures for duration of 5 h, i.e. 1000 and 1350 K for V2O5 and Na2SO4 + V2O5 mixtures, 1200 and 1350 K for Na2SO4. For temperatures at 1350 K, the reaction mechanism of V2O5 and the mixture of Na2SO4 + V2O5 are similar and LaVO4 is formed as the corrosive product, which leads to massive phase transformation from pyrochlore to tetragonal and monoclinic phases. Microstructural observations from planar reaction zone (PRZ) and melt infiltrated reaction zone (MIRZ) reveals that the present La2Zr2O7 coating exhibits good hot corrosion resistance in V2O5 environment and moderate for the mixture of Na2SO4 + V2O5, but is worst in Na2SO4 environment. 相似文献
8.
The effects of cold work and sensitization treatment on the microstructure and corrosion resistance of a nickel-free high nitrogen stainless steel (HNSS) in 0.5 M H2SO4 + 0.5 M NaCl, 3.5% NaCl and 0.5 M NaOH + 0.5 M NaCl solutions have been investigated by microscopic observations, electrochemical tests and surface chemical analysis. Cold work introduced a high defect density into the matrix, resulting in a less protective passive film as well as reduced corrosion resistance for heavily cold worked HNSS in a 3.5% NaCl solution. No obvious degradation in corrosion resistance took place in a 0.5 M H2SO4 + 0.5 M NaCl solution, possibly due to the stability of the passive film in this solution. Sensitized HNSSs showed reduced corrosion resistance with increasing cold work level in both 3.5% NaCl and 0.5 M H2SO4 + 0.5 M NaCl solutions due to a reduction in the anti-corrosion elements in the matrix during the cold work-accelerated precipitation process. The cold work and sensitization treatment had no influence on the corrosion resistance of the HNSS in the 0.5 M NaOH + 0.5 M NaCl solution even though the property of the passive film changed. The effects of cold work and sensitization treatment on the characteristics of passive films formed in the three solutions are discussed. 相似文献
9.
Scanning electron microscopy, X-ray diffraction and electrochemical measurement technique were applied to investigate the corrosion of SM 80SS tube steel in stimulant solution with carbon dioxide (CO2) and hydrogen sulfide (H2S) at variable conditions of PCO2/PH2S and temperature. The results suggest that there exists a synergism of sweet corrosion and sour corrosion on the steel surface, corrosion attack increases in the initial stage and then decrease with the increase of PCO2 or PH2S; serious corrosion occurs in the PCO2/PH2S ranged from 31 to 520. In addition, the fitted parabola function equation Y = 0.47873 + 0.04014X - (3.23788E−5)X2 is established, and the most serious corrosion is 600 for PCO2/PH2S. Under the moderate contents of PCO2 and PH2S, the corrosion scale consists of FeS0.9 and FeCO3; for relatively high PH2S, additive product FeS comes into being at high temperature such as T = 150 °C, product FeO(OH) is found in the corrosion scale. The H2S corrosion has a significant effect on the whole reaction process and iron sulfide is superior to precipitating on the steel surface compared with iron carbonate. In addition, the surface scales of iron sulfide almost act as a diffusion barrier and inhibit the corrosion by a coverage effect strongly depending on H2S concentration by EIS measurement. 相似文献
10.
S. Sathiyanarayanan 《Electrochimica acta》2007,52(5):2068-2074
Organic coating strategies for corrosion protection with inherently conducting polymers have become important because of restriction on the use of heavy metals and chromates in coatings due to their environmental problems. This work presents the synthesis of polyaniline-TiO2 composites (PTC) and the corrosion protection behaviour of PTC containing coating on steel. PTC was prepared by chemical oxidation of aniline and TiO2 by ammonium persulfate in phosphoric acid medium. The PTC was characterized by FTIR, XRD and SEM techniques. Suitable coating with PTC was formed on steel using acrylic resin. Using electrochemical impedance spectroscopy, the PTC containing coating's behaviour in 3% NaCl immersion test and salt spray test has been found out. Results indicate that the coating containing PTC is able to maintain the potential of steel in passive region due to its redox property. The resistance of the coating containing PTC was more than 107 Ω cm2 in 3% NaCl solution after 60 days and 109 Ω cm2 in the salt spray test of 35 days. But the resistance of the TiO2 containing coating was found to be less than 104 Ω cm2 in both the cases. The high performance of PTC containing coating is attributed to the passivation of steel by polyaniline. 相似文献
11.
Vaibhav V. Nikam Sunniva R. Collins Peter C. Williams Gary W. Henrich 《Electrochimica acta》2008,53(6):2743-2750
One of the current challenges for application of PEM fuel cell is to find corrosion resistant, electrically conductive, light weight, cost competitive bipolar plate material. Low temperature carburization (LTC) of stainless steels is a novel, patented process by Swagelok Company. This paper addresses the corrosion resistance characteristics of LTC SS 316 for polymer electrolyte membrane fuel cell (PEMFC) bipolar plate applications. Corrosion properties of this material were studied using potentiodynamic and potentiostatic tests in simulated (1 M H2SO4 + 2 ppm HF, 0.5 M H2SO4, pH: 4.0, and 5% HCl + 5% Na2SO4) PEMFC conditions. LTC SS 316 showed excellent corrosion resistance in these conditions compared to SS 316. The mechanism of anodic dissolution and general corrosion of LTC SS 316 was observed to be similar to SS 316 however the extent of LTC SS 316 corrosion was less. LTC SS 316 showed corrosion currents well below 16 μA cm−2 in anodic and cathodic atmospheres under potentiostatic conditions. The potentiostatic current rapidly falls to ∼4.0 and ∼1.5 μA cm−2 under anodic and cathodic conditions, respectively. LTC SS 316 was observed to form a thinner oxide layer as compared to SS 316 after 24 h of potentiostatic testing. Moreover LTC SS 316 lowered the interfacial contact resistance by approximately 24% as compared to SS 316 after corrosion testing. Hence this study clearly states the performance advantage of using LTC SS 316 as bipolar plate material as compared to conventional materials. 相似文献
12.
Weiwei Chen 《Electrochimica acta》2010,55(22):6865-9102
Novel sol-enhanced Ni-TiO2 nano-composite coatings were electroplated by adding a transparent TiO2 sol into the traditional electroplating Ni solution. It was found that the structure, mechanical properties and corrosion resistance of the nano-composite coatings were largely determined by the sol concentration. The higher sol concentration in the plating electrolyte led to a higher content of TiO2 nano-particles in the coating matrix. The coating prepared at the sol concentration of 12.5 mL/L had the best microhardness, wear resistance and corrosion resistance. Adding excessive sol to the electrolyte changed the surface microstructure, caused cracking on the coating surface and deteriorated the properties. It was demonstrated that the corrosion resistance of the composite coatings is determined by two factors: surface microstructure and incorporation of TiO2 nano-particles. 相似文献
13.
Composite coatings Ni/Al2O3 were electrochemically deposited from a Watts bath. Al2O3 powder with particle diameter below 1 μm was codeposited with the metal. The obtained Ni/Al2O3 coatings contained 5-6% by weight of corundum. The structure of the coatings was examined by scanning electron microscopy (SEM). It has been found that the codeposition of Al2O3 particles with nickel disturbs the nickel coating's regular surface structure, increasing its microcrystallinity and surface roughness. DC and AC electrochemical tests were carried out on such coatings in a 0.5 M solution of Na2SO4 in order to evaluate their corrosion resistance. The potentiodynamic tests showed that the corrosion resistance of composite coating Ni/Al2O3 is better than that of the standard nickel coating. After 14 days of exposure the nickel coating corrodes three times faster than the Ni/Al2O3 coating. The electrochemical behaviour of the coatings in the corrosive solution was investigated by electrochemical impedance spectroscopy (EIS). An equivalent circuit diagram consisting of two RC electric circuits: one for electrode, nickel corrosion processes and the other for processes causing coating surface blockage, were adopted for the analysis of the impedance spectra. The changes in the charge transfer resistance determined from the impedance measurements are comparable with the changes in corrosion resistance determined from potentiodynamic measurements. 相似文献
14.
The aim of this work was studying the effects of addition of Al2O3 nanoparticles on the anticorrosion performance of an epoxy/polyamide coating applied on the AA-1050 metal substrate. For this purpose, the epoxy nanocomposites were prepared using 1, 2.5 and 3.5 (w/w) pre-dispersed surface modified Al2O3 nanoparticles. Field-emission electron microscope (FE-SEM) and ultraviolet–visible (UV–Vis) techniques were utilized in order to evaluate the nanoparticles dispersion in the epoxy coating matrix. The anticorrosion performance of the nanocomposites was studied by electrochemical impedance spectroscopy (EIS) (in 3.5 wt% NaCl solution for 135 days immersion) and salt spray test for 1000 h. The coating resistance against hydrolytic degradation was also studied by optical microscope and Fourier-transform infrared spectroscopy (FTIR). Results obtained from FE-SEM micrographs and UV–visible spectra showed that the nanoparticles dispersed in the coating matrix uniformly with particle size less than 100 nm even at high loadings. Results revealed that nano-Al2O3 particles could significantly improve the corrosion resistance of the epoxy coating. Nanoparticles reduced water permeability of the coating and improved its resistance against hydrolytic degradation. 相似文献
15.
Influence of grain size on the corrosion behavior of a Ni-based superalloy nanocrystalline coating in NaCl acidic solution 总被引:1,自引:0,他引:1
The effects of grain size on the electrochemical corrosion behavior of a Ni-based superalloy nanocrystalline (NC) coating fabricated by a magnetron sputtering technique, has been investigated in 0.5 M NaCl + 0.05 M H2SO4 solution. Coatings with grain sizes 10 nm, 50 nm and 100 nm were fabricated on glass and the superalloy substrates. The results indicate that a passive film with porous property, n-type semiconductive property and incorporation of chloride ions formed on the NC coating with 100 nm grain size, which increased the susceptibility to pitting corrosion. The NC coatings with 10 nm and 50 nm grain size formed compact, non-porous and p-type passive films without chloride ions, which improved resistance to pitting corrosion. The smaller grain size of the material decrease the amount of chloride ions adsorbed on the surface and promoted the formation of compact passive film, which significantly increased the material's resistance to pitting corrosion in acidic solution. 相似文献
16.
Studies on plasma sprayed bi-layered ceramic coating on bio-medical Ti-13Nb-13Zr alloy 总被引:1,自引:0,他引:1
S. SathishM. Geetha S.T. Aruna N. BalajiK.S. Rajam R. Asokamani 《Ceramics International》2011,37(4):1333-1339
Biomedical Ti alloys are prone to undergo degradation due to the combined effect of wear and corrosion. To overcome these problems, surface modification techniques are being used. In this paper, the biomedical Ti alloy Ti-13Nb-13Zr was plasma sprayed with nanostructured Al2O3-13 wt%TiO2, yttria stabilized zirconia powders and bilayer containing alternate layers of the two coatings to improve the corrosion resistance and microhardness of the substrate. The plasma sprayed coatings were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The microstructure, microhardness and surface roughness of the coatings were investigated. The corrosion resistance of the coatings was studied in simulated body conditions. The results show improved corrosion resistance for the bilayered coating compared to the individual plasma sprayed coatings on biomedical Ti-13Nb-13Zr alloy substrate. 相似文献
17.
Wei Zhou Ran Ran Zhihao Chen Pingying Zeng Hongxia Gu Wanqin Jin Nanping Xu 《Electrochimica acta》2007,52(22):6297-6303
A double-layer composite electrode based on Ba0.5Sr0.5Co0.8Fe0.2O3−δ + Sm0.2Ce0.8O1.9 (BSCF + SDC) and BSCF + SDC + Ag was investigated to be a promising cathode and also anode for the electrochemical oxygen generator based on samaria doped ceria electrolyte. The Ag particles in the second layer were not only the current collector but also the improver for the oxygen adsorption at the electrode. a.c. impedance results indicated that the electrode polarization resistance, as low as 0.0058 Ω cm2 was reached at 800 °C under air. In oxygen generator cell performance test, the electrode resistance dropped to half of the value at zero current density under an applied current density of 2.34 A cm−2 at 700 °C, and on the same conditions the oxygen generator cell was continual working for more than 900 min with a Faradic efficiency of ∼100%. 相似文献
18.
M.N. Ibarra Castro J.M. Almanza Robles D.A. Cortés Hernandez J.C. Escobedo Bocardo J. Torres Torres 《Ceramics International》2010
In order to improve the corrosion resistance of aluminosilicate refractories by molten aluminum, SrSO4 and BaSO4 powders were used. Mullite substrates with and without addition of 20 wt.% SrSO4 or BaSO4 were sintered at 1400 °C for 6 h. Corrosion and wetting experiments with molten pure Al and Al–7.5Si were carried out at 900 °C for 24 h and 900 °C for 2 h, respectively. The corrosion layer was thicker in the mullite sample (≥2 mm) than that of the SrSO4- or BaSO4-containing mullite samples (<50 μm). The contact angles for mullite samples containing SrSO4 or BaSO4 were higher (≈118° and 149°) than those of the mullite sample (≈109° and 127°), with both pure aluminum and Al–7Si alloy. This increase in the contact angle improves the corrosion resistance in mullite samples by means of non-wetting effect. 相似文献
19.
Coatings prepared from polyaniline-nano-TiO2 particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polyaniline (PANI) in aggressive environments. The corrosion studies were carried out on steel plates coated with these formulations containing 10 wt% polyaniline prepared with different concentrations of nano-TiO2. The electrochemical impedance spectroscopy was studied at periodic intervals during exposure to hot saline (65 °C) conditions for prolonged durations over a period of 90 h. The open circuit potential (OCP) was found to shift with time from −0.38 V SCE to more anodic side (−0.2 V SCE) much above that of bare steel (−0.5 V SCE). The presence of nano-TiO2 was found to be vital in the prevention of corrosion and the shift of OCP to anodic side. From these data, one could envisage more than 100 times improvement in the corrosion resistance especially for polyaniline prepared with 4.18 wt% nano-TiO2. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nano-size TiO2, redox properties of polyaniline as well as very large surface area available for the liberation of dopant due to nano-size additive. 相似文献
20.
To improve the oxidation resistance of TiAl intermetallic compound under high temperature condition, cathodic co-deposition of Al-Cr and Al-Ni alloy was carried out by constant potential control or potential pulse control in AlCl3-NaCl-KCl molten salt containing CrCl2 and/or NiCl2 at 423 K. Cathodic reduction of Ni and Cr starts at potential of 0.8 and 0.15 V versus Al/Al3+ in the molten salt, respectively. The co-deposition of Al, Cr, and Ni occurred at potentials more negative than −0.1 V to form a mixture of intermetallic compounds of Cr2Al, Ni3Al, and Al3Ni. Concentration of Cr in the deposit was enhanced to 43 at% at −0.1 V; however, concentration of Ni in the deposit was 6 at% at the same potential. The concentration of Ni further decreased with more negative potential to 1 at% at −0.4 V. The potential pulse technique enhanced the Ni concentration in the deposit to about 30 at%, due to anodic dissolution of Al content from the deposit at the higher side of potential on the potential pulse electrolysis. 相似文献