共查询到20条相似文献,搜索用时 0 毫秒
1.
Chromates conversion coatings provide very effective corrosion protection for many metals. However, the high toxicity of chromate leads to an increasing interest in using non-toxic alternatives such as molybdates, silicates, rare earth metal ions and etc. In this work, quartz crystal microbalance (QCM) was applied as an in-situ technique to follow the film formation process on zinc (plated on gold) in acidic solutions containing an inorganic inhibitor, i.e. potassium chromate, sodium silicate, sodium molybdate or cerium nitrate. Using an equation derived in this work, the interfacial mass change during the film formation process under different conditions was calculated, indicating three different film formation mechanisms. In the presence of K2CrO4 or Na2SiO3, the film growth follows a mix-parabolic law, showing a process controlled by both ion diffusion and surface reaction. The apparent kinetic equations are 0.4t = −17.4 + 20Δmf + (Δmf)2 and 0.1t = 19.0 + 8.4Δmf + 10(Δmf)2 respectively (t and Δm are in seconds and μg/cm2). In solutions containing Na2MoO4, a logarithmic law of Δmf = −24.7 + 6.6 ln t was observed. Changing the inhibitor to Ce(NO3)3, the film growth was found to obey an asymptote law that could be fit into the equation of Δmf = 55.1(1 − exp(−2.6 × 10−3t)). 相似文献
2.
Growth of passive films on Cr and Fe-Cr alloys with Cr concentrations ranging from 15% to 54% was studied in situ with the electrochemical quartz crystal microbalance (EQCM). Mass change and current transients were measured as the response to a potential change in the passive region from 0 to 800 mV (SHE) in a pH 1.5 sulfate electrolyte. From these measurements, the thickness change as well as integral and differential growth fractions were calculated. The growth fraction expresses the fraction of oxidized metal that remains in the film. It was found that higher Cr contents gave thicker films and an increase in the growth fraction. The thickness change curves were compared to film growth models assuming rate control at either a film interface or in the film itself through high field conductivity. The integral growth fraction for the potential change experiment was found to vary approximately linearly with the Cr bulk composition. The fraction of dissolved Cr calculated from EQCM data matched well with previous solution analysis results. 相似文献
3.
M. Scendo 《Corrosion Science》2005,47(7):1738-1749
The effect of potassium ethyl xanthate (EtX−) on the anodic dissolution of copper in acidic sodium chloride solutions was studied using voltammetry on a rotating disc electrode (RDE) and electrochemical quartz crystal microbalance (EQCM) techniques. The compound used at 5 × 10−3 M concentration acts as a strong inhibitor against copper dissolution. The inhibitory action increases with an increase in pH of the solution. The influence of EtX− on the spontaneous dissolution of copper was also investigated. The EQCM measurements show that an increase in pH was accompanied by an increase of inhibition efficiencies of EtX−. 相似文献
4.
Nitrogen doped tetrahedral amorphous carbon (ta-C:N) thin films were grown on p-Si(1 1 1) substrates using filtered cathodic vacuum arc (FCVA) deposition by varying nitrogen flow rate. The effect of nitrogen flow rate on the corrosion performance of the films was investigated through potentiodynamic polarization and immersion tests in 0.6 M NaCl solutions. The polarization results showed that the corrosion resistance of the films dropped with increased nitrogen flow rate due to formation of more sp2 bonds. The immersion tests revealed that the pH value of the solutions had a significant effect on the corrosion behavior of the ta-C:N films. 相似文献
5.
Si thin film is considered a good candidate for rechargeable Li-ion thin film battery anode material because it possesses large lithium adsorption capacity, good thermal and chemical stability. However, the fast capacity decay upon charge-discharge cycling has hindered the application of Si thin films. In this investigation, Si thin films were sputtered on Cu foils and characterized. One of the explanations for the bad cycling characteristics is the poor adhesion between the Si film and the Cu substrate. Some Cu foils were treated by Plasma Immersion Ion Implantation (PIII) method using rare-earth La element to improve the adhesion strength between the Si thin films and the Cu substrate in order to enhance the cycling performance. Electrochemical analysis revealed that La PIII surface treatment on the Cu foil substrate was effective in strengthening the interface adhesion between the Si thin films and the Cu substrates. Subsequently, the electrochemical performance of the Si thin film anodes was improved. 相似文献
6.
In acidic water-organic solvents of ethylene glycol (EGOH), propylene glycol (PGOH), methanol (MeOH) and ethanol (EtOH), iron corrosion was studied by monitoring the corrosion potential, the potentiodynamic polarization curves and electrochemical impedance diagrams. In these aqueous glycols and alcoholic solutions containing HCl having concentrations of 0.5 up to 9 M, it has been shown by electrochemical analysis (I-E curves) that dissolution mechanism of iron is similar to that one in pure acidic aqueous solutions if only we take into account the relative amount of water in the medium. Based in our experimental data, water has an important role in the transfer kinetics of protons to the metallic electrode and limits electro dissolution rate of iron. When water quantity is sufficient at the metal surface, the acidity is a governing factor in the evolution of corrosion process. 相似文献
7.
An automated thin-layer flow cell electrodeposition system was developed for growing Bi2Te3 thin film by ECALE. The dependence of the Bi and Te deposition potentials on Pt electrode was studied. In the first attempt,this reductive Te underpotential deposition (UPD)/reductive Bi UPD cycle was performed to 100 layers. A better linearity of the stripping charge with the number of cycles has been shown and confirmed a layer-by-layer growth mode, which is consistent with an epitaxial growth. The 4 : 3 stoichiometric ratio of Bi to Te suggests that the incomplete charge transfer in HTeO reduction excludes the possibility of Bi2Te3 formation. X-ray photoelectron spectroscopy (XPS) analysis also reveals that the incomplete charge transfer in HTeO2^ occurs in Te direct deposition. The effective way of depositing Bi2Te3 on Pt consists in oxidative Te UPD and reductive Bi UPD. The thin film deposited by this procedure was characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). A polycrystalline characteristic was confirmed by XRD. The 2 : 3 stoichiometric ratio was confirmed by XPS. The SEM image indicates that the deposit looks like a series of buttons about 0.3 - 0.4/~m in diameter, which is corresponding with calculated thickness of the epitaxial film. This suggests that the particle growth appears to be linear with the number of cycles, as it is consistent with a layer by layer growth mode. 相似文献
8.
The oxidation of cobalt in air is investigated for times ranging over three orders of magnitude up to 1000 hr and for temperatures ranging from room temperature up to 467°C. Three different growth processes are observed. When a clean surface is exposed to air at room temperature, an 8–10 Åfilm of Co(OH)
2
forms in seconds or less. For temperatures of 50–100°C, very little additional film forms for times up to 1000 hr. For temperatures of 100–225°C, a film of CoO grows in a manner which can be described empirically with a fourth root rate law with an activated rate constant. Between 225 and 325°C there is a transition to a quadratic rate law. At 425°C the film appears to be a mixture of CoO and Co
3O4. 相似文献
9.
Corrosion of carbon steels in high-temperature water studied by electrochemical techniques 总被引:1,自引:0,他引:1
Electrochemical methods were used to study the corrosion behavior of five Fe-Cr alloy steels and 304L stainless steel in high-temperature water. Passivity can be achieved on A-106 B carbon steel with a small content of chromium, which cannot be passivated at room temperature. The formation rate and the stability of the magnetite film increased with increasing Cr content in the steels. A mechanistic model was developed to describe the corrosion processes of steels in high-temperature water. The crack growth rate on steels was calculated from the maximum current of the repassivation curves according to the slip-oxidation model. There was a high crack growth rate on 304L stainless steel in high-temperature water. Of the four Fe-Cr alloys, the crack growth rate was lower on 0.236% Cr- and 0.33% Cr-steels than on 0.406% Cr steel and 2.5% Cr-1% Mo steel. The crack growth rate on 0.33% Cr steel was the smallest over the tested potential range.An increase in Cr content in the steel is predicted to reduce the corrosion rate of steel at high temperatures. However, this increase in Cr content is predicted not to reduce the susceptibility of steel to cracking at high temperatures. 相似文献
10.
Naoki Kikuchi 《Corrosion Science》2006,48(4):994-1003
The passivation process of nickel thin films during potentiodynamic polarization in acidic and alkaline sulfate solutions was analyzed by an electrochemical quartz crystal microbalance (EQCM) to separate the partial current density of nickel dissolution through the passive film, iNi2+, and the partial current density of film growth, iO2-. The values of iNi2+ and iO2- during potentiodynamic polarization (20 mV s−1) in the passive potential region could be separated by comparing the mass change rate and net polarization current as a function of electrode potential. It is found that iNi2+ is larger than iO2- in pH 3.0, 0.5 M sulfate solution, while the situation reverses in pH 12, 0.5 M sulfate solution. The sulfate concentration dependences of iNi2+ and iO2- in pH 3.0, sulfate solution were significant as compared to those in pH 12, sulfate solution. 相似文献
11.
The adsorption on steel of two compounds, ascorbic acid salts (SA) and 1‐hydroxyethylidene,1‐diphosphonic acid salts (SHEDP), used alone or simultaneously, was studied using an electrochemical quartz crystal microbalance (EQCM). These products are considered to be non‐toxic organic corrosion inhibitors. SA adsorption was greater at cathodic potentials than at the corrosion potential, while SHEDP adsorbed better at the corrosion potential. The effectiveness of these two inhibitors is discussed in relation to the polarization curves. Several hypotheses are discussed to explain the adsorption mechanism in the presence of the two compounds used either alone or together. 相似文献
12.
It is demonstrated that open circuit potential transients measurements are able to give the realistic and fast information on the rate of metal corrosion. The results of the studies of the rate of copper corrosion in naturally aerated unstirred acidic sulfate solutions obtained by this method are close to the results of electrochemical quartz crystal microgravimetry measurements. It was found that within the concentration range CuSO4: 0.001-0.01 M, H2SO4: 0.005-0.5 M, independently of whether 0.1 M K2SO4 is present in the solution or not, the rate of corrosion of thin (about several tens monolayers) and fresh deposits of copper does not depend on the solution composition and is limited by the transport of the dissolved oxygen. The rate of corrosion of such deposits sometimes exceeds the rate of corrosion of compact copper samples. 相似文献
13.
The corrosion of aluminum alloy AlSi8Cu3Fe(Zn) in ethanol and ethanol solutions containing 10 vol.% water and 10 vol.% acetic acid, respectively, was investigated by means of electrochemical impedance spectroscopy (EIS), polarization curve, immersion, optical microscopy, scanning electron microscopy and element mapping. The Al alloy in the ethanol and its solutions exhibited a capacitive loop in the measured Nyquist EIS spectra at high frequencies, which can be attributed to the ethanol’s dielectric response. Addition of 10 vol.% acetic acid increased the ethanol corrosivity more significantly than the same amount of water addition. The Al–Si–Cu–Mg precipitated zones in the alloy were susceptible to corrosion attack due to the micro-galvanic effect by the Cu-containing precipitates. 相似文献
14.
M. Scendo 《Corrosion Science》2007,49(2):373-390
The influence of the concentration of purine (PU) on the corrosion and spontaneous dissolution of copper in 1.0 M NaCl solutions (pH 6.8) was studied. The investigations involved electrochemical polarization methods as well as weight-loss measurements, electrochemical quartz crystal microbalance (EQCM) techniques and scanning electron microscopy (SEM). The inhibition efficiency (IE) increases with an increase in the concentration of PU. An adherent layer of inhibitor is postulated to account for the protective effect. The adsorption of PU has been found to occur on the surface of copper according to the Langmuir isotherm. Purine is chemically adsorbed on the copper surface. 相似文献
15.
Kunitsugu Aramaki 《Corrosion Science》2006,48(1):209-225
An ultrathin film of two-dimensional polymer was prepared on a passivated iron electrode by modification of a 16-hydroxyhexadecanoate ion self-assembled monolayer with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 and octadecyltriethoxysilane C18H37Si(OC2H5)3. This film prevented passive film breakdown examined by potentiodynamic anodic polarization of the coated electrode in the borate buffer solution containing 0.1 M of Cl−. Neither current spikes nor the pitting potential was observed in the passive and transpassive regions of polarization curve. The anodic current density was decreased in these regions markedly, implying hindrance to permeation of Cl− and water through the film. Structure of the film was clarified by X-ray photoelectron and FTIR reflection spectroscopies and contact angle measurement with a drop of water. Electron-probe microanalysis of the passivated surface coated with the film after anodic polarization scanning up to the transpassive region revealed that the polymer film prevents pit initiation by an attack on the passive film with Cl−. 相似文献
16.
Electrochemical preparation of Er-Co-Bi thin film in organic bath by cyclic electrodeposition method
Cyclic electrodeposition was used to investigate the preparation of Er-Co-Bi alloy thin film in DMSO system. Experimental results indicate that Er-Co-Bi alloy thin film containing 14.83 %- 32.65% Er is prepared from 0.1 mol/L ErCl3 0. 1 mol/L CoCl2 0. 1 mol/L Bi (NO3)3 0. 1 mol/L LiCl DMSO system by cyclic electrodeposition on Cu substrate. The optimum cyclic potential of electrodeposition is that upper potential is within a potential range from -0.50 V to -1.00 V and lower potential is within a potential range from -2.00 V to -2.60 V.The surface of alloy thin film observed by scanning electron microscope is black, adhesive and has metallic luster.The film is amorphous proved by the X-ray diffractometry. 相似文献
17.
Spinodal decomposition in a binary thin film is studied by a three-dimensional (3D) phase field model. A cubic thin film with
an (001) orientation is considered. The focus is on the effect of the types of substrate constraint on the morphological evolution
during spinodal decomposition as compared to the corresponding bulk. The elastic strain effect is incorporated by solving
the elasticity equations for an elastically inhomogeneous thin film with a free surface and constrained by a substrate. Temporal
evolution for the composition field, and thus the morphological evolution, is obtained by solving the Cahn-Hilliard equation
using a semi-implicit Fourier-spectral method. It is shown that a biaxial substrate constraint has essentially no effect on
the spinodally decomposed two-phase morphology which is primarily controlled by the cubically anisotropic elastic interactions.
The asymmetry in the strain components along the [100] and [010] directions from the substrate constraint results in the preferential
alignment along one of the two directions. In the particular case of a harder phase whose lattice parameter increases with
composition, a tensile substrate constraint along the film plane leads to the alignment of two-phase microstructures parallel
to the tensile direction.
This article is based on a presentation made in the 2003 Korea-Japan symposium on the “Current Issues on Phase Transformations”,
held at Marriott Hotel, Busan, Korea, November 21, 2003, which was organized by the Phase Transformation Committee of the
Korean Institute of Metals and Materials. 相似文献
18.
This paper describes the effects of using a TiN film as a possible protection layer for titanium in an aggressive chemical
environment. The TiN film as a barrier of hydrogen permeation into the material was evaluated by electrochemical cathodic
charging of the specimens in solutions with different pH values and temperatures. Results revealed that the thickness of hydride
on the surface of the uncoated titanium increased with the increase of charging time. Higher charging temperature and lower
pH value promoted the formation of hydride phases. For titanium coated with a TiN film, it effectively retarded the permeation
of hydrogen into the titanium substrate. However, this was at the sacrifice of the TiN film itself. 相似文献
19.
The effect of 2-mercaptobenzimidazole (2MBI) on the corrosion of Armco iron in NaCl media has been investigated in relation to the concentration of the inhibitor by various corrosion monitoring techniques. Surface morphology was studied by scanning electron microscopy (SEM). Results obtained revealed that 2MBI is a good anodic inhibitor. The addition of increasing concentrations of 2MBI moves the corrosion potential towards positive values and reduces the corrosion rate. EIS results show that the changes in the impedance parameters (Rt and Cdl) with concentrations of 2MBI is indicative of the adsorption of these molecules leading to the formation of a protective layer on iron surface. The adsorption of this compound is also found to obey Langmuir’s adsorption isotherm in NaCl. 相似文献
20.
《腐蚀工程科学与技术》2013,48(4):336-341
AbstractThe aim of this work is to study the protection of steel reinforcement against corrosion by pretreatment in phosphate (Na3PO4) solution. The work has been carried out using electrochemical techniques, i.e. corrosion potential E corr, polarisation resistance R P and electrochemical impedance spectroscopy (EIS) measurements. The results have been validated by a gravimetric method. It has been stressed that R P measurements, determined by DC techniques, include the charge transfer resistance R t plus the resistance associated with the redox process R ox, both determined by EIS. Also the results have demonstrated that the treatment of the rebar by immersion in the Na3PO4 (0·5M) solution favours the formation of a passive layer on the steel rebar surface, which is able to resist longer the action of chlorides to initiate corrosion. However, the resistance of the passive layer against chloride depends on the duration of the treatment by immersion of the rebar within the phosphate solution. 相似文献