共查询到20条相似文献,搜索用时 983 毫秒
1.
K. V. Rybalka V. S. Shaldaev L. A. Beketaeva A. N. Malofeeva A. D. Davydov 《Russian Journal of Electrochemistry》2010,46(2):196-204
Pitting corrosion of stainless steel 403 in the NaCl solutions is studied. It is shown that the experimental results obtained
under the potentiostatic conditions do not provide sufficient information on the behavior of steel under the conditions of
free corrosion. The corrosion experiments take long time, their results exhibit poor reproducibility; however, they are necessary
for obtaining reliable data on the corrosion behavior of steel. The development of corrosion process is reflected in the variation
of corrosion potential with time. The effect of concentration and temperature of NaCl solutions on the development of pitting
corrosion is studied. The peculiarities of the distribution of pits over the test specimen surface are revealed. In 1 M NaCl
solution at 20°C, few pits arise. Some of them repassivate; some pits grow, initially, in diameter and depth and, then, almost
only in depth. The examples of through pit formation on the specimens 4 mm thick are presented. 相似文献
2.
用动电位和恒电位极化法研究了A3碳钢在NaNO2_NaCl溶液体系中的电流波动特征.A3钢在不含Cl-的0.1mol/LNaNO2溶液中能保持良好的钝态,当加入一定浓度的Cl-后,电流出现了明显的快速上升,再缓慢下降的波动特征,表明此时碳钢表面生成了溶解较快而再钝化相对较慢的亚稳态孔蚀.实验中可观察到因电流波动而产生的累积腐蚀损伤的蚀孔.实验表明,随着Cl-浓度的增加,出现亚稳态孔蚀的初始电位Em降低,相应的电流波动峰值增大,峰频增加;而升高电位,则电流波动的峰值和峰频也都增加,况且再钝化时间延长,由此可见电位的升高促进了亚稳态孔的溶解,并能激活更多的活性点使孔诱发速率增大. 相似文献
3.
A. D. Davydov V. S. Shaldaev G. R. Engel’gardt 《Russian Journal of Electrochemistry》2006,42(2):121-128
The dependences of the pitting potential, determined by potentiodynamic method, on the NaCl solution concentration, pH, and temperature are found. The repassivation potential and the induction time for the pitting under different conditions are determined. The corrosion potential and kinetic parameters of the steel dissolution in pits are measured. The corrosion current is evaluated, leading to the determination of the steel dissolution rate in pits at the corrosion potential. 相似文献
4.
K. Yanada M. Sakairi T. Kikuchi Y. Oya Y. Kojima 《Surface and interface analysis : SIA》2010,42(4):189-193
An in situ artificial micro‐pit fabrication method with an area selective electrochemical measurement technique was applied to investigate the effect of the geometry of artificially formed pits on their localized corrosion behavior in anodized 1000 series aluminum. This technique enables the fabrication of artificial micro‐pits with different aspect ratios (pit depth/pit diameter) in solutions. The aspect ratios of the fabricated artificial micro‐pits in this experiment could be varied from 0.13 to 1.83 by controlling the irradiation time of the focused pulsed YAG laser beam. By applying a constant potential to the final laser‐beam‐irradiated spot in chloride environments, localized dissolution occurred only at the laser beam irradiated area, because the anodic oxide film acted as an insulator. The corrosion current and charge increase with increasing aspect ratio at any applied potential. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
6.
《Electrochemistry communications》2008,10(2):200-203
The role of acetic acid (HAc) on the pit growth in CO2 corrosion of carbon steel pipelines is studied by means of an artificial pit electrode. The current flowing between the artificial pit and the outer surface was measured with a zero resistance ammeter. It is shown that the corrosion potential increases with increasing HAc concentration. Depletion of HAc inside the pit imposed a potential difference that triggered the pit growth. The pit did not grow in absence of HAc. The pit growth was self-sustained only to a certain pit depth, beyond which the dissolution current at the bottom of the pit vanished. This is in good agreement with field observations mainly in the case of top-of-line corrosion phenomena. 相似文献
7.
Electrochemical behavior of stainless steel in 0.5 M NaCl solutions is studied. It is shown that, for this steel, under a considerable cathodic polarization of electrode, the oxygen electroreduction proceeds via a four-electron mechanism. The corrosion current is estimated. From the impedance spectra, elements of an equivalent circuit that describes the electrode behavior under the ac conditions are calculated. A mechanism of the steel passivation in the electrolyte is proposed. 相似文献
8.
Pitting corrosion of stainless steels causes tremendous damage in terms of material loss and resulting accidents. Organic surfactants have been tried as pitting inhibitors but the understanding of the inhibition mechanisms is mainly speculative. In the present study the inhibition of the pitting corrosion of 304 stainless steel by N-lauroylsarcosine sodium salt (NLS) in 0.1 M NaCl solutions at neutral pH was studied using an approach that combines surface chemical techniques with electrochemical ones. It was found that NLS increases the pitting resistance of 304 stainless steel, with possible complete inhibition at high NLS concentration (30 mM). Adsorption of NLS on 304 stainless steel particles was directly measured. NLS adsorbs significantly on 304 stainless steel with maximum adsorption density close to bilayer coverage. Electrophoretic mobility data for 304 stainless steel particles show that the surface of 304 stainless steel is negative in NaCl solution at neutral pH. The adsorption of NLS makes the interfacial charge even more negative. The relationship between pitting inhibition and adsorption density of NLS suggests that NLS does not adsorb preferentially on the pit nucleation sites and complete inhibition requires that the whole surface be covered completely by NLS. The inhibition mechanism of NLS is proposed to be due mainly to the blocking effect of a negatively charged NLS adsorption layer. This study shows that in addition to the adsorption amount of surfactant, interfacial charge also plays an important role in pitting inhibition. 相似文献
9.
The mechanism of pit growth of pure aluminum (Al) in sulfate ion (SO4
2–)- or nitrate ion (NO3
–)-containing 0.1 M sodium chloride solutions has been studied in terms of the morphological changes of artificial pits using
potentiodynamic polarization experiment, potentiostatic current transient technique and optical microscopy. The increase in
SO4
2– and NO3
– ion concentrations in NaCl solution raised the pitting potential E
pit of pure Al, which is ascribed to the impediment to pit initiation on pure Al by the addition of SO4
2– or NO3
– ions. From the potentiostatic current transients of artificial pits in aqueous 0.1 M NaCl solution, the average value of
the pit current was observed to increase with increasing SO4
2– ion concentration, whereas that value of the pit current in the presence of NO3
– ions increased up to ca. 0.4 M NO3
– ion concentration and then decreased abruptly with increasing NO3
– ion concentration. From observations of the morphologies of the pits, it appears that the pit grows preferentially in the
lateral direction or in the downward direction by adding SO4
2– or NO3
– ions to aqueous 0.1 M NaCl solution, respectively. Based upon the experimental results, two different pit growth mechanisms
by anion additives can be proposed: (1) pit growth by the preferential attack of both SO4
2– and Cl– to the pit wall in SO4
2–-containing solutions; (2) pit growth by the creation of an aggressive environment at the pit bottom up to 0.4 M NO3
– ion concentration due to the lower mobility of NO3
– than Cl– in NO3
–-containing solutions.
Electronic Publication 相似文献
10.
《Electrochemistry communications》2002,4(1):86-91
Corrosion of AISI 303 stainless steel in FeCl3 solution was studied in the magnetic field, whose direction was perpendicular to the corroding surface. The magnetic field inhibited corrosion in both quiet and stirred solutions. This was evident from the increased repassivation potential, the reduced number of pits and the decreased mass loss. By contrast, an accelerating effect of the magnetic field was observed on the single cathodic reaction of the corrosion process, viz. Fe(III) reduction to Fe(II). This was confirmed by voltammetric measurements on both platinum and stainless steel electrodes. The corrosion magnetoinhibition was explained in terms of field-assisted development of a passive layer, whose passivation capacity was higher than that under the field-free conditions. 相似文献
11.
Corrosion of iron in slightly acidified sodium sulphate solutions (mainly pH 4.5) in the open air was studied with a rotating disk electrode method at room temperature.Microscopic observations of corroded iron disk surfaces in the pH 4.5 solution revealed that iron initially corrodes locally with the formation of round pits of 10–30 μm in diameter and of(0.6–1.3) × 103 in number per apparent square centimetre followed by the U-shaped brown protective wall formation of precipitates (rust) outside the pits. Each protective wall is formed along the lines of flow of the solution adjacent to the iron surface and each pit is located near the upstream end of the wall. Steady state of corrosion sets in when the parts of surface area surrounded by the wall are completely covered with a microscopically non-porous rust film.The amount of iron in the rust film and the total amount of corrosion of iron including that in the film increase parabolically with the increase in the time of immersion. The amount of iron in the film increases in proportion to the total amount of corrosion independently of the speed of rotation of the disk electrode even in the steady state.The fraction of area of iron surface not covered with the film decreases with time and reaches a certain fixed value in the steady state: the value is smaller at higher rotational speed. The corrosion rate is proportional to the uncovered area, as the corrosion is near the steady state. The pH of the bulk solution increases as corrosion progresses.The corrosion rate of iron can be well interpreted by assuming that the rate is controlled by the diffusion of oxygen from the bulk solution to the surface of iron and that the rust film on iron impedes the diffusion of oxygen. 相似文献
12.
Effect of inhibitors on corrosion resistance of carbon steel in suspensed liquid combined fertilizer
F. F. Mozheiko T. N. Potkina I. I. Goncharik 《Russian Journal of Applied Chemistry》2008,81(9):1705-1709
Inhibitors against corrosion of metal surfaces in salt solutions, especially of carbon steel in reference 5% NaCl solution and in suspension fertilizer were selected. We examined a corrosion kinetics, effect of corrosion protection, and also a penetration and a corrosion depth in the presence of various inhibitors. 相似文献
13.
Anodic polarization behaviors of iron in pure H2SO4 and three mixed acidic solutions, H2SO4 NaCl,H2SO4 NaNO3 and H2SO4 NaCl NaNO3, were investigated. The potentiodynamie sweep curves showed that the current densities rose and dropped irregularly in H2SO4 NaCl solution at the more anodic potentials since the iron surface suffered pitting attack in the solution, but the pitting corrosion was inhibited effectively in the presence of nitrate ions. The surface morphological measurements indicated that pits appeared on the iron surface in H2SO4 NaCl solution and only a few unobvious corrosion spots were observed in H2SO4 NaCl NaNO3 sointian after the iron electrode was potentiostatically polarized at 1.3 V. The oscillatory properties of iron are associated with the susceptlbility of the iron to pitting. In H2SO4 NaCl solution, the regular potentiostatic current oscillations gradually evolved into the irreg-niar current fluctuations due to occurrence of the pitting; whereas in H2SO4 NaCl NaNO3 solution, the current oscillations took place regularly, like the oscillatory behavior in the pure H2SO4 solution. Thus, when the higher the oscillatory fre-quency, the more irregular oscillatory process and the more sensitive to pitting iron occurred. 相似文献
14.
Pit morphology of Inconel alloy 600 in sulphate (SO4
2-), nitrate (NO3
-) and bicarbonate (HCO3
-) ion-containing 0.5 M sodium chloride (NaCl) solution was analysed in terms of fractal geometry as functions of solution temperature and anion concentration using the potentiostatic current transient technique, scanning electron microscopy, image analysis and ac-impedance spectroscopy. Potentiostatic current transients revealed that the pitting corrosion is facilitated by the increase in solution temperature, irrespective of anion additives, and that it is hindered by the increase in NO3
- and HCO3
- ion concentration, regardless of solution temperature. Above 60 °C, it was also found that the addition of SO4
2- ions impedes pit initiation, but enhances pit growth. The value of fractal dimension D
f of the pits increased with increasing solution temperature and with decreasing NO3
- and HCO3
- ion concentration. Moreover, the value of D
f increased above 60 °C with increasing SO4
2- ion concentration. This is caused by the increase in the ratio of pit perimeter to pit area, implying the formation of pits with micro-branched shape due to the acceleration of the local attack in the pits. From the decrease of the depression parameter with increasing solution temperature, it is inferred that the roughness of the pits increased with increasing solution temperature. In addition, the depression parameter was found to increase with increasing NO3
- and HCO3
- ion concentration. But, above 60 °C, in the case of SO4
2- ion addition, the depression parameter decreased with increasing SO4
2- ion concentration. From the experimental findings, the three-dimensional pit morphology is discussed in terms of the values of D
f of the pits and the depression parameter, with respect to anion concentration and solution temperature. 相似文献
15.
Anodic potentiodynamic and chronoamperometric curves on nickel-chromium alloys (2–50 wt % Cr) are obtained in NaCl solutions at various concentration, pH, and temperature. The dependences of pitting and repassivation potentials on the concentration and temperature are determined for alloy with 20 wt % Cr. The effect of the Cr content and pH on the anodic behavior of the alloys, in particular, the transition from a pitting breakdown of passivity to transpassivation, is shown. Quantitative time dependences of the current in the passive range are obtained and the steady-state values of this current are determined. The corrosion potential of the alloy with 20 wt % Cr is measured. Cathodic voltamograms for passive and chloride-ion-activated surface of the alloy are obtained. 相似文献
16.
17.
Electrochemical instabilities induced by chlorides and bromides due to pitting corrosion of iron in sulfuric acid solutions
are investigated. Analysis of the electrochemical instabilities as a function of the applied potential and the nature and
concentration of the aggressive chemical species shows that the system exhibits a transition from aperiodic bursting of large-amplitude
to small-amplitude chaotic oscillations at a critical potential (bifurcation potential, E
bif). The E
bif is determined by the halide concentration inside the pits and coincides with the repassivation potential defined in corrosion
studies to explain pit repassivation due to changes in pit chemistry. Surface observations show that, at E < E
bif, an active-passive state dissolution (etching) occurs, while at E > E
bif, a polishing state dissolution is reached. Spatial interactions between early initiated pits and the adjacent electrode surface,
oxide film alteration, aggressive species accumulation around active pits, and formation of ferrous salt layers in front of
the Fe electrode are all considered to be associated with electrochemical instabilities emerging during pitting corrosion
of iron under different dissolution states.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 5, pp. 535–550.
The text was submitted by the authors in English. 相似文献
18.
A3钢在缓蚀颜料提取液中的EIS研究 总被引:1,自引:0,他引:1
应用EIS研究了A3钢在不同 pH值的磷酸锌或三聚磷酸铝 3.5 %NaCl提取液中的腐蚀行为 .结果显示 ,相同条件下 ,A3钢的电阻值随溶液 pH值增加而增加 ,电容值则相反 .在磷酸锌3.5 %NaCl提取液中 ,因磷酸锌的溶解度太小 ,没有足够的量对金属基底A3钢进行有效的保护 .在 pH值为 6的三聚磷酸铝 3.5 %NaCl提取液中 ,A3钢表现出较明显的缓蚀现象 ,可能是因为三聚磷酸根离子与腐蚀产物Fe2 + 、Fe3+ 络合并在钢表面形成了一层致密的保护膜 ,从而有效地阻止了腐蚀介质的进一步入侵 .防蚀颜料的溶解度大小是决定它的缓蚀性能优劣的重要因素之一 相似文献
19.
铝阳极氧化膜在中性NaCl溶液中的亚稳态点蚀研究 总被引:2,自引:0,他引:2
使用动电位极化法,电化学噪声和扫描电镜技术研究了工业纯铝L2经不同电流密度阳极氧化和不同方法封闭后于1mol/LNaCl中性溶液中的腐蚀行为.结果表明,阳极氧化能大大提高L2的耐蚀性,但当氧化膜较薄或氧化膜经长时间在溶液中浸泡后,试样表面仍能发生亚稳态点蚀,并在极化曲线上出现电流振荡和电位振荡.扫描电镜观察则表明,这些亚稳态点蚀孔径一般小于10μm,主要产生在膜中的金属间化合物周围.若氧化膜厚度增加或使用沸水和重铬酸盐封闭,均可有效地抑制亚稳态点蚀的发生. 相似文献
20.
碳钢缝隙内溶液化学和阳极极化行为研究 总被引:9,自引:0,他引:9
为研究缝隙腐蚀的溶液化学和缝中金属阳极极化行为,设计一种楔形缝隙模拟装置。以碳钢为研究对象,分别测试了在3.5%(wt)NaCl溶液中缝内各位置的电极电位,Cl^-浓度,pH值以及缝外阳极极化时电流密度的变化。 相似文献