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1.
《腐蚀工程科学与技术》2013,48(6):263-267
AbstractThe anodic behaviour of copper in air-saturated solutions at 25°, 60° and 90°c has been determined by stepwise potentiortatic polarisation. In 0·01 M NaHCO3, the critical breakdown potential of the protective oxide layer is displaced to considerably more positive potentials as the temperature increases. In 0·01 M NaHCO3 containing 0·01 M NaCl, the critical breakdown potential is displiiced tornore negative values with increasing temperature, but the corrosion potential–breakdown potential difference undergoes little change. In 0·01 M NaCl, the surface film on copper is essentially non-protective, and linear Tafelplots are observed. A change in the pH of 0·01 M NaHCO3, with or without 0·01 M NaCl, from 8·6 to 7·3 has little effect on the valuesof the breakdown potentials. The significance of the results in relation to the initiation of pitting corrosion of copper in natural waters is discussed. 相似文献
2.
《腐蚀工程科学与技术》2013,48(4):305-310
AbstractThe synergistic inhibition of aluminium bronze corrosion by 4-phenyl semicarbazide hydrochloride (PSC) and the iodide ion in HCl of pH (1·8-2) at 60°C has been assessed by polarisation studies, Tafel plots, X-ray photoelectron spectroscopy and Auger electron spectroscopy. The addition of 0·01M KI to 0·01M PSC improved the inhibition efficiency from 86 to 94% owing to the formation of a CuI-PSC complex which is more compact, protective and hard than the film formed in the absence of iodide. The inner layer of this protective film contains a small amount of aluminium oxide, which increases the protective nature of the film and retards the dissolution of the underlying aluminium bronze. 相似文献
3.
Janik 《腐蚀工程科学与技术》2013,48(1):36-41
AbstractThe influence of electrolyte composition and temperature on the pitting corrosion resistance of nitrogen bearing (0·015, 0·198, and 0·56%N) type 316L stainless steels has been investi gated. Anodic polarisation curves were determined in neutral chloride solution at room temperature and at elevated temperatures of 308, 318, and 333 K. Similar polarisation studies were also conducted at room temperature in 1N H2 SO4 and in an acidic chloride solution containing 1N H2 SO4 and 0·5M NaCl. The results show that the critical pitting potential Epp in neutral chloride and acidic chloride media increases as the nitrogen content of the alloy increases, indicating that resistance to pitting increases with the addition of nitrogen. However, in 1N H2 SO4 solution, the transpassive potential was almost independent of the nitrogen content. As the temperature of the neutral chloride medium was increased, the Epp values decreased, irrespective of nitrogen content. The decrease in Epp is attributed not only to the temperature induced modification of the passive oxide film but also to chloride induced activity at the passive film/solution interface. Nevertheless, the alloy con taining 0·56% nitrogen showed better resistance to pitting at 333 K than did the alloy with 0·015% nitrogen at room temperature. SEM examination of the pitted specimens showed clear evidence of pitting for the alloy with 0·015% nitrogen, but insignificant pitting attack for the alloy with 0·56%N. However, the alloy with 0·56%N displayed some pitting attack when the experiments were conducted at 333 K. 相似文献
4.
《腐蚀工程科学与技术》2013,48(6):435-441
AbstractThis paper aims to evaluate the ability of phosphate pretreatments applied on steel rebars to hinder the corrosion reinforcements using synthetic pore electrolyte and mortar contaminated by chloride ions. The electrochemical behaviour of the pretreated substrate was assessed by corrosion potential, polarisation resistance and electrochemical impedance spectroscopy measurements. 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 increases the resistance to corrosion initiation up to 0·3M Cl– instead of 0·1M Cl– without treatment. The pretreatment also provides enhancement of corrosion protection of the steel rebar in mortar. The evolution of the impedance spectra in function of chloride concentration is in a fairly good agreement with the results obtained from RP measurements. 相似文献
5.
《腐蚀工程科学与技术》2013,48(4):315-320
AbstractThe inhibitive action of triazoles on the corrosion of mild steel has been studied through weight loss and various electrochemical techniques. Results obtained show that these organic compounds are very good inhibitors. Triazoles are able to reduce the corrosion of steel more effectively in 1M HCl than in 0·5M H2 SO4 . Potentiodynamic polarisation studies clearly reveal the type of inhibitor. Changes in impedance parameters (the charge transfer resistance Rt and the double layer capacitance Cdl ) are related to adsorption of triazoles on the metal surface, leading to the formation of a protective film which grows with increasing exposure time. The adsorption of these inhibitors on the mild steel surface in both acids obeys the Langmuir adsorption isotherm. The comparative study of corrosion inhibition of triazole derivatives indicates that the efficiency of the 4-aminotriazole is greater than that of the 4H-triazole. 相似文献
6.
Formation and breakdown of surface films on magnesium and its alloys in aqueous solutions 总被引:3,自引:0,他引:3
The influences of surface films formed by open-circuit exposure to neutral solutions on the corrosion and electrochemical behaviour of pure Mg and Mg alloys have been examined by in situ ellipsometric analysis and electrochemical measurements. Surface films mainly composed of Mg(OH)2 grew rapidly during open-circuit exposure to 0.1 M NaCl and 0.1 M Na2SO4 solutions. These films had protective ability to passivate Mg in the solutions. However, they suffered local breakdown under anodic polarisation. The passive current density decreased and the breakdown potential increased with increasing immersion time and film thickness. Influences of purity and alloying elements on the passivity and its breakdown of Mg have been discussed. 相似文献
7.
《腐蚀工程科学与技术》2013,48(1):65-69
AbstractA study using electrochemical techniques of the susceptibility to corrosion in 0·1M NaCl solution (pH 3) of atomised and deposited Fe–40Al (at.-%) intermetallic material at room temperature is reported. Specimens were heat treated at temperatures of 600 and 900°C for 24 and 72 h. Potentiodynamic polarisation, linear polarisation resistance, potential–time, and electrochemical current noise data were collected. The untreated material displayed higher corrosion resistance than the heat treated material. In the treated material, the corrosion resistance increased with both the time and temperature of heat treatment. Also, untreated material was more susceptible to pitting corrosion than heat treated material. As the temperature or the time of heat treatment was increased, the material became more resistant to pitting. This improvement in resistance to pitting was related to a decrease in surface defects, such as pores and cracks, and an increase in grain size. Thus, heat treatment lowered the number of active sites and helped the material to establish a more protective film. 相似文献
8.
《腐蚀工程科学与技术》2013,48(1):68-71
AbstractStudies on the anode efficiency of magnesium and its alloys in battery electrolytes such as magnesium perchlorate, magnesium bromide, and magnesium chloride solutions were made by galvanostatic polarisation and corrosion rate measurements. The open circuit potential and corrosion rate of magnesium increase when lead is present in the alloy. The corrosion rates were observed to follow the order Mg> AP65 (Mg?(6·0?7·0) Al?(4·4?S·0)Pb) > AZ61(Mg?(5·8?7·2)Al?(0·5?1·5)Zn) > AZ31(Mg?(2·5?3·5)Al?(0·6?1·4)Zn) in all three electrolytes. Anode efficiency increased with increasing current density up to 40 mA cm?2, but decreased above this level. Galvanostatic polarisation results indicated that corrosion of magnesium and its alloys in these electrolytes occurs under cathodic control. Of the tested alloys, AZ31 and AZ61 were found to be most suitable in respect of corrosion rate and anode efficiency in 2M Mg(ClO4)2 solution. 相似文献
9.
none 《腐蚀工程科学与技术》2013,48(2):109-112
AbstractThe inhibition by aminophenols of the corrosion of Al–4% Cu alloy (B26S) in solutions of sodium hydroxide has been studied in relation to the concentration of alkali and of inhibitor, the period of immersion and temperature. In general, at constant alkaliconcentration, inhibitor efficiency increases with concentration of inhibitor but, at constant inhibitor concentration, decreases with increase in alkali concentration, the effect being less pronounced with o-aminophenol. The inhibitive efficiency remains almost constant with temperature in the range 20–50°c, but decreases as the period of immersion is increased. At an inhibitor concentration of O·01–2·0% in 0·1 M NaOH the efficiency increases in the order: p-aminophenol < m-aminophenol < phenol < o-aminophenol.The inhibitors appear to function through adsorption following the Freundlich adsorption isotherm. The comparatively better inhibitive efficiency of o-aminophenol appears to be due to chelate formation. From galvanostatic polarisation data all thefour compounds appear to be mixed type inhibitors. 相似文献
10.
《腐蚀工程科学与技术》2013,48(2):179-185
AbstractThe effect of chloride ions on passivation of pure Mg, Mg–0·6 vol.-%Mo composite, Mg–0·6 vol.-%Cu composite and Mg alloy AZ91D has been studied in 0·1M NaOH solution by cyclic polarisation and electrochemical impedance spectroscopy (EIS). An addition of even 0·05M of chloride ions was sufficient to cause breakdown of passivity. Cyclic polarisation curves revealed a positive hysteresis loop in the presence of chloride ions. Breakdown potentials decreased continuously, for all materials, with increasing addition of chloride. Electrochemical impedance spectroscopy studies revealed that the film resistance of all Mg based materials continuously decreased with the addition of chloride ions. The film resistance of Mg–0·6%Cu and Mg–0·6%Mo composites was lower than that of pure Mg and AZ91D. Mg–0·6%Mo composite showed the lowest film resistance in all the solutions. The increase in film capacitance, for pure Mg and Mg based composites, with the addition of chloride ions, was attributed to surface roughening. Mo reinforcements were more detrimental than copper reinforcements. 相似文献
11.
《腐蚀工程科学与技术》2013,48(4):230-235
AbstractThe behaviour of the Pt electrode in oxygenated 0.1 M NaHCO3 solution at 162° and 238°c has been investigated using open-circuit and potentiostatic polarisation techniques. The effects of temperature and concentration of O2 in the solution on the anodic and cathodic polarisation curves are discussed, and the parameters which control the rest potential of the electrode are identified. The electrode is not thermodynamically reversible but can provide a useful reference potential for electrochemical studies of corrosion processes in oxygenated solutions at elevated temperatures. Limiting currents for the diffusion of O2 were determined for several concentrations of O2 between 20° and 238°c and used to determine the activation energy of diffusion of O2. 相似文献
12.
《腐蚀工程科学与技术》2013,48(3)
AbstractThe inhibition of the corrosion of iron by 0·1 M sodium hydroxide and 0·1 M sodium tetraborate is accompanied by thickening of the air-formed oxide film, which is absent in the presence of 0·5 M sodium tartrate. It is concluded that in the pH range 9·3 – 12·6 general film thickening is not a necessity for inhibition, but arises as a consequence. 相似文献
13.
《腐蚀工程科学与技术》2013,48(4):192-195
AbstractThe effect of some fatty acids (caproic, caprylic, capric) on the anodic behaviour of iron in de-aerated 0·05 M Na2SO4 solutions of pH 6–12 was studied by ellipsometry and by measurements of the double layer capacitance (dlc). At certain concentrations of added fatty acids (e.g., caprylic acid at a concentration of 2 × 10?2 mole/l) the rate of anodic dissolution of iron and the dlc are both decreased.The most efficient inhibition is observed at pH 6. The surface films formed in solutions at pH 6 exhibit complex indices of refraction, n = (2·6 ± 0·2) {1—(0·16i ± O·02i)} and grow according to a logarithmic law. Similar optical properties and film growth kinetics are found for films formed in similar solutions at pH 12. These films are composed of iron oxide. At potentials below 500 m VNHE, an increase of pH in the range 6–10 causes a decrease in inhibitive efficiency of the fatty acids, an increase of dlc, and the formation of non-protective films with low refractive indices. At potentials above 500 mV the surface films are protective irrespective of the pH of the solution. 相似文献
14.
《腐蚀工程科学与技术》2013,48(4):186-190
AbstractA study has been made of the inhibitive efficiency of some monosaccharides (glucose, fructose, mannose, galactose, in the concentration range 10?3M–1·0M) on copper corrosion in HNO3 (0·01, 0·1 and 1·0 M) at temperatures of 15°, 25° and 35°c. It was found that the structures of the various saccharides (pyranosic or furanosic) affected neither the efficiency nor the mechanism of inhibition. Inhibition was practically zero at concentrations of the monosaccharides between 10?3 and 10?1 M, whereas, at 1·0 M, 65–70% inhibition was reached in 0·01 and 0·1 M HNO3, and 50–60% in 1·0 M HNO3.In 1·0 M HNO3 the saccharides act as cathodic inhibitors (reducing HNO2 present in the HNO3 solutions), whereas in 0·1 and 0·01 M HNO3 they also acted as anodic inhibitors through theformation of an organometallic compound with Cu2+, which gave slight protection to the metal surface. 相似文献
15.
《腐蚀工程科学与技术》2013,48(4):580-584
AbstractPolyaniline (PAn) coating was electrochemically synthesised on 304 stainless steel using cyclic voltammetry in 0·25M NaOH solution containing 0·1M aniline. Characterisation of the adhesive and stable PAn coating was carried out by cyclic voltammetry, Fourier transform infrared spectroscopy and scanning electron microscopy. The protective properties of PAn coating on 304 stainless steel were elucidated using linear anodic potentiodynamic polarisation and Tafel test in 3·5%NaCl solution. Linear anodic potentiodynamic polarisation test results proved that the PAn coating improved the degree of protection against pitting corrosion in NaCl solutions. Tafel test results showed that the PAn coating appeared to enhance protection for 304 stainless steel in 3·5%NaCl solution. 相似文献
16.
《腐蚀工程科学与技术》2013,48(3):221-226
AbstractThe photocorrosion of n-GaAs electrodes in aqueous solutions represents one of the most important factors limiting their application in solar energy conversion. In continuation of previous studies, the corrosion of n-GaAs has been investigated in 0·5M H2SO4 using a pllOtoelectrochemical cell. Illumination of the n-GaAs anode with white light of intensity 20 mW cm-2 generated a saturation photocurrent of 27 mA cm-2 at biasing voltages more positive than +0·45 V(SCE). This current corresponded to hydrogen discharge at the platinum counter electrode and to oxidation of the GaAs surface. When 0·01-6·0M LiI was added to the H2SO4 solution, 12 was formed at the n-GaAs electrode and dissolved in the iodide solution. The onset potential of the photocurrent (Ep) shifted from -0·36 to -0·73 V(SCE) as the concentration was varied from 0·01 to 6·0M I-. Addition of I-3 shifted Ep to more positive values. The extent of corrosion was studied by comparing the ratios of photogenerated I2 and H2. In 0·01, 1·0, and 6·0M I- solutions, I2/H2 was 0·38, 0·87, and ~1 respectively. These ratios imply that, at lower I- concentrations, the holes photogenerated at the n-GaAs surface were consumed in the simultaneous oxidation of I- and GaAs. However, in 6·0M I-, where I2/H2 = 1, surface oxidation of GaAs was completely suppressed owing to total consumption of the photogenerated holes by the oxidation of I-. The results are considered on the basis of the band model of the semiconductor/electrolyte interface. 相似文献
17.
The local breakdown of oxide films grown on nickel in air at 100–400°C was studied by determining the pit density after corrosion in 0·1N Na2SO4 + 0·013N NaCl. The susceptibility of nickel to the local breakdown of passivity was found dependent upon the thickness of the film and its growing kinetics. Up to ca. 25 Å the film grows according to a logarithmic law and the pit density decreases with film thickness. Thicker films than 25 Å grow according to a parabolic law, and in their case the pit density increases with thickness. 相似文献
18.
《腐蚀工程科学与技术》2013,48(3):201-208
AbstractThe influence of sulphide ions on the corrosion resistance of some special stainless steels in 40 wt-% H3PO4 with 330 ppm SO2?4 and 1000 ppm Cl? at 80°C has been investigated using electrochemical (polarisation curves) and spectroscopic (infrared, SIMS) techniques. The behaviour of ZI NCDU 25–20 and ZI CNDU 25–25 commonly used in the phosphoric acid industry is compared with that of ZI CN 25–20 to estimate the role of the alloying elements. The corrosive effect of sulphide ions is confirmed: they shift the corrosion potential to more negative values and increase the anodic current in the active and passive states. In order of increasing corrosion rate the three steels are ranked as follows: ZI CNDU 25–25, ZI NCDU 25–20, ZI CN 25–20. The corrosion products consist largely of magnetite in a more or less oxidised state with chromium and nickel substituted for iron. The film formed on the ZI CNDU 25–25 alloy is more protective because of the high chromium content of the mixed oxide and the effect of molybdenum. The film retards the diffusion of corrosive ions through to the metal andfacilitates the development of passivity. However, the presence of a sufficiently high concentration of sulphides in solution prevents the establishment of passivity. 相似文献
19.
《金属精饰学会汇刊》2013,91(2):101-106
AbstractAn investigation has been undertaken of the influence of the mixed nanocrystalline and amorphous microstructure on the corrosion behaviour of electroless Ni–5·5W–6·5P (wt-%) deposits on steel substrates. The effects of annealing temperature on microstructure evolution were investigated. The corrosion behaviour of the deposits was evaluated by potentiodynamic polarisation in 0·5M H2SO4 solution and EIS measurements in 3·5%NaCl solution. Relationships between the microstructure and corrosion mechanisms of the as plated and the annealed deposits were considered by reference to microstructural information, including degree of crystallisation, grain sizes of both nickel and Ni3P phases, porosity development, microstrains and residual stresses. 相似文献
20.
《腐蚀工程科学与技术》2013,48(4):297-300
AbstractThe electrochemical behaviour of 254SMO stainless steel in HCl solutions has been studied and compared with that observed for other alloys using open circuit potential measurements, potentiodynamic polarisation curves, and SEM analysis techniques. 254SMO does not display pitting corrosion at room temperature in HCl solutions having concentrations ≤5·0M. Its performance is comparable with that of Hastelloy C276 in HCl media in solutions of strength ≤1·0M. The critical pitting temperature for 254SMO exceeds 76°C in 3M HCl solutions. 相似文献