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1.
Corrosion behaviour of type 304 stainless steel was investigated, with particular attention to additive effects of hydrosulphite (Na2S2O4) on corrosion in 0.1 mol/l H2SO4 solution with various amounts of Na2S2O4 up to 60 mmol/l.Corrosion of SUS304 occurred below pH 3.0 at 30 °C in a 0.1 mol/l H2SO4 solution in which Na2S2O4 was added to 0.1-20 mmol/l. The maximum corrosion rate at 30 °C was measured as 7.2 g/m2 h (7.9 mm/y) in 0.1 mol/l H2SO4-10 mmol/l Na2S2O4 at pH 1.2. Microscopic surface observation revealed that active dissolution was accompanied by intergranular corrosion at the metal surface.The SUS304 was easily passivated in 0.1 mol/l H2SO4 solution with more than 30 mmol/l Na2S2O4. NiS was detected in the passivated film. 相似文献
2.
C. Rémazeilles 《Corrosion Science》2007,49(2):844-857
Fe(III) oxyhydroxides were synthesised in chlorinated environments via chemical or electrochemical processes in order to determine the conditions favouring the formation of akaganéite. Corrosion products were characterised using X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. The first method produced Fe(III) oxyhydroxides from the aerial oxidation of iron(II) precipitates which were obtained by mixing FeCl2 · 4H2O and NaOH solutions. Depending on the initial amounts of Fe2+, Cl− and OH−, goethite, lepidocrocite or akaganéite were then obtained. When a large excess of dissolved FeCl2 was present, akaganéite was formed independently of the oxygen flow. In the second method, steel electrodes were left in baths containing chloride with [Cl−] = 2 mol L−1, using either FeCl2 · 4H2O or NaCl. Akaganéite was obtained exclusively in the FeCl2 solutions, confirming that to obtain the formation of this compound, both iron(II) and chloride concentrations must be important. 相似文献
3.
The corrosion behavior of cold isostatically pressed (CIP) high purity alumina ceramics in aqueous HCl and H2SO4 solutions with various concentrations has been studied simultaneously at room temperature (25 °C). Corrosion tests were also performed with 0.65 mol/l HCl and 0.37 mol/l H2SO4 solutions at 40, 55 and 70 °C for 48 h. Chemical stability was monitored by determining the amount of Al3+, Mg2+, Ca2+, Na+ Si4+ and Fe3+ ions eluted in different concentrations of HCl and H2SO4 solutions by means of atomic absorption spectrometry (AAS). By increasing the concentration from 0.37 to 6.5 mol/l, it was notified that the corrosion susceptibility in HCl and H2SO4 solutions for the CIP alumina specimens at room temperature decreases. 相似文献
4.
Evaluation of the inhibitive effect of some plant extracts on the acid corrosion of mild steel 总被引:1,自引:0,他引:1
Emeka E. Oguzie 《Corrosion Science》2008,50(11):2993-2998
Corrosion inhibition of mild steel in 2 M HCl and 1 M H2SO4 by extracts of selected plants was investigated using a gasometric technique at temperatures of 30 and 60 °C. The studied plants materials include leaf extracts Occimum viridis (OV), Telferia occidentalis (TO), Azadirachta indica (AI) and Hibiscus sabdariffa (HS) as well as extracts from the seeds of Garcinia kola (GK). The results indicate that all the extracts inhibited the corrosion process in both acid media by virtue of adsorption and inhibition efficiency improved with concentration. Synergistic effects increased the inhibition efficiency in the presence of halide additives. Inhibition mechanisms were deduced from the temperature dependence of the inhibition efficiency as well as from assessment of kinetic and activation parameters that govern the processes. Comparative analysis of the inhibitor adsorption behaviour in 2 M HCl and 1 M H2SO4 as well as the effects of temperature and halide additives suggest that both protonated and molecular species could be responsible for the inhibiting action of the extracts. 相似文献
5.
Corrosion inhibition of copper in O2-saturated 0.50 M H2SO4 solutions by four selected amino acids, namely glycine (Gly), alanine (Ala), valine (Val), or tyrosine (Tyr), was studied using Tafel polarization, linear polarization, impedance, and electrochemical frequency modulation (EFM) at 30 °C. Protection efficiencies of almost 98% and 91% were obtained with 50 mM Tyr and Gly, respectively. On the other hand, Ala and Val reached only about 75%. Corrosion rates determined by the Tafel extrapolation method were in good agreement with those obtained by EFM and an independent chemical (i.e., non-electrochemical) method. The chemical method of confirmation of the corrosion rates involved determination of the dissolved Cu2+, using ICP-AES (inductively coupled plasma atomic emission spectrometry) method of chemical analysis. Nyquist plots exhibited a high frequency depressed semicircle followed by a straight line portion (Warburg diffusion tail) in the low-frequency region. The impedance data were interpreted according to two suitable equivalent circuits. The kinetics of dissolved O2 reduction and hydrogen evolution reactions on copper surface were also studied in O2-saturated 0.50 M H2SO4 solutions using polarization measurements combined with the rotating disc electrode (RDE). The Koutecky-Levich plot indicated that the dissolved O2 reduction at the copper electrode was an apparent 4-electron process. 相似文献
6.
New Pourbaix diagrams were calculated at 25, 75 and 95 °C for the Nb-H2O system. The species and were considered. Potentiodynamic polarization and mass loss experiments (14 days) were conducted in concentrated H2SO4 (20, 40 and 80 wt%) and HCl (20 and 38 wt%) solutions at 75 and 95 °C. Nb forms a metastable pentoxide (Nb2O5) in H2SO4 and HCl solutions which dissolves as . Corrosion rates decrease between the 40% and the 80% H2SO4 solutions. SEM micrographs show generalized pitting in the 20% and 40% H2SO4 solutions. Mass loss corrosion rates did not exceed 306 μm/yr. Corrosion rates estimated by Tafel extrapolation were within two orders of magnitude of those measured by mass loss and it is shown that this finding is consistent with the thickening of the oxide. 相似文献
7.
Hybrid coatings based on organically modified silicate (Ormosil)-NiZn ferrite/polyaniline (10-30 wt.%) were synthesized through a sol-gel technique. Tetraethylenepentamine, 3-glycidoxypropyltrimethoxysilane, tetraethoxysilane and Ni0.5Zn0.5Fe2O4/polyaniline were used as precursors for the hybrid coatings. These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection. The effects induced by the NiZn ferrite/polyaniline content on the chain dynamics, ferromagnetic behavior and corrosion performances of the coated samples were investigated. The rotating-frame spin-lattice relaxation times and scale of the spin-diffusion path length indicated that the configuration of the hybrid films was highly cross-linked, dense and adhered to the aluminum alloy substrates. The magnetic properties of the resulting hybrids showed super-paramagnetic behavior, such as zero coercive force (coercivity = 0 G) and a low blocking temperatures (45 K). Potentio-dynamic and salt-spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates. 相似文献
8.
Butyl triphenyl phosphonium bromide (BuTPPB) has been evaluated as a corrosion inhibitor for mild steel in 0.5 M H2SO4 solutions using galvanostatic polarisation and potentiostatic polarisation measurements. The study was also complemented by infra red (IR) spectroscopy, scanning electron microscopy (SEM) and quantum chemical calculations. Galvanostatic polarisation measurements showed that the presence of BuTPPB in aerated 0.5 M H2SO4 solutions decreases corrosion currents to a great extent and the corrosion rate decreases with increasing inhibitor concentration at a constant temperature. At 298K, inhibition efficiency was found to be 94.5% for 10−7 M BuTPPB which increased to about 99% for the BuTPPB concentration of 10−2 M. The effect of temperature on the corrosion behaviour of mild steel was studied at five different temperatures ranging from 298 to 338K. The polarisation curves clearly indicate that BuTPPB acts as a mixed type inhibitor. Adsorption of BuTPPB on the mild steel surface follows the Langmuir isotherm.Potentiostatic polarisation measurements showed that passivation was observed only for lower BuTPPB concentrations (10−5 and 10−7 mol l−1) for the mild steel in 0.5 M H2SO4. IR and SEM investigations also confirmed the adsorption of BuTPPB on the mild steel surface in 0.5 M H2SO4 solutions. The molecular parameters obtained using PM3 semi-empirical method, were correlated with the experimentally measured inhibitor efficiencies. 相似文献
9.
A.A. Hermas 《Corrosion Science》2008,50(9):2710-2717
Potentiodynamic polarization and EIS have been employed to compare the corrosion behaviour of 304 stainless steel in NH2SO3H and H2SO4 solutions. Corrosion tests were carried out as a function of the acid’s concentration (0.1-0.5 M) and solution temperature (20-60 oC). The corrosion rate is higher in H2SO4 than in H2NSO3H in all concentrations and temperatures. Values of the activation energy (Ea) revealed that the corrosion process is faster in H2SO4 than in NH2SO3H solution. EIS data showed that the display of Nyquist plots, and hence the mechanism of corrosion, depends not only on the acid concentration but also on the solution temperature. In 0.1 M concentration, the equivalent circuits Re(RctQdl) and Re(RctQdl)(RQ)ads describe the corrosion systems in H2NSO3H and H2SO4 solutions respectively. At concentrations ?0.2 M, the equivalent circuit Re(RctQdl)Qdiff is applicable. Adsorption of the counter ion of the acid on the steel surface and the stability of the surface complex may explain the observed corrosion rates. 相似文献
10.
Corrosion resistance and wear resistance are the two important parameters for high performance of zinc galvanic coating. In the present work, the improvement of these two characteristics was achieved by the incorporation of Al2O3-ZrO2 mixed oxide composite in the coating. Al2O3-ZrO2 mixed oxide composite was synthesized from ZrOCl2·8H2O. Aluminium rich zinc coatings with high sliding wear resistance was developed from a galvanic bath containing the mixed oxide. Based on the performance of the coating during physicochemical and electrochemical characterization, the concentration of mixed oxide composite in the bath was optimized as 0.50 wt% Al2O3-0.50 wt% ZrO2. While rich in Al-metal content in the coating caused high corrosion resistance, the incorporation of the mixed oxide improved structural characteristics of the coating resulting in high wear resistance also. The coating was nonporous in nature and even the interior layers had high stability. The coatings have potential scope for high industrial utility. 相似文献
11.
The title compound (PyS)2 has been synthesized and its inhibiting action on the corrosion of mild steel in 1-5 M H2SO4 solutions at 35-50 °C has been investigated by polarization resistance (Rp), polarization curves and electrochemical impedance spectroscopy (EIS). (PyS)2 showed excellent performance and its efficiency did not affect either by increasing the acid concentration or rise of temperature. Polarization curves indicated that (PyS)2 behaves mainly as anodic inhibitor in 1 M H2SO4 solutions and as a mixed-type inhibitor in 3 and 5 M H2SO4 solutions at different temperatures. Adsorption of (PyS)2 on the steel surface followed Temkin’s adsorption isotherm with a very high negative value of the free energy of adsorption . The activation parameters of the corrosion process were calculated. EIS showed that the charge transfer controls the corrosion process in the uninhibited and inhibited solutions. 相似文献
12.
Three ferrocene derivatives, namely 1,1′-diacetylferrocene (Diacetyl Fc), 1,1′-diformylferrocene (Diformyl Fc) and 2-benzimidazolythioacetylferrocene (BIM Fc) were synthesized and their inhibitive effects against mild steel corrosion in aerated 0.5 M H2SO4 and 1 M HCl solutions were evaluated. Corrosion measurements based on polarization resistance (Rp), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) indicate that Diacetyl Fc, in most cases, accelerates mild steel corrosion in HCl while Diformyl Fc and BIM Fc act as weak inhibitors. In H2SO4 solution, ferrocene derivatives show good inhibition performance. The efficiency of the inhibitors follows the order: BIM Fc > Diformyl Fc ? Diacetyl Fc. Adsorption of both Diacetyl Fc and Diformyl Fc obey Langmuir adsorption isotherm with very low value of free energy of adsorption ΔG° for the Diformyl Fc (physisorption) while adsorption of BIM Fc follows that of Frumkin with high negative value of ΔG° (chemisorption). Both Diformyl Fc and BIM Fc act as mixed-type inhibitors with predominant effect on the anodic dissolution of iron. Analysis of the polarization curves and impedance spectra indicates that charge transfer process mainly controls mild steel corrosion in H2SO4 solution without and with ferrocene compounds. The mechanism of corrosion inhibition or acceleration by ferrocene derivatives was discussed in the light of the molecular structure of the additives. 相似文献
13.
The corrosion behaviour of die-cast AZ91D magnesium alloys in sulphate solutions was investigated by SEM, FTIR and polarization measurements. For immersion times less than 48 h, no pitting corrosion occurred and only generalized corrosion was apparent. According to the polarization curves, the corrosion rate order of the die-cast AZ91D Mg alloy in three aqueous solutions was: NaCl > MgSO4 > Na2SO4. The main corrosion products were Mg(OH)2 and MgAl2(SO4)4·22H2O in the sulphate solutions and the product film was compact. Precipitation of MgAl2(SO4)4·22H2O required a threshold immersion time. 相似文献
14.
On the inhibition of mild steel corrosion by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol 总被引:1,自引:0,他引:1
Ahmed Y. Musa Abdul Amir H. Kadhum Mohd Sobri Takriff Siti Kartom Kamarudin 《Corrosion Science》2010,52(2):526-533
The corrosion inhibition of mild steel in a 2.5 M H2SO4 solution by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was studied at different temperatures, utilising open circuit potential, potentiodynamic and impedance measurements. The results indicate that APTT performed as an excellent mixed-type inhibitor for mild steel corrosion in a 2.5 M H2SO4 solution and that the inhibition efficiencies increased with the inhibitor concentration but decreased proportionally with temperature. The kinetic and thermodynamic parameters for adsorption of APTT on the mild steel surface were calculated. A chemisorption mechanism of APTT molecules on the mild steel surface was proposed based on the thermodynamic adsorption parameters. 相似文献
15.
The influence of salt deposits on the atmospheric corrosion of high purity Al (99.999%) was studied in the laboratory. Four chloride and sulfate-containing salts, NaCl, Na2SO4, AlCl3 · 6H2O and MgCl2 · 6H2O were investigated. The samples were exposed to purified humid air with careful control of the relative humidity (95%), temperature (22.0 °C), and air flow. The concentration of CO2 was 350 ppm or <1 ppm and the exposure time was four weeks. Under the experimental conditions all four salts formed aqueous solutions on the metal surface. Mass gain and metal loss results are reported. The corroded surfaces were studied by ESEM, OM, AES and FEG/SEM equipped with EDX. The corrosion products were analyzed by gravimetry, IC and grazing incidence XRD. In the absence of CO2, the corrosivity of the chloride salts studied increases in the order MgCl2 · 6H2O < AlCl3 · 6H2O < NaCl. Sodium chloride is very corrosive in this environment because the sodium ion supports the development of high pH in the cathodic areas, resulting in alkaline dissolution of the alumina passive film and rapid general corrosion. The low corrosivity of MgCl2 · 6H2O is explained by the inability of Mg2+ to support high pH values in the cathodic areas. In the presence of carbon dioxide, the corrosion induced by the salts studied exhibit similar rates. Carbon dioxide strongly inhibits aluminum corrosion in the presence of AlCl3 · 6H2O and especially, NaCl, while it is slightly corrosive in the presence of MgCl2 · 6H2O. The corrosion effects of CO2 are explained in terms of its acidic properties and by the precipitation of carbonates. In the absence of CO2, Na2SO4 is less corrosive than NaCl. This is explained by the lower solubility of aluminum hydroxy sulfates in comparison to the chlorides. The average corrosion rate in the presence of CO2 is the same for both salts. The main difference is that sulfate is less efficient than chloride in causing pitting of aluminum in neutral or acidic media. 相似文献
16.
Effects of pretreatment on the aluminium etch pit formation 总被引:1,自引:0,他引:1
The effect of chemical pretreatments on the electrochemical etching behavior of aluminium was investigated with the topographic studies of surface and the analysis of initial potential transients. Two-step pretreatments with H3PO4 and H2SiF6 result in a high density of pre-etch pits on aluminium surface by the incorporation of phosphate ion inside the oxide film and the removal of surface layer by aggressive fluorosilicic acid solution. It generates a high density of etch pits during electrochemical etching and results in the capacitance increase of etched Al electrode by expanding the surface area, up to 61.3 μF/cm2 with the pretreatment solution of 0.5 M H3PO4 at 65 °C and 10 mM H2SiF6 at 45 °C. 相似文献
17.
The work addresses the influence of Mn and Mo additions on corrosion resistance of AISI 304 and 316 stainless steels in 30 wt.% H2SO4 at 25 and 50 °C. Corrosion mechanism was determined by gravimetric tests, DC polarization measurements and electrochemical impedance spectroscopy (EIS). The morphology and nature of the reaction products formed on the material surface were analysed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Reduction of temperature from 50 to 25 °C drastically decreased the corrosion rate of AISI 304 and 316 stainless steels in sulphuric acid solution. Mn additions did not affect significantly the general corrosion resistance due to its low ability to form insoluble compounds in acid medium. Meanwhile, the formation of molybdenum insoluble oxides enhanced the corrosion performance. 相似文献
18.
Ilaria Perissi Ugo Bardi Stefano Caporali Alessandro Lavacchi 《Corrosion Science》2006,48(9):2349-2362
The corrosion behaviour of several metals and metal alloys (copper, nickel, AISI 1018 steel, brass, Inconel 600) exposed to a typical ionic liquid, the 1-butyl-3-methyl-imidazolium bis-(trifluoromethanesulfonyl) imide, ([C4mim][Tf2N]), has been investigated by electrochemical and weight-loss methods. Corrosion current densities have been determined by extrapolation from Tafel plots and by polarization resistance measurements and 48 h immersion tests were performed at 150, 250, 275 and 325 °C. Room temperature results show low corrosion current densities (0.1-1.2 μA/cm2) for all the metals and alloys investigated. At 70 °C, the corrosion current for copper dramatically increases showing a strongly dependence on temperature. At 150 °C copper shows significant weight-loss while nickel, AISI 1018, brass and Inconel do not. At higher temperatures (?275 °C), the copper sample crumbles and localized corrosion occurs for the other metals and alloys. 相似文献
19.
Nanotubular oxide layer formation was achieved on biomedical grade Ti-13Nb-13Zr alloy using anodization technique in 1 M H3PO4 + 0.5 wt.% NaF. The as-formed and heat treated nanotubes were characterized using SEM, XRD and TEM. Corrosion behaviour of the nanotubular alloy was investigated employing potentiodynamic and potentiostatic polarization. The alloy after nanotubular oxide layer formation exhibited significantly higher corrosion current density than the bare alloy. The lower corrosion resistance of the nanotubular alloy was suggested to be associated with the distinctly separated barrier oxide/concave shaped tube bottom interface. A heat treatment at 150 °C appreciably enhanced the corrosion resistance property. 相似文献
20.
The high temperature sulphidation behaviour of Fe-46Cr-xSn (x = 0; 0.2; 0.5; 1; 2) alloys has been studied at temperatures of 1073, 1173 and 1273 K in H2/H2S mixtures with different sulphur vapour partial pressures of 10−1, 10−3 and 10−5 Pa. Thermogravimetric studies in combination with scanning electron microscope (SEM), with energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) techniques, have displayed a significant influence of the sulphur partial pressure on the composition and growth rate of the sulphide scale. The results have shown that addition of tin increases the sulphidation rate of Fe-46Cr alloys but not considerably (except at temperatures of 1073 and 1173 K combined with sulphur partial pressure of 10−5 Pa). The metallic core of the studied samples was enriched in tin and iron, moreover tin was found in the internal layer close to the metallic core as metallic FexSny inclusions with tin concentrations of up to 12 at.%. 相似文献