饱和NaCl溶液浸泡下混凝土试块中有机阻锈剂对钢筋腐蚀行为的影响

利用电化学阻抗谱(EIS)、半电池腐蚀电位(Ecorr)和宏观电池腐蚀电流密度(Icorr)测量技术,在饱和NaCl溶液浸泡的硬化混凝土试块中,研究了4种醇胺基阻锈剂对钢筋电极腐蚀电化学行为的影响和长期阻锈性能.在浸泡初始的100d内,与空白样相比,添加阻锈剂后钢筋电极腐蚀电位升高,阻抗膜值增大,腐蚀电流密度值降低,表明电极表面处于钝态,阻锈剂表现出良好的阻锈性能.随浸泡时间延长,电极腐蚀电位和阻抗膜值下降,腐蚀电流密度增大.浸泡后期,除添加醇胺基CI-4样外,电极电位和腐蚀电流密度与空白样相比无明显差别,表明电极由钝态转变为活性腐蚀状态.但添加CI-4样品,钢筋电极始终保持在钝化状态,阻锈性能最好.基于阻锈剂与Cl-间的竞争吸附,分析探讨了可能的阻锈机理.     

Effect of acetic acid on CO2 corrosion of carbon steel in NaCl solution

Potentiodynamic sweep and electrochemical impedance spectroscopy measurements were applied to investigate the effects of both temperature and acetic acid (HAc) on the anodic and cathodic reactions in CO₂ corrosion of P110 steel in 3.5% NaCl solution. The temperatures were controlled at 30 and 60 °C. The concentrations of HAc were controlled at 0, 1000, 3000 and 5000 ppm. In this work, the corrosion parameters of polarization curves, such as corrosion potential (E_corr), corrosion current density (i_corr), and anodic and cathodic branch slopes (b_a and b_c), are presented and discussed in detail. In addition, the equivalent circuit models and ZsimpWin software were utilized to discuss the Nyquist plots. The plots showed that the E_corr values shifted in the positive direction as the HAc concentration increased. The i_corr values increased with the increase in HAc concentration, indicating that HAc could accelerate the corrosion. The impedance spectra measured at 30 and 60 °C have different time constants and characterization. The coverage fraction θ and the thickness L of corrosion film are two most important controlled variables that influence and control the CO₂ corrosion mechanisms. Copyright © 2010 John Wiley & Sons, Ltd.     

Influence of caffeine and temperature on corrosion-resistance of CoCrMo alloy

The inhibitory activity of caffeine (1,3,7-trimethyl xanthine) on artificial saliva was studied on a CoCrMo alloy using different electrochemical methods: open circuit potential (OCP), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The results show that caffeine produces an inhibitory effect on the anodic currents due to its adsorption on the surface of the alloy. Temperature is another parameter with an influence on corrosion processes, so thermodynamic data were obtained from Arrhenius plots and Langmuir adsorption isotherms. The protective action of caffeine is enhanced at high temperatures at OCP, while for potentiodynamic experiments high temperatures block the inhibitory activity of caffeine and the corrosion rate increases. The process may also be studied by a simulation, determining the functional dependence between OCP, corrosion current density (i _corr), corrosion potential (E _corr), breakdown potential (E _bd) and temperature and amount of caffeine in artificial saliva, for Heraenium® CE. The neural network-based methodology applied in this work provides accurate results, thus proving to be an efficient modelling technique.     

Corrosion mitigation on orthodontic wire made of SS 18/8 alloy using esomeprazole tablet (Esiloc-40 mg) in artificial saliva

The corrosion inhibition of orthodontic wire made of SS 18/8 alloy in artificial saliva, with and without the presence of tablet esomeprazole − 40 mg has been investigated by electrochemical analysis. Polarisation study indicates that in the presence of the mentioned tablet, polarisation resistance (R_p) value increases and corrosion current (I_corr) decreases. That is, the corrosion resistance of SS 18/8 alloy in artificial saliva increases. AC impedance spectroscopy reveals that charge transfer resistance value (R_ct) value increases and double layer capacitance value (C_dl) decreases. The open circuit potential (OCP) values for the inhibited system are more negative than that of the uninhibited blank system. The vibration peaks obtained from the FTIR spectra indicates the presence of functional group in esomeprazole pill and these characteristic peaks are slightly shifted in the analyzed scratched film from the surface of the orthodontic wire after immersion. AFM micrograph image of the polished specimen sample immersed in artificial saliva (AS) with esomeprazole tablet solution shows lesser degree of surface deterioration than those for SS 18/8 specimen immersed only in artificial saliva. From the present work, it is reported that people clipped with orthodontic wire made of SS 18/8 alloy need not worry about orthodontic corrosion for taking esomeprazole tablet for the treatment of gastro esophageal reflux disease and other medicinal purpose.     

Enhancement corrosion resistance of (3-methacryloxypropyl)silsesquioxane hybrid films and its validation by gas-molecule diffusion coefficients using MD simulation

In the first part of this work, based on silsesquioxanes (SSO) derived from hydrolytic condensation of (3-methacryloxypropyl)trimethoxysilane (MPMS) and tetraethoxysilane (TEOS), two hybrid films, f-MPMS-SSO (f-MS) and f-MPMS-TEOS-SSO (f-MTS) modified with 15 wt% TEOS, were prepared. The anticorrosion properties (corrosion potential, E _corr, and corrosion current density, I _corr) of the bare aluminum alloy (AA) and the two films on AA were tested by electrochemical measurements with typical potentiodynamic polarization curves. The I _corr values of three samples are significantly different with the order of f-MTS < f-MS < AA which implies that the TEOS addition in the f-MTS coating indeed enhances the electrochemical corrosion resistance. Correlations between the structures of two films and anticorrosion properties were discussed. In the second part of this work, two different 3D-amorphous cubic unit cells, cell(f-MS) and cell(f-MTS), as models were employed to investigate self-diffusion coefficients by molecular dynamics (MD) simulation for the NO₂, SO₂ and H₂O molecules. All three self-diffusion coefficients of NO₂, SO₂ and H₂O diffusing in cell(f-MTS) were less than the coefficients in cell(f-MS), which validates the corresponding anticorrosion-experiment results. Two reasons why the addition of TEOS in the system of f-MTS leads to a lowering of the gas self-diffusion coefficient compared to the f-MS system, were discussed. An erratum to this article can be found at     

Determination of corrosion rate of molybdenum,rhenium and their alloys in sodium chloride solution by the method of Tafel extrapolation

Based on the measured voltammograms, the corrosion potentials and corrosion current densities of Mo, Re, and several their alloys in the NaCl solutions were determined by the method of Tafel extrapolation. The dependences of E _corr and i _corr on the alloy composition, including the corresponding values for the metals (alloy components), were plotted. The obtained values of i _corr and the corrosion rates in the linear units were compared with the literature data.     

Poly(4-vinylpyridine-hexadecyl bromide) as corrosion inhibitor for mild steel in acid chloride solution

The influence of the addition of poly(4-vinylpyridine-hexadecyl bromide) P4VP-Alkyl 50?% newly synthesized on the corrosion of mild steel in molar hydrochloric acid has been investigated by weight-loss measurements combined with linear potential scan voltammetry (I?CE) and electrochemical impedance spectroscopy (EIS). The polymer reduces the corrosion rate and the inhibition efficiency (E?%) of P4VP-Alkyl 50?% increases with its concentration and attains 95?% at 300?mg/L. E?% obtained from cathodic Tafel plots, EIS, and gravimetric methods were in good agreement. The inhibitor was adsorbed on the iron surface according to the Langmuir adsorption isotherm model. Polarization measurements also show that the compound acts as a cathodic inhibitor.     

Hydrogen evolution reaction on Sn, In, and Sn–In alloys in carboxylic acids

The cathodic behavior of tin, indium, and tin–indium alloys in 0.5-M solutions of oxalic, malic, and citric acids has been investigated using potentiodynamic techniques at temperature range of 30–60 °C. The results showed that the corrosion rate (I _corr) is higher at lower indium percent (0.5% In) and starts to decrease gradually as increase of the In percent up to 5% In (although it is still higher than that of pure tin and lower than that of indium at 5% In) in all examined acids. The positive shift in corrosion potential with simultaneous increase in corrosion rate can be explained on the basis of the depolarizing action of β-InSn₄ phase compared with pure tin. The negative shift in the corrosion potential with much higher corrosion rate in case of alloys IV and V (10% and 20% In, respectively) can be ascribed to the formation of γ-In₃Sn phase which leads to the increase in the anodic to cathodic area ratio. The corrosion of the two investigated metals and their alloys is affected by the formation of soluble complex species with organic acid anions. The aggressiveness of the studied metals and their alloys decreases in the following order of the organic acids employed oxalic > malic > citric acid. The observed activation energy values support that the tested electrodes exhibit higher corrosion rates in oxalic acid solution than the corresponding values in the other investigated acids. X-ray diffraction and scanning electron microscopy photographs elucidated the types of phases formed in the prepared alloys. The presence of a definite amount of indium in tin alloy improves the hardness.     

Anodic polarization of Al-Sn alloy in H3PO4 solutions

The anodic polarization behaviour of Al-Sn alloy (5.6% Sn) was studied in aerated 1, 1.5 and 2 M H₃PO₄ acid solutions using potentiodynamic and potentiostatic techniques. Anodic behaviour of Al and Sn metals was investigated for comparison. The results show that the alloy exhibits active-passive transition behaviour. The passivation of the examined alloy is due to the formation of oxide film for both Al and Sn incorporated with their phosphates. In general, at constant concentration of PO₄ ³⁻ ion, the passive current density (I _pass) is decreased with increase of pH in the range 2.5–5. Further, the influence of Cl⁻ ions on the passivity of the given alloy was studied. It was found that the aggressive effect of Cl⁻ ions on the passive film is inhibited with increase in phosphate concentration and pH. However, the addition of organic compounds (2- and 3-picoline and 2-aminopyridine) shows that only 2-aminopyridine inhibited the attack of Cl⁻ ions. Received: 24 October 1997 / Accepted: 5 February 1998     

Corrosion resistance of electroless Cu–P and Cu–P–SiC composite coatings in 3.5% NaCl

The Cu–P and Cu–P–SiC composite coatings on carbon steel substrates were deposited via electroless plating. The anti-corrosion properties of Cu–P and Cu–P–SiC coatings were studied in 3.5% NaCl solution. The anti-corrosion properties of Cu–P and Cu–P–SiC coatings were investigated in 3.5% NaCl solution by the weight loss, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) techniques. It has been found that the shift in the corrosion potential (E_corr) towards the noble direction, decrease in the corrosion current density (I_corr), increase in the charge transfer resistance (R_ct) and decrease in the double layer capacitance (C_dl) values indicated an improvement in corrosion resistance with the incorporation of SiC particles in the Cu–P matrix. The effects of varying the SiC concentration on the corrosion resistance of carbon steel were investigated and it was found that the best anti-corrosion property of Cu–P–SiC is at 5 g L^?1 SiC in the bath formulation.     

Electrochemical performance of Mg–9Al–1Zn alloy in aqueous medium

A systematic study on the corrosion and passivation behavior of AZ91D alloy in relation to the influence of concentration, temperature, pH, and immersion time was made in aqueous sulfate solution using electrochemical techniques including open-circuit potential, potentiodynamic polarization and impedance spectroscopy. It was found that the corrosion and pitting potentials (E _corr and E _pit) of the alloy drift to more active values with increasing either concentration (0.01–1.0 M) or temperature (278–338 K) of the test solution, suggesting that sulfate solution enhances the alloy dissolution, particularly at higher temperatures. On the other hand, values of the total film resistance (R _T) indicate that neutral solution (pH 7.0) supports the formation of a better protective layer on AZ91D surface than alkaline (pH 12.5) or acidic (pH 1.0) medium. The growth of a protective film on the alloy surface at short immersion times (up to ∼50 h) is evinced by a rapid positive evolution of E _corr and fast decrease in the corrosion rate (i _corr). However, for a long-term exposure (up to 500 h) E _corr drifts negatively and i _corr increases due to breakdown of the protective film, which causes a decrease in the alloy stability. Fitting the impedance data to equivalent circuit models suitable to each behavior assisted to explore the mechanism for the attack of the sample surface at various testing times. The results obtained from the three studied electrochemical techniques are in good agreement.     

Ethanol extracts of Hemidesmus indicus leaves as eco-friendly inhibitor of mild steel corrosion in H2SO4 medium

The inhibitory action of an extract of Hemidesmus indicus leaves as a potential corrosion inhibitor for steel in H₂SO₄ solutions was examined using conventional mass loss, gasometric techniques, electrochemical polarisations and electrochemical impedance spectroscopy. The results revealed that the extract of Hemidesmus indicus leaves performed well as an inhibitor for the corrosion of the metal employed in an accelerating medium. The inhibition efficiencies for all the experimental techniques employed increased with increasing the concentration of the plant extract but decreased with a rise in temperature. Both the cathodic hydrogen evolution and the anodic dissolution of mild steel were inhibited, hence the active molecule of the extract studied acted as a mixed-type corrosion inhibitor.     

锌合金阳极在不同pH值Ca(OH)_2溶液中的电化学行为

应用恒电位法测定锌合金阳极在不同pH值的Ca(OH)2溶液中的极化曲线,X-射线衍射分析了该锌合金阳极的腐蚀产物.实验表明:在不同pH值的碱性溶液中锌合金阳极表现出完全不同的电化学行为:在不稳定钝化区内出现了3个零电流电位;根据锌合金阳极在Ca(OH)2溶液中极化曲线测定了活化区内各不同pH值下的零电流电位、腐蚀电流密度,以及钝化区间内的维钝电流密度、钝化膜破裂电位等电化学参数;绘制电位-pH图,并与纯锌-水系的电位-pH图进行比较.     

Experimental and theoretical investigation of adsorption and inhibition properties of 2-Amino-1,3,5-triazine-4,6-dithiol against corrosion in hydrochloric acid solution on mild steel

In this work, 2-Amino-1,3,5-triazine-4,6-dithiol (2-ATD) as novel and high efficiency corrosion inhibitor has been investigated for mild steel (MS) corrosion in 0.5 M HCl solution using electrochemical methods, scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDX), atomic force microscopy (AFM) and quantum chemical calculation methods. Potentiodynamic polarization (PDP) curves indicate that 2-ATD is mixed type inhibitor, corrosion inhibition efficiency increased with increasing inhibitor concentration and reached its value of 96.5%. Evolution of exposure time versus corrosion behavior of 2-ATD is examined in corrosive medium. While corrosion potential (E_corr) shifted more negative values, polarization resistances (R_p) decreased after 120 h exposure time due to the corrosion process. H₂ volume is measured in uninhibited and inhibited solutions (10 mM 2-ATD) after 120 h exposure time. Very low volume (3.6 mL cm⁻²) of H₂ is obtained on MS electrode in inhibited solution after 120 h of exposure, indicating that 2-ATD covers the entire surface against aggressive attack and retards the both anodic dissolution of MS and cathodic hydrogen evolution reactions. The adsorption process proposal is the Langmuir isotherm which is most suitable. Adsorption and thermodynamic parameters show that 2-ATD has a strong adsorption effect onto MS surface and includes mixed adsorption style (physical and chemical). Corrosion current density increases with increasing temperature and high activation energy (Ea) proves the strong adsorption of 2-ATD on the MS surface. Anti-corrosion mechanism of 2-ATD is described more detail with the potential of zero charge method. SEM, EDX and AFM analysis support the obtained results of electrochemical methods and confirm the existence of protective layer and strong adsorption of 2-ATD on the MS surface. Chronoamperometry test shows that current densities are almost constant whole experiment in the presence of organic film. Finally, quantum chemical calculation method of 2-ATD in blank solution is performed to investigate the active sites for possible attachment with MS surface.     

Fermentation product of Streptomyces griseus (albomycin) as a green inhibitor for the corrosion of zinc in H2SO4

Abstract

Inhibitive and adsorption properties of albomycin as a green inhibitor for the corrosion of zinc in H₂SO₄ solutions were studied using weight loss and hydrogen evolution methods. The results obtained, indicate that albomycin is a good adsorption inhibitor for the corrosion of zinc in H₂SO₄ solution. The inhibition potentials of albomycin for the corrosion of zinc in H₂SO₄ solutions are attributed to the adsorption of the inhibitor on the surface of zinc and its inhibition efficiency increases with increase in the concentration of the inhibitor but decreases with increasing temperature. The range obtained for the values of activation energy and free energy of adsorption were within the limit expected for the mechanism of physical adsorption. Also, the adsorption of albomycin on zinc surface was spontaneous, exothermic, and supported the Langmuir adsorption model. Optimized structure of 2-[[2-[[5-[acetyl(hydroxy)amino]-2-[[5-[acetyl(hydroxy)amino]-2-[[5-[acetyl(hydroxy)amino]-2-aminopentanoyl]amino] pentanoyl] amino] pentanoyl]amino]-3-hydroxypropanoyl]amino]-3-[(2R,3S,4R,5R)-3,4-dihydroxy-5-(3-methyl-2,4-dioxopyrimidin-1-yl)thiolan-2-yl]-3-hydroxypropanoic acid; iron(3 + ) (albomycin)     

Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5 M H2SO4 solution

A study on the use of the methanol extract of Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5?M of sulfuric acid has been carried out by using potentiodynamic polarization curves, electrochemical impedance spectroscopy and gravimetric tests. Testing temperatures were 25°C, 40°C and 60°C. Results showed that M. sativa is a good corrosion inhibitor, with its efficiency increasing with its concentration and with time, but decreasing with the temperature. M. sativa forms a passive film on top of the steel with a passive current density and pitting potential values lower than that for uninhibited solution, and remained on the steel for 8–12?h. This film formed by iron ions and heteroatoms present in OH^? and amine groups from the extract are adsorbed on the steel and form a protective film on to the steel.     

Synthesis and Electrochemical Properties of 2-(4-R 1 -Phenyl)-6-(4-R 2 -phenyl)-4-phenyl-3,4-dihydro1,2,4,5-tetrazin-1(2 H )-yls

A new methodology for creating electroactive components for organic batteries, based on the construction of a molecular platform including stable 3,4-dihydro-1,2,4,5-tetrazin-1(2H)-yl radicals was described. A series of 2-(4-R1-phenyl)-6-(4-R2-phenyl)-4-phenyl-3,4-dihydro-1,2,4,5-tetrazin-1(2H)-yls with substituents of various nature was obtained. It was shown that the substituents R1 in the aromatic ring at position 2 of the tetrazinyl fragment influence the value of the oxidation potential in the radical, but do not influence the value of the reduction potentials, while the substituent R2 of the aromatic ring at position 6 influence the values of the reduction potentials and practically do not influence oxidation potential values. Based on the obtained electrochemical data, a correlation structure–potential value was revealed for the cathodic and anodic process, with the help of which triarylsubstituted 3,4-dihydro-1,2,4,5-tetrazin-1(2H)-yl radicals with high values of the electrochemical gap were obtained.     

Electrochemical response of natural and induced passivation of high strength duplex stainless steels in alkaline media

The passivation of two high strength duplex stainless steels (HSSS) was investigated in alkaline solutions simulating the pore solution of concrete by the growth of natural and induced passive films. Induced passive films were generated both by cyclic voltammetry and by chronoamperometry. Natural passive films were spontaneously grown by the immersion of the steel in the alkaline electrolyte. These passive layers were characterised by electrochemical impedance spectroscopy, corrosion current density (i _corr) and corrosion potential (E _corr) monitoring. The effect of significant parameters, such as the pH in the HSSS/alkaline solution interface, the composition of the duplex stainless steels and the ageing of the passive layer, on the electrochemical performance of both induced and spontaneously grown passive films has been analysed. The increase of alkalinity highly influences the electrochemical performance of the passive film by promoting the formation of a passive layer with a less resistant electrochemical response. The electrochemical behaviour of the passive layer is also affected by the alloying elements like Mo or Ni. Both natural and induced passive films show similar electrochemical trend with respect to significant parameters such as the pH and the composition of the steel. The ageing of the spontaneously grown passive layer promotes a higher resistive electrochemical response which might be related to the enrichment of the passive layer in non-conducting (or semi-conducting) oxides.     

Crystal and molecular structure and electronic structure of a copper(II) complex with 10-(1-phthalazinylazo)-9-phenanthrol (HL) [Cu2(L)2(H2O)4](ClO4)2

The [Cu₂(L)₂(H₂O)₄](ClO₄)₂ compound (I) have been synthesized by the reaction of 10-(1-phthalazinylazo)-9-phenanthrol (HL) with tetraamminecopper(II) perchlorate, and its crystal and molecular structure has been determined by X-ray crystallography. The L anion acts as a tridentate chelating ligand and is coordinated to the Cu atom through the O(1) atoms of the phenanthrenequinone moiety, the N(1) atom of the phthalazinyl moiety, and the N(3) atom of the azo group to form two five-membered chelate rings. The coordination polyhedron of each Cu(1,2) atom is completed to a prolate tetragonal (4 + 1) pyramid by two water molecules with the O(2)(H₂O) atom in the axial position. The molecular and electronic structures of the HL molecule and [Cu(L)(H₂O)₂]⁺ ion have been determined by the density functional theory method. The results of quantum-chemical calculation are shown to fit well to the values found by X-ray crystallography.     

Crystal Structure of Tetrakis (phenacetin) Dihydrogentetraiodide Dihydrate {[H5C2OC6H4N (H)C(CH3)O]4·H2I4·2H2O}

(Phenacetin)₄·₂I₄·2H₂O is triclinic, a = 13.641 (7), b = 12.807 (6), c = 7.201 (3) Å, α = 99.8 (4), b? = 86.5 (4), γ = 104.0 (5)°, P1 , Z = 1. The ordered crystal structure has been refined to R_F = 0.050, using 4173 independent reflections measured on a four-circle diffractometer with MoKa (graphite monochromator) radiation. The crystals are composed of alternating positively and negatively charged slices; each positive slice contains a double layer of stacks of hemi-protonated phenacetin molecules which are H-bonded through their carbonyl groups (d(O - - - O) = 2.432 (4) Å) while each negative slice contains a single layer of I^2?₄-ions linked in chains along [100] through H-bonds to pairs of water molecules. The axes of the phenacetin stacks are parallel to the planes of the (I^2?₄·2H₂O)-layers. The I^2?₄-ion is centro-symmetric and can be approximately represented as I^?- - - I–I- - - I^? (d(I^? - - - I) = 3.404 (1) Å; d(I–I) = 2.774 (1) Å). The compound is a pseudo-type A basic salt.