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1.
The film thickness, d of a p-hydroxymethylbenzene - C6H4CH2OH (HOMB) self-assembled monolayer (SAM) adsorbed on iron via a covalent bond was increased by multistep modification with tetraethoxysilane (C2H5O)4Si (TES) and 1,8-octanediol HO(CH2)8OH (C8DO) and subsequently with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 (BTESE) and akyltriethoxysilane CnH2n+1Si(OC2H5)3 (CnTES, n = 8 or 18). The protective ability of the film against iron corrosion was examined by polarization measurement of the iron electrode coated with the film in an oxygenated 0.5 M NaCl after immersion in the solution for many hours. The values of protective efficiency, P for the films, the HOMB SAM modified with TES and C8DO twice and subsequently with BTESE and CnTES were high, more than 81% at n = 8 and 85% at n = 18 in the range of the immersion time, t up to 240 h, respectively. The maximal P values of the respective films were 88.0% and 92.2%, of which approximate d values were 4.6 and 5.8 nm. The high protection of iron against corrosion was attributed to increases in the film thickness and interconnection between the adsorbed molecules with Si-O polymer linkages. The protective ability of the film was remarkably persistent during immersion in the solution for many hours. A slight enhancement of P was observed by additional modification of the modified HOMB SAM with C8TES due to increases in interconnection and close packed arrangement. The formation of strong adsorption bonds, σ-covalent bond and back-donating π-bond, between the carbon atom of HOMB moiety and iron atom was discussed. 相似文献
2.
A self-assembled monolayer (SAM) of p-hydroxymethylbenzene HOCH2C6H4 - (HOMB) moiety adsorbed on iron by the formation of a covalent bond between carbon and iron atoms was prepared by electrochemical derivatization of an iron electrode with p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH2C6H4N2BF4. The electrode covered with the HOMB SAM was modified with alkyltriethoxysilanes CnH2n+1Si(OC2H5)3 (CnTES, n = 8 or 18) to prepare a film of one-dimensional polymer. The protective ability of the polymer film was determined by polarization measurement of the covered electrode in an aerated 0.5 M NaCl solution. The ability was enhanced by modification of the HOMB SAM with CnTES markedly. The iron surface coated with the one-dimensional polymer film of the HOMB SAM modified with C8TES was characterized by contact angle measurement and FTIR reflection and X-ray photoelectron spectroscopies. The persistence in the protective ability of the polymer film against iron corrosion in 0.5 M NaCl may be associated with the strong adsorption via the covalent bond, revealed by electron-probe microanalysis. 相似文献
3.
Additional modification of the ultrathin two-dimensional polymer film, a p-hydroxymethylbenzene C6H4CH2OH self-assembled monolayer modified with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 (BTESE) and alkyltriethoxysilane CnH2n+1Si(OC2H5)3 (CnTES, n = 8 or 18), was attempted to improve the protective ability of the film against iron corrosion. The ability of the film was examined by polarization measurement of an iron electrode coated with the film in an oxygenated 0.5 M NaCl solution after immersion in the solution for 1.5 to 72 h. Marked improvement of the protective efficiency, P was not obtained by additional modification to the polymer film with BTESE. The P values of the two-dimensional polymer films were markedly increased by additional modification with C8TES. The increases in P were ascribable to improvement of alkyl tail arrangement and additional interconnection in the polymer films. The film on the iron surface was characterized by contact angle measurement, FTIR reflection spectroscopy and X-ray photoelectron spectroscopy. The protective abilities of the two-dimensional polymer films additionally modified with C8TES were persistent during immersion for 72 h. 相似文献
4.
An iron electrode was modified by electrolytic reduction in deaerated acetonitrile solution of p-toluenediazonium tetrafluoroborate CH3C6H4N2BF4 (TDFB) or p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH2C6H4N2BF4 (HOTDFB) below 10 °C to form a self-assembled monolayer (SAM) of toluene CH3C6H4- or hydroxymethylbenzene HOCH2C6H4- (HOMB) moiety, probably adsorbed on the electrode by the formation of a covalent bond between carbon and iron atoms, as shown in references. The protective ability of the layer was examined by polarization measurement of the electrode in an aerated 0.5 M NaCl solution. The protective efficiencies of these two SAMs were not high, around 30%, a little higher than that of the toluenethiol CH3C6H4SH SAM which was anchored on iron via a coordinate bond between sulfur and iron atoms. The iron surfaces modified with TDFB and HOTDFB were characterized by contact angle measurement, FTIR reflection spectroscopy and X-ray photoelectron spectroscopy. The persistence in protection of iron against corrosion by coverage with the HOMB SAM was confirmed by polarization measurements after immersion in 0.5 M NaCl for a long period of the time. 相似文献
5.
Kunitsugu Aramaki 《Corrosion Science》2007,49(4):1963-1980
Ultrathin films of one- and two-dimensional polymers were prepared on a zinc electrode coated with a hydrated cerium(III) oxide Ce2O3 layer by modification of a 16-hydroxyhexadecanoate ion self-assembled monolayer (SAM) with alkyltriethoxysilanes. The protective efficiency, P of the film was determined by polarization measurements of the electrodes bare and covered with the polymer films in an oxygenated 0.5 M NaCl solution. The respective P values for the one-dimensional polymers of the HOC16A− SAM modified with octyltriethoxysilane C8H17Si(OC2H5)3 (C8TES) and octadecyltriethoxysilane C18H37Si(OC2H5)3 (C18TES) were 94.4 and 95.1%. The values for the two-dimensional polymers of the HOC16A− SAM modified with 1,2-bis(triethoxysilyl)ethane (C2H5)3Si(CH2)2Si(C2H5)3 plus C8TES and C18TES were 95.4 and 96.5%, respectively, indicating higher than those of the one-dimensional polymers. Structures of the polymer films were characterized by contact angle measurement with a drop of water and X-ray photoelectron and FTIR reflection spectroscopies. 相似文献
6.
For enhancing the protective efficiency, P of a film prepared by modification of a p-hydroxymethylbenzene HOC6H4 (HOMB) self-assembled monolayer (SAM) adsorbed on iron by the formation of a covalent bond, an increase in the film thickness, d was attempted. The HOMB SAM was modified with tetraethoxysilane (C2H5O)4Si (TES), 1,8-octanediol HO(CH2)8OH (C8DO), 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 (BTESE) and alkyltriethoxysilane CnH2n+1Si(OC2H5)3 (CnTES, n = 8 or 18). The P value of the film was determined by polarization measurement of a covered iron electrode in an aerated 0.5 M NaCl solution after immersion in the solution for 1.5–72 h of the immersion time, t. High values of P, more than 82% were obtained for the films of HOMB SAM modified with TES, C8DO and CnTES and with TES, C8DO, BTESE and CnTES in the range of t up to 72 h. The highest value was 93.2%, for the film of HOMB SAM modified with TES, C8DO, BTESE and C18TES, of which d was 4.7 nm. The film of HOMB SAM modified with TES, C8DO and C8TES was characterized by contact angle measurement, X-ray photoelectron spectroscopy and FTIR reflection spectroscopy. 相似文献
7.
Kunitsugu Aramaki 《Corrosion Science》2010,52(4):1464-1471
An ultrathin, ordered and two-dimensional polymer coating was prepared on a passivated iron electrode by modification of 16-hydroxyhexadecanoate ion HO(CH2)15CO2− self-assembled monolayer with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 and octadecyltriethoxysilane C18H37Si(OC2H5)3. Subsequently, the electrode was healed in 0.1 M NaNO3. Protection of passivated iron against passive film breakdown and corrosion of iron was examined by monitoring of the open-circuit potential and repeated polarization measurements of the polymer-coated and healed electrode in an aerated 0.1 M NaCl solution during immersion for many hours. Localized corrosion was markedly prevented by coverage with the polymer coating and the healing treatment in 0.1 M NaNO3. Prominent protection of iron from corrosion in 0.1 M NaCl was observed before the breakdown occurred. The electrode surface covered with the healed passive film and polymer coating was analyzed by contact angle measurement, X-ray photoelectron spectroscopy and electron-probe microanalysis. 相似文献
8.
Kunitsugu Aramaki 《Corrosion Science》2010,52(9):2766-2772
A two-dimensional polymer coating, the self-assembled monolayer of 16-hydroxy hexadecanoate ion HO(CH2)15 modified with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 and octadecyltriethoxysilane C18H37Si(OC2H5)3 was prepared on the passivated iron electrode and further, the passive film was healed by additional treatment in 0.1 M NaNO3. This electrode was immersed in oxygenated 0.1 M KClO4 solutions with and without 1 × 10−4 to 1 × 10−2 M of Cl−. Protection of passive film against breakdown by covering the electrode with the polymer coating was examined by monitoring the open-circuit potential during immersion in the solutions for many hours to determine the time for passive film breakdown, tbd. Repeated polarization measurements were carried out during immersion in these solutions for obtaining the protective efficiency, P. The tbd value of the passivated, polymer-coated and healed electrode in 0.1 M KClO4 solutions with and without Cl− increased with a decrease in the concentration of Cl−. No breakdown occurred on the electrode during immersion in 0.1 M KClO4 solutions with and without 1 × 10−4 of Cl− for 360 h. The P values were extremely high, more than 99.9% before tbd, indicating complete protection of iron from corrosion. The effect of healing treatment in 0.1 M NaNO3 on passive film breakdown was investigated by electron-probe microanalysis. 相似文献
9.
A self-assembled monolayer (SAM) of toluene moiety CH3C6H4- was prepared on an iron electrode by electrochemical modification in a deaerated acetonitrile (AN) solution of p-toluenediazonium tetrafluoroborate CH3C6H4N2BF4 (TDFB). The protection of the modified electrode was examined by polarization measurements in an oxygenated 0.5 M NaCl solution after immersion in the solution for 1.5 and 4.0 h. The average values of protective efficiency, P for the films prepared by modification in the TDFB solution at −1.013 V/Ag/Ag+AN for the modification time, tm more than 5 min were fairly high, 78.1% and 53.6% at 1.5 and 4.0 h of the immersion time, t, respectively. However, X-ray photoelectron spectra of the iron surface modified with TDFB for 10 min revealed that the film thus prepared on iron was a polymer of the toluene moieties. A layer formed by the cathodic modification in the TDFB solution for 1 min seemed to be a monolayer of the toluene moiety, revealed by X-ray photoelectron spectra of the surface coated with the layer. The contact angle on the coated surface using a drop of water supported the formation of toluene SAM. The P values of the layer for iron corrosion in 0.5 M NaCl were 31.8% and 28.9% at 1.5 and 4.0 h of t, respectively, being a little higher than those of the toluenethiol CH3C6H4SH SAM. The higher values may be attributed to the formation of a strong covalent bond between carbon and iron atoms. 相似文献
10.
Kunitsugu Aramaki 《Corrosion Science》2010,52(1):1-6
For preparing an ultrathin two-dimensional polymer coating adsorbed on passivated iron, a 16-hydroxyhexadecanoate ion HO(CH2)15CO2− self-assembled monolayer (SAM) was modified with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 and octadecyltriethoxysilane C18H37Si(OC2H5)3. Protection of passivated iron against passive film breakdown and corrosion of iron was investigated by monitoring of the open-circuit potential and repeated polarization measurements in an aerated 0.1 M Na2SO4 solution during immersion for many hours. The time required for passive film breakdown of the polymer-coated electrode was markedly higher in this solution than that of the passivated one, indicating protection of the passive film from breakdown by coverage with the polymer coating. The protective efficiencies of the passive film covered with the coating were extremely high, more than 99.9% in 0.1 M Na2SO4 before the passive film was broken down, showing prominent cooperative suppression of iron corrosion in the solution by coverage with the passive film and polymer coating. The polymer-coated surface was characterized by contact angle measurement and electron-probe microanalysis (EPMA). Prevention of passive film breakdown and iron corrosion for the polymer-coated electrode healed in 0.1 M NaNO3 was also examined in 0.1 M Na2SO4. 相似文献
11.
Kunitsugu Aramaki 《Corrosion Science》2004,46(10):2563-2581
A film composed of a one-dimensional polymer was fabricated by modification of a 16-hydroxyhexadecanoate ion HO(CH2)15CO2− self-assembled monolayer (SAM) adsorbed on a passivated iron electrode with octadecyltriethoxysilane C18H37Si(OC2H5)3. The pitting potential, Epit of the passivated electrode coated with this film was measured by anodic polarization in a borate buffer solution containing 0.1 M of Cl−. The Epit value of the electrode coated with the film was markedly shifted from the value of the bare electrode in the positive direction, indicating prevention of passive film breakdown. No breakdown occurred over the potential range of passive region in some cases. Structure of the modified SAM was discussed by X-ray photoelectron and FTIR reflection spectroscopies and contact angle measurement of the electrode surface covered with the film. Suppression of Cl− accumulation at a defect of the passive film was revealed by electron-probe microanalyses of the surfaces uncoated and coated with the SAM modified with octyltriethoxysilane C8H17Si(OC2H5)3 after anodic polarization in the borate buffer containing Cl−. 相似文献
12.
An ultrathin, ordered and two-dimensional polymer coating was prepared on passivated iron by modification of 16-hydroxyhexadecanoate ion HO(CH2)15CO2− self-assembled monolayer (SAM) with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 and octadecyltriethoxysilane C18H37Si(OC2H5)3. Protection of passivated iron against passive film breakdown and corrosion of iron was examined by monitoring of the open-circuit potential and repeated polarization measurements in an aerated 0.1 M NaNO3 solution during immersion for many hours. Passive film breakdown on the polymer-coated electrode in the solution was not observed during immersion for 480 h, whereas that of the passivated one occurred at 18.1 h, indicating protection of the passive film from breakdown by coverage with the polymer coating. The protective efficiencies of the passive film covered with the coating were extremely high, around 99.9% in the initial region of the immersion time up to 72 h and more than 98.3% thereafter, indicating prominent cooperative suppression of iron corrosion in 0.1 M NaNO3 by coverage with the passive film and polymer coating. The polymer-coated surface was characterized by contact angle measurement and electron-probe microanalysis. 相似文献
13.
Kunitsugu Aramaki 《Corrosion Science》2002,44(6):1375-1389
Self-healing protective films of 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 (abbreviated to BTESE) polymer containing sodium silicate Na2Si2O5 (water glass) and cerium(III) nitrate Ce(NO3)3 were prepared on a zinc electrode previously treated in a 1×10−3 M Ce(NO3)3 solution at 30 °C for 30 min. After the surface of coated electrode was crosswise scratched with a knife edge, the electrode was immersed in an aerated 0.5 M NaCl solution at 30 °C for many hours and polarization measurements of the scratched electrode were carried out for estimating the self-healing effects of the films on zinc corrosion at the scratches. The optimal quantities of Na2Si2O5, Ce(NO3)3 and BTESE in the films were determined by polarization measurements and observation of pit formation at the scratches. No pitting corrosion occurred at the scratches on the zinc electrode covered with a film composed of their optimal quantities after immersion in the solution for 72 h. 相似文献
14.
Prevention of iron corrosion in an aerated 0.1 M NaCl solution was investigated by polarization and mass-loss measurements of a passivated iron electrode covered with ultrathin and ordered films of two-dimensional polymers. The films were prepared on the passivated electrode by modification of a 16-hydroxyhexadecanoate ion self-assembled monolayer with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 and alkyltriethoxysilane CnH2n + 1Si(OC2H5)3 (n = 8 or 18). Because crevice corrosion occurred at the initial stage of immersion in the solution preferentially, the edge of electrode covered with the polymer film was coated with epoxy resin. The open-circuit potentials of the covered electrodes in the solution were maintained high, more than −0.2 V/SCE for several hours, indicating that no breakdown of the passive film occurred on the surface. The protective efficiencies of the films were extremely high, more than 99.9% unless the passive film was broken down. The efficiencies after immersion for 24 h almost agreed with those obtained by mass-loss measurements. X-ray photoelectron spectroscopy and electron-probe microanalysis of the passivated surface covered with the polymer film after immersion in the solution for 4 h revealed that pit initiation on the passive film was suppressed by coverage with the polymer film completely. 相似文献
15.
An ultrathin and ordered polymer coating 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 octyltriethoxysilane C8H17Si(OC2H5)3. Further, the passivated and polymer-coated electrode was healed by treatment in 1.0 M NaNO3 for 4 h. Prevention of passive film breakdown and iron corrosion for the passivated, polymer-coated and healed electrode was examined by monitoring of the open-circuit potential and repeated polarization measurements in oxygenated 0.1 M KClO4, 0.1 M Na2SO4 and 0.1 M NaCl for many hours. The values of the time for passive film breakdown, tbd were >240, 22.2 and 9.5 h in these solutions, respectively. The protective efficiencies for the electrode were extremely high, more than 99.9% before tbd, indicating complete protection of substrate iron against corrosion in these solutions, unless passive film breakdown occurred. The presence of on the passive surface by treatment in 1.0 M NaNO3 was detected by X-ray photoelectron and FTIR reflection spectroscopies. The self-healing activity of adsorbed to suppress passive film breakdown was discussed. 相似文献
16.
E.E. Abd El Aal 《Corrosion Science》2008,50(1):47-54
The open circuit potentials of Zn electrode were followed as a function of time in different concentrations Na2B4O7 solutions until steady-state, Est., values were attained. The potential shifts immediately towards positive values, indicating film thickening and repair. The effect of addition of NaCl, NaBr and NaI as aggressive agent on the steady-state potential of a Zn electrode previously equilibrated in a passivating borate solution was also established. For each Na2B4O7 concentration, the variation in the potential with the quantity of aggressive anions follows an S-shaped relationship. The new potentials are established after an induction period which decreases with the increase in the concentration of the aggressive anion, Cagg., and/or decreases in that of the passivator anion, Cpass.. The concentration, Cagg., that can be tolerated by a certain concentration of the passivator anion, Cpass., is given by the relation: log Cpass. = k + n log Cagg., where k and n are constants. This is derived on the basis of competitive adsorption of both types of anion and the structure of the double layer at the metal/solution interface. The implications of the equations are briefly discussed. 相似文献
17.
Kunitsugu Aramaki 《Corrosion Science》2004,46(10):2533-2548
A self-assembled monolayer (SAM) of 16-hydroxyhexadecanoate ion HO(CH2)15CO2−(HOC16A−) has been prepared on an iron electrode passivated in a borate buffer solution (pH 8.49) in the preceding paper. In this work, the HOC16A− SAM on the passivated electrode was modified with octyltriethoxysilane C8H17Si(OC2H5)3 to form a film composed of one-dimensional polymer. Prevention of passive film breakdown was examined by anodic polarization measurements of the electrodes uncoated and coated with the modified SAM in the borate buffer containing 0.1 M of Cl−. The pitting potential, Epit of the coated electrode shifted from that of the uncoated electrode in the positive direction, indicating prevention of passive film breakdown. The anodic current density was decreased in the passive and transpassive regions by coverage with the modified SAM. Neither current spikes nor Epit was observed in the curve of the passive region in some cases, demonstrating complete protection of the passive film against breakdown in the Cl− solution. The modified SAM on the electrode was characterized by X-ray photoelectron and FTIR reflection spectroscopies and contact angle measurement. 相似文献
18.
Kunitsugu Aramaki 《Corrosion Science》2006,48(10):3298-3308
A self-assembled monolayer (SAM) of hexadecanoate ion (C16A−) was prepared on a zinc electrode covered with a layer of hydrated cerium(III) oxide Ce2O3. The protection of zinc against corrosion was examined for the electrode coated with the Ce2O3 layer and the C16A− SAM in an oxygenated 0.5 M NaCl solution. A more positive open-circuit potential of the coated electrode was maintained during immersion in the solution for 4 h than that of the uncoated one and polarization curves showed marked suppression of the anodic process, implying that the layer modified with the SAM acted as a passive film. The protective efficiency of the modified layer was extremely high, more than 99%. The zinc surface coated with the Ce2O3 layer and the C16A− SAM was characterized by X-ray photoelectron and FTIR reflection spectroscopies and contact angle measurement with a drop of water. 相似文献
19.
Kunitsugu Aramaki 《Corrosion Science》2005,47(6):1582-1597
The effect of an ultrathin, regularly arranged polymer film on prevention of passive film breakdown on iron in the presence of chloride ion was investigated. The film of two-dimensional polymer was prepared by modification of a 16-hydroxyhexadecanoate ion self-assembled monolayer adsorbed on a passivated iron electrode with 1,2-bis(triethoxysilyl)ethane(C2H5O)3Si(CH2)2Si(OC2H5)3 and octyltriethoxysilane C8H17Si(OC2H5)3. The pitting potentials of the passivated electrodes bare and covered with the polymer film were determined by anodic polarization measurements in a borate buffer solution containing 0.1 M of Cl−. The pitting potential of the coated electrode was higher than that of the uncoated one, indicating prevention of passive film breakdown. No breakdown was observed over the potential range in the passive and transpassive regions by covering the passive film with the well-arranged two-dimensional polymer film. The film was characterized by X-ray photoelectron and FTIR reflection spectroscopies and measurement of the contact angle with a drop of water. 相似文献
20.
A film of two-dimensional polymer was prepared on an iron electrode passivated in a borate buffer solution at pH 8.49, derivatized with 16-hydroxyhexadecanoate ion and then modified with 1,2-bis(triethoxysilyl)ethane (C2H5O)3Si(CH2)2Si(OC2H5)3 and octadecyltriethoxysilane C18H37Si(OC2H5)3. The protective ability of the polymer film adsorbed on passivated iron was examined by polarization measurement in oxygenated 0.1 M KClO4 solutions with and without 1 × 10−4 and 1 × 10−3 M of Cl−. The values of the open-circuit potential, Eoc were monitored with the immersion time, t in these solutions. The Eoc value of the passivated electrode in 0.1 M KClO4 was maintained high, more than −0.2 V/SCE in the initial region of t up to 10 h, indicating the presence of a passive film on the electrode. Thereafter, Eoc decreased to −0.4 V/SCE abruptly, exhibiting breakdown of the passive film. The value of the passivated electrode covered with the polymer film remained almost constant around −0.04 V/SCE during immersion for 45 h. The protective efficiency, P (%) of the polymer film on passivated iron was extremely high, more than 99.9% unless the passive film was broken down, indicating complete protection of iron against corrosion. The times for breakdown on the passivated electrode and polymer-coated one diminished with an increase in the concentration of Cl−. The polymer-coated surface was analyzed by electron-probe microanalysis after immersion in 0.1 M KClO4 for 24 h. 相似文献