共查询到20条相似文献,搜索用时 10 毫秒
1.
C. Gabrielli 《Electrochimica acta》2007,52(27):7706-7714
The local breakdown of the iron passive layer and the resulting pitting corrosion of iron were studied for massive material and for a thin film on an electrochemical quartz crystal microbalance (EQCM). The initiation and the propagation of a single pit on iron were controlled through the local production of chloride anion thanks to the silver chloride reduction at the tip of the scanning electrochemical microscope (SECM). Experiments were performed in borate buffer and in KOH solution, in order to investigate the influence of the solution pH. The influence of the iron potential and of the amount of chloride anion necessary for the breakdown of the passive layer were also investigated. The frequency response of the quartz was correlated to the pit evolution with respect to time. After the breakdown of the passive layer, the frequency changes were then directly linked to the generation of Fe(II) during the pit growth. 相似文献
2.
The corrosion resistance of carbon steel specimens was compared, using different surface treatment methods such as blasting and zinc phosphate treatment on carbon steel followed by application of different coating thickness. Specimen surface morphology was observed by SEM. The corrosion performance of epoxy coated carbon steel was examined by electrochemical impedance spectroscopy (EIS), along with immersion test in 0.5N-NaCl solution and NORSOK M 501 cyclic test, respectively. EIS results showed that higher thickness of epoxy coating and zinc phosphate treatment on carbon steel showed better corrosion protection than rest of the specimens. Specimens with no treatment and blasting treatment followed by epoxy coating, showed poor corrosion protection. Results of NORSOK M 501 cyclic test showed similar trend as those of EIS results however degradation of specimens was more severe than those from immersion test. 相似文献
3.
A high temperature cured self-healing epoxy is demonstrated by incorporating microcapsules of poly(dimethylsiloxane) (PDMS) resin and separate microcapsules containing an organotin catalyst. Healing is triggered by crack propagation through the embedded microcapsules in the epoxy matrix, which releases the healing agents into the crack plane initiating crosslinking reactions. A series of tapered double-cantilever beam (TDCB) fracture tests were conducted to measure virgin and healed fracture toughness. Healing efficiencies, based on fracture toughness recovery, ranged from 11 to 51% depending on the molecular weight of PDMS resin, quantity of healing agent delivered, and use of adhesion promoters. 相似文献
4.
Fracture and fatigue response of a self-healing epoxy adhesive 总被引:2,自引:0,他引:2
A self-healing epoxy adhesive for bonding steel substrates is demonstrated using encapsulated dicyclopentadiene (DCPD) monomer and bis(tricyclohexylphosphine)benzylidine ruthenium (IV) dichloride (Grubbs’ first generation) catalyst particles dispersed in a thin epoxy matrix. Both quasi-static fracture and fatigue performance are evaluated using the width-tapered-double-cantilever-beam specimen geometry. Recovery of 56% of the original fracture toughness under quasi-static fracture conditions occurs after 24 h healing at room temperature conditions. Complete crack arrest is demonstrated for fatigue test conditions that render neat resin and control samples failed. Inspection of fracture surfaces by electron microscopy reveals evidence of polymerized DCPD after healing. These results are the first mechanical assessment of self-healing for thin (ca. 360 μm) films typical of adhesives applications. 相似文献
5.
In this study, it has been aimed to investigate the corrosion protection properties of an epoxy/polyamide coating loaded with different concentrations (ranged from 3 to 6% (w/w)) of the polysiloxane surface modified silica nanoparticles (nano-SiO2). The nanocomposites were applied on the steel substrates. Field emission scanning electron microscope (FE-SEM) and UV–vis techniques were utilized in order to investigate the nanoparticles dispersion in the coating matrix. The effects of addition of nanoparticles on the corrosion resistance of the coating were studied by an electrochemical impedance spectroscopy (EIS) and salt spray test. The coating surface degradation was studied by optical microscope and Fourier transform infrared radiation (FT-IR) spectroscopy. Results obtained from UV–vis and FE-SEM analyses revealed proper and uniform distribution of surface modified nanoparticles in the epoxy coating matrix. It was shown that the coating corrosion protection properties were significantly enhanced in the presence of 5 wt% silica nanoparticles. Less degradation occurred on the surface of the coatings loaded with 5 wt% nanoparticles. 相似文献
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7.
Electrochemical behavior of mild steel in the presence of zinc acetylacetonate (Zn(acac)2) and benzimidazole (BIMIDA) was evaluated by electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution and compared to zinc phosphate (ZP) pigment and zinc potassium chromate (ZPC) pigment extracts. Results showed superior performance of Zn(acac)2 and BIMIDA mixture (ZBM) compared to ZP pigment, while it introduced inferior inhibitive action compared to ZPC pigment. The epoxy coatings were formulated with ZBM as anticorrosive additive, ZP and ZPC pigments. The disbonding rate of coated steel follows the order: Blank > ZP > ZBM > ZPC. EIS results showed a complex film could be formed at the hole area for the coatings formulated with ZP, ZBM and ZPC. It is concluded that the stronger the complex film on the surface, the lesser the cathodic disbonding rate would be. 相似文献
8.
采用环氧富锌作为底漆、氯化橡胶作为面漆,研究了涂层体系腐蚀过程中电化学阻抗谱(EIS)的变化。结果表明,腐蚀初期环氧富锌/氯化橡胶涂层体系中底漆的厚度比例与涂层的防护性能无关,而在腐蚀中后期,随底漆厚度比例适当增大,涂层自修复能力增强,离子等腐蚀介质在涂层中的传输速度得到显著延缓,涂层吸水率和孔隙率明显降低,涂层防护性能出现短时间升高。当环氧富锌底漆为涂层总厚度的2/3左右时,涂层体系的防护性能最好,而仅有底漆或面漆的体系则不具备良好的防护性能。 相似文献
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10.
We report the first measurements of a self-healing polymer that combines a microencapsulated liquid healing agent and shape memory alloy (SMA) wires. When a propagating crack ruptures the embedded microcapsules, the liquid healing agent is automatically released into the crack where it contacts a solid catalyst embedded in the matrix. The SMA wires are then activated to close the crack during the healing period. We show that dramatically improved healing performance is obtained by the activation of embedded SMA wires. We conclude that improved healing is due to a reduction of crack volume as a result of pulling the crack faces closed, and more complete polymerization of the healing agent due to the heat produced by the activated SMA wires. 相似文献
11.
Tetraglycidyl-4,4′-diaminodiphenyl methane cured with 4,4′-diaminodiphenyl sulphone was irradiated with varying dosages of 0.5 MeV electrons and 1.17 and 1.33 MeV gamma rays and was studied using electron spin resonance. The radical concentration increases with increasing radiation dose and decays, at ambient temperature, in a way consistent with a model that assumes two simultaneous second-order reactions occurring in different zones. 相似文献
12.
To Thi Xuan Hang Trinh Anh Truc Marie-Georges Olivier Catherine Vandermiers Nathalie Guérit Nadine Pébère 《Progress in Organic Coatings》2010
This work is an extension of studies into the mechanisms of corrosion protection of mild steel by an epoxy resin containing organically modified clay (Hang et al. [1]; Truc et al. [2]). In a previous study (Truc et al. [2]), it was shown that indole-3 butyric acid (IBA)-modified clay improved the corrosion performance of epoxy. In the present study, it was shown that the IBA is an anodic inhibitor and its efficiency was about 93%. Exfoliation and dispersion of the IBA-modified clay in the epoxy coating were checked by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The improvement of the corrosion performance of the epoxy coating containing IBA-modified clay by comparison with pure epoxy coating was confirmed for a low film thickness (10 μm). Local electrochemical impedance measurements performed on scratched samples revealed the inhibitive action of IBA at the carbon steel/coating interface. It was shown that the inhibitor release from the IBA-modified clay was favoured for high pH values. Thus, in neutral media, the corrosion process which induces a local increase of pH will increase the self-healing performance. 相似文献
13.
I. M. Zin R. L. Howard S. J. Badger J. D. Scantlebury S. B. Lyon 《Progress in Organic Coatings》1998,33(3-4):203-210
Investigations of the mechanism of the protective action of strontium chromate pigment in an epoxy primer were carried out with electrochemical impedance spectroscopy (EIS), atomic absorption spectroscopy (AAS), scanning reference electrode techniques (SRET) and water uptake measurements. Epoxy primers applied to galvanized steel were studied in a corrosion environment which models the atmospheric precipitation of European countries. Corrosion and electrochemical properties of samples of bare galvanized steel and coated galvanized steel were investigated. It was established that the protective function of the chromate in the primer is primarily due to a cathodic/mixed inhibition of the surface of galvanized steel in defect areas of the polymer coating. It is suggested that the process of leaching of chromate ions from epoxy primer into the environment takes place because the decrease in pH at anodic defect sites causes the destruction of the primer film and accelerates the dissolution of the chromate pigment. 相似文献
14.
新型环氧树脂增韧剂的合成与研究 总被引:8,自引:2,他引:8
以聚醚和酸酐反应,再与环氧树脂反应,合成了一种新型的以环氧基封端的内增韧活性增韧剂,讨论了该增韧剂的固化特性和最佳掺合比例,在100份环氧树脂中加入10份这种增韧剂,环氧树脂固化物综合力学性能较好,剪切强度为23.6MPa,压缩强度达70.2Mpa。 相似文献
15.
Organic coatings based on epoxy and polyurethane matrices containing polyaniline doped with dodecyl benzene sulfonic acid (Pani-DBSA) were prepared and applied over steel plates (SAE 1020). The plates were submitted to salt spray chamber for up to 30 days in order to evaluate the corrosion protection of these coatings. The properties of the coated plates were analyzed as a function of time by electrochemical impedance spectroscopy, open circuit potential, optical microscopy, and Raman spectroscopy. In general, results indicate a decrease in the electrical resistance, increase in capacitance and decrease in open circuit potential. Epoxy based coatings have improved performance when Pani-DBSA is used as pigment, whereas for the polyurethane coatings, Pani-DBSA seems to play an adverse effect. Raman spectroscopy indicates a possible chlorination of the epoxy matrix after 30 days exposure to salt spray chamber. 相似文献
16.
M. K. Jensen B. J. Love J. W. Grant J. Cotton J. R. Keiser D. F. Wilson 《International Journal of Adhesion and Adhesives》2000,20(6):437-444
There are instances where efficiency and safety may be compromised as a result of deteriorating fluid transport systems. Thus, it is worth evaluating other methods that can repair the damage for a temporary period without shutting down the operation. The objective was to evaluate the durability of an epoxy-bonded steel in aqueous environments that would represent such a repair. EPON® 828 was chosen as the epoxy resin, and dicyandiamide and polyamidoamine were two types of curing agents evaluated in this study. The epoxy-bonded steel joints were exposed in either distilled water or 3.4% NaCl solution for various times. The mechanical strength of the bonded joints was evaluated using a three-point flexure test. The interfacial shear strength of unaged samples ranged from 0.93 to 0.32 MPa. It was found that the interfacial shear strength decreased with aging time for both epoxy-bonded systems. Scanning electron microscopy (SEM), optical microscopy, and X-ray photoelectron spectroscopy (XPS) were used to determine the locus of failure of the bonded joints. It was concluded that failure occurred cohesively within the oxide layer if oxides were present on the substrate surface prior to the bonding procedure. 相似文献
17.
J.B Bajat V.B Miškovi?-Stankovi? M.D Maksimovi?D.M Dra?i? S Zec 《Electrochimica acta》2002,47(25):4101-4112
ZnCo alloys electrochemically deposited on steel under various deposition conditions were investigated. The influence of deposition current density, temperature and composition of deposition solution on the phase structure and corrosion properties of ZnCo alloys were studied. It was found that ZnCo alloy obtained from chloride solution at 5 A dm−2 showed the best corrosion properties, so this alloy was chosen for further examination. Epoxy coating was electrodeposited on steel and steel modified by ZnCo alloy using constant voltage method. The effect of ZnCo alloy on the corrosion behavior of the protective system based on epoxy coating is interpreted in terms of electrochemical and transport properties, as well as of thermal stability. 相似文献
18.
《Progress in Organic Coatings》2000,39(2-4):127-135
The electrochemical and transport properties and thermal stability of epoxy coatings electrodeposited on hot-dip galvanized steel and steel modified by Zn–Ni alloys were investigated during exposure to 3% NaCl solution. Zn–Ni alloys were electrodeposited on steel by direct and pulse current. From the time dependence of pore resistance, coating capacitance and relative permittivity of epoxy coating, diffusion coefficient of water through epoxy coating, D(H2O) and thermal stability, it was shown that Zn–Ni sublayers significantly improve the corrosion stability of the protective system based on epoxy coating. Almost unchanged values of pore resistance were obtained over the long period of investigated time for epoxy coatings on steel modified by Zn–Ni alloys, indicating the great stability of these protective systems, due to the existence of the inner oxide phase layer and the outer layer consisting of basic salts. 相似文献
19.
Atomistic molecular modelling of crosslinked epoxy resin 总被引:1,自引:0,他引:1
In the present study, a new method was developed to construct atomistic molecular models of crosslinked polymers based on commercially important epoxy resin. This method employed molecular dynamics/molecular mechanics schemes and assumed close proximity. The generic Dreiding2.21 force-field and advanced compass force-field were used for the construction of models and prediction of properties, respectively. A polymer network with conversion up to 93.7% was successfully generated by this method. Density and elastic constants of the system were calculated from the equilibrated structure for the validation of the generated models. The simulated results compared reasonably with experimental data available. The developed method would hold great promise in further molecular simulations for structure and properties of epoxy resin or other cured systems. 相似文献
20.
The influence of hot-dip galvanized steel (HDG) surface pretreatment with phosphate coatings on the corrosion stability and adhesion characteristics of epoxy coatings electrodeposited on HDG steel was investigated. Phosphate coatings were deposited on hot-dip galvanized steel from baths with different concentrations of NaF (0.1, 0.5 and 1.0 g dm−3) and at different temperatures (50, 65 and 80 °C). The influence of fluoride ion concentration in the phosphating bath, as well as the deposition temperature of the bath, on the adhesion characteristics and corrosion stability of epoxy coatings on phosphated HDG steel was investigated. The dry and wet adhesions were measured by a direct pull-off standardized procedure, as well as indirectly by NMP test, while corrosion stability was investigated by electrochemical impedance spectroscopy (EIS). 相似文献