scholarly journals Protective properties of epoxy coatings electrodeposited on steel electrochemically modified by Zn-Fe alloys

2004 ◽  
Vol 58 (10) ◽  
pp. 450-456
Author(s):  
Jelena Bajat ◽  
Vesna Miskovic-Stankovic ◽  
Zorica Kacarevic-Popovic

Epoxy coatings were electrodeposited on steel and steel modified by Zn-Fe alloys using the constant voltage method. Zn-Fe alloys were electrodeposited on steel at different current densities. The effect of the Zn-Fe alloy on the corrosion behavior of the epoxy coating was interpreted in terms of the electrochemical and transport properties. It was shown that the best properties, i.e. the largest values of the pore resistance and the smallest values of the coating capacitance, a longer period of almost constant Rp and Cp values, and the smallest diffusion coefficient of water through the epoxy coating, as well as the smallest amount of water absorbed inside the epoxy coating, were found for epoxy coatings on steel modified by a Zn-Fe alloy deposited at 4 A dm-2. During prolonged exposure to 3% NaCl, this Zn-Fe alloy significantly improves the corrosion stability of the epoxy coating: almost unchanged values of Rp and Rct were observed, due to the formation of a pseudo-passive layer of corrosion products, which is a good barrier to the transport of water, oxygen and electrolyte ions.

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Van T. H. Vu ◽  
Thanh T. M. Dinh ◽  
Nam T. Pham ◽  
Thom. T. Nguyen ◽  
Phuong T. Nguyen ◽  
...  

Silica/Polypyrrole nanocomposites (SiO2/PPy) incorporating oxalate as counter anion (SiO2/PPyOx) were chemically polymerized in the solution with the presence of pyrrole, silica, and sodium oxalate. Nanocomposites SiO2/PPyOx at different concentrations of oxalate anion were characterized with FTIR, XRD, EDX, TGA, and TEM. The corrosion protective properties for carbon steel of nanocomposites in epoxy coating were studied by electrochemical techniques including electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP). FTIR results of nanocomposites show a slightly red-shift in terms of wavelength compared with the case of PPy and SiO2 spectra. It may be due to a better conjugation and interactions between PPy and SiO2 in nanocomposite structure. TEM image indicated that nanocomposites have spherical morphologies with diameters between 100 and 150 nm. The EIS results showed that |Z| modulus values of epoxy coatings containing SiO2/PPyOx composites reached about 109.7 Ω.cm2, always higher than that of epoxy coating. These results are also confirmed by OCP results. It proves that the presence of oxalate anion can enhance the resistance against corrosion and it has been shown that the content of counter anion strongly affects the anticorrosion ability.


2007 ◽  
Vol 72 (12) ◽  
pp. 1383-1392 ◽  
Author(s):  
Jelena Bajat ◽  
Vesna Miskovic-Stankovic ◽  
Dragutin Drazic

One of the most important factors in corrosion prevention by protective coatings is the loss of coating adhesion under environmental influence. In this work, the adhesion of epoxy cataphoretic coatings was examined on steel and steel modified by Zn-Fe and Zn-Co alloys. The dry and wet adhesions of epoxy primers were measured by the direct pull-off standardized procedure, as well as indirectly by the NMP test. The corrosion stability of the coated samples was investigated by electrochemical impedance spectroscopy. It was shown that under dry testing conditions all the samples exhibited very good adhesion. However, different trends of adhesion loss of different protective systems during exposure to a corrosive agent (3 % NaCl solution) were observed. The lowest adhesion values were obtained for epoxy coating on the steel substrate. The change in adhesion of the epoxy coating on steel modified by Zn-Co alloy during immersion in 3 % NaCl solution for 24 days was the smallest of all the investigated samples. Electrochemical impedance measurements in 3 % NaCl solution confirmed the good protective properties of this protective system, i.e., greater values of pore resistance were obtained.


2000 ◽  
Vol 65 (12) ◽  
pp. 923-933 ◽  
Author(s):  
Vesna Miskovic-Stankovic ◽  
Jelena Bajat ◽  
Miodrag Maksimovic ◽  
Zorica Kacarevic-Popovic

The electrochemical and transport properties, as well as the thermal stability of epoxy coatings electrodeposited on steel and steel modified by Zn-Ni alloys were investigated during exposure to 3% NaCl. The Zn-Ni alloys were electrodeposited on steel using direct and pulse current. From the time dependence of the pore resistance of the epoxy coating (impedance measurements), the diffusion coefficient of water through the epoxy coating (gravimetric liquid sorption measurements) and the thermal stability of the epoxy coating (thermogravimetric analysis), it was shown that Zn-Ni sublayers significantly improve the corrosion stability of a protective system based on an epoxy coating. The values of the pore resistance were almost unchanged over a long period of immersion time for epoxy coatings on steel modified by Zn-Ni alloys, inidicating the great stability of these protective systems.


Author(s):  
Александр Михайлович Ефремов ◽  
Петр Дмитриевич Волянский ◽  
Павел Олегович Ревин ◽  
Сергей Владимирович Ануфриев

При сооружении трубопроводов в России, странах Европы и Африки наиболее распространенным является применение труб с трехслойными полиэтиленовыми покрытиями. В то же время опыт строительства магистральных нефте- и газопроводов в США, Канаде, ряде других стран свидетельствует о возможности использования эпоксидных покрытий в качестве эффективной антикоррозионной защиты труб. В этой связи была начата научно-исследовательская работа по определению целесообразности применения двухслойных эпоксидных покрытий для антикоррозионной защиты магистральных трубопроводов подземной прокладки, эксплуатируемых организациями системы «Транснефть». Цель настоящего исследования - оценка технической и экономической целесообразности использования эпоксидных покрытий как альтернативы полиэтиленовой изоляции трубопроводов. Были проведены лабораторные исследования образцов трех систем эпоксидных покрытий, осуществлен сравнительный анализ технических свойств эпоксидной и полиэтиленовой изоляции. Установлено, что эпоксидные покрытия превосходят полиэтиленовые по ряду свойств, в частности обладают повышенной стойкостью к температурным воздействиям, УФ-излучению, катодному отслаиванию, а также повышенной механической прочностью, что позволяет обеспечить сохранность покрытия при строительстве трубопроводов методом наклонно-направленного бурения и прокладке в скальных грунтах. Основные мощности по производству сырья для эпоксидных порошковых покрытий локализованы в России, в то время как сырье для полиэтиленовых покрытий в основном производится за рубежом. Установлена экономическая целесообразность применения двухслойного эпоксидного покрытия как альтернативы трехслойному полиэтиленовому покрытию для трубопроводов больших диаметров - более 720 мм. Для внедрения труб с двухслойным эпоксидным покрытием на объектах ПАО «Транснефть» проводится его апробация, включающая строительство опытного участка трубопровода. When constructing pipelines in Russia, Europe, and Africa, it is the most common to use pipes with threelayer polyethylene coatings. At the same time, the oil and gas pipeline construction experience in the USA, Canada, and a number of other countries, as well as the construction of the Zapolyarye - Purpe elevated main pipeline by Transneft PJSC, indicates the possibility of using epoxy coatings as an effective pipe corrosion protection solution. In respect thereof, research study to determine the feasibility of using two-layer epoxy coatings for corrosion protection of underground pipelines operated by the Transneft system entities was instituted. The purpose of this study is to assess the technical and economic feasibility of using epoxy coatings as an alternative to polyethylene insulation of pipelines. Laboratory studies of samples of three epoxy coating systems, as well as a comparative analysis of the process properties of epoxy and polyethylene insulation were conducted. It has been established that epoxy coatings are superior to polyethylene coatings in a number of properties, in particular, they are characterized by increased resistance to temperature effects, UV radiation, cathodic disbondment, as well as increased mechanical strength, which makes it possible to ensure safety of the coating during the construction of pipelines by directional drilling and laying in rocky soils. The main production facilities for raw materials for epoxy powder coatings are localized in Russia, while raw materials for polyethylene coatings are mainly produced abroad. The economic feasibility of using a twolayer epoxy coating as an alternative to a three-layer polyethylene coating for pipelines of large diameters (over 720 mm (28 in)) was established. Testing for the introduction of pipes with a two-layer epoxy coating at the Transneft PJSC facilities is being performed, including construction of an experimental pipeline section.


Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 844 ◽  
Author(s):  
Xuepei Miao ◽  
An Xing ◽  
Lifan He ◽  
Yan Meng ◽  
Xiaoyu Li

In this paper, hyperbranched polyether functionalized graphene oxide (EHBPE-GO) was prepared by a facile one-step method. Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), thermogravimetric analyzer (TGA), and trans-mission electron microscopy (TEM) results confirmed the formation of EHBPE-GO. Then, EHBPE-GO was cured with phenolic amides at room temperature to prepare epoxy coatings. The corrosion resistance of epoxy coatings was investigated systematically by using electrochemical and traditional immersion methods. Results show that a small amount of EHBPE-GO (8 wt % of Diglycidyl ether of bisphenol A (DGEBA)) in epoxy coating achieves 50% higher improvement in acid-resistance than unmodified neat DGEBA resin. For the nanocomposite epoxy coating, the superior acid-resistance is attributed to the increased crosslink density and the impermeable 2D structure of EHBPE-GO. This work provides a facile strategy to develop the effective improved corrosion resistance nanofiller for epoxy coating.


Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1702
Author(s):  
Marjetka Conradi ◽  
Aleksandra Kocijan ◽  
Tadeja Kosec ◽  
Bojan Podgornik

An AISI 316L surface was functionalized by the adsorption of hydrophilic epoxy and epoxy/TiO2/epoxy coatings and hydrophobic epoxy/fluoroalkylsilane-functionalized FAS-TiO2/epoxy coatings. We characterized the coatings’ wettability, morphology and average surface roughness and discussed the influence of surface wettability and morphology on the coefficient of friction and the wear resistance. Experiments were performed in dry, distilled water and in a simulated physiological solution (Hank’s solution). In the case of dry sliding, a lower coefficient of friction is achieved for both TiO2 coatings compared to the pure epoxy coating. In a water environment the same level of friction is shown for all three coatings, whereas in Hank’s solution the friction is reduced for the hydrophilic epoxy/TiO2/epoxy coating, increased for the hydrophobic epoxy/FAS-TiO2/epoxy coating and has no effect on the pure epoxy coating. The results show that the corrosion resistance is significantly improved for the hydrophobic epoxy/FAS-TiO2/epoxy coating compared to the hydrophilic pure epoxy and epoxy/TiO2/epoxy coatings.


2005 ◽  
Vol 47 (3) ◽  
pp. 823-834 ◽  
Author(s):  
Z.Ž. Lazarević ◽  
V.B. Mišković-Stanković ◽  
Z. Kačarević-Popović ◽  
D.M. Dražić

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
R. E. Núñez-Jaquez ◽  
J. E. Buelna-Rodríguez ◽  
C. P. Barrios-Durstewitz ◽  
C. Gaona-Tiburcio ◽  
F. Almeraya-Calderón

Concrete is a porous material and the ingress of water, oxygen, and aggressive ions, such as chlorides, can cause the passive layer on reinforced steel to break down. Additives, such as fly ash, microsilica, rice husk ash, and cane sugar bagasse ash, have a size breakdown that allows the reduction of concrete pore size and, consequently, may reduce the corrosion process. The objective of this work is to determine the corrosion rate of steel in reinforced concrete by the addition of 20% sugar cane bagasse ash by weight of cement. Six prismatic specimens (7×7×10 cm) with an embedded steel rod were prepared. Three contained 20% sugar cane bagasse ash by weight of cement and the other three did not. All specimens were placed in a 3.5% NaCl solution and the corrosion rate was determined using polarization resistance. The results showed that reinforced concrete containing sugar cane bagasse ash has the lowest corrosion rates in comparison to reinforced concrete without the additive.


2012 ◽  
Vol 66 (2) ◽  
pp. 187-192
Author(s):  
Rade Surudzic ◽  
Sanja Erakovic ◽  
Vesna Miskovic-Stankovic

In order to improve corrosion stability and biocompatibility of titanium surfaces, hydroxyapatite (Ca10(PO4)6(OH)2, HAP) has been used as coating material due to the fact that it possess similar chemical composition as bone tissue. Lignin?s (Lig) usage in medical applications could be interesting because it could lead to thermal stability, hydrophilicity, biocompatibility and biodegradability of different materials. Bioceramic hydroxyapatite/lignin (HAP/Lig) coatings on titanium were obtained from ethanol suspension by electrophoretic deposition method. The uniform and compact HAP/Lig coatings were deposited at constant voltage of 60 V for 45 s and sintered at 900?C in argon atmosphere. The corrosion stability of sintered HAP/Lig coatings in simulated body fluid (SBF) at 37?C was investigated by open circuit potential-time measurements and electrochemical impedance spectroscopy (EIS). The greater values of open circuit potential, as well as EIS results, indicated improved corrosion resistance and good corrosion stability of HAP/Lig coatings in simulated body fluid at 37?C .


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