Corrosion protection by epoxy coating containing multi-walled carbon nanotubes

Epoxy coatings that contained multiwalled carbon nanotubes (MWCNTs) were prepared. Further, the effect of the MWCNTs on the hydrophobicity and water transport behavior, and hence, on corrosion resistance provided by the epoxy coating were examined using hygrothermal cyclic tests and electrochemical impedance spectroscopy (EIS). The water transport behavior of epoxy coatings with higher MWCNT content decreased to a larger extent for coatings with higher surface hydrophobicity. The corrosion protection of carbon steel coated with epoxy coating that contained MWCNTs correlated well with water transport behavior and hydrophobicity.     

不同表面处理条件下复合涂层体系失效过程的EIS特征

研究了不同表面处理条件下环氧富锌/环氧云母氧化铁/氯化橡胶涂层体系的电化学阻抗谱特征。利用Bode图、涂层吸水率、涂层电阻及特征频率的变化评价了表面处理对涂层防护性能的影响。结果表明,基材表面状态不同的复合涂层体系吸水率相对稳定阶段所持续的时间长短顺序为：手工打磨>表面锈蚀>表面未处理,与涂层的防护寿命长短、涂层/基材间的黏附力大小顺序一致。此外,不论基材表面处理程度如何,当涂层体系的特征频率增加到1400 Hz左右时,涂层电阻均发生较快降低,吸水率发生较大增长,涂层失去防护作用。     

Tribological and corrosion performance of epoxy resin composite coatings reinforced with graphene oxide and fly ash cenospheres

In this work, a novel graphene oxide (GO)-fly ash cenospheres (FACs) hybrid fillers was introduced to improve the wear and corrosive resistance of epoxy resin (ER) composite coatings. The tribological behavior and the corrosion performance of three kinds of coatings (pure ER, GO/ER and GO-FACs/ER coatings) were studied and the reinforced mechanisms of coatings filled by different fillers were analyzed. The friction coefficient and wear rate of the ER coatings were decreased with the addition of GO-FACs hybrids. The scanning electron microscope images showed that the dispersibility and compatibility of GO-FACs hybrids were effectively improved compared with that of GO sheet. The water contact angle examination indicated that the hydrophobicity of the GO-FACs/ER coatings increased. The electrochemical impedance spectroscopy (EIS) results demonstrated that the GO-FACs/ER coatings have better anticorrosion performance compared with the pure ER coatings and the GO/ER coatings. The hydrophobic surface and the well dispersed fillers constitute the dual barrier to resist the corrosion medium.     

Enhancement of Corrosion Performance of Epoxy Coatings by Chemical Modification With GPTMS Silane Monomer

In this paper, commercial epoxy resin was chemically modified by different amounts of 3-glycidoxypropyltrimethoxysilane (GPTMS) monomer using an organotin compound as catalyst, aiming to improve the anti-corrosion performance of epoxy coatings on 2024-T3 aluminum alloy substrate. Electrochemical impedance spectroscopy (EIS) was used to evaluate the barrier properties against water permeation and protectiveness of silane-modified epoxy coatings. The results showed that all the modified coatings presented higher barrier performance and better corrosion performance than pure epoxy coating, which were characterized by higher charge transfer resistance (R _ct) and lower double-layer capacitance (C _dl) at the electrolyte/metal interface. The improvements in corrosion performance and wet adhesion of modified epoxy coatings were also observed by the Machu test and boiling water test, respectively. Interestingly, it was found that the glass-transition temperature (T _g) of silane-modified epoxy coatings decreased only slightly during immersion in 3.5 wt% NaCl solution, in contrast with pure epoxy coating, which was observed to decrease significantly after water permeation. The corrosion performance of epoxy coatings was, thus, improved when the amount of chemically grafted silane monomer increased in the content range investigated in the present work.     

The influence of ultra-fine glass fibers on the mechanical and anticorrosion properties of epoxy coatings

The effects of different contents of ultra-fine glass fiber on mechanical and anticorrosion properties of epoxy coatings have been investigated. The FTIR and SEM have been used to analyze the surface nature and microstructure of the coatings. Electrochemical impedance spectroscopy (EIS) and a salt spray test have also been used to characterize the contents of ultra-fine glass fibers on the impedance of the coatings. When 10%, 20%, 30% of ultra-fine glass fibers are added to the coatings, their hardness and adhesion increases by 67%, 67%, 200% and 21.6%, 39%, 40%, respectively, compared with the properties of the pure coating. But the anticorrosion properties of the coatings containing high ultra-fine glass fiber content decreased with respect to the pure coatings properties.     

Evaluation of the effects of surface treatments on the cathodic delamination and anticorrosion performance of an epoxy-nanocomposite on steel substrate

The St-37 type steel substrates were pretreated with Cr(VI) and Cr(III) conversion coatings where the latter was then post-treated with Co(II) and Ni(II) chemical treatments. The epoxy coatings containing 3.5 wt% nano-sized ZnO particles were applied over the chemically treated steel samples. The corrosion resistance of the samples was studied by a DC polarization technique. A scanning electron microscope (SEM) was utilized to investigate the morphology of the pretreated and post-treated samples. Electrochemical impedance spectroscopy (EIS) was utilized to investigate the corrosion resistance of the epoxy nanocomposites for different immersion times in 3.5 wt% NaCl solution. The adhesion strengths of the coatings were measured before and after 120 days of immersion in the corrosive electrolyte using a pull-off test. The cathodic delamination (CD) of the painted samples was also investigated. Results showed that conversion coatings can significantly increase the corrosion resistance and adhesion strength of the epoxy coating on the steel, and also reduce the rate of CD in comparison with an untreated sample. The adhesion strength and corrosion resistance of the epoxy coating on the Cr(III) pretreated samples were significantly greater than on the Cr(VI) sample. The increase in adhesion strength and corrosion resistance was more pronounced on the samples that were post-treated with Co(II) and Ni(II) chemical treatments. The cathodic disbonded areas of the Cr(III)–Co(II) and Cr(III)–Ni(II) post-treated samples were significantly lower than the Cr(III) and Cr(VI) pretreated samples. Results showed that Cr(III)-based conversion coatings can improve the anticorrosion performance and reduce CD compared with those with Cr(VI).     

Effect of cross linking degree and adhesion force on the anti-corrosion performance of epoxy coatings under simulated deep sea environment

Deep sea exploitation represents the future direction for its abundant resources, while organic coatings can play a very important role in ocean engineering for corrosion protection. In this paper, under simulated deep sea environment in the laboratory, the effect of the crosslink density and the adhesion force of the coatings on the anti-corrosion performance of two different types of epoxy coatings was studied by using electrochemical impedance spectroscopy (EIS) and adhesion test. The results showed that the deterioration of coatings’ property of corrosion protection under simulated deep sea environment was much faster than that of under normal pressured seawater. However, the diffusion velocity of water molecule through epoxy coatings decreased with increasing of the crosslink density and the adhesion force of the coatings. Therefore, the capability of corrosion protection could be improved by increasing the density of crosslink of the coatings within some extent and by increasing the adhesion force of the coatings.     

聚苯胺/环氧复合阴极电泳涂料防腐蚀性能的研究

运用插层聚合的方法制备了蒙脱土／聚苯胺复合材料，并进行了表征。将该复合材料通过共混的方式加入聚酰胺／环氧阴极电泳（CED）涂料中配制成聚苯胺／环氧复合阴极电泳涂料，并利用电化学阻抗谱方法对各电泳涂层的防腐性能进行了分析。研究发现：在3．5％NaCl溶液中浸泡10d后，腐蚀介质不能到达涂层／基底金属界面，金属表面没有发生腐蚀反应。随着聚苯胺含量的增加，复合电泳涂膜的阻抗值增加，具有较好的防腐性能。当聚苯胺含量相同时，与掺杂态聚苯胺复合电泳涂膜相比，本征态聚苯胺复合电泳涂膜具有很高的阻抗值，表现出更好的防腐性能。     

Excellent corrosion protection performance of epoxy composite coatings filled with silane functionalized silicon nitride

Silicon nitride was firstly used as anticorrosive pigment in organic coatings. An effective strategy by combining inorganic fillers and organosilanes was used to enhance the dispersibility of silicon nitride in epoxy resin. The formed nanocomposites were applied to protect Q235 carbon steel from corrosion. The anticorrosive performance of modified silicon nitride with silane (KH-570) was investigated by electrochemical impedance spectroscopy (EIS), water absorption and pull-off adhesion methods. With the increase of immersion time, the corrosion resistance as well as adhesion strength of epoxy resin coating and unmodified silicon nitride coating decreased significantly. However, for the modified silicon nitride coating, the corrosion resistance and adhesion strength still maintained 5.7×10¹⁰ Ω cm² and 7.6 MPa after 2400-h and 1200-h immersion, respectively. The excellent corrosion resistance performance could be attributed to the chemical interactions between KH-570 functional groups and silicon nitride powders, which mainly came from the easy formation of Si-O-Si bonds. Furthermore, the modified silicon nitride coating formed a strong barrier to corrosive electrolyte due to the hydrophobic of modified silicon nitride powder and increased bonds.     

Effect of Ti amount on wear and corrosion properties of Ti-doped Al2O3 nanocomposite ceramic coated CP titanium implant material

Al₂O₃ and Ti-doped Al₂O₃ nanocomposite ceramic coatings were prepared by using a sol-gel dip-coating process. Corrosion and wear resistance of Al₂O₃ ceramic coatings in relation to Ti amount were carried out using pin-on-disk tribotester, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Surface characterizations before and after the corrosion and wear tests were investigated by the scanning electron microscope (SEM) and X-ray diffraction (XRD) and hardness analysis. The results of corrosion and wear tests exhibited that the corrosion and wear resistance of nanocomposite ceramic coatings became better than uncoated samples. Also, corrosion and wear resistance of nanocomposite ceramic coatings improved with Ti doping content increased.     

Studying the effects of micro and nano sized ZnO particles on the corrosion resistance and deterioration behavior of an epoxy-polyamide coating on hot-dip galvanized steel

The effects of micro and nano sized ZnO particles on the corrosion resistance and hydrolytic degradation of an epoxy coating were studied. Different analytical techniques including scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), dynamic thermal mechanical analysis (DMTA) and nano-indentation were utilized to evaluate the hydrolytic degradation as well as the corrosion resistance of the coatings in exposure to 3.5 wt% NaCl solution. It was found that the epoxy coating resistance against corrosive electrolyte was significantly improved using nano and micro sized ZnO particles. The corrosion resistance of the nanocomposite was considerably greater than the one reinforced with the micro-ZnO particles. Moreover, the resistance of the coating reinforced with the nano sized particles against hydrolytic degradation in exposure to the corrosive electrolyte was considerably greater than the one reinforced with the micro sized particles. Decrease in both nano hardness and cross-linking density of the epoxy coating reinforced with nanoparticles after exposure to the corrosive electrolyte were considerably lower than the blank sample and the sample reinforced with the micro sized ZnO particles. Using nano sized particles the coating adhesion loss decreased.     

The effects of zinc aluminum phosphate (ZPA) and zinc aluminum polyphosphate (ZAPP) mixtures on corrosion inhibition performance of epoxy/polyamide coating

The epoxy/polyamide coating was loaded with different pigment mixtures of the zinc phosphate (ZP), zinc aluminum phosphate (ZPA) and zinc aluminum polyphosphate (ZAPP) pigments. The electrochemical impedance spectroscopy (EIS) and salt spray test were used to investigate corrosion inhibition performance of the coatings. The adhesion strengths of the coatings were measured by a pull-off test. Results revealed lower coating pull-off strength loss when the ZPA and ZAPP pigments were used. A significant decrease in number of blisters together with low pull-off strength loss and best corrosion inhibition properties were observed when the mixture of 80:20 of ZAPP:ZPA was used.     

Designing of corrosion resistant epoxy coatings embedded with polypyrrole/SiO2 composite

Polypyrrole/SiO₂ composite was synthesized by chemical oxidative polymerization of pyrrole using FeCl₃. The synthesized polymer composite was loaded in epoxy resin to develop coatings for mild steel substrates using powder coating technique. SEM and TEM images reveal homogenous dispersion of SiO₂ particles in polypyrrole matrix. TGA analysis confirms good thermal stability of the polymer composite. Tafel polarization and electrochemical impedance spectroscopy (EIS) results exhibit remarkably high corrosion protection efficiency of epoxy coatings with polymer composite in 3.5% NaCl solution. Corrosion studies of coatings with an artificial defect reveal the passivation of defect by the polymer composite present in the epoxy coatings. Salt spray test results revealed superior corrosion resistance offered by the polymer composite.     

Effect of nano-sized mesoporous silica MCM-41 and MMT on corrosion properties of epoxy coating

This study investigated the effect of co-incorporation of two different kinds of nano materials with different forms, layers (Na-MMT) and mesoporous silica particles (MCM-41), into the polymer matrix on the corrosion performance of epoxy resin. Correspondingly corrosion performance of the coatings was studied by electrochemical impedance spectroscopy (EIS) in 3.5% NaCl aqueous solution and salt spray test. The X-ray diffraction (XRD) measurement showed that the Na-MMT layers were exfoliated and the hexagonal framework structure of MCM-41 was retained during and after the composite preparation. The co-incorporation of Na-montmorillonite (Na-MMT) and MCM-41 into the epoxy coating possessed the best corrosion resistance than incorporating either Na-MMT or MCM-41 particles separately due to different interfacial structures between the fillers and the matrix.     

聚苯胺颗粒对水性环氧树脂涂层防腐性能的影响

以盐酸为掺杂剂、过硫酸铵为氧化剂、咪唑类离子液体为稳定剂,采用化学氧化聚合法合成了导电聚苯胺(PANI)颗粒,将其分散到水性环氧树脂(ER)中制成聚苯胺水性环氧防腐涂层,研究了聚苯胺颗粒对涂层防腐性能和机械性能的影响。结果表明,添加聚苯胺显著提高了水性环氧涂层的阻隔性能,信号频率f=0.01 Hz时,PANI/ER涂层的阻抗(|Z|f=0.01Hz)均高于纯ER涂层。添加5.0wt% PANI时ER涂层阻隔性能最好,浸泡0~168 h时|Z|f=0.01Hz稳定在约8.0×108 Ω?cm2,浸泡168 h后|Z|f=0.01Hz=7.5×108 Ω?cm2,远高于ER和其它PANI/ER体系。中性盐雾实验结果表明,聚苯胺赋予了涂层钝化腐蚀的能力,显著提高了涂层的防腐性能,且其添加量越高,防腐性能越好。弯曲和冲击实验结果表明,涂层的机械性能随聚苯胺含量增加先上升后降低,当聚苯胺添加量不超过5.0wt%时,涂层的机械性能优异,附着力和韧性均较好;PANI添加量增至7.0wt%时,ER涂层的脆性明显变大,机械性能下降。聚苯胺在水性环氧体系中的最宜添加量为5.0wt%,此时涂层的机械性能良好,综合防腐性能最优。     

Preparation,morphology, and properties of silane‐modified MWCNT/epoxy composites

Both epoxy resin and acid‐modified multiwall carbon nanotube (MWCNT) were treated with 3‐isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 52%. Flexural strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES‐MWCNT content by 2 orders and 6 orders of magnitude, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

环氧树脂基复合涂层摩擦磨损性能研究

研究了不同质量分数石墨、碳纤维、纳米ZrO2对环氧树脂(EP)涂层摩擦磨损性能的影响,并用扫描电子显微镜观察了涂层磨损表面形貌并探讨了磨损机理。结果表明:石墨质量分数为20%时复合涂层的磨损率仅为纯EP的7.75%;纳米ZrO2质量分数为4%时复合涂层的磨损率为纯EP的30%;纳米ZrO2与碳纤维以及石墨的协同作用提高了EP的摩擦磨损性能。EP复合涂层的磨损机理以粘着磨损、磨粒磨损以及疲劳磨损为主。     

无溶剂重防腐环氧涂料的制备与研究

采用中低相对分子质量树脂体系以及改性脂环胺固化剂,以化学、物理防锈颜料,体质填料为粉料体系制备无溶剂重防腐环氧涂料。通过 EIS、划线盐雾剥离、耐 3. 5% NaCl溶液和 10% NaOH溶液、混合溶液浸泡后的附着力,研究了涂层屏蔽性、耐碱性、湿态附着力。结果表明：铁钛粉、 绢云母粉、长石粉粉料体系涂层屏蔽性、耐碱性最佳;改性脂环胺固化剂屏蔽性好,湿态附着力性能优异;采用 EIS、划线盐雾剥离,耐 3. 5% NaCl溶液、 10% NaOH溶液浸泡以及混合溶液浸泡后附着力下降程度来评价涂层屏蔽性、耐碱性、湿态附着力性能具有一定的可参考性,研究结果与涂层耐阴极剥离实验性能正相关,可用于涂层耐阴极剥离性能的早期评价与判断。     

Multifunctional,environmental coatings on AA2024 by combining anodization with sol-gel process

The present work proposes the development of multifunctional composite coatings on AA 2024 by combining anodization and sol-gel process. To render the surface of AA 2024 with maximum corrosion resistance, eco-friendly citric-sulfuric acid (CSA) electrolyte with low sulphur content was used for anodization at 20 V for a duration of 30 min. The obtained anodized layer was porous. Ambient curable hybrid sol-gel coating with 8-hydroxy quinoline (8-HQ) as corrosion inhibitor was used as a sealant for the porous anodized layer to enhance the corrosion resistance with self-healing properties. Surface pre-treatments were carried out using sand blasting and alkaline etching to ensure high surface activity prior to anodization. The surface morphology and chemical composition of samples with and without coatings were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopic analysis (EDX). Adhesion strength and wettability of the coatings were measured by tape adhesion test and water contact angle analysis respectively, which revealed excellent binding strength and hydrophobic nature. The corrosion resistance of the coatings was evaluated using electrochemical impedance spectroscopic (EIS), potentiodynamic polarization and salt spray tests. The results revealed improved corrosion resistance of anodized + 8-HQ sealed AA2024. Moreover, when the coated samples were scribed and exposed to the corrosive medium, the SEM/EDX mapping confirmed presence of corrosion inhibitors at the location of the defect, thereby confirming the self-healing property. Hence, the proposed system is a chromium-free, environment friendly multifunctional system exhibiting excellent self-healing corrosion protection and can be a promising substitute for chromic acid anodization.     

Effect of pH and carbon nanotube content on the corrosion behavior of electrophoretically deposited chitosan–hydroxyapatite–carbon nanotube composite coatings

In the first stage, chitosan (CH)–hydroxyapatite (HA)-multiwalled carbon nanotube (MWCNT) composite coatings were synthesized by electrophoretic deposition technique (EPD) on 316L stainless steel substrates at different levels of pH and characterized by X-ray diffraction (XRD), Raman spectroscopy, FTIR and field emission scanning electron microscopy (FESEM). A smooth distribution of HA and MWCNT particles in a chitosan matrix with strong interfacial bonding was obtained. In the next stage, effects of pH and MWCNT content of the suspension on the corrosion behavior and deposition mechanism were studied. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) curves revealed that increasing pH level of the suspension increases the corrosion protection properties of the deposited composite coating in simulated body fluid (SBF). Furthermore, Nyquist plots showed that increasing MWCNT content of the suspension resulted in higher amounts of R_p, but because of the capillary properties of MWCNTs and degradability of the chitosan matrix, corrosion protection level of the coatings containing HA–CH–MWCNT was lower than those of coatings containing solely HA–CH. Amperometric curves in different pH levels of the suspension revealed that the system is diffusion controlled at elevated pH values.