Study on preparation and anticorrosive performance of a new high hydrophobic anticorrosive coating

Water-based anticorrosive coatings have poor water resistance, which easily lead to coating deterioration and metal corrosion. In order to improve the anticorrosion performance of waterborne coating, herein, the polytetrafluoroethylene/dimethyl siloxane/epoxy resin (PTFE/PDMS/EP) hydrophobic anticorrosive coating was prepared by layer-by-layer construction. The spatial structure and microscopic morphology of the hydrophobic coating were analyzed by XRD, FTIR, and SEM. The hydrophobicity and corrosion resistance of the composite coating were analyzed by hydrophobicity test, electrochemical polarization curve, hydrophobicity and corrosion resistance test of the mixed layer, Tafel polarization curves, and AC impedance spectrum. The results showed that the water contact angle of PTFE/PDMS/EP coating reached 141° and the protection efficiency of PTFE/PDMS/EP coating was 98.62%. After soaking for 7 days, the corrosion process still stays at the initial stage, which was mainly due to the good sealing and barrier properties and high anticorrosion efficiency of PTFE/PDMS/EP coating. The coating has high corrosion protection efficiency and long service life, which is of great significance to metal corrosion protection in harsh marine environments.     

改性石墨烯对环氧树脂涂层耐腐蚀性能的影响

将改性后石墨烯粉末通过球磨机均匀分散于环氧树脂涂料中以提高7A52铝合金表面有机涂层的耐腐蚀性能。通过接触角、吸水率、红外光谱、开路电位及交流阻抗测试,分别评价改性石墨烯环氧树脂涂层的表面润湿性、耐水性能、耐蚀性,并通过扫描电子显微镜对石墨烯粉末及环氧树脂涂层断面形貌进行分析。结果表明:环氧树脂涂料中添加0.8%改性石墨烯粉体后,接触角由86.77°增加至101.43°,提高16%,表面由亲水性变为疏水性,涂层的耐水性提高,吸水率降低0.21%。0.8%改性石墨烯涂层在3.5%NaCl溶液中稳定后的开路电位较未添加石墨烯涂层增加0.14 V,阻抗值高出未添加改性石墨烯涂层半个数量级,且电荷转移电阻R_ct比未添加改性石墨烯涂层R_ct高出1.78×10 ⁷ Ω/cm ²,涂层的耐腐蚀性大大提高。红外光谱表明,改性石墨烯并未改变环氧树脂结构,涂层中的改性石墨烯是影响涂层性能发生变化的重要因素。研究表明改性石墨烯的加入可以有效提高涂层的耐蚀性,并且当改性石墨烯添加量为0.8%时,涂层具有优异的耐腐蚀性能。     

Effect of the incorporation of montmorillonite-layered double hydroxide nanoclays on the corrosion protection of epoxy coatings

A series of layered double hydroxide (LDH)/montmorillonite (MMT) nanocomposite coating, LDH nanocomposite coating, and MMT nanocomposite coating were successfully prepared. The nanocomposite materials were characterized by X-ray diffraction and scanning electron microscopy (SEM). To understand the effect of MMT and LDH on the corrosion inhibition performance of epoxy resin coatings immersed in 3.5 wt% saline solution at 90°C, electrochemical impedance spectroscopy and an autoclave test were performed on epoxy resin; epoxy resin blended with LDH, MMT, and LDH + MMT (LM) coatings painted on Q345 steel. The metal/coating interfaces were observed by SEM and energy-dispersive spectroscopy. Results showed that addition of LDH and MMT improved the protection properties of the epoxy resin coatings. The corrosion protection of the LM nanocomposite coating was superior to that of the other coatings. This finding can be attributed to the ionic selectivity and barrier effect of MMT and LDH nanoclay platelets dispersed within the composite coatings.     

氧化石墨烯改性环氧树脂涂料的制备及防腐性能

环氧树脂在溶剂蒸发过程中容易产生微孔,影响其防腐蚀性能。为了提高其对腐蚀介质的阻碍能力,本文采用密闭氧化法制备氧化石墨烯,再利用湿式转移法将氧化石墨烯水溶液分散在环氧树脂中,制备氧化石墨烯/环氧树脂防腐涂料。通过红外光谱（FTIR）、X射线衍射（XRD）和拉曼光谱（Raman）分析氧化石墨烯的结构变化,利用开路电位测试（OCP）、水接触角、腐蚀形貌和气体透过率分析氧化石墨烯/环氧树脂涂料的防腐性能。结果表明,氧化石墨烯/环氧树脂（GO/EP）涂料的开路电位和水接触角分别为0.181V和86.12°,与纯环氧树脂涂料相比,分别提高了0.066V和10.5°;当GO/EP浸泡在3.5%NaCl溶液中腐蚀20天后,表面仅产生了粗糙化,涂层稳定性好,屏障性能强;与EP涂层相比,GO/EP涂层的O₂和H₂O渗透率分别降低了51.2%和65.5%。     

Synthesis and characterization of hybrid materials based on graphene oxide and silica nanoparticles and their effect on the corrosion protection properties of epoxy resin coatings

This study focuses on the use of tetraethyl orthosilicate (TEOS) as a silica source to decorate the surface of graphene oxide (GO) nanosheets and the use of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (Z-6020) as a coupling agent through a one-step in-situ sol-gel process. The results of the Fourier transform infrared spectroscopy (FT-IR), UV-visible, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) revealed that fine SiO₂ nanoparticles have successfully been synthesized on the basal plane of GO by covalent bonding. The dispersion of GO sheets and GO–SiO₂ nanohybrids within the epoxy matrix was studied using XRD and SEM techniques. Then, the effect of incorporating 0.1?wt% GO sheets and GO–SiO₂ nanohybrids on the corrosion protection and barrier performance of the epoxy coating was also investigated. The results showed that the incorporation of GO–SiO₂ into the epoxy matrix improved its thermal stability. The electrochemical impedance spectroscopy (EIS) test, potentiodynamic polarization and cathodic disbonding test showed that the corrosion protection performance was significantly enhanced by the incorporation of GO–SiO₂ hybrids into the epoxy resin compared to epoxy/GO and neat epoxy resin, respectively. The water contact angle (CA) results confirmed the reduction of the hydrophobic nature of the surface after the incorporation of GO–SiO₂ hybrids.     

磺化聚苯胺/硅树脂涂层的制备及防腐蚀性能

分别以十二烷基硫酸钠(SDS)和木质素磺酸钠(LGS)为掺杂剂,通过化学氧化法合成了两种磺化聚苯胺(PANI-SDS和PANI-LGS),并将合成的磺化PANI混入溶胶-凝胶法制备的硅树脂(SiR)中,刷涂在Q235钢表面制备了复合防腐蚀涂层。采用FTIR表征了磺化PANI的结构;对比了PANI-LGS和PANI-SDS的基本性能,考察了SiR、PANI-SDS/SiR和PANI-LGS/SiR复合涂层的耐水性、附着力、机械性能及防腐蚀性能,并分析了复合涂层的防腐蚀机理。结果表明:制备的PANI-LGS/SiR复合涂层疏水性能较好,接触角达到113.0°,吸水率仅为7.58%。电化学测试结果表明,该复合涂层对Q235钢具有良好的防腐蚀性能,腐蚀速率为5.56×10~(-3) mm/a,复合涂层是通过物理屏蔽和阳极保护作用实现对金属的腐蚀防护。     

Synergic enhancement of the anticorrosion properties of an epoxy coating by compositing with both graphene and halloysite nanotubes

The aim of this research was to improve the corrosion resistance of metal surfaces with polymer coatings. Both graphene and halloysite nanotubes (HNTs) were introduced together into the epoxy resin coating for the enhanced barrier protection of the metallic surface. The anticorrosion behaviors of different coatings were comparatively evaluated by the potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), and neutral salt spray (NSS) tests. The potentiodynamic polarization curves showed that the coating containing 0.5 wt % HNTs and 0.8 wt % graphene (H05G08EP) together had the most positive corrosion potential and the minimum corrosion current density. The EIS results revealed that graphene endowed the composite coatings with excellent electrochemical performance for anticorrosive purposes. The NSS tests indicated that H05G08EP endured the longest NSS time. These results suggest that H05G08EP had the best corrosion resistance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47562.     

Hydrophobic benzoxazine-cured epoxy coatings for corrosion protection

A hydrophobic benzoxazine-cured epoxy coating (EPB) was prepared by a dip coating and thermal curing method using benzoxazine monomer (B-TMOS) as curing agent. Fourier transform infrared (FTIR) analyses confirmed the presence of thermal curing reactions and hydrogen-bonding interactions in the epoxy/polybenzoxazine system. The hydrophobicity of epoxy coatings induced by the incorporation of B-TMOS was enhanced significantly, and the water contact angles of resultant EPB coatings were higher than 98°. The corrosion protection ability of epoxy coatings was investigated by open-circuit potentials, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results showed that the charge transfer resistance (R_ct) of EPB coatings was increased by about three orders of magnitude compared with bare mild steel, and the protection efficiency values of all EPB samples were more than 98%. This increased corrosion protection property could be attributed to the high hydrophobic performance of EPB coatings.     

Incorporation of silica network and modified graphene oxide into epoxy resin for improving thermal and anticorrosion properties

In this study, the silica network and functionalized graphene oxide (GO) were incorporated into the epoxy coating systems, which was aimed to improve the thermal property and corrosion resistance of epoxy coatings. First, tetraethyl orthosilicate (TEOS) oligomers and epoxy hybrid was fabricated through sol–gel method. Then the (3-aminopropyl) triethoxysilane (APTES) modified graphene oxide (FGO) was added into the epoxy hybrid composite to obtain anticorrosion coatings. Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), Raman spectrum, and X-ray photoelectron spectrum were conducted to evaluate the structural information of GO and APTES modified GO nanosheets. The results indicated that the APTES successfully grafted onto the surface of GO sheets. Besides, TGA curves, electrochemical measurements and salt spray test were also carried out to characterize the thermal performance and corrosion resistance of GO based epoxy coatings. The TGA results revealed that the thermal performance of epoxy coating containing silica network and FGO nanofiller (ES/FGO) was significantly strengthened compared to pure epoxy. The initial degradation temperature of epoxy coating was increased from 300 to 343.7°C after incorporation of silica component and FGO. The EIS measurements demonstrated that the impedance modulus of ES/FGO was significantly higher than neat epoxy, which indicated that the corrosion resistance of epoxy was substantially strengthened after introduction of silica component and FGO. The corrosion rate and inhibition efficiency of epoxy composite coatings were also shifted from 1.237 × 10⁻⁷ mm/year and 76.6% (for neat epoxy) to 1.870 × 10⁻⁹ mm/year and 99.6% (for ES/FGO), respectively. The salt spray test also revealed that the silica and FGO can improve the corrosion resistance of epoxy coating. Additionally, the dispersion of GO sheets was also enhanced after the modification of APTES siloxane.     

石墨烯改性涂层防护性能研究

为减少团聚,提高石墨烯在涂层中的分散性,研究采用纳米分散技术预先制备了石墨烯分散液,再将其分散至环氧树脂中获得石墨烯改性复合涂层。通过对石墨烯含量为 0、0.3%、0.6%的复合涂层进行盐水浸泡、盐雾、阴极剥离实验及电化学性能测试,证明石墨烯的加入显著增强了涂层的防护性能。石墨烯复合涂层在 3.5%盐水中浸泡 1 008 h后,涂层低频阻抗仍大于 106 Ω·cm²比未添加石墨烯的涂层提高了 3个数量级,且盐雾实验 6 000 h后涂层表面仍保持完好;含 0.6%石墨烯,的涂层耐蚀行为劣于石墨烯含量为 0.3%的涂层。     

疏水改性氧化石墨烯/环氧复合涂料的制备及其防腐性能研究

以叔碳酸缩水甘油酯(E-10P)为疏水单体,通过环氧与羧酸的共价键合,在氧化石墨烯(GO)表面引入疏水性支化碳链,改性后的氧化石墨烯(F-GO)作为防锈填料加入环氧树脂中得到F-GO/环氧复合涂料。通过红外光谱、拉曼光谱、X-射线衍射、热重分析对F-GO的结构进行表征,通过场发射扫描电镜观察F-GO及复合涂料的微观形貌,并通过电化学阻抗、极化曲线和盐雾试验测试了复合涂料的防腐性能。结果表明:E-10P可利用其空间效应阻碍片层的团聚;疏水效应可提高F-GO的热稳定性和与环氧树脂的相容性;与空白环氧涂层相比,当复合涂料中F-GO质量分数为0.2%时,厚度为20~25 μm的防腐涂层的腐蚀电流可由2.358 6×10 ^-6 A/cm ²下降至2.000 2×10 ^-11 A/cm ²,阻抗值可由1.1×10 ⁷ Ω·cm ² 提升至6.9×10 ⁹ Ω·cm ²。     

Facile fabrication approach for a novel multifunctional superamphiphobic coating based on chemically grafted montmorillonite/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-polydimethylsiloxane binary nanocomposite

In this paper, a novel multifunctional superamphiphobic coating for anticorrosion was successfully prepared on aluminum substrate via a simple spraying technique. Al₂O₃ nanoparticles were chemically grafted onto montmorillonite (MMT) nanosheets via coupling effect of NH₂-C₃H₆-Si(OC₂H₅)₃ (KH-550) and then modified by low surface energy material polydimethylsiloxane (PDMS). The ethylene tetrafluoroethylene (ETFE) composite coating with 25 wt% MMT/Al₂O₃-PDMS binary nanocomposite exhibited well-designed nano/μ structures and possessed superamphiphobicity with high contact angles towards water (164°), glycerol (158°) and ethylene glycol (155°). This coating demonstrated outstanding self-cleaning ability and strong adhesive ability (Grade 1 according to the GB/T 9286). The superhydrophobicity could be maintained after 8000 times abrasion or annealing treatment for 2 h under 350 °C. The coating still retained high water-repellence after immersion in 1 mol/L HCl (146°), 1 mol/L NaOH (144°) and 3.5 wt% NaCl (151°) solutions for 30 d. It should be noted that this superamphiphobic coating revealed excellent long-term corrosion protection with extremely low corrosion rate (4.3 × 10^?3 μm/year) and high protection performance (99.999%) after 30 d immersion in 3.5 wt% NaCl solutions based on electrochemical corrosion measurements. It is believed that such integrated functional coating could pave new way for self-cleaning and anticorrosion applications under corrosive/abrasive environment.     

Stearic acid grafted chitosan/epoxy blend surface coating for prolonged protection of mild steel in saline environment

Chitosan (CS) is a promising candidate for green anticorrosive coating owing to its film forming nature, complexation with metals, biocompatibility, and varied surface functionalization. This paper illustrates the surface properties of chitosan film which is modified by grafting with stearic acid via a water-soluble coupling agent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). The interaction between chitosan and stearic acid were investigated theoretically by Gaussian 09 package. The purified co polymeric films so formed were characterized by FTIR-ATR, NMR, XRD, TGA, CHNSO, SEM, AFM and EDX techniques. Stearic acid grafted CS film was developed on mild steel surface via dip coating technique and investigated for its corrosion resistance in 3.5% NaCl via electrochemical techniques. EIS measurements and potentiodynamic polarization studies have proven that the grafted CS when blended with epoxy resin offers better corrosion protection to mild steel in saline environment. The coating offers prolonged protection for the metal surface with enhanced barrier properties and hydrophobic nature.     

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.     

Synthesis of low-electrical-conductivity graphene/pernigraniline composites and their application in corrosion protection

Graphene can be a corrosion-promotion material because of its high electrical conductivity. This paper aims at eliminating the undesired corrosion-promotion effect of graphene, and reports a promising application of graphene/pernigraniline composites (GPCs) for the corrosion protection of copper. The composites were synthesized by an in situ polymerization-reduction/dedoping process. The synthesized composites have a flake-like structure, and their conductivity is as low as 2.3 × 10⁻⁷ S/cm. The GPCs are then embedded into polyvinylbutyral coating (PVBc) to modify the coating. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements reveal that the GPC-modified PVBc is an outstanding barrier against corrosive media compared with pernigraniline or reduced graphene oxide (rGO) modified PVBc. Scratch tests also show that the corrosion-promotion effect of rGO in GPCs is inhibited. The enhanced corrosion protection performance is observed because on the one hand the pernigraniline growing on rGO surface avoids graphene–graphene/metal connections increasing the electrical resistance of coating; on the other hand the as-prepared GPCs are less flexible than polymer-free rGO and they are more likely to unfold during the coating process, which can greatly prolong the diffusion pathway of corrosive media in the coating matrix.     

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.     

Hydrophobic interfacing layers for improvement of corrosion protection by polymeric coatings

Water sorption of coating materials is the main cause of coating deterioration, adhesion loss and substrate corrosion. By introducing alkanethiol self-assembled monolayers (SAMs), a hydrophobic interfacing layer between coating and substrate metal can be constructed. The effect of the hydrophobic SAMs interfacing layer on the corrosion protection of epoxy coatings was evaluated using electrochemical techniques including Tafel polarization, electrochemical impedance spectroscopy and impedance–time transition measurement. It was found that the SAMs interfacing layer improved the corrosion protection of the coating significantly. The improvement was attributed to the strong interaction between SAMs and the metal substrate, the compact structure and low water affinity of the SAMs interfacing layer, which prevent water absorbed by the coating from reaching the coating–metal interface and spreading along the interface.     

Synergistic effect of potassium metal siliconate on silicate conversion coating for corrosion protection of galvanized steel

Silicate conversion coating is considered as an alternative to hexavalent chromium conversion coating for corrosion protection of galvanized steels. However, the coating must be treated with hot air afterward in order to obtain a water resistant silicate layer and to increase corrosion resistance of the coating. Moreover, it is difficult to apply the uniform thermal treatments on the large irregular shaped metal parts. Furthermore, the heat treatment is an energy consuming process. In this work, the effects of adding potassium methyl siliconate (PMS) into the silicate conversion coating on the anti-corrosion properties were studied. The silicate coating layers were formed by the simple immersion into the silicate solutions and the subsequent ambient drying at room temperature. It was verified that the addition of PMS increased the temporary corrosion protection ability without the post-thermal treatments. Coating thickness was around 100 nm and K ion was distributed preferentially at zinc-silicate interface. It was proved that the more hydrophobic surface was formed mainly due to the substantial decrease of the concentration of K ion at the coating surface by the addition of PMS. It was a methyl group of PMS that changed the hydrophilic silicate layers into hydrophobic ones. Subsequently, the enhanced water barrier property of the hydrophobic silicate layers increased the corrosion resistance of the silicate-coated galvanized steel.     

Enhancement of adhesion,mechanical strength and anti-corrosion by multilayer superhydrophobic coating embedded electroactive PANI/CNF nanocomposite

Traditional insulative coatings usually suffer from pitting corrosion in harsh corrosive environment. Herein, in this work, electroactive polyaniline/carboxylated carbon nanofiber (PANI/CNF) nanocomposite was prepared via in situ chemical polymerization and first incorporated into superhydrophobic coating with better barrier effect. Multilayer coatings were constructed by facial spraying using polyphenylene sulfide (PPS) and ethylene tetrafluoroethylene (ETFE) with gradient weight ratios as film-forming materials. The composite coating with 40 wt% ETFE in top layer (denoted as ETFE-40) possesses best superhydrophobicity and highest oleophobicity with water contact angle (CA) and glycerol CA of 160° and 155° as well as low water sliding angle (SA) and glycerol SA of 2.2° and 8.8°, respectively. The lotus-like nano/micro structures, low surface energy material ETFE and modification of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS) should contribute to the superior liquid repellency. Especially, robust mechanical strength and durable anti-wettability are obtained with high WCA of 151° and glycerol CA of 147° after 8000 cycles abrasion. The composite coating also exhibits strong adhesion and superior self-cleaning. The enhanced electrochemical corrosion resistance of the coating in 3.5 wt% NaCl solution can be attributed to the outstanding barrier function of superhydrophobic surface and the passivation effect of electroactive PANI/CNF. This novel and effective coating system would definitely benefit the development of robust protective coating and promise wider engineering application.     

Corrosion protection of epoxy‐coated steel using different silane coupling agents

To suppress steel corrosion at elevated temperature and in humid condition, silane coupling agents N‐β‐aminoethyl aminopropyltrimethoxysilane (AAPS), γ‐glycidoxypropyltrimethoxysilane (GPS), and bis[3‐(trimethoxysilyl)‐1‐phenylpropyl]tetrasulfide (RC‐2) were introduced as primers into an epoxy/steel system. Silane coupling agents and epoxy were coated onto the steel surface using the solution casting method. The polymer degradation and steel corrosion formation after heat and humid treatment were investigated by Fourier transform infrared reflection and absorption spectroscopy (FTIR–RAS) and scanning electron microscopy (SEM). Compared to various silane treated epoxy/steel systems, the AAPS‐treated epoxy/steel (AAPS/epoxy = 6 : 4) system suppressed steel corrosion at 400°C for 10 min in air and for 5 days at 60°C in 100% relative humidity. This is due to the formation of Si O Si linkage and Fe O Si bond on steel surface, which are resistant to water diffusion and thermally stable at elevated temperature. The relationship between chemical bonding at the steel–epoxy interface and corrosion protection on the steel surface was also investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 585–593, 1999