Corrosion protection with polyaniline and polypyrrole as anticorrosive additives for epoxy paint

Accelerated immersion tests have been carried out in the laboratory to investigate the performance of polyaniline emeraldine salt and polypyrrole composite with carbon black as additives of an epoxy paint coating. The steel panels coated with paint modified with polyaniline emeraldine salt presented the best protection after 720 h of exposure in 3.5% NaCl solution. The results indicated that this conducting polymer might works as both corrosion inhibitor and adhesion promoter. The protective mechanism imparted by conducting polymers is also discussed.     

The effect of epoxy coating containing emeraldine base and hydrofluoric acid doped polyaniline on the corrosion protection of AZ91D magnesium alloy

Corrosion protection of epoxy coatings containing emeraldine base polyaniline (PANI) or hydrofluoric acid doped PANI on AZ91D magnesium alloy were studied by EIS and Pull-Off Adhesion Test. The results indicated that the addition of emeraldine base PANI or hydrofluoric acid doped PANI could improve the corrosion resistance of epoxy coating. The epoxy coating containing hydrofluoric acid doped PANI had the best performance of the corrosion protection among three systems under investigation. The corrosion product film was analyzed by XPS indicating that PANI changed the chemical structure of the corrosion film. The protective mechanism imparted by PANI was discussed.     

Application of multilayered particles formed by poly(3,4‐ethylenedioxythiophene) and poly(N‐methylpyrrole) as anti‐corrosive additives of conventional organic coatings

Multilayered systems containing 3 or 5 layers of poly(3,4‐ethylenedioxythiophene) and poly(N‐methylpyrrole) have been prepared using a layer‐by‐layer electrodeposition technique. These multilayered systems have been found to present very high electroactivities suggesting that their performance as anti‐corrosive additive of conventional organic coatings (paints) could be even better than that of single‐component conducting polymers. The performance of the prepared multilayered systems as anti‐corrosive additives of epoxy paints has been checked. For this purpose, accelerated corrosion tests were performed using an aggressive solution medium. Analysis of the corroded area indicates that the addition of a low concentration (0.2% w/w) of these multilayered systems to the paint formulation enhances significantly the corrosion protection imparted by the coating.     

Preparation,Surface Characterization and Anticorrosive Behavior of Polyaniline and Poly(3,4-ethylenedioxythiophene) Deposited on Aluminum Alloy AA2024-T3

This work is focused on studying the preparation and characterization of two different conducting polymers, polyaniline and poly(3,4-ethylenedioxythiophene), on aluminum alloy AA2024-T3. In addition to the direct electrochemical deposition of the conducting polymers onto an untreated aluminum substrate, the alloy surface pre-treatments based on single chemical acid pickling or chemical acid pickling followed by application of self-assembled monolayers have been also considered before the coating application. Coatings electrochemically deposited onto both untreated and pre-treated substrates have been characterized by physicochemical and electrochemical techniques, whereas their protective performance has been evaluated by means of polarization electrochemical techniques and accelerated corrosion tests. Although conducting polymers are widely used as protective coatings for steel substrates, the results obtained in this work indicate that their protective effect is not improved when deposited onto aluminum.     

Electrochemical impedance spectroscopy investigation of chlorinated rubber‐based coatings containing polyaniline as anticorrosion agent

Corrosion protection of mild steel by a newly developed chlorinated rubber (CR)‐based coating system containing the inherently conductive polymer polyaniline (PAni) as an anticorrosion agent was studied. The synthesis of PAni and preparation of CR‐based paint containing this polymer are described herein. The corrosion behavior of mild steel samples coated with a CR resin, CR/PAni‐EB (emeraldine base), CR/PAni‐ES (emeraldine salt), and CR/DBSA‐doped PAni were investigated in 3.5% NaCl solution. For this purpose, electrochemical impedance spectroscopy and corrosion potential versus time measurements were utilized. It was found that the addition of the two forms of PAni, doped and undoped, to the CR resin increased its corrosion protection efficiency.     

聚苯胺对丙烯酸涂层防腐性能的影响

目前,开发聚苯胺防腐涂料已成为高分子导电材料的应用和涂料研究开发领域的一个新的热点。为了研究本征态聚苯胺对丙烯酸涂层防腐性能的影响,制备了本征态聚苯胺质量分数分别为0％,1％,3％,5％及10％的聚苯胺／丙烯酸防腐涂层,应用Tafel极化曲线和电化学阻抗谱方法对比了其在3．5％NaCl溶液中的防腐性能。研究表明,聚苯胺在丙烯酸涂层中的含量对涂层的防腐性能有较大影响,聚苯胺质量分数为3％时,涂层具有最佳的防腐性能。     

聚苯胺含量对镁合金上聚苯胺环氧涂层防腐性能的影响

在AZ31B镁合金表面制备了含本征态聚苯胺O%,1%,2%,4%,6%的聚苯胺/环氧防腐涂层,通过Tafel极化曲线、电化学阻抗谱测试及中性盐雾实验对比了其在3.5%NaCl溶液中的防腐性能.结果表明:聚苯胺的含量时聚苯胺环氧涂层的防腐性能有较大影响,聚苯胺的质量分数为2%时,涂层具有最佳的防腐性能.     

水性环氧防腐涂料研究

目的研制具有优异防腐性能的水性环氧类防腐蚀涂料。方法采用水性环氧树脂乳液与水性环氧固化剂聚酰胺作为成膜树脂,异丙醇、丙二醇甲醚作为助成膜剂,湿法绢云母、重晶石粉、滑石粉作为填料,防锈颜料体系采用氧化铁红、三聚磷酸铝、磷酸锌,并在涂料体系中添加防闪锈剂、去离子水、分散剂、消泡剂、防沉剂,经过高速分散、研磨制成水性环氧防腐涂料。通过物理机械性能试验,耐酸、碱、盐溶液浸泡和耐中性盐雾试验,测试涂层的综合性能。结果涂层的附着力、柔韧性和耐冲击性能分别达到1级、1 mm和50 cm。涂层的耐酸性(5%H_2SO_4,168 h)、耐碱性(5%NaOH,168 h)、耐盐水性(3%NaCl,30 d)和耐盐雾性能(按GB/T 1771—2007,1000 h)良好,各试样完成后,涂层完好。结论成膜树脂采用环氧当量为500±50的水性环氧树脂乳液与聚酰胺类水性环氧固化剂,控制环氧基与活泼氢当量配比为1:1,颜料体积浓度为30%,并使用三聚磷酸铝、磷酸锌与氧化铁红复配作为防锈颜料,所制备的涂层有优良的物理机械性能和防腐性能。     

Conducting polyaniline based paints on low carbon steel for corrosion protection

Conducting polyaniline powder was synthesized chemically and paints containing conducting polyaniline powder were applied on low carbon steel samples. The conducting polyaniline powder was characterized by UV-Visible absorption spectroscopy and the morphology of paint coating on low carbon steel was studied by scanning electron microscopy. The corrosion protection performance of the coating was evaluated by using potentiodynamic polarization techniques and electrochemical impedance spectroscopy. It has been found that the 2 wt % polyaniline-hydrochloric acid based paint coating offers maximum corrosion protection to low carbon steel in chloride medium.     

聚苯胺对环氧涂层防腐蚀性能的影响

制备了本征态聚苯胺在涂层中质量分数分别为0%、1.5%、3%、5%、7%、10%的聚苯胺/环氧防腐蚀涂层,通过Tafel极化曲线和电化学阻抗谱测试对比了其在35%NaCl溶液中的腐蚀性能,结果表明,聚苯胺含量对涂层的防腐蚀性能有较大影响:涂层中聚苯胺含量较小时,随着其在涂层中含量的增加,涂层的腐蚀电位相应提高,而随着聚苯胺含量的进一步增加,涂层的防腐蚀效果开始下降.涂层中聚苯胺质量分数含量为5%时,涂层具有最佳的防腐蚀性能.     

Towards all-polymer field-effect transistors with solution processable materials

We have fabricated polymer field-effect transistors (FET) from solution processable polymers. Starting with an inorganic structure using only an organic semiconductor (regio-regular poly(3-hexylthiophene)), the transistor performance was studied as the inorganic materials were replaced with polymeric alternatives one at a time. We see a gradual increase in subthreshold swing and off-currents and an increased threshold voltage when substituting the inorganic materials with polymer materials. The small reduction in transistor performance when going from inorganic substrate and insulator to polymeric materials indicates that it is possible to make flexible polymer devices from solution processed materials suitable for roll-to-roll processing. The all-polymer FET was realized using two different conducting polymers, polyaniline for the source and drain electrodes and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate), PEDOT:PSS, for the gate electrode.     

环氧富锌聚苯胺杂化金属重防腐水性涂料的研制

通过溶液聚合方法,把不同的聚苯胺产品与环氧富锌杂化制成了金属重防腐使用的水性涂料.经过与国际著名的金属重防腐溶剂型油漆进行对比检测,这种水性重防腐涂料的优异防腐性能得到了印证.由于不使用有机溶剂,所以制成的金属重防腐水性涂料是VOC含量很低和对环境友好的金属重防腐工业涂料.     

Novel flexible,freestanding and transparent organic/inorganic hybrid materials formed between polyaniline and polyphosphate gel

In this paper we report the synthesis and characterization of new polyaniline/polyphosphate hybrid materials. The synthetic approach involves a single-step procedure in which the polyphosphate inorganic host structure (arising from a sol–gel transition) develops first, providing a restricted environment in which the conducting polymer is entrapped within the gel network. Polyaniline was formed as the green, conducting emeraldine salt form. The samples were characterized by thermogravimetric analysis and UV–vis, Raman, EPR and ³¹P-MAS-NMR spectroscopies. We have synthesized homogeneous, flexible, freestanding and transparent materials in which the conducting polymer presents a coiled conformation typical of primary doped polyaniline. Upon exposition to ammonia vapors the polymer can be converted to the emeraldine base form, which can be reverted by exposition to HCl vapors. Powdered samples present dc conductivities up to 0.2 S cm⁻¹.     

Cadmium- and chromate-free coating schemes for corrosion protection of 15CDV6 steel

Electrodeposits of cadmium- and chromate-based inorganic inhibitor pigments in paint formulations are extensively used in the aerospace industry to provide long-term corrosion protection for high-strength steel hardware. Due to environmental concerns and worker safety issues, there is a pressing need to identify and adopt alternative ecofriendly coatings with equivalent performance. In this work, an ecofriendly cadmium- and chromatefree coating scheme comprised of zinc nickel alloy plating, trivalent chromium- based passivation, followed by a primer based on polyaniline phosphate, is studied for its anticorrosive properties. Long-term performance evaluation studies of this eco-friendly coating scheme were carried out on 15CDV6 steel, an ultra-high- strength steel used in the aerospace industry.For comparative purposes, two extensively used cadmium- and chromate-based schemes complying to aerospace and military specifications comprised of cadmium plating, hexavalent chromium-based passivation followed by two different chromate-based primers were studied on 15CDV6 steel substrate. Electrochemical impedance spectroscopic studies and salt fog exposure tests were carried out to evaluate the anticorrosive properties of the coat- ing schemes. Cadmium- and chromate-free scheme exhibited excellent performance in the long-term corrosion evaluation studies. The results obtained in accelerated tests show the possibility of replacement of cadmium- and chromate-based schemes for corrosion protection of steels with an eco-friendly option.     

Study of iron benzoate as a novel steel corrosion inhibitor pigment for protective paint films

The aim of this work was to study the lab-synthesized iron benzoate as a novel steel corrosion inhibitor pigment to formulate anticorrosive paint films. The iron benzoate anticorrosive properties were studied by electrochemical and spectroscopic essays employing pigment suspensions. In a second stage, it was evaluated the performance of anticorrosive paint films containing iron benzoate by accelerated (salt spray and humidity chambers) and EIS tests. The protective layer nature grown under the paint films in the salt spray chamber was also assessed.Experimental results shown that ferric benzoate was adequate to formulate anticorrosive paint films with improved anticorrosive assessed.     

Polyaniline-coated iron: studies on the dissolution and electrochemical activity as a function of pH

Polyaniline coatings were electrodeposited from an oxalic acid solution onto iron and their electrochemical activity and corrosion protection properties studied as a function of pH. It was found that the coating (emeraldine salt) had a limited effect on the corrosion protection of iron in acidic solutions. However, in an alkaline borate solution, where the conducting polyaniline was converted to the emeraldine base, the coating had a clear beneficial effect on the local breakdown of iron by chloride anions; much higher pitting potentials were recorded following a 2 h immersion period for the polyaniline-coated substrate relative to the uncoated electrode. Relatively small anions, such as acetates, nitrates and borates, were transported readily across the polymer interface. However, the emeraldine base inhibited the transport of the much larger ethylenediamine tetraacetate (EDTA) species to the iron interface, preventing complexation of the iron by EDTA.     

On the use of conducting polymers to improve the resistance against corrosion of paints based on polyurethane resins

This work analyzes the physical properties of several paints and the resistance against corrosion that they impart after being modified by adding a conducting polymer. Five different formulations were selected: four polyurethane resins (two varnish and two aqueous based) and one multicomponent system containing polyester, melamine and cellulose acetobutyrate. The physical properties of the coatings were examined by FTIR, thermal analyses and viscosity measurements. Corrosion resistance of carbon steel coated with these paints was studied by means of accelerated laboratory tests. The results provided by the original formulations and those modified by adding 1 % w/w of polypyrrole or poly(3‐decylthiophene‐2,5‐diyl) regioregular were compared. Although the general behavior was irregular, showing dependence with the paint formulation, excellent results were achieved for an aqueous based polyurethane resin modified with polypyrrole. Accelerated immersion experiments in salt and acid solutions showed fast degradation of the film without conducting polymer, while the polymeric film with polypyrrole offered a higher resistance.     

聚苯胺/石墨烯原位复合水性防腐涂料耐蚀性能的研究

目的研究聚苯胺/石墨烯水性防腐涂料的耐蚀性能。方法采用盐酸为掺杂酸,以聚乙烯基呲咯烷酮(PVP-K30)为空间稳定剂,利用原位聚合法,以苯胺和石墨烯为原料,过硫酸铵为氧化剂,制备聚苯胺/石墨烯复合材料。将聚苯胺/石墨烯、纯聚苯胺、石墨烯分别添加到HG-54C乳液中制备水性防腐涂料,利用动电位极化曲线和盐雾试验对比分析聚苯胺/石墨烯、纯聚苯胺、石墨烯水性涂层的防腐性能,再通过傅里叶红外光谱(FTIR)、扫描电镜(SEM)对比分析其结构和微观形貌。结果聚苯胺均匀地覆盖在石墨烯的片层结构上形成氧化插层结构。当复合材料浸泡在3.5%Na Cl溶液中,腐蚀电流密度为2.3955×10-7A/cm2。盐雾试验表明,聚苯胺/石墨烯的防腐性能优于添加纯聚苯胺和石墨烯的性能。结论聚苯胺/石墨烯涂层具有良好的耐蚀性能,其耐蚀性能优于纯聚苯胺涂层和石墨烯涂层。     

Suitability of emeraldine base polyaniline-PVA composite film for carbon dioxide sensing

A CO₂ sensor based on a composite thin film of emeraldine base polyaniline and poly (vinyl alcohol) cast from N-methyl pyrrolidone on an interdigitated electrode was characterized using impedance spectroscopy. The response of the sensor was slow and smaller in magnitude as compared to reports in the literature for similar sensors. Materials characterization indicated that the desired emeraldine base phase was not present after heat treatment. In addition, the mechanism for carbon dioxide detection previously reported in the literature cannot explain the CO₂ sensitivity, because the pH established between CO₂ and carbonic acid in the water dissolved in the poly (vinyl alcohol) matrix is not sufficient to induce a significant change in the conductivity of the emeraldine base polyaniline.     

湿固化型石墨烯改性重防腐涂料的性能研究

目的 为延长如输电塔架等金属构件的服役期限,制备一种湿固化型石墨烯改性重防腐涂料,并测试表征和分析漆膜的防腐性能和作用机制。方法 以湿气固化型聚氨酯树脂为主要成膜物,铝鳞片代替传统锌粉为主要防腐填料,石墨烯为改性剂搭配形成复合导电填料体系,借助定位排列剂等助剂制备了湿固化型石墨烯改性重防腐涂料。通过沉降测试、结合强度测试、水接触角测试、电化学测试、扫描电镜（SEM）分析、耐中性盐雾实验等手段,对涂层的常规理化性能、防腐蚀性能及微观形貌进行了表征分析,并探讨了石墨烯-铝鳞片复合填料防护体系的防腐蚀作用机理。结果 定位剂有助于提高涂料的分散性和稳定性,经过石墨烯改性后,重防腐涂层的结合强度、耐盐水性、耐候性等常规理化性能明显提升,固含超过70%,达到高固含的环保要求;水接触角增至115°,涂层疏水性有效改善;中性耐盐雾试验进行1000 h时涂层划痕处有明显的腐蚀迹象,但表面未发生起泡、剥落等缺陷,单边扩蚀小于2 mm,石墨烯质量分数为0.8%的涂层性能达到最佳,耐盐雾时间达5000 h以上,此时涂层湿结合强度仍达到8.3 MPa,电化学腐蚀速率仅为0.011 673 mm/a,耐腐蚀性能优异。结论 石墨烯-铝鳞片复合防护体系的力学性能、机械封闭和阴极保护功能优异,属于一种底面合一的涂料,适用于湿热工业-海洋大气环境的腐蚀防护工作。