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.     

Polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene) as additives of organic coatings to prevent corrosion

The aim of this work is to compare the protection against corrosion imparted by different conducting polymers when these materials are used as anticorrosive additives in the formulation of conventional epoxy paints. Specifically, the polymers employed as anticorrosive additives are polyaniline emeraldine salt, polyaniline emeraldine base, polyaniline emeraldine salt composite with carbon black, polypyrrole composite with carbon black and poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonate). Initially, the structural, thermal and mechanical properties of the unmodified epoxy paint as well as the modified coatings, obtained by the addition of 0.3 wt.% of conducting polymers, have been characterized. After this, controlled accelerated corrosion assays in an aggressive solution medium were developed using coated steel panels. Results indicate that the protection against corrosion imparted by the formulations modified by the addition of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonate), polyaniline emeraldine salt and, especially, polyaniline emeraldine base is significantly higher than that of the unmodified paint. In contrast, the use of conducting polymer composite with carbon black reduces the efficacy of the coating. Results indicate that some conducting polymer compositions should be considered as a suitable alternative to replace inorganic anticorrosive pigments currently used in paint formulations.     

浮头式碳钢水冷器的防腐蚀涂装

介绍了本公司十余年来浮头式碳钢水冷器的腐蚀防护涂装简税 ,概括了阻垢,导热和耐蚀的氨基环氧涂料涂装工艺和应用情况。     

Synthesis and anticorrosion properties of polydiphenylamine blended vinyl coatings

Inherently conducting polymers such as polyaniline and polypyrrole containing organic coatings have been found to offer corrosion protection of steel in acid and neutral media. In this study, the use of polydiphenylamine in vinyl coating for corrosion protection of steel in 3% NaCl solution is reported. The polydiphenylamine was prepared by chemical oxidative method of diphenylamine by ammonium persulfate in hydrochloric acid medium. The synthesized polydiphenylamine (PDPA) was blended with vinyl resin at 0–5% concentrations and the corrosion protection performance of the coating on steel was evaluated by EIS for a period of 80 days. It has been found that the coating containing 3% PDPA is able to protect steel more effectively.     

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.     

Influence of polyaniline and ceria nanoparticle additives on corrosion protection of a UV-cure coating on carbon steel

Influence of a few percents additives of polyaniline doped with phosphoric acid (PAni-PA) and ceria nanoparticle on corrosion protection of a new ultraviolet (UV)-cure polyester acrylate coating have been studied for coil coating on carbon steel by electrochemical measurements during exposure to a NaCl solution. The results demonstrate that the presence of ceria nanoparticles improves the barrier property and stability of the coating. Adding the PAni-PA results in active corrosion protection for carbon steel due to passivation of the steel, and the combination of both additives greatly enhances the protection property over that of the coating matrix alone.     

Optisches Verfahren zur Bestimmung der Korrosionsneigung von Automobilfeinblechen

Determination of the corrosion behaviour of car-body steel by optical methods For optimum corrosion protection in car manufacturing it is of importance to test the corrosion properties of the low carbon steel in addition to the quality of the surface coating. For this purpose it is necessary to apply methods which can be used on-line as it is the case by reflectance spectroscopy. The composition and the thickness of the oxide layer on the steel can be determined by analyzing the spectral absorption of the oxide layer. It is sufficient to detect the intensity of the reflected light at three different wave-lengths by a filter system. From these intensities a corrosion index can be calculated with a high correlation to the corrosion under paint. Various data from other investigations will be presented and analyzed by factor analysis.     

Corrosion characteristics of polyaniline-coated 316L stainless steel in sulphuric acid containing fluoride

The corrosion resistance of conducting polyaniline (PANi) coatings deposited on 316L stainless steel (316L SS) at various cycle numbers of cyclic voltammetry (2-, 3- and 4-cycles) by electro-polymerization in sulphuric acid solution containing fluoride was investigated by electrochemical techniques. The corrosion resistance of the 316L SS substrate was considerably improved by the PANi coating. The increase of the cycle number of cyclic voltammetry increased the thickness and enhanced the performance of the PANi coating due to low porosity.     

石墨烯防腐涂层对油罐沉积水的防腐机制研究

目的探究石墨烯基防护涂层/碳钢体系在原油储罐沉积水中的防护机制。方法以实际原油储罐的沉积水为腐蚀介质,以自制石墨烯底漆和石墨烯面漆为防护涂层体系,采用交流阻抗谱、动电位极化曲线,结合盐雾实验探究石墨烯涂层体系在沉积水中的腐蚀行为和失效衍化机制。结果石墨烯底漆在浸泡初期对碳钢具有一定的防护效果,随着浸泡时间的延长,水分子逐渐渗透涂层,涂层逐渐失效。采用石墨烯面漆和石墨烯底漆搭配,可显著提高涂层对碳钢在沉积水中的防护性能,浸泡46 d后,涂层电阻仍为162 M?·cm。结论石墨烯底漆和石墨烯面漆涂层体系对储罐底板在沉积水中具有良好的防护性能,研究成果对油罐底板涂层防护选材具有理论指导意义。     

Corrosion protection by multilayered conducting polymer coatings

Multilayered coatings, consisting of combinations of the conducting polymers polyaniline (Pani) and polypyrrole (Ppy), were galvanostatically deposited on to both carbon steel and stainless steel. Potentiodynamic polarisation was used to assess the ability of these copolymers to provide an effective barrier to corrosion in chloride environments. For carbon steel the performance of these multilayered coatings on carbon steel were not sufficiently better than for single Pani coatings to justify their more complicated deposition procedures. However, in the case of stainless steels the new multilayered coatings proved to be significantly better than previously reported single Pani coatings, especially at protecting against pitting corrosion. It was found that the degree of protection was a function of the deposition order of the copolymer, with films consisting of a Pani layer over the top of a Ppy layer yielding the best results. Scanning electronic microscopy observations and adhesion measurements, along with the electrochemical data suggested that the ability of a conducting polymer film to act as electronic and chemical barriers were more important in providing corrosion protection than its ability to act as a physical barrier.     

本征态聚苯胺的防腐性能

研究了分散的颗粒状本征态聚苯胺(EB)对冷轧钢(CRS)的腐蚀防护作用，在去离子水或NaCl溶液的作用下，EB颗粒可在CRS表面形成一层致密的氧化物钝化层，该氧化物层使CRS的腐蚀电位升高了200mV，并显著降低了腐蚀电流密度．在3．0mass％NaCl溶液中，单独的EB膜稳定性较差，不能提供有效的防腐性能，分散在环氧树脂中的EB保持了EB的氧化-还原特性，这种涂层材料能使CRS钝化，具有极好的稳定性，因而可提供极好的防腐性能．EB的存在使环氧树脂涂层的阻隔作用下降，因此需要涂敷较好阻隔作用的面漆．在含有EB的环氧树脂涂层上涂覆具有良好阻隔作用的面漆，可显著提高其防腐性能．     

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.     

Wear and corrosion studies of Fe–B–Cr alloy coating on en 24 steel by HVOF thermal spray method

This work investigate the wear behavior of Fe–B–Cr coatings on medium carbon steel (EN24) substrate is used for several automotive parts. The high velocity oxy-fuel (HVOF) method was used to create the new crystalline coating of Fe–B–Cr (composition of 59%Fe–26%B–15%Cr in wt %) on a medium carbon steel substrate (AISI 4340). The characteristics of powder and coating are investigated using scanning electron microscopy (SEM) merged with energy dispersive spectroscopy (EDS), optical microscopy (OM) and thermogravmentric analysis (TGA) which were undertaken in the partial characterization of the coating. The phase contents of both powder and coatings were studied by X-ray diffraction (XRD). The coatings consist of melted and un-melted particles identified in the coatings. Moreover, oxides and micro-cracks were observed at the surface. The mechanical property of the coatings was characterized using a microhardness test. The hardness value increased three times more than the substrate. The coated surface showed lower levels of porosity. Moreover, the electrochemical investigation found Fe–B–Cr coating on medium carbon steel. The corrosion test was carried out in an environment with 0.5 M of NaCl, which showed that the corrosion resistance improved by coating.     

Enhanced corrosion protection by powder coatings on hot rolled steel (HRS) for high-temperature applications

Hot rolled steel (HRS) has long been a major product to the motor industry for bodywork, as galvanised steel (zinc coatings), and it is widely used in building and as tinplate (including tin and chrome oxide coatings) for food, etc. can-making. Among more specialist uses its moderate production costs makes it suitable for the manufacturing process. In this study, newly developed corrosion protection enhanced silicone based powder coating was evaluated on hot rolled steel (HRS). The powder coating in this study was developed to withstand high temperatures up to 550°C without any degradation. In the study silicone resin was incorporated with fillers, corrosion inhibitors and fibres at various compositions to achieve maximum heat resistance and improved corrosion resistance. Protective behaviours of the differently formulated powder paints were investigated before and after heat exposure. The developed paint system was evaluated using various test methods such as heat resistance, salt spray, Electrochemical Impedance Spectroscopy (EIS), adhesion test and microstructure study using SEM. The evaluation of test results revealed that powder coating combining zinc dust particles and mineral fibres have better performance due to better corrosion and adhesion stability in the corrosive environment before and after heat exposure up to 550°C.     

The corrosion behavior of zinc-rich paints on steel: Influence of simulated salts deposition in an offshore atmosphere at the steel/paint interface

The corrosion behavior of an epoxy zinc-rich paint on interface-contaminated carbon manganese-silicon steel was studied. SEM observation on the cross-section of the paint indicates that the zinc corrosion products grew from the surface to the inner of the paint and salts contamination promoted the growth at locations close to the steel/paint interface. The results of electrochemical impedance spectroscopy show that the corrosion resistance of the contaminated paint was significantly influenced by diffusion of zinc corrosion products during the initial stage of immersion, and diffusion of iron corrosion products at the end of immersion. Three transmission line models were applied to account for the corrosion process of the uncontaminated and contaminated zinc-rich paints.     

BTA@SPANI-POSS环氧涂层的制备及防腐性能

为提高环氧涂层在腐蚀环境下的防腐性和持久性,合成一种负载有缓蚀剂苯并三唑(BTA)的苯并三唑@磺化聚苯胺功能化倍半硅氧烷(BTA@SPANI-POSS),随后将 BTA@SPANI-POSS 与环氧树脂共混得到 BTA@SPANI-POSS 环氧涂料, 最后在 Q235 碳钢上制备数种复合环氧涂层。通过红外光谱、紫外可见光谱、扫描电子显微镜对 BTA@SPANI-POSS 的结构、 缓蚀性能、表面形貌进行表征,利用接触角测量仪、电化学工作站研究所制备涂层的疏水性能和防腐性能。研究表明,随着 SPANI-POSS 的添加,涂层沾湿性能降低。电化学阻抗谱(EIS)和塔菲尔极化曲线测试结果表明,与 SPANI-POSS 环氧涂层相比,负载有 BTA 的 BTA@SPANI-POSS 环氧涂层对金属基底具有更高和更持久的保护能力,其中试样 EB_1.5%的腐蚀电流密度 i_corr为 16.67 ? A·cm^?2 ,其极化电阻 R_p为 2.467 M?·cm² ,具有较低的腐蚀动态速率。在 3.5 wt.% NaCl 溶液中浸泡 15 d 后环氧涂层仍具有良好的防腐蚀效果,其阻抗值 Z_0.01Hz 仍保留有第 1 d 时的 26.89%,表现出优异的长期稳定性和防腐性能。归因于 SPANI-POSS 与 BTA 之间的协同作用,所制备的 BTA@SPANI-POSS 环氧涂层在浸泡过程中与碳钢基底发生络合反应,从而起到长时间的保护作用。     

Corrosion behavior of carbon steel coated with a zinc-rich paint containing metallic compounds under wet and dry cyclic conditions

The corrosion behavior of carbon steel coated with a zinc-rich paint containing two metallic compounds, Al₂(SO₄)₃ and CaO, as anticorrosive additives was examined under wet and dry cyclic corrosion test conditions. The zinc-rich paint coating without the two metallic compounds formed a white corrosion product and red iron rust on the surface after the corrosion test, whereas the coating with the metallic compounds showed reduced surface corrosion products. The corrosion current density of the painted steel substrate decreased drastically due to the incorporation of metallic compounds in the paint. The zinc-rich paint coating modified with the metallic compounds contained dispersed simonkolleite (Zn₅(OH)₈Cl₂·H₂O) phase and possibly very fine CaSO₄ particles, which remarkably improved the protectiveness of the zinc-rich paint coating.     

An electrochemical study of zinc-containing epoxy coatings on mild steel

A comparative electrochemical study has been carried out between conventional zinc-rich and novel zinc-containing paints. To study the cathodic protection performance of these coatings an assessment method based on a galvanic couple was employed. Current and potential were monitored with immersion time in 3.5% NaCl. The zinc-rich paint offered cathodic protection for about 7 days compared with 40 days for the new paint. However, the steel coupled with the zinc-rich remained corrosion free for a further period. This was probably due to the inhibitive effect of zinc salts deposited at the cathode. Thereafter a reversal in polarity was obtained once rust formed. Thus it is concluded that established cathodic protection criteria cannot be solely used to assess the protection properties of zinc-containing paints. Electrochemical impedance spectroscopy was also used to study the state of the coating with time. Diffusion parameters indicated that the new paints were covered with a lesser amount of corrosion products.     

Improvement of anticorrosion and adhesion to magnesium alloy by phosphate coating formed at room temperature

A new surface protection process was developed to magnesium alloy against corrosion in aggressive environments. Firstly, a phosphate coating was formed on rinsed magnesium alloy. Then, powder painting was carried out on the phosphated magnesium alloy. Surface morphologies and phase compositions of the phosphate coating were investigated by X-ray diffraction （XRD） and scanning electron microscope （SEM）. The results show that the phosphate coatings formed in bath containing earth additives at room temperature have dense and fine microstructure. The phosphate coating provides excellent paint adhesion to the magnesium alloy. Salt spray tests indicate that the corrosion resistance of the phosphate coating plus paint could meet the demand of magnesium alloy automobile components in aggressive environments.     

碳黑掺杂型导电有机涂层的防护机制

 利用碳黑掺杂的方法制备熔融结合环氧(FBE)导电涂层，选用电化学阻抗谱法(EIS)、热重分析(TGA)和差示扫描量热(DSC)等手段研究了其在3%NaCl溶液中失效过程及防护机制.结果表明:与相应的含有少量碳黑的绝缘FBE涂层相比,导电FBE涂层体系的防护性能显著提高,这得益于导电涂层中碳黑连续网络增加了腐蚀介质的传输阻力；对涂层保护下金属基材腐蚀形貌的分析均证明了此结论.   