Conductivity and anticorrosion performance of polyaniline/zinc composites: Investigation of zinc particle size and distribution effect

Polyaniline/zinc composites and nanocomposites were prepared using solution mixing method. Zinc (Zn) particles with an average particle size of 60 μm and zinc nanoparticles with an average particle size of 35 nm were used as fillers in polyaniline (PANI) matrix. Films and coatings of PANI/Zn composites and nanocomposites were prepared by the solution casting method. Electrical conductivity and anticorrosion properties of PANI/Zn composite and nanocomposite films and coatings with different zinc loadings were evaluated. According to the results, electrical conductivity and anticorrosion performances of both PANI/Zn composites and nanocomposites were increased by increasing the zinc loading. Also results showed that the PANI/Zn nanocomposite films and coatings have better electrical conductivity and corrosion protection effect on iron coupons compared to that of PANI/Zn composite.     

Enhanced corrosion protective coating based on conducting polyaniline/zinc nanocomposite

Conducting polyaniline (PANI) is being explored as promising material for protection of metals against corrosion. It has the possibility of making smart coatings on metals, which can prevent corrosion even in scratched areas where bare metal surface is exposed to the aggressive environment. However, PANI coatings have poor barrier and mechanical properties. The barrier property of coatings can be enhanced by the addition of appropriate filler particles. Also it has been demonstrated that nanoparticulate fillers give much better barrier properties even at lower concentrations. In this study, the effect of zinc nanoparticles on the anticorrosive property of PANI coating on iron samples has been investigated. The PANI/Zn nanocomposite was synthesized by in situ polymerization of aniline in the presence of Zn nanoparticles. The nanocomposite was characterized by using FTIR, conductivity measurement, cyclic voltammetry, and AFM techniques. Results showed that PANI/Zn nanocomposite coating has improved corrosion protection effect when compared with pure PANI coating. The corrosion current of PANI/Zn coated samples were found to be much lower than that of pure PANI coated samples. The results were referred to the good barrier properties of Zn nanoparticles and improvement in electrochemical corrosion protection of PANI coating in the presence of Zn nanoparticles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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。     

Aminic epoxy resin hardeners as reactive solvents for conjugated polymers: polyaniline base/epoxy composites for anticorrosion coatings

Polyaniline (PANI) has much been studied in the context of corrosion prevention, particularly on steel and aluminium. To prepare epoxy coatings consisting of PANI has turned to be nontrivial, due to its relatively rigid conformation and poor solubility. Therefore, as the aim has typically been first to dissolve PANI in the epoxy component before curing, auxiliary solvents have been required, and less attractive Lewis-type hardeners have been required if the conducting salt form has been used. In this work, we describe a particularly simple concept where emeraldine base (EB) form of PANI is first dissolved in specific aminic hardeners which are observed to be solvents for EB at low concentrations, and the mixtures are unconventionally cross-linked upon adding epoxy resin, diglycidyl ether of bisphenol-A (DGEBA). Suitable hardeners are N,N,N′,N′-tetrakis(3-aminopropyl)-1,4-butanediamine (DAB-AM-4) and trimethylhexanediamine (TMDA). Even if the subsequent cross-linking promotes phase separation, the forming cross-link sites may also control the phase separation. As a result, sufficiently homogeneous coatings are identified which contain only 1 wt% EB in the cured EB/DGEBA/TMDA composites where in aqueous 3.5% NaCl solution the corrosion front propagation is suppressed, and electrochemical impedance studies indicate the formation of a charged interface or reaction product layer between EB and steel. For reference, similar net EB/DGEBA/TMDA-compositions were prepared, where EB was first mixed in DGEBA without any solubility and which were cured by added TMDA, and they gave essentially no anticorrosion effect. We expect that the present concept opens new ways to prepare cured epoxy composites also with other conjugated or nonconjugated polymers for anticorrosion and other functional purposes.     

Anticorrosion efficiency of zinc-filled epoxy coatings containing conducting polymers and pigments

The dependence of the corrosion-inhibiting properties of zinc-filled organic coatings on the nature of the conducting polymers and conducting pigments added and on the pigment particles’ surface coating with conducting polymer layers were investigated. The following materials were selected to examine the corrosion-inhibiting properties of the conducting polymers: polyaniline phosphate (PANI), polypyrrole (PPy), natural graphite, and carbon nanotubes. Conducting pigment combinations for application in coating materials were formulated by applying pigment volume concentrations (PVC) of 0.3%, 0.5% and 1%, which were completed with Zn dust to obtain pigment volume concentrations/critical pigment volume concentrations (PVC/CPVC) = 0.64. Such conducting pigment/zinc dust combinations represented corrosion inhibitors to be used as ingredients in protective coatings. Solvent-based 2K epoxy resin based coating materials containing the corrosion inhibitors so formulated were prepared to examine their anticorrosion properties. The pigmented coatings were subjected to laboratory corrosion tests in simulated corrosion atmospheres and to standardized mechanical resistance tests. The protective coatings so obtained exhibited a higher efficiency than coating materials containing zinc dust alone. The coating material containing carbon nanotubes at PVC = 1% and the coating material containing graphite coated with polypyrrole (C/PPy) at PVC = 0.5% emerged as the best zinc-filled coating materials with respect to their corrosion-inhibiting efficiency. Treatment with the conducting polymers had a beneficial effect on the coating materials’ mechanical properties.     

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.     

Investigation of corrosion protection performance of epoxy coatings modified by polyaniline/clay nanocomposites on steel surfaces

In this study, polyaniline (PANI) and polyaniline/clay nanocomposites were prepared via in situ oxidative polymerization. The morphology of nanocomposites structures was investigated by X-ray diffraction (XRD). The chemical structures of PANI and PANI/clay nanocomposites were examined via Fourier transform infrared (FT-IR) spectroscopy. Polyaniline-based pigments were introduced into epoxy paint and applied on steel substrates. The effect of clay addition and the type of clay cation, including Na⁺ in natural clay (MMT) and alkyl ammonium ions in organo-modified montmorillonite (OMMT), on the anticorrosion performance of epoxy-based coatings was investigated through electrochemical Tafel test, electrochemical impedance spectroscopy and immersion measurements in NaCl solution. The stability of the adhesion of the neat and modified epoxy coatings to the steel surface was also examined. The results indicated that introduction of PANI/OMMT nanocomposite into epoxy paint results in improved anticorrosion properties in comparison with PANI/MMT and neat PANI.     

SiAlON nanoparticles effect on the corrosion and chemical resistance of epoxy coating

Effect of incorporating SiAlON nanoparticles at different loading levels (0?C12?wt%) on chemical resistance of epoxy coating was investigated by immersion in basic (Na₂CO₃, pH?=?11) and salty (NaCl 3.5?wt%) (environments at 85?°C for 60?days. Epoxy resin chemical resistant coating grade based on bisphenol A was used with polyamine hardener as a curing agent. In these testes, surface morphology changes of the samples were studied and compared owing to initiation and propagation of cracks. Results indicate an enhancement in the epoxy nanocomposite chemical resistance due to the addition of small fraction of SiAlON nanoparticles. Samples containing 3 and 5?wt% of SiAlON nanopowders were considered as optimum samples compared to all the other samples, because they showed more resistances to initiation and propagation of cracks and lower permeability in chemical environment in comparison with neat resin and other samples. Also, epoxy coatings containing SiAlON nanoparticles were successfully coated on steel substrates and corrosion electrochemical behavior of these nanocomposite coatings were characterized by electrochemical impedance spectroscopy (EIS). The electrochemical monitoring of the coated steel over 35?days of immersion in 3.5?wt% NaCl solution at room temperature suggested the positive role of nanoparticles in improving the corrosion resistance of the coated steel.     

Preparation and anticorrosive properties of PANI/Na-MMT and PANI/O-MMT nanocomposites

Nanocomposites of polyaniline (PANI) with organophilic montmorillonite (O-MMT) and hydrophilic montmorillonite (Na-MMT) were prepared. The nanocomposites were characterized using FT-IR, D.C. electrical conductivity measurement and cyclic voltammetry techniques. It was found that PANI/Na-MMT nanocomposite has lower (5.8%) and PANI/O-MMT nanocomposite has higher (29.4%) conductivity compared to pure polyaniline. Cyclic voltammetry experiments showed that both nanocomposites are electroactive. The anticorrosive properties of a 100 μm thickness coating of nanocomposites on iron coupons were evaluated and compared with pure polyaniline coating. According to the results PANI/MMT nanocomposites have enhanced corrosion protection effect in comparison to pure polyaniline coating. Results showed also that the PANI/Na-MMT and PANI/O-MMT nanocomposites have considerably different corrosion protection efficiencies in various corrosive environments.     

Preparation,characterization and anticorrosive properties of a novel polyaniline/clinoptilolite nanocomposite

Nanocomposite of polyaniline (PANI) with natural clinoptilolite (Clino) was prepared. Formation of nanocomposite and incorporation of polyaniline in the clinoptilolite channels was confirmed and characterized using FTIR spectroscopy studies, X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and cyclic voltammetry techniques. The anticorrosive properties of a 20 μm thickness coating of PANI/Clino nanocomposite with various weight ratios (1, 3 and 5%, w/w) of clinoptilolite content on iron coupons was evaluated and compared with pure polyaniline coating. According to the results in acidic environments PANI/Clino nanocomposite has enhanced corrosion protection effect in comparison to pure polyaniline coating. Comparative experiments revealed that PANI/Clino nanocomposite with 3% (w/w) clinoptilolite content has the best protective properties. Further experiments showed that the PANI/Clino nanocomposite has considerably different corrosion protection efficiencies in various corrosive environments.     

New approach for simultaneous enhancement of anticorrosive and mechanical properties of coatings: Application of water repellent nano CaCO3–PANI emulsion nanocomposite in alkyd resin

New alkyd coatings were prepared by addition of water-based polyaniline–4% CaCO₃ (PAC) nanocomposites into alkyd resin. Pure polyaniline (PANI) and PAC were synthesized using ultrasound assisted emulsion polymerization and added to alkyd resin to form nanocomposite coating. Nano CaCO₃ was added in different percentage ranging from 0% to 8% of monomer during the synthesis of polyaniline. XRD and TEM reveals that water repellent nano CaCO₃ is thoroughly dispersed in PANI matrix. The effect of PANI and PAC nanocomposite on mechanical and anticorrosion performance of alkyd coating was evaluated. An electrochemical measurement (Tafel Plots) shows that corrosion current I_corr was decreased from 0.89 to 0.03 μA/cm², when PAC nanocomposite was added to neat coatings. Positive shift of E_corr. also indicates that PAC nanocomposite acts as an anticorrosive additive to alkyd coating. Presence of water repellant nano CaCO₃ in PAC nanocomposite has exhibited dual effect, such as improvement in mechanical and anticorrosion properties. The experimental results have shown superiority of PAC nanocomposite over PANI when PAC nanocomposite added to alkyd coatings.     

Anticorrosion properties of smart coating based on polyaniline nanoparticles/epoxy-ester system

In this study, the anticorrosive effect of dodecylbenzenesulfonicacid-doped polyaniline nanoparticles [n-PANI (DBSA)] as a conductive polymer was investigated using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) techniques. Initially, the n-PANI (DBSA) were successfully synthesized via inverse microemulsion polymerization leading to the spherical nanoparticles with an average diameter less than 30 nm. Two coating systems including 1 wt% n-PANI(DBSA) blended epoxy ester (n-PANI(DBSA)/EPE) and neat epoxy ester (EPE) were coated on the carbon steal substrate. The anticorrosion performance of the prepared coatings was studied using EIS measurement in 3.5% NaCl solution during 77 days. The experimental data was modeled using Zview software according to the appropriate equivalent circuit model. The results clearly showed the better corrosion protection of the n-PANI(DBSA)/EPE coating compared to the EPE coating. This behavior was attributed to the ability of n-PANI(DBSA) in releasing dopant anion when the corrosion process is initiated on the metal substrate emphasizing the smart protection of n-PANI(DBSA)/EPE coating. Accordingly, the released dopant anions along with the iron cations provide a secondary barrier layer, which passivates the substrate.     

Self-healing and anticorrosive properties of Ce(III)/Ce(IV) in nanoclay–epoxy coatings

The self-healing and anticorrosion effects of cerium nitrate in epoxy–clay nanocomposite coatings systems were studied. Different amounts of cerium (III) were added to epoxy–montmorillonite clay composites and the nanocomposite coatings were prepared and applied on cold rolled steel panels. Ultrasonication was applied to disperse the nanoclay into the epoxy cerium nitrate composition. Electrochemical impedance spectroscopy (EIS) was used to study the self-healing and anticorrosion behaviors of the coatings. The structure of the dry coating and the protective mechanism of the pigments in the coating were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) analysis and field emission electron microscopy (FESEM). Transmission electron microscopy (TEM) illustrated the separation of clay layers which interacted with the epoxy resin. Electrochemical impedance data indicated that the epoxy cerium (III)–montmorillonite nanocomposite coatings were superior to the epoxy coatings in corrosion protection properties. The self-healing behavior of such coatings was due to the presence of cerium nitrate that could be released at the defects within the coating and hindered the corrosion reactions at the defective sites. It was shown that the best corrosion protection was achieved with nanocomposite coatings containing 4 wt% clay and 2 wt% cerium nitrate.     

Preparation of epoxy–clay nanocomposite and investigation on its anti-corrosive behavior in epoxy coating

An epoxy–clay nanocomposite was synthesized using a quaternary ammonium-modified montmorillonite clay and diglycidyl ether of bisphenol A (DGEBA) type epoxy resin, in order to produce anti-corrosive epoxy coating. Anti-corrosive properties of the nanocomposite were investigated using salt spray and electrochemical impedance spectroscopy (EIS) methods. The results showed an improvement in the barrier and anti-corrosive characteristics of epoxy-based nanocomposite coating and a decrease in water uptake in comparison with pure epoxy coating. Wide-angle X-ray diffraction (WAXD) patterns and transmission electron microscopy (TEM) analysis showed that the interlayer spacing of clays increased after addition of epoxy resin along with applying shear force and ultrasound sonicator. The best performance of this coating was achieved at 3 and 5 wt.% clay concentration.     

The performance of epoxy coatings containing polyaniline (PANI) nanowires in neutral salt,alkaline, and acidic aqueous media

PANI/epoxy coatings have great promise applications in the industry as the metal corrosion protection coating, and their performance directly determines the life span of the coating and equipment durability. In this study, the performance of epoxy coatings with and without PANI nanowires immersed in 12 wt% NaCl, 5 wt% HCl, and 5 wt% NaOH solutions at different temperature were investigated for the first time. The performance and the degradation reactions of the coating cooperated with PANI nanowires were characterized by the variety of techniques and methods, including ultraviolet–visible spectrophotometry (UV–vis), field emission scanning electron microscopy (SEM), Attenuated Total Reflectance-Fourier transform Infrared spectroscopy (ATR-FTIR), and thermogravimetric analysis (TGA). The experiment results indicated that the failure mechanism of the different coatings varied with the different temperatures and solutions. Electrochemical impedance spectra (EIS) results showed that an appropriate content of PANI nanowires improve the protection performance of epoxy coatings in 12 wt% NaCl, 5 wt% HCl, and 5 wt% NaOH solutions, which is attributed to the passivation ability and shielding effect of PANI nanowires.     

Studying the influence of nano-Al2O3 particles on the corrosion performance and hydrolytic degradation resistance of an epoxy/polyamide coating on AA-1050

The aim of this work was studying the effects of addition of Al₂O₃ nanoparticles on the anticorrosion performance of an epoxy/polyamide coating applied on the AA-1050 metal substrate. For this purpose, the epoxy nanocomposites were prepared using 1, 2.5 and 3.5 (w/w) pre-dispersed surface modified Al₂O₃ nanoparticles. Field-emission electron microscope (FE-SEM) and ultraviolet–visible (UV–Vis) techniques were utilized in order to evaluate the nanoparticles dispersion in the epoxy coating matrix. The anticorrosion performance of the nanocomposites was studied by electrochemical impedance spectroscopy (EIS) (in 3.5 wt% NaCl solution for 135 days immersion) and salt spray test for 1000 h. The coating resistance against hydrolytic degradation was also studied by optical microscope and Fourier-transform infrared spectroscopy (FTIR). Results obtained from FE-SEM micrographs and UV–visible spectra showed that the nanoparticles dispersed in the coating matrix uniformly with particle size less than 100 nm even at high loadings. Results revealed that nano-Al₂O₃ particles could significantly improve the corrosion resistance of the epoxy coating. Nanoparticles reduced water permeability of the coating and improved its resistance against hydrolytic degradation.     

Investigation on the anticorrosion,adhesion and mechanical performance of epoxy nanocomposite coatings containing epoxy-silane treated nano-MoO3 on mild steel

Abstract

The effect of introducing MoO₃ (Molybdenum oxide) nanoparticle in the epoxy coating was analyzed by EIS and SECM methods in natural seawater. The aminopropyl triethoxy silane (APTES) was treated with the nanoparticle for the proper dispersion and chemical interaction of nanoparticle with the epoxy resin. The introduction of MoO₃ nanoparticle in the epoxy coating enhances the charge transfer resistance (R_ct) as well as the film resistance (R_f). The observation of iron dissolution and oxygen consumption was carried out by applying the appropriate SECM tip potential in the MoO₃ modified nanocomposite coated steel. The epoxy and epoxy-MoO₃ nanocomposite-coated samples were used to study the mechanical, adhesion and anticorrosion properties. The analysis using SEM/EDX displayed that the enriched Mo was detected in the nanocomposite coated steel. The presence of the nano level corrosion product containing Mo was confirmed by FIB-TEM analysis. The high corrosion protection properties of the epoxy based nanocomposite coating was due to the complex nanoscale layer formed and chemical interactions of epoxy resin with surface-modified nanoparticle in nanocomposites.     

The effect of mixture of mercaptobenzimidazole and zinc phosphate on the corrosion protection of epoxy/polyamide coating

The protective performance of solvent-borne epoxy/polyamide coatings formulated with zinc phosphate anticorrosion pigment was improved through the addition of 2-mercaptobenzimidazole as an organic corrosion inhibitor. In addition to determining the optimum percentage of mercaptobenzimidazole, the electrochemical impedance spectroscopy data could show the influence of inhibitor concentration on the epoxy behavior within 35 days of immersion in 3.5 wt% NaCl solution. The improved corrosion protection and adhesion strength in the presence of the pigment and inhibitor were connected to the deposition of a protective layer at the coating/substrate interface which might limit active zones for electrochemical reactions. The precipitation was confirmed using electrochemical impedance spectroscopy, polarization curves and SEM/EDX surface analysis.     

Positive effect of the addition of polyaniline on the anticorrosive property of polyethersulfone two-layer composite coating

In order to prepare a coating with better corrosion resistance, the double-layer coatings are designed to work together in this article. The double-layer coatings are made of polyethersulfone and epoxy resin as the matrix resin. Polyaniline (PANI) of different contents was added to the matrix resin by weight to form the primer coats, which was named as d-0, d-20, d-40, d-60. And polytetrafluoroethylene was introduced into the matrix resin to prepare the surface coats. A two-layer coating was prepared by coating the surface layer on the primer layer, named as S-0, S-20, S-40, S-60. The surface morphology of the primer coatings and the cross section morphology of the two-layer coatings were determined by field emission scanning electron microscopy. The anticorrosion property of the coatings was studied by water absorption, adhesion, salt spray corrosion acceleration test and electrochemical impedance test. The results indicate that the 40 wt% PANI composite coating shows the best corrosion resistance.     

Preparation and characterization of a novel conducting nanocomposite blended with epoxy coating for antifouling and antibacterial applications

In this study, novel epoxy-based paint was synthesized to be applied on carbon steel. The composition of the paint mainly contains epoxy mixed with an electronically conductive polymer, polyaniline (PANI), alone and combined with its nanocomposite derivation containing ZnO nanorods as an additive. The antifouling properties of the paint applied on carbon steel were investigated. The conductive nanocomposite was synthesized by an in situ chemical oxidative method of aniline in the presence of ZnO nanorods and then well characterized. The antifouling behavior was evaluated for 9 months in the Caspian Sea and Persian Gulf. Results revealed that epoxy/PANI–ZnO nanocomposite coating can prevent accumulation of marine macroorganisms on the coated panel. In addition, the epoxy coating comprising PANI–ZnO nanocomposite as well as the epoxy/ZnO coating exhibit significant antibacterial characteristics against (E. coli and S. epi). We interpret the antifouling and antibacterial behavior of the paint with (i) the presence of emeraldine salt structure in PANI which develops a surface pH in a range of 4–5 preventing the adhesion of microorganisms on the surface and (ii) the antibacterial and antifouling properties of zinc oxide nanorods that occurred by the production of hydrogen peroxide on the surface of the coating.