Electro-Synthesis of Nano-Colloidal PANI/ND Composite for Enhancement of Corrosion-Protection Effect of PANI Coatings

The polyaniline/nanodiamond (PANI/ND) nanocomposite coating was prepared on mild steel via electrochemical polymerization using cyclic voltammetry technique. The ultrasonic irradiation was used for effectively dispersing ND particles in electropolymerization solution. The prepared nanocomposite films were found to be nano-colloidal, and very adherent with low porosity. The corrosion performance of the coatings was investigated in 0.5 M H₂SO₄ solution by electrochemical impedance spectroscopy and polarization methods. The obtained results showed that the presence of ND particles significantly enhanced the corrosion protection performance of the PANI films in 0.5 M H₂SO₄ corrosive medium. X-ray diffraction and FT-IR techniques confirmed the intercalation of the nanoparticles in PANI matrix.     

Comparison study on anticorrosion performances of the epoxy coatings with two different nano‐polyanilines for Q235 steel

Sulfuric acid doped nano‐polyaniline was prepared by direct mixed oxidation in two different systems. A novel approach for preparing polyaniline (PANI) in FeCl₂/H₂O₂ system was developed. The PANI possessed an excellent dispensability. Corrosion protection of epoxy coatings containing two kinds of polyaniline (PANI) on Q235 steel was studied by electrochemical impendance spectroscopy (EIS) technique and Tafel polarization test in 3.5 wt% sodium chloride (NaCl) aqueous solution. The results indicated that the epoxy coating containing PANI obtained in FeCl₂/H₂O₂ system had the best performance of the corrosion protection among three systems under investigation. The possible protective mechanism of PANI was discussed.     

Corrosion inhibition of aluminum alloy in chloride mediums by undoped and doped forms of polyaniline

Corrosion inhibition of Al 3003 alloy by pure undoped PANI (emeraldine base) and PANI doped with p-toluene-sulfonic, camphorsulfonic and dodecylbenzenesulfonic acids was investigated. Corrosion resisting properties of PANI coatings with an artificially created hole defect were evaluated by electrochemical impedance spectroscopy (EIS) in aqueous 3.5% NaCl and 0.1 N HCl solutions. The highest corrosion inhibition factor was obtained for undoped PANI being equal to 12 and 4.4 in neutral and acidic media, respectively. The results indicated that corrosion protection of the bare aluminum alloy surface resulting from a defect of the PANI coating is in line with an increase of the thickness of the oxide layer protecting the aluminum alloy surface. The efficiency of corrosion protection of mild steel and aluminum alloy by polyaniline coatings was compared.     

Application of polyaniline to galvanic anodic protection on stainless steel in H2SO4 solutions

A stand-alone polyaniline (PANI) film electrode was made and then applied to protect 1Cr13 stainless steel (a type of stainless steel typically used in China, 0–15% C, 13% Cr) from corrosion in highly acidic solution, up to 5 M H₂SO₄. The stand-alone PANI electrode and 1Cr13 were coupled to study their galvanic interactions. PANI is a cathode while 1Cr13 is an anodic. The results indicate that PANI with a certain area can quickly passivate the stainless steel and effectively maintain the steady passive state for a long period of time. This specific method of PANI preventing 1Cr13 from corrosion is called galvanic anodic protection (GAP). Moreover, the efficiency, mechanism, and security of GAP were discussed. The results demonstrate that the stand-alone PANI electrode may have a potential application to galvanic anodic protection on stainless steel in highly corrosive H₂SO₄ solutions.     

Effect of current density on the corrosion protection performance of polyaniline coated AISI 4140 steel

The present work reports on electropolymerisation of aniline onto AISI 4140 steel substrate at room temperature in oxalic acid media by the potentiodynamic electrodeposition method. The effect of coating current density on the morphology of conductive polymer films and their corrosion behaviour has been investigated. The electrolyte solution comprised 0.1 M aniline?+?0.3 M oxalic acid. The effects of deposition current density changes (0.1, 0.2, 0.3, 0.4 and 0.5?mA cm^?2) on the films were investigated. The PANI film was characterised using cyclic voltammetry and optical microscopy; it was covered with a dark green-yellow homopolymer film of strongly adherent homogeneous characteristic. The corrosion behaviour of steel electrodes with and without polyaniline (PANI) film in 3.5 wt-% NaCl solution was investigated through anodic polarisation curves. The results indicated that the PANI coating obtained under 0.2?mA cm^?2 was the most corrosion protective.     

Electrically conducting nylon 6,6–polyaniline short composite fibres synthesised by the solvent coagulation method

Polyaniline (PANI) was blended with nylon 6,6 in concentrated H₂SO₄ and HCl solutions. The solvent coagulation method was utilised to extract short composite fibres of a centimetre in length. A solution of n-butyl acetate, acetone, toluene, 1 μM HCl and chloroform were used as coagulating bath to extract the fibres. The diameters of the fibres ranged from 200 to 300 nm, while the length measured approximately 1 cm, as determined from Scanning Electron Microscopy (SEM). The electrical conductivity varied from 10⁻⁴ to 10⁻² S/cm for different mass fractions of PANI (x_PANI) in the composite fibres. The percolation threshold was reached at x_PANI values between 0.15 and 0.2, and further addition of PANI resulted in saturation of the conductivity of the composite fibre. To observe the effect of MWCNTs on the electrical conductivity of the nylon–PANI fibres, 0.04 g, 0.08 g, 0.4 g and 0.5 g of MWCNTs (1, 2, 10, 12.5 weight percentage, respectively) were added into the nylon–PANI solution and were extracted as fibres in the aforementioned solvents. The electrical conductivity of the short fibres increased by an order of magnitude (0.372 S/cm at 12.5 wt.%) when they were extracted in the presence of the MWCNTs. PANI doped in concentrated HCl exhibited an electrical conductivity of 4.46 S/cm.     

A study on mechanism of corrosion protection of polyaniline coating and its failure

Polyaniline (PANI) coatings were electrochemically deposited on substrates of stainless steel and platinum in solutions of 0.2 M H₂SO₄ and 0.1 M aniline by cyclic voltammetry. The corrosion protection of the PANI coatings and their failure were investigated in 0.2 M H₂SO₄ solution. It was observed that the corrosion protection ability of the coating to steel substrate was increased with the increase of the coating thickness. The corrosion protection ability was mainly attributed to the passivating effect of PANI due to its oxidizing ability in its emeraldine state. During its operation, the PANI coating in emeraldine state tended to gradually lose its corrosion protection ability. This gradual failure of the PANI coating, but faster than expected, was confirmed to be related to a gradual reduction of the emeraldine PANI and a gradually increased resistance between the PANI coating and the stainless steel substrate. These findings lead to a new mechanism for the corrosion protection of PANI coating and its failure.     

Synthesis and characterization of Ag nanoparticles–polyaniline composite powder material

The chemical deposition of silver particles in polyaniline (PANI) powder has been carried out via the reduction of Ag⁺ ions by PANI in various concentrations of AgNO₃ aqueous solutions. It is found that the rate of Ag(I) reduction and the size of the metal particles incorporated were strongly dependent on the reaction medium, the PANI redox form and the stirring method used. Homogeneous distribution of silver nanoparticles into PANI matrix was obtained at low Ag(I) concentration, PANI in emeraldine base form and short reaction time under ultrasonic stirring. The presence of silver particles dispersed into porous polyaniline structures was confirmed using X-ray diffraction, scanning electron microscopy and cavity microelectrode (CME) technique in acidic aqueous electrolyte. The electrochemical study of Ag-PANI composite by CME showed that the redox system of silver depends on the size and the distribution of metal particles incorporated into PANI.     

One-Step Synthesis of the Polyaniline–Single-Walled Carbon Tubes Nanocomposite in Formic Acid and Its Electrochemical Properties

A one-step synthesis of a stable dispersion of nanocomposite consisting of polyaniline (PANI) and single-walled carbon nanotubes (SWCNTs) was carried out by the oxidative polymerization of aniline with benzoyl peroxide (PB) in concentrated formic acid (FA). Electrically conductive film coatings were obtained by direct application of this dispersion to an electrode. The coatings have high specific electrochemical capacitance and stability during prolonged cycling in an aprotic electrolyte (1 M LiBF₄ in γ-butyrolactone).     

Effects of electrolyte ph on the electrochemical behavior of Fe-based bulk metallic glass

The effects of electrolyte pH on the electrochemical behavior of Fe-based bulk metallic glass with a composition of Fe_68.8C_7.0Si_3.5B₅P_9.6Cr_2.1Mo_2.0Al_2.0 were investigated at an ambient temperature. The results indicate that corrosion behavior is strongly dependent on the pH values. The corrosion current densities and capacitance values decrease with an increase in pH values in acidic electrolytes, while the opposite tendencies are obtained in alkaline electrolytes. While the corrosion product of the outer layer in low pH conditions is an amorphous structure, crystalline ferric oxide is obtained in the electrolyte with pH=14. The electrochemical behavior is discussed on the basis of the results of electrochemical and microstructural analysis.     

Influence of tungstate ion dopants in corrosion protection behavior of polyaniline coating on mild steel

Electropolymerization of polyaniline (PANI) and polyaniline‐tungstate (PANIW) coatings on mild steel were successfully performed using cyclic voltammetry technique. Processes were carried out in aqueous electrolyte solutions of 0.3 M oxalic acid + 0.1 M aniline and 0.3 M oxalic acid + 0.1 M aniline + 0.001 M sodium tungstate dehydrate. Corrosion protection of PANI and PANIW coatings was evaluated with the help of open circuit potential (E_ocp) monitoring and electrochemical impedance spectroscopy (EIS) methods. All the results reveal the influence of additional doping agent (i.e., tungstate) in corrosion protection behavior of PANI coating.     

Electropolymerization of PANI coating in nitric acid for corrosion protection of 430 SS

A smooth and adherent polyaniline (PANI) coating was electropolymerized in HNO₃ solution by cyclic voltammetry in order to protect the ferritic and economic 430 stainless steel (SS) from corrosion. The corrosion resistance was evaluated in 3.5 wt.% NaCl solution by anodic polarization, potentiodynamic polarization, and electrochemical impedance spectroscopy. The PANI coating shifts the corrosion potential of SS to the passive region and provides a strong and steady corrosion resistance. A low growth rate leads to a compact PANI coating that acts as a good physical barrier. However, the strong corrosion inhibition is mainly attributed to the dense oxide layers formed by the catalytic effect of PANI at the polymer/metal interface. The composition of the oxide layers was analyzed via depth profiling using X-ray photoelectron spectroscopy alternating with sputtering. Compared with layers formed on uncoated SS, the iron and chromium oxide layers under the PANI are thinner and denser, absorbing less oxygen, and providing a stronger corrosion inhibition.     

Corrosion Protection of Mild Steel with Polyaniline–Thiokol Rubber Composite Coatings

The anti-corrosion performance of polyaniline-thiokol rubber (PANI/TR) composite coating applied to mild steel samples in artificial brine and hydrochloric acid environments is for the first time evaluated in this paper. The PANI/TR composite -coatings on mild steel were electropolymerized in a nonaqueous solution. EDS, XPS and SEM were concurrently used to characterize the structure, as well as composition of the coating and show that the structure is favorable to the corrosion protection. Both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that the PANI/TR coating outperforms PANI coating both in the adhesion to the substrate and its corrosion protection, making the free corrosion potential by about 100mV more positive. As a result, the mild steel corrosion was greatly impeded by applying PANI/TR composite conductive polymer coating.     

Effect of Aspergillus niger Tiegh. L-10 on the physical and chemical properties of a polyaniline coating in the growth substrate

The influence of the growth of Aspergillus niger Tiegh. fungi on the morphological, chemical and electrochemical properties of the polyaniline (PANI) modified Ni surface has been investigated. The strain of Aspergillus niger Tiegh. L-10 was cultivated on the malt extract agar (DIFCO OXOID). A PANI film was synthesized by potentiodynamic polymerization in an aqueous 0.3 M H₂C₂O₄ solution containing 0.1 M aniline on the Ni electrode. The electrochemical behaviour of polymer films was determined in a 0.05 M H₂SO₄ solution by the cyclic voltammetry method. The composition of PANI and Aspergillus niger Tiegh. treated PANI surfaces have been characterized using X-ray photoelectron spectroscopy (XPS). The morphology has been studied using scanning electron microscopy (SEM). The attachment of a polymer film via the metabolic product resulted in oxidation of the surface. It was estimated that at the PANI/microorganism interface, a Ca-complexed carboxylate interfacial reaction product was formed.     

Corrosion inhibition performance of polymer-alloy bilayer coatings: electropolymerised polyaniline and electrodeposited ZnNi with different layer orders

Polyaniline (PANI) conducting polymer coatings have been obtained galvanostatically with various current densities (from 0·1 to 0·4 mA cm^?2) and ZnNi alloy coatings have been obtained galvanostatically at 30 mA cm^?2 current density. Corrosion protection performances of monolayered PANI and ZnNi alloy coatings and multi-layered ZnNi/PANI and PANI/ZnNi coatings on st-37 low carbon mild steel (MS) have been investigated by an open circuit potential method, Tafel extrapolation method and electrochemical impedance method in 3·5 wt-% NaCl solution. In addition, the surface morphology of the coatings has been characterised by using scanning electron microscopy (SEM). Synthesising PANI films between two metal layers provided better corrosion protection to the steel. MS/PANI/ZnNi layer formation exhibited the biggest corrosion protection performance among all layer formations of the films and protected MS for up to 72 h.     

Using thionates for noise eperiments – a reasonable combination?

The detection of intergranular corrosion (IGC) initiation of austenitic stainless steel (AISI 347) coupon specimens was investigated using electrochemical noise (EN) measurements. The tests were performed in acidic sodium tetrathionate (Na₂S₄O₆) solution. The IGC initiation in tetrathionate solution could not be clearly detected by the electrochemical potential noise signal due to interferences of the noise signal with chemical processes which occurred in the test solution. This was confirmed by tests with inert platinum specimens. It was concluded that EN results obtained by tests in thionate or comparable sulfur containing solutions should be regarded with great care and verified, e.g., by tests with inert specimens.     

聚苯胺在防腐方面的研究及应用现状

聚苯胺(PANI)具有良好的热稳定性和环境稳定性,经掺杂后,具有导电性及电化学性,可作为填料应用于金属防腐领域。但其分子链骨架刚性强、分子间作用力大,不易加工成型,不溶于常规的有机溶剂,当其作为填料应用到防腐涂料中存在溶解性、分散性差且与金属基底附着力不强等缺点,如能对其进行合理有效的改性,则可解决上述问题。简要探讨了溶液聚合法、反相微乳液聚合法、模板聚合法以及电化学聚合法等PANI的制备方法,并针对PANI在防腐涂料应用中存在的问题,重点阐述了PANI的质子酸掺杂改性及复合改性等不同改性方法,通过掺杂不同的质子酸对PANI进行化学改性,可降低PANI分子链之间的相互作用,从而提高其溶解性、导电性和防腐性能。将不同性能的材料与PANI进行复合改性,改善分子间作用力,能提高其加工性,从而更好的应用于金属的腐蚀防护工作。最后介绍了PANI在腐蚀防护过程中的作用、在防腐蚀涂料中的应用及相关理论的研究现状,并指出PANI防腐涂层的研究重点和发展方向。     

Effects of cathodic electrodeposition parameters of cerium oxide film on the corrosion resistance of the 2024 Al alloy

Cerium oxide thin films obtained by cathodic electrodeposition on 2024 aluminium alloy have been studied. The coatings, obtained with electrochemical deposition, offer an effective corrosion protection and require a lower deposition time when compared to chemical conversion coatings. The coatings were obtained at room temperature by deposition from CeCl₃/H₂O₂ aqueous solutions and the influence of several parameters (CeCl₃ concentration, H₂O₂ concentration, deposition time, current intensity) on the corrosion resistance was studied. The composition, morphology and microstructure of the films have been characterized by SEM, XPS and AFM. The corrosion resistance was investigated through potentiodynamic tests in 3% NaCl solution.     

Electrical and morphological properties of PP and PET conductive polymer fibers

Conductive fibers were obtained using two experimental processes (melt spinning and coating process). In melt spinning process, polyaniline (PANI), polypyrrole (PPy) and graphite were used in order to obtain conductive polypropylene (PP) based fibers with specific electrical and mechanical properties. PANI was treated using dodecylbenzene sulfonic acid (DBSA) to improve the solubility and the dispersion of PANI in xylene. PANI coating on PET yarns were performed by absorption of yarns through PANI solution. The electrical resistance and morphological characteristics of conductive yarns were investigated. These yarns are supposed to be used to create smart clothing, corrosion protection or conductive fabrics for electromagnetic shielding applications.     

Open circuit potential transients and electrochemical quartz crystal microgravimetry measurements of dissolution of copper in acidic sulfate solutions

It is demonstrated that open circuit potential transients measurements are able to give the realistic and fast information on the rate of metal corrosion. The results of the studies of the rate of copper corrosion in naturally aerated unstirred acidic sulfate solutions obtained by this method are close to the results of electrochemical quartz crystal microgravimetry measurements. It was found that within the concentration range CuSO₄: 0.001-0.01 M, H₂SO₄: 0.005-0.5 M, independently of whether 0.1 M K₂SO₄ is present in the solution or not, the rate of corrosion of thin (about several tens monolayers) and fresh deposits of copper does not depend on the solution composition and is limited by the transport of the dissolved oxygen. The rate of corrosion of such deposits sometimes exceeds the rate of corrosion of compact copper samples.