Adhesion of electrochemically formed polypyrrole coatings to low carbon steel

The lap shear strength of polypyrrole coatings formed on low carbon steel (～ 23 MPa) is shown to be significantly higher (by ～ 60%) than that obtained using uncoated steel as the adherend. The lap shear (adhesion) strength of polypyrrole‐coated steel varied with the pH of the monomer–electrolyte solution and the applied current. The low carbon steel‐containing polypyrrole coatings formed at low pH (pH ≤ 2.4) have higher adhesion strength than those coated with polypyrrole at higher pH (pH ≥ 6.0). However, poly(N‐methyl pyrrole)‐coated steel showed significantly lower adhesion strength. Increasing the applied current density decreased the adhesion strength. The surface free energies of polypyrrole coatings, ～ 49–53 mJ/m² are similar to that obtained for uncoated low carbon steel, ～ 53 mJ/m², indicating that polypyrrole will effectively wet low rbon steel. The extent of wetting of low carbon steel by the coatings was additionally confirmed by an interaction parameter, ?, of unity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2757–2763, 2002     

Characterization of the passive inorganic interphase and polypyrrole coatings formed on steel by the aqueous electrochemical process

Polypyrrole coatings have been successfully formed on steel from aqueous oxalic acid‐pyrrole solutions by electrochemical polymerization. Formation of the coatings was found to be dependent on the pH of the reaction solution and the applied current. In acidic medium, the formation of polypyrrole was characterized by an induction (passivation) period before electropolymerization of pyrrole. At the end of the induction period, a crystalline passive interphase was formed. The morphology and composition of the electrodeposited passive interphase and the resultant polypyrrole coatings were investigated by scanning electron microscopy, reflection‐absorption infrared spectroscopy, and X‐ray photoelectron spectroscopy. Our results reveal that the chemical composition of the passive interphase was similar to that of iron(II) oxalate dihydrate, FeC₂O₄ · 2H₂O, crystals. Size and orientation of the crystalline passive interphase varied with electrochemical process variables. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2075–2086, 1999     

Synthesis and electrochemical evaluation of polypyrrole coatings electrodeposited onto AA-2024 alloy

Polypyrrole coating was successfully deposited on anodized 2024 unclad aluminum alloy showing that the presence of the anodic film is the key factor to ensure better adhesion to the polymer coating. Corrosion resistance of the conductive polymer layers grown for three and five cycles were evaluated in a 3 wt.% NaCl solution using polarization curves and impedance spectroscopy. It was found that the thermally treated polymer coating with higher thickness (five cycles) exhibited the best corrosion performance. This best coating shifts the corrosion potential towards nobler values, about 650 mV, and the exchange current density decreases two orders of magnitude regarding the anodic layer. The partial reduction of the structure of the polymer promoted by the thermal treatment plays a key role in the corrosion resistance of the coating allowing to the thermally treated polymer layer to act as a physical barrier against corrosion.     

Formation of stable passive film on stainless steel by electrochemical deposition of polypyrrole

Stable passive film has been formed on 304 stainless steel during the electrochemical deposition of polypyrrole (PPy) from sulfuric acid solution. The stability of passive film under PPy increases with aging in H₂SO₄ and this film has much higher resistance to pitting than that formed by anodic polarization under the same condition of aging. XPS studies indicate that the content of chromium components in the oxides under PPy layer is about twice that of the anodically formed passive film with larger value of the ratio Cr₂O₃/Cr(OH)₃. Higher content of iron with a ratio of Fe²⁺/Fe³⁺ more than unity is also observed with a considerable lower hydration and sulfate content in the oxides under PPy layer. It is suggested that sulfate ion is consumed as a dopant in the formation of PPy film and the oxidation of stainless steel is achieved under the environment of lower concentration of water and sulfate molecules. This may result in the enhancement of formation of corrosion-resisting oxides rather than hydroxides and sulfates.     

Growing spherical polypyrrole nanoparticles onto the magnetic carbon aerogel for improving electrochemical performance for supercapacitors

Journal of Porous Materials - In this work, hierarchical porous magnetic activated carbon aerogels (aCA)/polypyrrole (PPy) composites were synthesized by a facile and cost effective in situ...     

The effect of process parameters on the morphology of polypyrrole coatings formed on carbon fibers

Polypyrrole coatings have been electropolymerized onto carbon fibers. Several process parameters, including the type of electrolyte, the monomer concentration, the electrolyte concentration, the applied voltage, and the electropolymerization time were systematically varied, and their effect on the morphology and composition of the coatings assessed. The SEM micrographs of the coated samples revealed several distinguishable morphologies. The presence of the counterion, derived from the electrolyte, in the coatings was confirmed by EDAX analysis, elemental analysis, and infrared spectroscopy. The doping and formation of the polypyrrole coatings occurred concuriently. The morphology of the coatings was greatly influenced by the type of electrolyte, electrolyte concentration, and the applied voltage.     

Development of supercapacitor active composites by electrochemical deposition of polypyrrole on carbon nanofibres

In this study, pyrrole monomer is polymerized on carbon nanofibres (CNFs) via electropolymerization. This is a new technique to produce a chemically bonded CNF–polypyrrole composite. Deposition of the polypyrrole (PPy) on the nanofibres was optimized by varying the degree of deposition and deposition speed. Optimization studies have proven that the high deposition amounts result in blocks of polymers, which can be overcome through tuning the degree of polymerization by means number of cycles of electropolymerization and the scan rate of the electropolymerization.     

Inhibition of corrosion of mild steel by homopolymer and bilayer coatings of polyaniline and polypyrrole

Homopolymers and bilayers of polyaniline (PAni) and polypyrrole (PPy) coatings have been electropolymerized on mild steel by potentiodynamic synthesis technique in aqueous oxalic acid solutions. Characterization of coatings was carried out by cyclic voltammetry. Corrosion behavior of the polymer coated mild steel electrodes was investigated using linear anodic potentiodynamic polarization, Tafel test and electrochemical impedance spectroscopy (EIS) techniques in various aqueous corrosive solutions. Corrosion test results clearly showed that PPy and PAni/PPy bilayer coatings served as a stable host matrix on mild steel against corrosion. However, bilayers of PAni and PPy did not exhibit good combined properties of each polymer, unlike expected. PPy exhibited the best corrosion resistance among all coatings.     

Anticorrosive properties of polypyrrole films modified with zinc onto SAE 4140 steel

Polypyrrole (PPy) films modified with zinc were electrosynthesized onto SAE 4140 steel in presence of bis(2-ethylhexyl) sulfosuccinate (AOT). The Zn and PPy electrodeposition was realized by using cyclic voltammetry at different temperatures. The corrosion protection properties of the films were examined in chloride solution by open circuit measurements, linear polarization and electrochemical impedance spectroscopy (EIS). The obtained results indicate that the presence of Zn in the polymer matrix improves the anticorrosive performance of PPy films. The best anticorrosion efficiency was obtained for the coatings modified at 20 °C which provided anodic protection to the steel substrate for a long period of immersion in chloride solution. Cathodic protection was observed when the electrodeposition temperature was increased. Adherence and anticorrosive properties declined sharply for the coatings electrosynthesized at 5 °C.     

Nano-composite of polypyrrole/modified mesoporous carbon for electrochemical capacitor application

Nano-thin polypyrrole (PPy) layers were coated on chemically modified ordered mesoporous carbon (m-CMK-3) by an in situ chemical polymerization. Structural and morphological characterizations of m-CMK-3/PPy composites were carried out using field emission scanning electron microscopy. Pseudo-capacitive behavior of the deposited PPy layers on m-CMK-3 was investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. As results of this study, the thin layer of PPy in the composite electrode was effective to obtain fully reversible and very fast Faradaic reaction. A maximum discharge capacity of 427 F g⁻¹ or 487 F g⁻¹ after correcting for weight percent of PPy phase at the current density of 5 mA cm⁻², could be achieved in a half-cell setup configuration for the m-CMK-3/PPy composites electrode, suggesting its potential application in electrode material for electrochemical capacitors.     

Corrosion protection properties of polypyrrole electropolymerized onto steel in the presence of salicylate

The corrosion performance of a polypyrrole coating constituted by hollow rectangular microtubes was monitored in chloride solutions using open circuit potential measurements, potentiostatic polarization and electrochemical impedance spectroscopy. The coating was electrosynthesized onto 316 L stainless steel from a salicylate solution and it provided a very good corrosion resistance to the substrate. It was found that polypyrrole films with granular morphology electrodeposited from a salicylate solution with lower concentration behave better in terms of protective behavior. In order to improve the corrosion protection imparted by the polypyrrole coating formed by the microtubes a system of two layers was electrodeposited, the first one consisted of polypyrrole with a granular morphology and the second one, on the top, was constituted by the microtubes. This bilayered system exhibited an excellent protective behavior during considerably long immersion time.     

The corrosion protection of mild steel by single layered polypyrrole and multilayered polypyrrole/poly(5-amino-1-naphthol) coatings

Electrochemical synthesis of polypyrrole (PPy) and top coat of poly(5-amino-1-naphthol) (PANAP) on PPy films from oxalic acid solution was achieved on mild steel (MS) by cyclic voltammetry technique. The morphology and the structure of the films were investigated by scanning electron microscopy (SEM). The corrosion performance of this multilayer coating and single PPy coating were investigated in 3.5% NaCl solution by using open circuit potential (E_ocp)–time curves, polarization curves and electrochemical impedance spectroscopy (EIS). It was found that the multilayer PPy/PANAP coating could provide much better protection than single PPy coating for corrosion of MS. It was observed that corrosion performance of coatings was increasing with immersion period. This was explained by auto-undoping properties of PPy coatings during immersion in corrosive solution. The improved corrosion performance in the presence of PANAP top coat on PPy was explained by increase in barrier effect of bilayer films.     

Formation of Dy-Fe alloy films by molten salt electrochemical process

The electrochemical formation of Dy-Fe alloy films was investigated in a molten LiCl-KCl-DyCl₃ (0.50 mol%) system at 773 K. The deposition potential of Dy metal was 0.47 V (vs. Li⁺/Li) at a Mo electrode. Repetition of the potential sweep treatment at a fresh Fe electrode was effective in increasing the rate of formation of Dy-Fe alloys. Using an Fe electrode activated by repetition of the potential sweep treatment, a DyFe₂ film was formed by potentiostatic electrolysis at 0.55 V. However, the alloy film was thin and not adhesive. An adhesive DyFe₂ film was formed at the activated Fe electrode by potentiostatic anodic electrolysis at 0.55 V after cathodically electrodepositing Dy meal at 0.40 V. By using a similar procedure, Dy₆Fe₂₃ was formed at 0.68 V. The equilibrium potential for (2/11)Dy₆Fe₂₃+Dy(III)+3e⁻?(23/11)DyFe₂ was estimated as 0.62 V.     

Influence of Si nanoparticles on the electrochemical behavior of organic coatings on carbon steel in chloride environment

Scanning electrochemical microscopy (SECM) is an excellent technique to detect electrochemical processes with high spatial resolution. In this work, the effect of silicon (Si) nanoparticles on the corrosion protection performance of epoxy-coated steel was examined by electrochemical impedance spectroscopy (EIS) and SECM analysis. The EIS was performed in continuous immersion in 0.1?M NaCl_(aq) solution. The addition of Si nanoparticles increased the coating film resistance (R _f) and the charge transfer resistance (R _ct) of coated steel. SECM mapping and line scan analysis was performed in order to estimate the coating performance with Si nanoparticles in 0.1?M NaCl_(aq) solution. SECM results indicated that the tip current at ?0.70?V was decreased by the addition of Si nanoparticles in epoxy film. These results suggested that the dissolved oxygen (DO) was consumed by anodic dissolution of Si nanoparticles. Surface analysis showed that the Si was enriched at the scratched region of the coated steel after a corrosion test. From these results, Si was dissolved as Si ⁿ⁺ and transferred to the scratched area, and then consumed the DO in the solution. Thus, the anodic dissolution of Fe at the scratched area was suppressed by the Si nanoparticles, which implies the sacrificial effect of Si from the coating against the steel corrosion. Hence, it was concluded that the Si nanoparticles had a beneficial effect on enhancing the corrosion resistance of the coated steel.     

Fabrication of ZnO-functionalized polypyrrole microcomposite as a protective coating to enhance anticorrosion performance of low carbon mild steel

In the present work, PPy, ZnO, and polypyrrole/zinc oxide (PPy/ZnO) microcomposites (1, 2, and 5 wt%) were prepared and their properties have been tuned for anticorrosion applications on low carbon mild steel. The synthesized products: ZnO, PPy, and composites were characterized by various sophisticated analytical techniques such as XRD, FTIR, Raman, FESEM, EDX, UV–VIS, TGA, and BET. The band frequencies observed at 480 and 588 cm⁻¹ in FTIR spectrum correspond to stretching vibrations of Zn-O and N-H bonds, respectively, broadening of the bands in the composites indicate strong interactions between ZnO and PPy matrix. The potentiodynamic polarization study of PPy and PPy/ZnO composite was carried out in 3.5% NaCl solution to investigate the corrosion resistance efficiency. PPy/1 wt% ZnO (I_corr = 190 nA) composite coating on low carbon mild steel was observed to exhibit best corrosion protection property compared to PPy (121 μA), 2 and 5 wt% ZnO (242, 295 nA) composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48319.     

Room-temperature synthesis of single-wall carbon nanotubes by an electrochemical process

Single-wall carbon nanotubes (SWCNTs) were produced by an electrochemical route by applying a small negative potential to a solution of acetic acid over a Au surface supporting Ni nanocatalysts. Ni nanocatalysts were grown electrochemically on Au surface and their particle sizes were controlled by deposition time. Raman spectroscopy and scanning probe microscopy observations of the catalyst and as-deposited samples and revealed that the catalyst structure strongly affects the SWCNT diameter distribution. The deposited carbon structure depended on the catalyst particle size and structure. Raman spectra confirmed the existence of selectively grown semiconducting SWCNTs with very narrow diameter distribution.     

Facile preparation of functional and hybrid coatings by precipitations of polypyrrole and lysozyme via co-assembly process

The integration of biological matters and functional polymers to generate novel hybrids with multi-functional properties has attracted an increasing attention in organic/organic systems, possessing a great promise for sensor, medical, and materials science applications. In this work, a facile co-precipitation method was developed to prepare conductive composite via a co-assembly process with one-step. Lysozyme was employed as an assembly template, and the pyrrole monomers were polymerized and aggregated with the lysozyme nanoparticles via oxide polymerization, forming a hybrid and functional coating with significant conductivity of ca. 6.7 × 10⁻⁵ S. The structure and morphology of the hybrid is performed by X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, transmission electron microscopy, field emission scanning electron microscope, and laser scanning confocal microscope, and so on. The results showed that the coating was composed of homogenously and densely hybrid nanoparticles with the diameter of ca. 250 nm, possessing a certain degree of bio-adhesion from the lysozyme precipitations according to the 3 M peeling test. In addition, the composite performed good infrared radiation shielding property when it was coated onto normal gauze. It suggests that the composite consisting of lysozyme and polypyrrole precipitations in nanoscale may possess significantly potential applications as conductive and shielding materials.     

Study of the corrosion and inhibition processes of a carbon steel in a low conductivity medium by electrochemical methods

Ohmic drop corrected steady-state current—voltage curves and electrochemical impedance diagrams have been obtained for carbon steel rotating disc electrodes in 200 mg l⁻¹ NaCl solutions with and without addition of 1 g l⁻¹ of the association of oleylamino propylene and amino-tri[methyl-phosphonic] acid (FA + TMPA). Corrosion rates determined from both steady state and impedance data are in fairly good agreement with those determined from gravimetric measurements carried out on a semi-pilot scale circuit. Because impedance measurements are non-destructive and not affected by low electrolyte conductivity, they allow us to follow the evolution of the corrosion rate as a function of time: in the absence of inhibitor the corrosion rate increases during the early stages of immersion whereas it decreases in the presence of 1 g l⁻¹ (FA + TMPA). Impedance diagrams obtained in inhibited solutions reveal a high frequency loop unobserved in the absence of the inhibitor; the very low value (1–2 μF cm⁻²) of the capacity associated to this loop suggests that the inhibitor (FA + TMPA) acts in forming a relatively thick and compact protective film on the metal surface.