Of polyaniline pdf

Click here to sign up. Download Free PDF. A short summary of this paper. Download Download PDF. Translate PDF. Box , D Ahrensburg, Federal Republic of Germany Abstract The anti-corrosion performance of polyaniline coated mild steel samples exposed to artificial brine and dilute hydrochloric acid environments was evaluated. Samples of mild steel UNS GlOlOO coated with polyaniline deposited from solution, and overcoated with an epoxy barrier paint, when scratched to expose precise areas of bare metal, exhibited corrosion rates in aqueous 3.

Mechanistic information, and quantitative corrosion rates were obtained by Tafel Extrapolation, Potentiodynamic Polarization, Galvanic Coupling and Electrochemical Impedance Spectroscopic techniques. These studies, in conjunction with surface analysis by ESCA and Auger techniques, indicate that the corrosion protection, even for exposed bare steel areas, occurs by the formation of passivating iron oxide y - Fez03 and Fe,04 surface layers. The formation of these specific oxide layers occurs when the polyaniline is galvanically coupled to the steel.

This is evident by the fact that the dimensions of the exposed bare steel area that can be protected in a scratch can be large, but are limited in each corrosion environment.

Passivation was found to occur by the formation of an oxide layer The possibility for anodic protection of steel and other on mild steel induced by contact with the polyaniline. This was metals was proposed over 10 years ago by MacDiarmid [l]. In evident by removal of the polyaniline layer which revealed a gray DeBerry [2] found that polyaniline electrochemically matted surface and persistent passivated behavior.

The electrochemical deposition of protection of mild steel provided by both doped and undoped PAni was preceded by the formation of a passive oxide layer on forms of polyaniline in brine solutions and in dilute hydrochloric the steel surface.

The doped PAni layer in electrochemical acid. We were especially interested in characterizing the contact with the steel stabilized the passive oxide layer against mechanism of protection, if any, in exposed bare steel areas dissolution and reduction. More recent studies by Troth-Nagels scratches on coated samples.

It was also our intent to et al [3] on the electrochemical deposition of PAni and quantitatively characterize the levels of corrosion protection, as polypyrrole on mild steel showed that PAni provided no well as determine the limiting dimensions of a scratch in the corrosion resistance, but polypyrrole did. Sekine et al [4] also coatings that would be passivated under the various corrosion found that electrochemically deposited PAni provided very little conditions.

Neutral ef al [6] for samples solution coated with polyaniline. Wessling urea [9] or NMP. The polyaniline coatings were allowed to dry [7] just recently reported that mild steel, stainless steel, and in air at room temperature for several days. Experiments in copper were all found to passivate by repeatedly dipping clean which doped polyaniline was used, the coated samples were surfaces of the metals into dispersions of doped polyaniline exposed to an aqueous solution of p-toluene sulfonic acid VersiconTM [S].

Lu et al. All the corrosion cell configuration shown in Figure 1 with the samples were then topcoated with a curable epoxy resin Ciba- exposed steel area located in the center of the cell. To study the measurements were made on the samples during the test period. It can be seen that of layers in each sample exposing clean metal surfaces no oils were the samples exposed to HCI, the samples containing polyaniline used.

Control samples were prepared as above but without the were considerably protected against corrosion rust. For the polyaniline layer. The initial corrosion which severely corroded within a few hours.

Electrochemical Impedance measurements were carried out O. Table 2 lists corrosion potentials at various I Working electrode steel times for samples exposed to the two test environments.

Several interesting features are evident: 1 in all cases, except the sample Figure 1. The first those in NaCl showed shifts to more active potentials with sample configuration was a mild steel coupon coated only with exposure time.

While these measurements indicate potential epoxy paint. A hole 1. These films could be easily peeled off the glass substrate. Films cast from hexafluoroisopropanol were covered by a Petri-dish in order to allow for a slow evaporation of the solvent at room temperature.

Deprotonation process Several methods were used to deprotonate the PN. After the deprotonation process, all powder samples were dried at room temperature -4 under vacuum 10 mbar for 24 h.

DC electrical conductivity was measured by the standard four-point method. Since PN-salt films are hydroscopic, films were stored under dynamic vacuum until the conductivity measurements. The thickness of the films was measured by a Tencor Instruments Alpha step profilometer. Prior to spectroscopic measurements, all solutions were diluted with an appropriate amount of solvent in order to adjust the absorption of the sample to a level of between 0 and 2.

Absorption spectra were obtained using quartz cuvettes and pure solvents were used as the reference. IR spectra display several characteristic peaks that are associated with the reduced, half oxidized, and fully oxidized form of PANI respectively. Major differences in the spectra of PNB and EB are observed in the region between -1 -1 cm and cm. The same feature was observed previously for oxidized aniline oligomers [12,13]. Earlier studies have also suggested that the IR -1 -1 absorption modes at about cm and cm are associated with aromatic ring -1 stretching.

Tang et al. Furthermore, these two bands in PNB are slightly shifted about 10 -1 cm to lower frequency when compared to EB. Leucoemeraldine does not absorb at this frequency, in contrast to the emeraldine and pernigraniline forms. However, this absorption in PNB is split into two peaks at -1 -1 -1 cm and cm ; additionally a broad band centered at cm appears. A new peak appears at around cm that is interpreted as the C-H in plane bending of the ring [17].

In summary, the spectrum of the PNB prepared in the present work is in good agreement with the one reported by Epstein et al. The spectrum of PNB shows absorption bands centered around nm 2. For EB, only two peaks are observed at nm 1.

These values are in close agreement with the results of MacDiarmid et al. However, both films are green and exhibited identical absorption spectra, characteristic of the protonated EB form.

These results suggest that PN. CSA 1. However, when cast from formic acid, PN. We also noted that PNB and PN salt films prepared from formic acid have a semicrystalline character, as clearly evidenced by the wide angle X-ray diffractograms of these films. Table 1 summarizes the room temperature electrical conductivity data for protonated forms of EB and PN. It should be pointed out that, as previously reported [21], the conditions of film preparation strongly affect the final conductivity.

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