SEM image of polyaniline base. 

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... presence of both materi- als and the structure of each other. Figs. 3-5 respectively show the SEM images of polyaniline, clinoptilolite and PANI/Clino nanocom- posite. The SEM image of PANI/Clino nanocomposite (Fig. 5) shows that the orientation of polyaniline chains in the nanocomposite structure has increased in compare to the pure polyaniline (Fig. 3). The SEM image of clinoptilolite (Fig. 4) shows the layered structure of clinoptilolite with layer thicknesses in nanometer range (less than 100 nanometer). Also the SEM image of nanocomposite (Fig. 5) reveals that the size of polyaniline chains grown in clinoptilolite channels is in nanometer rage. ...

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... in an aqueous ammonia solution (1 M) under vigorous stirring for 4 h. The blue precipitate was filtrated and washed with 80/20 water/methanol solution until the under washing solution became neutral. Emeraldine base powder was finally obtained after the filtrate was dried in an oven at 50 ◦ C for 48 h. One gram of the emeraldine base form of polyaniline or its nanocomposite was added (over 5 h) to 40 ml of NMP solvent under magnetically stirred condition at room temperature for 7 h. It has been found that if the polyaniline powder was added too rapidly to the NMP, it tended to aggregate. The resulting viscous solution was filtered to remove any undissolved particles. Coating of iron samples by polyaniline or nanocomposite was carried out by cast- ing the viscous solution of polyaniline or nanocomposite in NMP (1 ml) on the surface of iron plates followed by drying in an oven at 50 ◦ C for 48 h. The PANI/Clino nanocomposite was characterized using FTIR technique. The characteristic peaks observed in the FTIR spectra of PANI/Clino nanocomposite give valuable information regarding to the conformation of polyaniline in the clinoptilolite channels and possible interaction between clinoptilolite and polyaniline chains. Fig. 1 shows the FTIR spectra of clinoptilolite, PANI/Clino nanocomposite base with 5% (w/w) clinoptilolite content and pure polyaniline as emeraldine base. FTIR spectra of PANI/Clino nanocomposite exhibits bands characteristic of polyaniline as well as of clinoptilolite which confirms the presence of both components in the PANI/Clino nanocomposite. In the PANI/Clino nanocomposite, the observed peaks for polyaniline were shifted to lower wave numbers which indicates complete interaction between polyaniline and clinoptilolite and also reveals the presence of physicochemical interactions, such as hydrogen bonding between clinoptilolite and polyaniline. Noticeable changes were observed for bands which are related to the structural OH vibrations in the region between 3500 and 3700 cm − 1 related to the bridging OH groups in Al–OH–Si and other hydrogen atoms on different oxygen atoms in the framework of clinoptilolite [22]. Changes in these regions indicate that there is complete coverage between polyaniline and OH groups existing in the intrachannels and extrachannels surfaces of clinoptilolite. In other word, because of the presence of OH groups in and outside of the channels in clinoptilolite structure, and regarding the complete disappearance of OH characteristic absorption peak in FTIR spectra of nanocomposite (Fig. 1), it can be concluded that there are complete interactions between all OH groups (in and outside of the clinoptilolite channels) and polyaniline chains and therefore polyaniline chains have grown in and outside of the clinoptilolite channels. X-ray diffraction is a versatile and non-destructive technique used for identification of the crystalline phases present in solid materials and for analyzing structural properties of the phases such as stress, grain size, phase composition, crystal orientation and defects. Therefore, X-ray diffraction patterns were recorded for clinoptilolite, polyaniline base and PANI/Clino nanocomposite base with 5% (w/w) clinoptilolite content (Fig. 2). For clinoptilolite the characteristic peaks were observed at 2 Â = 9.85 ◦ , 22.4 ◦ and 30.0 ◦ . Presence of these peaks in the XRD pattern recorded for PANI/Clino nanocomposite, confirms the presence of clinoptilolite in the nanocomposite composition. The intensity of the XRD pattern peaks can be influenced by crystallinity or by polyaniline chains order in nanocomposite structure. According to Fig. 2, XRD pattern of polyaniline suggests that it has relatively amorphous structure, but by encapsulation of polyaniline in the clinoptilolite channels, the alignment and arrangements of polyaniline chains were significantly improved and as a result, the intensity of the peaks related to the nanocomposite were increased (Fig. 2). It should be mentioned that the treatment of clinoptilolite in acidic medium (HCl 0.1 M) which was described in Section 2.3, not caused to the structural distortion of clinoptilolite because of the low concentration of acid solution (0.1 M). Also the comparison of XRD patterns of acid treated clinoptilolite (Fig. 2) and clinoptilolite which not treated with acid (Ref. [22]) shows no difference, and this confirms the non-destructive effect of acid treatment on clinoptilolite structure. Scanning electron microscopy (SEM) was used to investigate the surface morphology of polyaniline, clinoptilolite and PANI/Clino nanocomposite and evaluate the effect of presence of both materials and the structure of each other. Figs. 3–5 respectively show the SEM images of polyaniline, clinoptilolite and PANI/Clino nanocomposite. The SEM image of PANI/Clino nanocomposite (Fig. 5) shows that the orientation of polyaniline chains in the nanocomposite structure has increased in compare to the pure polyaniline (Fig. 3). The SEM image of clinoptilolite (Fig. 4) shows the layered structure of clinoptilolite with layer thicknesses in nanometer range (less than 100 nanometer). Also the SEM image of nanocomposite (Fig. 5) reveals that the size of polyaniline chains grown in clinoptilolite channels is in nanometer rage. Cyclic voltammetry studies were carried out to evaluate the electrochemical behavior and electrochemical stability of PANI/Clino nanocomposite. A gold electrode (0.5 cm × 0.5 cm) coated with a thin layer (20 ␮ m thickness) of nanocomposite was used as working electrode. Various solutions including HCl (1 M) and H 2 SO 4 (1 M) were used as electrolyte. Figs. 6 and 7 show the cyclic voltammograms of PANI/Clino (5%, w/w) nanocomposite films in HCl (1 M) and in H 2 SO 4 (1 M) electrolytes respectively with consecutively forty times scans at 25 mV/s scan rate. Regard- ing the results, it was found that PANI/Clino nanocomposite is electroactive similar to pure polyaniline and present two pairs of oxidation/reduction peaks in cyclic voltammogram. Also results showed that the electrochemical behavior of the nanocomposite is completely reversible and the nanocomposite has good electrochemical stability. The electrochemical Tafel slope analysis was used to evaluate the anticorrosive performance of PANI/Clino nanocomposite coating on iron samples. Tafel plots for pure polyaniline coated and nanocomposite coated iron samples were recorded by sweeping the potential from equilibrium potential toward negative and pos- itive potentials against Ag/AgCl reference electrode in H 2 SO 4 (1 M), HCl (1 M) and NaCl (3.5%, w/w) electrolytes. The iron coupons were coated with 20 ␮ m thickness coatings of pure polyaniline and PANI/Clino nanocomposite. Figs. 8–10 show the Tafel plots for polyaniline and PANI/Clino nanocomposite with 1, 3 and 5% (w/w) clinoptilolite content coated iron samples respectively in H 2 SO 4 (1 M), HCl (1 M) and NaCl (3.5%, w/w) solutions. In Tables 2–4 the values related to the corrosion current ( I corr ), corrosion potential ( E corr ) and corrosion rate ( C R ) calculated from Tafel plots for polyaniline and PANI/Clino nanocomposite with 1, 3 and 5% (w/w) clinoptilolite content coated iron samples respectively in H SO (1 M), HCl (1 M) and NaCl (3.5%, w/w) solutions have been shown. It can be seen that the corrosion potential of PANI/Clino (3%, w/w) nanocomposite coated sample is more positively shifted than PANI/Clino nanocomposites with 1 and 5% (w/w) clinoptilolite content coated samples specially in NaCl (3.5%, w/w) solution ( E ≈ 0.262 V vs. polyaniline coated sample). Also it was found that in acidic environments, corrosion current of PANI/Clino (3%, w/w) nanocomposite coated sample is much lower than that of pure polyaniline coated sample and PANI/Clino nanocomposite coated samples with 1 and 5% (w/w) clinoptilolite content. An important point that exists here is encapsulation of polyaniline in the clinoptilolite channels. Clinoptilolite channels would increase the corrosion rate of the iron substrate if the polyaniline were not in the clinoptilolite channels. In fact clinoptilolite channels could act as a pathway for diffusion of corrosive agents. Therefore, it was found that the encapsulation of polyaniline in the clinoptilolite channels and dispersion of clinoptilolite layers in polyaniline matrix, promotes the anticorrosive efficiency of PANI/Clino nanocomposite coating on iron samples. However enhanced corrosion protection of PANI/Clino nanocomposite compared to pure polyaniline coated samples might result from layers of clinoptilolite dispersed in polyaniline matrix which increases the tortuosity of diffusion pathway of corrosive agents. The preparation of PANI/Clino nanocomposite was successfully performed by in situ polymerization method and the incorporation of polyaniline in the clinoptilolite channels was confirmed by FTIR and XRD studies. The SEM image of PANI/Clino nanocomposite showed that the alignment of polyaniline chains was increased and also confirmed the nanometer size range of polyaniline chains in clinoptilolite channels. The reversible electroactive behavior of PANI/Clino nanocomposite and its electrochemical stability were found by cyclic voltammetry technique. Results of the corrosion studies showed that in acidic environments corrosion current of PANI/Clino (3%, w/w) nanocomposite coated iron samples is much lower than the pure polyaniline coated and PANI/Clino nanocomposite with 1 and 5% (w/w) clinoptilolite content coated iron samples. The financial support of this research by the University of Tabriz is gratefully ...