Synthesis of poly(aniline‐co‐o‐toluidine) coatings and their corrosion‐protection performance on low‐carbon steel

Abstract

Strongly adherent poly(aniline-co-o-toluidine) coatings were synthesized on low-carbon-steel substrates by the electrochemical copolymerization of aniline with o-toluidine with sodium tartrate as the supporting electrolyte. These coatings were characterized with cyclic voltammetry, ultraviolet-visible absorption spectroscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and scanning electron microscopy. The formation of the copolymer with the mixture of monomers in the aqueous sodium tartrate solution was ascertained by a critical comparison of the results obtained from the polymerizations of the individual monomers, aniline and o-toluidine. The optical absorption spectrum of the copolymer was drastically different from the spectra of the respective homopolymers, polyaniline and poly(o-toluidine). The extent of the corrosion protection offered by poly(aniline-co-o-toluidine) coatings to low-carbon steel was investigated in aqueous 3% NaCl solutions by opencircuit-potential measurements and a potentiodynamic polarization technique. The results of the potentiodynamic polarization measurements showed that the poly(anilineco-o-toluidine) coatings provided more effective corrosion protection to low-carbon steel than the respective homopolymers. The corrosion rate depended on the feed ratio of o-toluidine used for the synthesis of the copolymer coatings.

A correlation of electrochemical and spectroelectrochemical properties of poly(o-toluidine)

“…5 depicts the plot of resistivity versus applied electrode potential in 1.5 M H 2 SO 4 for the POT film deposited on a two band gold electrode. As observed with PANI [19][20][21][22][23][24][25][26][27][28][29][30][31], the resistivity of POT is high in its reduced leucoemeraldine and fully oxidized pernigraniline states (where no charge carriers are present in either case). A sharp decrease in the resistivity occurs as the potential is increased beyond E SCE = 0.10 V followed by a sharp increase at E SCE = 0.60 V. Minimum resistivity is observed in the potential range between E SCE = 0.30 and 0.60 V, where POT is present in its half-oxidized emeraldine form (when radical cations are present and can act as charge carriers) [52].…”

“…For instance poly(o-toluidine) (POT), the polymer derived from o-toluidine (OT), (a substituted aniline with a -CH 3 group at the aromatic ring in the ortho position) has been reported to show structural properties and redox and electrochromic behavior closely related to PANI [14][15][16][17][18][19]. We [20][21][22][23] as well as others [24,25] have investigated the synthesis and characterization of polymers based on homopolymerization and copolymerization of toluidines (for an overview see: [26,27]). …”

Synthesis and corrosion protection aspects of poly(o-toluidine)/CdO nanoparticle composite coatings on mild steel

“…Several studies have been carried out in most recent times or are in progress in which various conducting polymers in different configurations were evaluated for corrosion protection of oxidizable metals. [13][14][15][16] Mengoli et al 17 were the first to examine the protective behavior of polyaniline on stainless steel and then in 1985, DeBerry 18 showed that the electrochemically synthesized polyaniline acts as corrosion protective layer on stainless steel in 1 M H 2 SO 4 . Since then, several research groups [19][20][21][22][23] have systematically investigated the electrochemical synthesis of various conducting polymers on oxidizable metals for corrosion protection purposes.…”

Corrosion protective bi‐layered composites of polyaniline and poly(o‐anisidine) on low carbon steel

“…We have reported recently, the synthesis of poly(aniline-co-o-toluidine) coatings on LCS from aqueous salicylate solution using cyclic voltammetry and investigated the corrosion properties of these copolymer coatings in aqueous 3% NaCl. 28 It was found that the poly(aniline-co-o-toluidine) coatings provide better protection for LCS against corrosion than corresponding homopolymer coatings. The corrosion rates of PANI, poly(o-toluidine) (POT) and poly(aniline-co-o-toluidine) (with feed ratio of o-toluidine as 0.5) coated LCS are found to be $3, 20, and 50 times lower than that observed for uncoated LCS.…”