• B V Appa Rao

      Articles written in Journal of Chemical Sciences

    • Tungstate as a synergist to phosphonate-based formulation for corrosion control of carbon steel in nearly neutral aqueous environment

      B V Appa Rao M Venkateswara Rao S Srinivasa Rao B Sreedhar

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      Synergistic inhibition of corrosion of carbon steel in low chloride aqueous medium using tungstate as a synergist in combination with $N,N-bis$(phosphonomethyl) glycine (BPMG) and zinc ions is presented. The synergistic action of tungstate has been established through the present studies. The new ternary inhibitor formulation is effective in neutral and slightly acidic as well as slightly alkaline media. Potentiodynamic polarisation studies inferred that the formulation functions as a mixed inhibitor. Impedance studies of the metal/solution interface revealed that the surface film is highly protective. Characterisation by X-ray photoelectron spectroscopy (XPS) of the surface film formed in presence of the inhibitor revealed the presence of iron, phosphorus, nitrogen, oxygen, carbon, zinc and tungsten in the surface film. The chemical shifts in the binding energies of these elements inferred that the surface film is composed of iron oxides/hydroxides, zinc hydroxide, heteropolynuclear complex [Fe(III), Zn(II)-BPMG] and WO3. Reflection absorption FTIR spectroscopic studies also supported the presence of these compounds in the surface film. Morphological features of the metal surface studied in the absence and presence of the inhibitor by scanning electron microscopy (SEM) are also presented. Based on all these results, a plausible mechanism of corrosion inhibition is proposed.

    • Self-assembled 1-octadecyl-1H-benzimidazole film on copper surface for corrosion protection

      B V Appa Rao M Marsihma Reddy

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      Films of 1-octadecyl-1H-benzimidazole (OBI) have been formed on copper surface by selfassembly method. Optimum conditions viz. the solvent, concentration of OBI, immersion period and temperature for the formation of a protective film on copper have been established using impedance studies. The OBI film has been characterized by X-ray photoelectron spectroscopy, reflection absorption Fourier transform infrared (FTIR) spectroscopy, contact angle measurements and atomic force microscopy. Efficiency of the OBI film to protect copper from corrosion has been investigated in aq. HCl solution using electrochemical impedance spectroscopy, potentiodynamic polarization method, cyclic voltammetry, scanning electron microscopy and gravimetry. Results of these studies inferred that the OBI film has an inhibition efficiency in the range of 97-99% under different conditions. Polarization studies inferred that the OBI film functions as a cathodic inhibitor. Cyclic voltammetric studies showed that the film is stable even after 15 cycles, when the copper electrode is polarized to an anodic potential of 0.35V vs. Ag/AgCl electrode.

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