SYNERGISTIC EFFECT OF N,N-BIS(PHOSPHONOMETHYL) GLYCINE AND ZINC IONS IN CORROSION CONTROL OF CARBON STEEL IN COOLING WATER SYSTEMS |
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| Authors: | B V Appa Rao M Venkateswara Rao S Srinivasa Rao B Sreedhar |
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| Affiliation: | 1. Department of Chemistry , National Institute of Technology Warangal (NITW) , Warangal, Andhra Pradesh, India boyapativapparao@rediffmail.com;4. chemysri@yahoo.com;5. Department of Chemistry , National Institute of Technology Warangal (NITW) , Warangal, Andhra Pradesh, India;6. Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology , Hyderabad, Andhra Pradesh, India |
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| Abstract: | A protective film has been developed on the surface of carbon steel in low chloride aqueous environment using a synergistic mixture of an environmentally friendly phosphonic acid, N,N-bis(phosphonomethyl) glycine (BPMG), and zinc ions. Impedance studies of the metal/solution interface indicated that the surface film is highly protective against the corrosion of carbon steel in the chosen environment. Potentiodynamic polarization studies showed that the inhibitor is a mixed inhibitor. X-ray photoelectron spectroscopic analysis (XPS) of the film showed the presence of the elements iron, phosphorus, nitrogen, oxygen, carbon, and zinc. Deconvolution spectra of these elements in the surface film showed the presence of oxides/hydroxides of iron(III), Zn(OH)2, and Zn(II)-BPMG] complex. This inference is further supported by the reflection absorption Fourier transform infrared spectrum of the surface film. Analysis by SEM is presented for both the corroded and protected metal surfaces. Based on all these results, a plausible mechanism of corrosion inhibition is proposed. |
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| Keywords: | BPMG Carbon steel Impedance Inhibitor film Synergism XPS |
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