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Kumar R.S.,Bharathiar University | Kumar R.S.,Sree Krishna Polytechnic College | Chandrasekaran V.,Salem College
Oriental Journal of Chemistry | Year: 2015

The effect of marine algae Sargassum wightii extract on corrosion inhibition of brass in phosphoric acid was investigated by weight-loss method, potentiodynamic polarization and electrochemical impedance spectroscopy studies. The inhibition efficiency is found to increase with increasing concentration of extract and decreases with rise in temperature. The inhibitive effect could be attributed to the phytochemical constituents present in the inhibitor containing N, S, O atoms. The activation energy, thermodynamic parameters (free energy, enthalpy and entropy change) and kinetic parameters (rate constant and half-life) for inhibition process were calculated. These thermodynamic and kinetic parameters indicate a strong interaction between the inhibitor and the brass surface. The inhibition is assumed to occur via adsorption of inhibitor molecules on the brass surface, which obeys Temkin adsorption isotherm. The adsorption of inhibitor on the brass surface is exothermic, physical, and spontaneous, follows first order kinetics. The polarization measurements showed that the inhibitor behaves as a mixed type inhibitor. Inhibition efficiency values were found to show good trend with weight-loss method, potentiodynamic polarization and electrochemical impedance spectroscopy studies. Surface study techniques (FT-IR and SEM) were carried out to ascertain the inhibitive nature of the algal extract on the brass surface.


Selva Kumar R.,Bharathiar University | Selva Kumar R.,Sree Krishna Polytechnic College | Chandrasekaran V.,Salem College
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2016

The effect of marine alga Valoniopsis pachynema extract on corrosion inhibition of brass in phosphoric acid was investigated by weight-loss method, potentiodynamic polarization, and electrochemical impedance spectroscopy studies. The inhibition efficiency is found to increase with increasing concentration of extract and decreases with rise in temperature. The activation energy, thermodynamic parameters (free energy, enthalpy, and entropy change) and kinetic parameters (rate constant and half-life) for inhibition process were calculated. These thermodynamic and kinetic parameters indicate a strong interaction between the inhibitor and the brass surface. The inhibition is assumed to occur via adsorption of inhibitor molecules on brass surface, which obeys Temkin adsorption isotherm. The adsorption of inhibitor on the brass surface is exothermic, physical, and spontaneous, and follows first-order kinetics. The polarization measurements showed that the inhibitor behaves as a mixed type inhibitor and the higher inhibition surface coverage on the brass was predicted. Inhibition efficiency values were found to show good trend with weight-loss method, potentiodynamic polarization, and electrochemical impedance spectroscopy studies. Surface study techniques (FT-IR and SEM) were carried out to ascertain the inhibitive nature of the algal extract on the brass surface. © 2015, The Minerals, Metals & Materials Society and ASM International.

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