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2010 - 20177

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Author: search.filters.author.Nityananda Shetty, A.N.Subject: search.filters.subject.SEM

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    Studies on corrosion of annealed and aged 18 Ni 250 grade maraging steel in sulphuric acid medium
    (2010) Poornima, T.; Jagannatha, N.; Nityananda Shetty, A.N.
    The corrosion behavior of aged and annealed sample of 18 Ni 250 grade maraging steel was investigated in varied conditions of concentration and temperature of sulphuric acid medium, using electrochemical techniques like Tafel polarization and electrochemical impedance spectroscopy (EIS). The results obtained from both the techniques are in good agreement. These results have shown increase in corrosion rate of aged specimen with increase in concentration and temperature of sulphuric acid. With increase in concentration of sulphuric acid from 0.025 M to 0.25 M the corrosion rate of annealed sample was found to increase, but there after in 0.5 M, 0.75 M and 1 M, the rate of corrosion decreases, indicating passivation of alloy surface at higher concentration of sulphuric acid. The corrosion rate of aged specimen was found to be higher than that of the annealed specimen. Similar observations are revealed by SEM images. The thermodynamic parameters like activation energy, enthalpy of activation and entropy of activation were calculated.
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    3-Methyl-4-amino-5-mercapto-1,2,4-triazole as corrosion inhibitor for 6061/Al-15 (vol-%) sic(p) composite in 0.5M sodium hydroxide solution
    (2011) Kumari, P.D.R.; Nayak, J.; Nityananda Shetty, A.N.
    3-Methyl-4-amino-5-mercapto-1,2,4-triazole (MAMT) was investigated for its inhibition action on the corrosion of 6061/Al - 15 (vol-%) SiC(p) composite in 0.5M sodium hydroxide solution at different temperatures by potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The effect of inhibitor concentration, temperature and concentration of the corrosion medium on the inhibitor action was investigated. The inhibition efficiency increased with the increase in the concentration of inhibitor but decreased with the increase in temperature. Both thermodynamic and activation parameters were calculated and discussed. The adsorption of MAMT on the composite was found to be through physisorption obeying Langmuir's adsorption isotherm.
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    Corrosion behaviour of 18%Ni M250 grade maraging steel under welded condition in hydrochloric acid medium
    (2013) Kumar, P.; Nityananda Shetty, A.N.
    The corrosion behaviour of welded maraging steel in hydrochloric acid solutions was studied over a range of acid concentration and solution temperature by electrochemical techniques like Tafel extrapolation method and electrochemical impedance spectroscopy. The corrosion rate of welded maraging steel increases with the increase in temperature and concentration of hydrochloric acid in the medium. The energies of activation, enthalpy of activation and entropy of activation for the corrosion process were calculated. The surface morphology of the corroded sample was evaluated by surface examination using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS).
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    Electrochemical investigations on the corrosion behaviour of magnesium alloy ZE41 in a combined medium of chloride and sulphate
    (National Engg. Reaserch Center for Magnesium Alloys zhangdingfei@cqu.edu.cn, 2013) Dinodi, N.; Nityananda Shetty, A.N.
    The magnesium alloy ZE41 encompasses a wide spectrum of applications as a structural material. An extremely high susceptibility to corrosion limits widespread utility of ZE41. In the present study it has been attempted to understand the corrosion behaviour of ZE41 alloy employing electrochemical techniques like Tafel extrapolation and electrochemical impedance spectroscopy (EIS) in aqueous salt solutions containing mixture of sodium chloride and sodium sulphate over a varying range of electrolyte concentrations and solution temperatures. The morphology of the metal surface has been established by means of scanning electron microscopy (SEM). The results indicate that the rate of corrosion of ZE41 alloy increases with the increase in temperature and ionic concentration of the medium. The results of corrosion rates at varying temperatures have been utilized in the calculation of activation parameters such as activation energy, enthalpy of activation and entropy of activation for the corrosion process. © 2013 National Engineering Research Center for Magnesium Alloys of China, Chongqing University.
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    Corrosion inhibition effect of 2,5-bis (3,4,5-trimethoxy phenyl)-1,3,4-oxadiazole (BTPO) on 18 Ni M250 grade welded maraging steel in 1.0 M sulphuric acid medium
    (Mohammed Premier University jmaterenvironsci@gmail.com, 2014) Kumar, P.; Nityananda Shetty, A.N.
    Corrosion inhibition of welded maraging steel in 1.0 M sulphuric acid was studied in the presence of different concentrations of 2,5-bis (3,4,5-trimethoxy phenyl)-1,3,4-oxadiazole (BTPO) by electrochemical techniques. The results confided that BTPO was a good inhibitor, and the inhibition efficiencies obtained from potentiodynamic polarization and electrochemical impedance methods were in good agreement. The inhibitor, BTPO, acted essentially as a mixed-type inhibitor with its inhibition action through its surface adsorption. The inhibition effciency was found to increase with the increase in BTPO concentration but decreased with the increase in temperature. The activation parameters for the corrosion of the alloy and thermodynamic parameters for the adsorption of BTPO on the alloy surface were calculated and discussed. The adsorption of BTPO on welded maraging steel surface was predominantly through physisorption and obeyed the Langmuir adsorption isotherm. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) study confirmed the formation of an anticorrosion protective film of BTPO on the metal surface.
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    Influence of sulfate ion concentration and pH on the corrosion of Mg-Al-Zn-Mn (GA9) magnesium alloy
    (National Engg. Reaserch Center for Magnesium Alloys zhangdingfei@cqu.edu.cn, 2015) Shetty, S.; Nayak, J.; Nityananda Shetty, A.N.
    The corrosion behavior of Mg-Al-Zn-Mn (GA9) alloy in sodium sulfate solutions was studied over a range of concentrations and solution temperatures at different pH conditions by electrochemical techniques like Tafel extrapolation and electrochemical impedance spectroscopy (EIS). The studies were carried out in solutions with sodium sulfate concentrations 0.1M, 0.5M, 1M, 1.5M and 2M; and at five different temperatures of 30, 35, 40, 45 and 50 °C in a pH range of 3-12. As per the experimental data, the corrosion rate of the alloy increased with the increase in temperature, and also with the increase in concentration of sodium sulfate in the medium. It was observed that the rate of corrosion decreased with the increase in pH. The activation parameters like activation energy, enthalpy of activation and entropy of activation for the corrosion process were calculated. The surface morphology of the alloy was examined before and after corrosion using scanning electron microscopy (SEM). © 2015.
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    Electrochemical investigation on the effects of sulfate ion concentration, temperature and medium pH on the corrosion behavior of Mg–Al–Zn–Mn alloy in aqueous ethylene glycol
    (National Engg. Reaserch Center for Magnesium Alloys zhangdingfei@cqu.edu.cn, 2017) Medhashree, H.; Nityananda Shetty, A.N.
    The effects of sulfate ion concentration, temperature and medium pH on the corrosion of Mg–Al–Zn–Mn alloy in 30% aqueous ethylene glycol solution have been investigated by electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy methods. Surface morphology of the alloy was examined before and after immersing in the corrosive media by scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) analysis. Activation energy, enthalpy of activation and entropy of activation were calculated from Arrhenius equation and transition state theory equation. The obtained results indicate that, the rate of corrosion increases with the increase in sulfate ion concentration and temperature of the medium and decreases with the increase in the pH of the medium. © 2017