Faculty Publications
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Item Studies on corrosion of Mg-Al-Zn alloy in 30% aqueous ethylene glycol(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Medhashree, H.; Nityananda Shetty, A.The Mg-Al-Zn alloy is used in the coolant systems of automobile engines. Corrosion of Mg-Al-Zn engine components by coolants, which consist of 30% aqueous ethylene glycol as a coolant composition, is an important issue in automobile industries. With this preview, in the present study it is intended to study the effect of environmental contaminant sulphate ions on the corrosion behavior of Mg-Al-Zn alloy in 30% (v/v) aqueous ethylene glycol solution. Electrochemical investigations were carried out by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Scanning electron microscopy (SEM) and energy dispersion X-ray analysis (EDX) were used to study the surface morphology and composition of the alloy. Activation parameters for the corrosion process were calculated by conducting the corrosion studies at different temperatures. It was observed that corrosion rate of the alloy in 30% (v/v) aqueous ethylene glycol increases with the increase in the concentration of sulphate ions and also with the increase in temperature. © (2015) Trans Tech Publications, Switzerland.Item EIS study and role of chloride ions concentration and temperature on passivity of AZ91D Mg alloy(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Arya, S.B.; Kanaujia, A.Mg alloy shows higher specific strength and ductility relative to aluminum and also lower machining and casting costs over to steels. However, it also shows limitation to use in many industrial applications due to the relatively poor corrosion resistance in many aqueous solutions. Corrosion and passivation study of magnesium alloy (AZ91D) in various Cl¯ ions concentrations and temperatures were carried out using electrochemical impedance spectroscopy (EIS) in NaCl solutions of 0.4, 0.6, 0.8 & 1.0 molar (M) concentrations. The passivation behavior was also observed at temperature of 45°C, 55°C and 65 °C in 3.5 wt% NaCl solutions. The total polarization resistance was observed about 5530, 4030, 2465 and 2000 Ohms.cm2 in solutions of 0.4, 0.6, 0.8 & 1.0 M NaCl respectively indicate reduction of film stability at higher chlorides concentration. A similar trend was found on increasing temperatures of 3.5 wt% NaCl solutions at 45°C, 55°C and 65 °C and noticed about 970, 600 and 300 Ohms.cm2 respectively showed significant decline of passivity and more pitting tendency. © (2015) Trans Tech Publications, Switzerland.Item Corrosion of aged and annealed 18 Ni 250 grade maraging steel in phosphoric acid medium(2010) Poornima, T.; Nayak, J.; Nityananda Shetty, A.N.The corrosion behavior of aged and annealed sample of 18 Ni 250 grade maraging steel was investigated in phosphoric acid over a range of acid concentration and solution temperature by using electrochemical techniques like Tafel extrapolation and electrochemical impedance spectroscopy. The studies have revealed that the corrosion rate of both aged and annealed samples increase with increase in temperature and increase in concentration of phosphoric acid in the medium. The corrosion rate of annealed sample is found to be less than that of aged sample. The thermodynamic parameters like activation energy, enthalpy of activation and entropy of activation for the corrosion process were calculated. © 2010 by ESG.Item 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.Item Adsorption and inhibitor action of 4-(N,N-dimethylamino) benzaldehyde thiosemicarbazone on 6061 Al/SiC composite and its base alloy in sulfuric acid medium(2011) Geetha, G.M.; Nayak, J.; Nityananda Shetty, A.N.The inhibitive action of 4-(N,N-dimethylamino)benzaldehyde thiosemicarbazone (DMABT) on the corrosion behavior of 6061 Al -15 vol. pct. SiC(p) composite and its base alloy was studied at different temperatures in sulfuric acid medium containing varying concentrations of it, using Tafel extrapolation technique and AC impedance spectroscopy (EIS). Results showed that DMABT was an effective inhibitor, showing inhibition efficiency of 70% in 0.5 M sulfuric acid. The adsorption of DMABT on both the composite and base alloy was found to be through physisorption obeying Langmuir adsorption isotherm. The thermodynamic parameters such as free energy of adsorption and activation parameters were calculated. © Taylor & Francis Group, LLC.Item 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.Item CORROSION BEHAVIOR OF 18% Ni M250 GRADE MARAGING STEEL UNDER WELD-AGED CONDITION IN SULFURIC ACID MEDIUM(2012) Sanatkumar, B.S.; Nayak, J.; Nityananda Shetty, A.N.The corrosion behavior of 18% Ni M250 grade maraging steel under weld-aged condition was investigated in sulfuric acid medium of different concentrations (0.1-2 M) at different temperatures (30°-60°C). Electrochemical measurements were carried out using the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results showed an increase in the corrosion rate with the increases in temperature as well with increase in the concentration of the corrosion medium. The results obtained from the Tafel extrapolation technique and electrochemical impedance spectroscopy were in good agreement. Activation parameters were evaluated using the Arrhenius equation and transition state equation. The surface morphology of the corroded specimen was compared with that of the un-corroded sample by using scanning electron microscopy (SEM). © 2012 Copyright Taylor and Francis Group, LLC.Item A study on corrosion behavior of electrodeposited Zn-rutile TiO2 composite coatings(2012) Kumar, M.K.P.; Venkatesha, T.V.; Pavithra, M.K.; Shetty, A.The Zn and Zn-TiO2 composite coatings were fabricated by electrolyzing respective plating solutions of Zn and Zn-TiO2. The rutile TiO2 nanoparticles (size ?100nm) were used for the preparation of composite coatings. The corrosion behavior of the deposits was examined by electrochemical methods. The anticorrosive property of coatings was supported by measuring their corrosion potential, polarization resistance, charge transfer characteristic peak and break frequency. The surface morphology of deposits was studied by scanning electron microscopy, energydispersive X-ray diffraction spectroscopy, and X-ray diffraction techniques. The change in morphology of Zn-TiO2 composite with respect to Zn is correlated with their corrosion behavior. Copyright © Taylor & Francis Group, LLC.Item 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).Item Electrochemical investigation on the corrosion of 18%Ni M250 grade maraging steel under welded condition in sulfuric acid medium(2013) Kumar, P.; Nityananda Shetty, A.N.The corrosion behavior of welded maraging steel in sulfuric acid solutions has been studied over a range of acid concentrations and solution temperatures by electrochemical techniques such as Tafel extrapolation and electrochemical impedance spectroscopy. The studies have revealed that the corrosion rate of welded maraging steel increases with the increase in temperature and increase in concentration of sulfuric acid in the medium. The thermodynamic parameters such as activation energy, enthalpy of activation and entropy of activation for the corrosion process are calculated. The results obtained through the two techniques are in good agreement. The surface morphology and surface composition of the corroded samples have been examined by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis, respectively. © 2013 Allerton Press, Inc.