Faculty Publications
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Item Effect of aging and protective coating on the corrosion behavior of 6061 Al / SiCp composite in chloride solutions(Trans Tech Publications Ltd ttp@transtec.ch, 2011) Rajasekaran, S.; Udayashankar, N.K.; Nayak, J.Metal matrix composites considered especially for marine application are typically aluminum-based. Utilization of the composites in marine environments requires adequate corrosion resistance. In this work, the effect of aging and aluminum as resistive coating on the corrosion behavior of 6061 Al / SiC p composite in 1N and 3.5N NaCl solution in the temperature range of 30°C-50°C is studied by means of electrochemical techniques, scanning electron microscope (SEM) and weight loss measurements. Aging results in precipitation of intermetallics in the matrix, this in turn leads to galvanic and pitting corrosion. Pitting initiation and propagation as the main corrosion mechanism was driven by the aging kinetics which is ruled by the reduction in the retained vacancy concentration and at the same time by dislocation density due to the presence of SiCp. Sputtered aluminum coating on the composite effectively resists the pitting initiation and propagation and hence corrosion process. Also the intermetallic precipitates are unexposed to the Chloride solution by the presence of aluminum coating. Hence aluminum coating acts as corrosion resistive coating for the 6061 Al / SiCp aged composites. © (2011) Trans Tech Publications.Item Corrosion Inhibition Using 2-Mercaptobenzimidazole on T6 Treated 6061 Al-SiCp Composite in Acetic Acid(Elsevier Ltd, 2015) Chacko, M.; Nayak, J.6061 Al-SiCp composite was T6 treated by solutionizing the sample at 350°C and water quenching. It was then underaged at 140°C and aging profile was obtained using Rockwell B hardness. Corrosion characteristics of the underaged composite was studied at varying temperatures. Acetic acid in altered concentrations was used as medium for corrosion studies. 2-mercaptobenzimidazole was added in different concentrations for inhibiting the corrosion reaction. Inhibition efficiency and thermodynamic parameters supported that 2-mercaptobenzimidazole is an effective inhibitor which adsorbed on to the surface by mixed adsorption where chemisorption was predominant. © 2015.Item Corrosion behaviour of 6061 Al - 15vol. Pct. SiC composite and its base alloy in a mixture of 1:1 Hydrochloric and sulphuric acid medium(2009) Geetha, G.M.; Nayak, J.; Nityananda Shetty, A.N.Silicon carbide particulate - reinforced aluminum (SiCp-Al) composites possess a unique combination of high specific strength, high elastic modulus, good wear resistance and good thermal stability than the corresponding non-reinforced matrix alloy systems. These composites are potential structural material for aerospace and automotive applications. The corrosion characteristics of 6061 Al/SiCp composite and the base alloy were experimentally assessed. The corrosion test was carried out at different temperatures in 1:1 mixture of hydrochloric acid and sulphuric acid at a concentration range of 0.01 to 1N for each of the acid, as corrosion media using Tafel extrapolation technique and Electrochemical impedance spectroscopy (EIS). The results obtained from Tafel extrapolation technique and Electrochemical impedance spectroscopy were in good agreement. The results showed an increase in the corrosion rate with increases in temperature as well as the increase in the concentration of the corrosion media. The thermodynamic parameters like energy of activation were calculated using Arrhenius theory equation and, enthalpy of activation and entropy of activation were calculated using transition state theory equation. © 2009 by ESG.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 Corrosion inhibition of aluminum type 6061 Al-15 vol. pct. SiC(p) composite in 0.5-M sodium hydroxide solution by 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol(Emerald Group Publishing Ltd. Howard House Wagon Lane, Bingley BD16 1WA, 2014) Reena Kumari, P.D.; Nayak, J.; Nityananda Shetty, A.Purpose: The purpose of this paper is to report the studies on the corrosion inhibition property of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol (APTT) for the corrosion of 6061 Al-15 vol. pct. SiC(p) composite. Design/methodology/approach: The corrosion behavior of 6061 Al-15 vol. pct. SiC(p) composite was studied at different temperatures in 0.5-M sodium hydroxide (NaOH) solution in the presence of APTT by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopic techniques. The effect of inhibitor concentration and temperature on the inhibitor effect of APTT was studied. The surface morphology of the metal surface was investigated by scanning electron microscopy. The activation parameters for the corrosion of the composite and base alloy, as well as the thermodynamic parameters for the adsorption of APTT on the composite and alloy surfaces, were calculated. Findings: The inhibition efficiency of APTT increases with the increase in the concentration of the inhibitor and decreases with the increase in temperature. The adsorption of APTT on the composite was found to be through physisorption, obeying Langmuir's adsorption isotherm. APTT acts as a mixed inhibitor with predominant cathodic action on the composite. Practical implications: APTT can be used as an inhibitor for the corrosion of 6061 Al-15 vol. pct. SiC(p) composite in the NaOH medium. Originality/value: This paper provides information regarding the corrosion inhibition property of APTT on 6061 Al-15 vol. pct. SiC(p) composite. An attempt was made to explain the mechanism of the inhibition action by APTT. © Emerald Group Publishing Limited.Item Corrosion behavior of 6061/Al-15 vol. pct. SiC(p) composite and the base alloy in sodium hydroxide solution(Elsevier B.V., 2016) Reena Kumari, P.D.; Nayak, J.; Nityananda Shetty, A.The corrosion behavior of 6061/Al-15 vol. pct. SiC(p) composite and 6061 Al base alloy was investigated in a sodium hydroxide solution. The electrochemical parameters were derived from potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. The results showed that the corrosion resistance of the composite was lower than that of the base alloy in selected corrosion media. The corrosion rates of both the composite and the base alloy increased with the increase in the concentration of sodium hydroxide and also with the increase in temperature. The surface morphology of the metal surface was investigated using scanning electron microscope (SEM). Activation energy was evaluated using Arrhenius equation, and enthalpy of activation and entropy of activation values were calculated using transition state equation. © 2012