Browsing by Author "Shetty, A. Nityananda"

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Studies on Corrosion Inhibition of 18% Ni M 250 Grade Maraging Steel under Weld Aged Condition in Acidic Media
(National Institute of Technology Karnataka, Surathkal, 2013) B. S., Sanatkumar; Shetty, A. Nityananda; Nayak, Jagannatha
The corrosion behaviour of 18 % Ni M250 grade maraging steel under weld aged conditions in two different acid media, namely, hydrochloric acid and sulphuric acid in various concentrations and temperatures have been studied by Tafel polarization and electrochemical impedance spectroscopy techniques. The corrosion rate in the sulphuric acid medium was higher than in the hydrochloric acid medium. Five organic inhibitors were synthesized and characterized using spectral and elemental analysis. The five inhibitors were 1(2E)-1-(4-aminophenyl)-3-(2-thienyl) prop-2-en-1-one (ATPI), 2-(4-chlorophenyl)-2-oxoethyl benzoate (CPOB), 2-(4- bromophenyl)-2-oxoethyl- 4-chlorobenzoate (CPOM), (E)-1-(2,4-dinitrophenyl)-2-[1- (2-nitrophenyl) ethylidene] hydrazine (DNPH) and 5-diethylamino-2-{[2-(2,4- dinitrophenyl) hydrazin-1-ylidene]methyl} - phenol (DDPM). The results pertaining to the corrosion inhibition studies of five inhibitors in two different acid media at different temperatures in the presence of varying concentrations of inhibitors are reported in the thesis. Activation parameters for the corrosion of the alloy and thermodynamic parameters for the adsorption of the inhibitors have been calculated and the results have been analysed. The adsorption of first four inhibitors on the alloy was through both physisorption and chemisorption, with predominant physisorption in both the media. The mode of adsorption for the DDPM predominantly chemisorption in both the media. The adsorption of all the five inhibitors on alloy surfaces follows Langmuir adsorption isotherm. The inhibition efficiencies of first four inhibitors decrease with the increase in temperature, the inhibition efficiency of DDPM increases with the increase in temperature.
Studies on corrosion inhibition of 18% Ni M 250 grade maraging steel under welded condition in acidic media
(National Institute of Technology Karnataka, Surathkal, 2014) Kumar, Pradeep; Shetty, A. Nityananda
The corrosion behaviour of 18% Ni M250 grade maraging steel under welded conditions in two different acid media, namely, hydrochloric acid and sulphuric acid in various concentrations and temperatures have been studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The corrosion rate in the sulphuric acid medium was higher than in the hydrochloric acid medium. The effect of corrosion inhibition on welded maraging steel was carried out by using five inhibitors, n a m e l y , 2,5-Bis (3,4,5-trimethoxy phenyl)-1,3,4-oxadiazole (BTPO), 1-Phenyl-4-(4-nitrophenyl) thiosemicarbazide (PNPT), 3,4,5-Trimethoxy benzoicacid(3,4,5-trimethoxy-benzylidene) hydrazide (TBTBH), 2-(5-Chloro-1Hbenzoimidazol-2-yl) phenol (CBP), 2-(4-Methoxy-phenyl)-benzo[d]imidazo[2,1-b] thiazole (MPBIT). The results pertaining to the corrosion inhibition studies of five inhibitors in two different acid media at different temperatures in the presence of varying concentrations of inhibitors are reported in the thesis. Activation parameters for the corrosion of the alloy and thermodynamic parameters for the adsorption of the inhibitors have been calculated and the results have been analysed. The adsorption of all five inhibitors on the alloy was through both physisorption and chemisorption, with predominant physisorption in both the media. The adsorption of all the five inhibitors on alloy surfaces follows Langmuir adsorption isotherm. The inhibition efficiencies of all five inhibitors decrease with the increase in temperature and increase in concentration of acidic media.
Study on Corrosion Behavior and Corrosion Inhibition of Magnesium Alloy Ze41
(National Institute of Technology Karnataka, Surathkal, 2014) K, Nandini; Shetty, A. Nityananda
The alloys of magnesium are in the spot-light lately. With applications that run the gamut from automobile parts to medical implants, this class of alloys truly deserve all the adulation coming their way. ZE41 is one such cast alloy, which is lighter than aluminium, can be cast or machined into variety of desired shapes and has good damping and shock absorption abilities. A very low resistance to corrosion puts the otherwise remarkable efficacy of ZE41 in jeopardy. Hence understanding the corrosion of ZE41 and developing the measures to combat the same are indispensable. In the present thesis the corrosion of ZE41 and its mitigation were analyzed using techniques like potentiodynamic polarization and AC impedance, along with SEM and EDX analyses. Sodium sulfate and its mixture with sodium chloride were chosen as two corrosive media. The blank corrosion studies were performed at various medium concentrations, pH and temperatures. The results revealed a trend of higher corrosion rate associated with higher medium concentration, lower pH and higher temperature. Five different long chain alkyl monocarboxylates namely stearate, palmitate, myristate, laurate and caprylate were synthesized and tested as corrosion inhibitors for ZE41. The calculated activation and thermodynamic parameters have been documented in the thesis. The carboxylates were predominantly physisorbed and adsorption was in accordance with Langmuir adsorption isotherm. The studied carboxylates were found to function as mixed-type inhibitors which predominantly suppressed anodic reaction. The carboxylates were more efficient at lower temperatures and in combined medium. At an optimum concentration the efficiencies of the carboxylates decreased in the order: stearate > palmitate > myristate > laurate > caprylate and this has been accredited to the reduction in aliphatic chain length. The proposed mechanism attributed the cathodic inhibition to the blockage of the reaction spots by chemisorbed carboxylates. The anodic inhibition resulted from the compaction of porous film by precipitated magnesium carboxylate salts.