Conference Papers
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Item Performance of concrete structures in the marine environment of Karnataka, India(2003) Devadas Bhat, S.; Samaga, B.R.Well-made concrete often survives better than might otherwise be expected, simply because of its impermeability and its ability to withstand the ingress of corrosive materials. The less the surplus voids the greater is the resistance to deterioration. Corrosion of steel is a multibillion-dollar problem worldwide. However, there are many structures, which show early deterioration, namely those exposed to aggressive environments. In the past and even at present times, too much emphasis is placed on concrete compressive strength rather than on environmental factors, which are known to affect concrete durability. This is one of the main reasons for serious deterioration of concrete structures that is prevalent today. The long-term behaviour of concrete structures has shown that their main cause of distress is reinforcement corrosion. One of the most aggressive exposure conditions for concrete is the marine environment In these condition chloride penetration and chloride induced reinforcement corrosion rates can be very high, often leading to a reduced service life. This paper describes a series of case studies of different types of concrete structures, subjected to marine environment in the West-Coast of Karnataka (INDIA), that have suffered extensive deterioration due to corrosion.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 and Characterization of Thermal Sprayed Coating of Nickel Chromium Cermet on Low Carbon Steel(Elsevier Ltd, 2018) Amudha, A.; Shashikala, H.D.; Nagaraja, H.S.Corrosion is the major problem faced by Navy, especially when pumps, ship impellers and other components have to work in harsh environments like sea water. Therefore, high corrosion resistant metal ceramic matrix 75Cr3C2- 25 (NiCr) cermet has been one of the good choices for coating. In this study, we are discussing the HVOF (High Velocity Oxy Fuel) coating of 75Cr3C2-25(NiCr) on the low carbon steel substrate, IS 2062 grade B. The as coated samples were annealed at 600°C for 1 hour, 2hour and 3hours. The electrochemical tests were conducted for corrosion evaluation. Structural analysis was done by using X-Ray diffraction technique. Microstructure and thickness of the coating was studied using Scanning Electron Microscopy (SEM). Density measurement studies were done on as-coated and annealed coupons. © 2017 Elsevier Ltd.Item Corrosion Damage Identification and Lifetime Estimation of Ship Parts using Image Processing(Institute of Electrical and Electronics Engineers Inc., 2018) Naladala, I.; Raju, A.; Aishwarya, C.; Koolagudi, S.G.Corrosion is a process that leads to early failure of ship parts, high maintenance costs and a shortened service life of the ship, as a whole. Human visual inspection is currently the most widely used method to assess corrosion. In this paper, we propose the use of image processing to determine the extent of corrosion and estimate the time period within which the ship parts have to be replaced. In the case of availability of pre-corrosion images, the histograms of the pre-corrosion and post-corrosion images are compared and their similarity is quantified as the Sum of Squared Distances (SSD) value. Our method then produces a numerical output which signifies the level of corrosion. We then correlate extent of damage and ship part replacement period. In the absence of pre-corrosion images, we classify superpixels in the post-corrosion image as undamaged or damaged with an accuracy of 92 per cent, using Random Forest classifier. We have also evaluated the performance of corrosion prevention measures such as galvanization, painting, etc on different parts of the ship, for example, parts exposed to only air and parts exposed to both saline water and air. © 2018 IEEE.Item Microstructure and Corrosion behavior of wrought AZ80 Mg alloys after the combined processes of ECAP and Hot Rolling(IOP Publishing Ltd, 2019) Naik, G.M.; Gote, G.D.; Narendranath, S.; Satheesh Kumar, S.S.In the current work, wrought AZ80 Mg alloys were subjected to equal channel angular pressing (ECAP) followed by hot rolling (HR). Then, combined effects of ECAP and HR on microstructure and electrochemical corrosion behavior were investigated in 3.5wt.% NaCl solution. The microstructure and corrosion morphology study was made through optical and scanning electron microscope respectively. The results show that the use of hot rolling after ECAP significantly decreases the grain size compared to as-received and ECAP-4 pass processed Mg alloys. In addition, electrochemical impedance spectroscopy and potentiodynamic polarization results have shown that the hot rolling of AZ80 Mg alloy after ECAP exhibited lower corrosion current and higher corrosion resistance is due to fine grain microstructure and continuous and uniform distribution of secondary phases. This was evidently observed during this study. © Published under licence by IOP Publishing Ltd.Item The Role of Processing Temperature in Equal Channel Angular Extrusion: Microstructure Mechanical Properties and Corrosion Resistance(Springer Science and Business Media Deutschland GmbH, 2020) Naik, G.M.; Narendranath, S.; Satheesh Kumar, S.S.Equal channel angular extrusion, patented in Russia by V. M. Segal in 1977, has become a promising technique to enhance tensile strength and corrosion resistance of Mg alloys. It is believed that the processing temperature ensures the production of ECAE-processed billet without surface defects. Indeed, ECAE processing temperature affects microstructure, tensile behavior, and corrosion resistance of the material. Therefore, this chapter investigates the impact of ECAE pressing temperature on microstructure, mechanical behavior, and corrosion resistance of AZ80 Mg alloys. The processing temperature of 533 and 663 K was selected based on the recrystallization temperature of Mg alloys. As a result, the processing temperature has a substantial impact on material properties. The axial tensile strength and hardness decrease by 25.45% and 6.56%, respectively, due to thermal softening of materials. The corrosion resistance increases by 84% due to grain size reduction and distribution of secondary phases, when the ECAP-4P processing temperature is increased from 533 K to 663 K. © 2020, Springer Nature Singapore Pte Ltd.Item Performance evaluation of deep beams using self-compacting concrete subjected to corrosion(Springer Science and Business Media Deutschland GmbH, 2021) Manjunath, R.; Narasimhan, M.C.; Bibesh Nambiar, C.Effect of corrosion on RCC–SCC deep beams subjected to three different percentages of corrosion have been investigated in the present study. These SCC mixes were designed for obtaining a cube strength of M-30 grade using river sand as finer portions of the aggregate and 12.5 mm downsize jelly as coarse aggregate. Design of SCC reinforced concrete deep beams was carried out as per IS-456:2000 and the accelerated corrosion technique has been employed for carrying out the corrosion. All the trial SCC mixes were subjected to different flow ability tests in order to evaluate their SCC property as per the EFNARC guidelines. From the obtained test results, it can be observed that for the lower percentage of corrosion decrease in ultimate flexural strength was observed due to decrease in arch action. Further with increase in percentage of corrosion showed an increased ultimate flexural strength due to increase in arch action. © Springer Nature Singapore Pte Ltd 2021.Item Predicting the Service Life of Reinforced Concrete by Incorporating the Experimentally Determined Properties of Steel–Concrete Interface and Corrosion(Springer Science and Business Media Deutschland GmbH, 2021) Sumukh, E.P.; Goudar, S.K.; Das, B.B.Service life of a reinforced concrete structure depends on its durability in aggressive exposure conditions. In the case of reinforced concrete structures, the phenomenon that directly affects its durability is corrosion of rebar, which has direct influence on the residual service life. Corrosion in reinforced concrete basically initiates at its weakest zone called steel–concrete interface due to its porous nature. The extent of this porous zone is being represented in terms of Porous zone thickness which has been extensively reported by various researchers. This porous zone thickness is one of the key influencing factors in the prediction of residual service life of the reinforced concrete structure. Several mathematical models were proposed by various researchers to estimate the time required for cover cracking of concrete due to rebar corrosion by assuming different values of porous zone thickness (PZT) without any systematic experimental investigation. Assuming a steady value of PZT for all kinds of concrete without any practical justification will misinterpret the predicted residual service life. In the present work, an effort has been made to evaluate an existing analytical model to predict the time to concrete cover cracking by incorporating the experimentally obtained and published data on porous zone thickness. It was found that the porous zone thickness and rate of corrosion have a major role in evaluating the residual service life of reinforced concrete structures. © 2021, Springer Nature Singapore Pte Ltd.Item Elucidating Corrosion Behavior of Hastelloy-X Built Using Laser Directed Energy Deposition-Based Additive Manufacturing in Acidic Environments(Springer Science and Business Media Deutschland GmbH, 2021) Diljith, P.K.; Jinoop, A.N.; Paul, C.P.; Krishna, P.; Bontha, S.; Bindra, K.S.This paper reports an investigation on the electrochemical corrosion behavior of laser directed energy deposition (LDED)-based additive manufacturing built Hastelloy-X (Hast-X) bulk samples for the first time in various acidic environments (2M HNO3, 2M HCl, and 2M H2SO4). Open-circuit potential results reveal that corrosion activity is more in HCl than the other two media. The corrosion rate (CR) estimated using the Tafel extrapolation method shows that the corrosion rate (CR) is the most in HCl and least in HNO3. Potentiodynamic studies reveal active–passive behavior of Hast-X in all the media and it is seen that the material stays in passivation for a longer potential range in HCl. Further, pitting potential is observed to be comparable in all three media. The cyclic polarization curve shows no loops, which points out the absence of pitting in the samples immersed in any of the media. The estimated CR for Hast-X in all the acidic environments under investigation comes within the acceptable CR for nickel-based alloys (4 mpy). The morphology of the corroded surface is analyzed using stereo microscope and it confirms the absence of pitting in all the three samples. These observations confirm the suitability of LDED built Hast-X components for applications in investigated acidic environments. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.