Faculty Publications
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Item Influence of Chloride Content and Exposure Time on Corrosion Behavior of AZ80 Wrought Mg Alloy(Springer Nature, 2020) Gote, G.D.; Naik, G.M.; Narendranath, S.This study aims to investigate the corrosion behavior of wrought AZ80 magnesium alloys in different chloride ion concentrations and exposure time. During the study, the effect of exposure time and chloride content on the corrosion resistance of AZ80 wrought Mg alloy has been studied with 2, 3.5, and 5 wt% NaCl aqueous solution for 12 h and 24 h exposure time. Charge transfer resistance for each sample was established using the Nyquist plot and corrosion rate obtained from polarization curve by adopting Tafel extrapolation method. Corrosion morphology was examined using scanning electron microscopy and XRD. The study revealed that corrosion product layer formed at initial stage was observed unstable after short exposure time which results in decrease in corrosion resistance at initial stage. An increase of chloride content in aqueous environment reduces the corrosion resistance of AZ80 wrought Mg alloy. © 2020, Springer Nature Singapore Pte Ltd.Item Corrosion Characteristics of Metal Matrix Composites(Elsevier, 2021) Bhat Panemangalore, D.; Bhat K, U.To tackle significant challenges posed by industries and environment with respect to materials degradation, we need to have a clear understanding of the impact of corrosion in different components. Composites are designed for a specialized application using different material combinations. This article presents an overview on different corrosion characteristics of metal matrix composites. Several types of corrosion have been addressed along with different corrosion methodologies. Corrosion of aluminum MMCs, magnesium MMCs, etc., have been discussed, along with different processing related problems. Different aspects involved in determining the corrosion behavior of metal matrix composites have been addressed. © 2021 Elsevier Ltd. All rights reserved.Item Electrochemical methods in tribocorrosion(Elsevier, 2021) Arya, S.; Joseph, F.J.Corrosion and wear mechanisms play a significant role in the degradation of components in various domains such as the petroleum industries, the automobile sector, and manufacturing and biomedical applications. The complex mechanisms of both corrosion and wear, including synergism, need to be well understood in order to design any system with maximum efficiency possible. This chapter is a brief on the concepts of electrochemistry in relation to tribocorrosion concepts. A three-electrode potentiostat system has proved to be a powerful tool in analyzing the chemical interactions within a specimen. The current-voltage response of the system enables the study of behavior of the surface and subsurface mechanisms in the specimen under existing tribocorrosive conditions. The passivation behavior in materials can be revealed with a detailed examination of electrochemical techniques. It also enables the monitoring of the response of coatings in the components in order to provide resistance against tribocorrosive attack. Various electrochemical techniques, such as open circuit potential, electrochemical impedance spectroscopy, polarization analysis, and their application in tribological systems, are discussed. © 2021 Elsevier Inc. All rights reserved.Item Failures Investigation of Marine Propellers in Corrosive Environments(Springer Nature, 2021) Mirashi, V.U.; Johnson, S.; Hegde, S.; Vijayan, V.; Cadambi, S.Marine corrosion failure of fishing boat propellers made of cast Nickel Aluminium Bronze were investigated. Specimens extracted from the corroded propellers were characterized by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The alloy comprises several Fe3Al (κ1, κ2, κ4), NiAl (κ3) type intermetallic precipitates and β’ martensite embedded in Cu-rich α-matrix. Transverse sections of the corroded region showed two distinct zones; a non-uniform top oxide layer and a partially corroded zone with selective corrosion of the β’ martensite which run parallel to the κ3 precipitates. From the microstructural analysis it is adjudged that the aggressive local corrosion of the matrix is preceded by cracking of the oxide by erosion, cavitation, etc., A slow growth of the oxide layer follows that reduces the corrosion rate. However, the corrosion cycle repeats on erosion or cracking of the oxide layer when the propeller is used in marine waters. Coupon specimens immersed in actual marine conditions is presented that supports the above theory. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Effect of pH on Electrodeposition of Ni–Cd Alloy Coatings and Their Anticorrosion Performance(Springer Nature, 2022) Gonsalves, C.N.; Sneha, I.M.; Hegde, A.C.Electroplating is a complex process controlled by bath composition and operating parameters. Among many operating parameters, the pH of the bath plays an important role in the process of deposition and properties of coatings. The present paper reports the effect of pH in the electrodeposition process of Ni–Cd alloy coatings from a low concentration bath of Ni–Cd alloy, using glycine as an additive. The experimental results revealed that change of pH over a wide range (from lower acidic to higher basic conditions) has a significant effect on the structure, morphology, and composition of the alloy electrodeposits. A considerable increase in the uniformity of coatings was found with an increase in bath pH. Electrochemical corrosion study carried out in 3.5% NaCl medium demonstrated higher corrosion resistance for Ni–Cd alloy coating, deposited at pH 8.0 compared to those deposited at lower pH. A change in the process of electro-crystallization was found with the change of pH, confirmed by the scanning electron microscopy (SEM) study. The improved corrosion resistance of alloy coatings was ascribed to the change of codeposition from anomalous to normal type, known by its Ni content confirmed by the energy dispersive X-ray spectroscopy analysis (EDAX). A change in phase structure was found with the change of pH, confirmed by the X-ray Diffraction (XRD) technique. Experimental results are analyzed in light of the theory of alloy deposition, and results are discussed. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Surface Engineered Titanium Alloys for Biomedical, Automotive, and Aerospace Applications(Springer Nature, 2023) Gudala, G.; Ramesh, M.R.; Srinath, M.S.This chapter provides an overview of surface modification of titanium alloy for applications in aerospace, automotive, and biomedical field. Current uses for titanium alloys are found in biomedical, automotive, aerospace, and other industrial applications. For aerospace uses, titanium alloys can be used for about 70% of the total, including engine components and airframe structures. Titanium alloys provide a notable advantage in several industrial applications, including heat exchangers, cooling systems in power stations, and chemical industries. In recent times, titanium alloys have been used in oil and gas drilling industries. It was observed that surface degradation of titanium alloy was observed in all the above applications after a certain amount of time or cycle. To enhance the surface properties of titanium alloy, surface engineering of titanium alloy with the appropriate surface modification technique is essential. The present trends predicted that industrial and commercial segments of titanium alloys could triple in the next five years. This chapter presents several case studies involving surface engineering techniques used for titanium alloys for potential automotive, biomedical, and aerospace applications. The demand for applications like the aerospace, biomedical, and automotive industry of titanium alloy boosts the ever-increasing demands for improving the surface modification of titanium alloys to meet the various needs. However, these alloys cannot possess all the desired attributes, especially important surface properties like wear and corrosion resistance. Therefore, surface modification techniques have to be used to enhance surface properties and satisfy the specific needs for various applications. This chapter discusses various surface modification methods used for titanium alloys to protect them from degradation. Titanium and titanium alloys can be extensively used in biomedical components and devices, especially in cardiac and cardiovascular applications, as hard tissue replacements. However, titanium alloys cannot meet all clinical requirements. Surface modification is often required to improve the biological, chemical, and mechanical properties. The present chapter also highlights the various surface modification techniques pertaining to titanium alloys, including thermal spraying, sol–gel, electrochemical treatment, and ion implantation from biomedical engineering. The present study focuses on improving the surface properties of titanium alloy for better wear resistance, corrosion resistance, and other biological properties using appropriate surface modification techniques while the desirable bulk attributes are retained. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.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.