Faculty Publications

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    Effect of hydrodynamics on the flow accelerated corrosion (FAC) and electrochemical impedance behavior of line pipe steel for petroleum industry
    (Elsevier Ltd, 2019) Ajmal, T.S.; Arya, S.; Udupa, K.R.
    The present work focuses on the flow accelerated corrosion (FAC) study of API X70 steel in a synthetic solution of oilfield water under a turbulent flow with 3 m/s velocity in a loop system. Multiple electrodes are located at intrados and extrados of the 90° pipe elbow. The influence of flow on corrosion and passivation were examined using potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) tests. Corrosion current density for all the located specimens at intrados and extrados of the elbow are found to be increased however charge transfer resistances were significantly decreased along the fluid flow path. Corrosion rates of the electrodes located at the intrados are more than that at the extrados. Shear stresses are simulated using computational fluid dynamics (CFD) method and it is observed that the corrosion rate is inversely promotional to shear stresses. Surface morphology and corrosion products were examined using SEM and Raman spectroscopy. Raman spectroscopy indicates that the compositions of corrosion compounds formed by FAC are FeCO3, ?-Fe2O3, ?-Fe2O3, ? – FeOOH, and ? – FeOOH. © 2019
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    Failure analysis of service exposed austenitic stainless steel pipelines
    (Elsevier Ltd, 2020) Sreevidya, N.; Abhijith, S.; Albert, S.K.; Vinod, V.; Banerjee, I.
    Several leaks appeared in Austenitic Stainless Steel (ASS) pipelines installed for transporting water in a test loop after a few years of operation at Indira Gandhi Centre for Atomic Research, Kalpakkam. The locations of leaks were mostly on pipe fittings like bends, but a few were noticed on the pipe away from the fittings too. This paper presents the results of failure analysis carried out on leaking of pipes and fittings. Investigation carried out include optical as well as scanning electron microscopy, energy dispersive spectroscopy, electron back scattered diffraction analysis and microhardness measurements. In addition, double loop electrochemical potentio-kinetic reactivation experiments were conducted on specimens extracted from the pipe side and fitting side of a weld that was found leaking. Further ASS pipe welds prepared with different surface finish conditions were exposed to the environment of the installed pipeline and surface degradation in these pipe welds were compared to reveal the effect of surface treatment on degradation of the welds. It is found that the sensitization along with residual stress generated during welding facilitated intergranular stress corrosion cracking in pipe fittings made of AISI 304 stainless steel resulting in the leaks observed in the pipe fittings. Cracks initiated from the corrosion pits present near the weld, which most likely would have formed due to improper cleaning given to the weld zone after completion of the weld. Leak observed in the pipe is attributed to the crevice corrosion that progressed from a defect present in the pipe making it grown across the thickness. The defect itself was result of an improper repair by arc welding, of a discontinuity that was found in the pipe. The pipe is produced from sheets by resistance welding and the origin of the discontinuity is the poor joint formation during resistance welding. The paper also gives recommendation on good fabrication practices to be followed so that similar kind of failures could be avoided in future. © 2019 Elsevier Ltd
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    A study on the behavior of CO2 corrosion on pipeline using computational fluid dynamics, experimental and artificial neural network approach
    (IOP Publishing Ltd custserv@iop.org, 2020) Nayak, N.; Anarghya, A.; Al Adhoubi, M.
    Corrosion of the piping systemis a genuine problem in the oil and gas industry.Most oil and gas industries used a carbon steel pipeline for the transportation of crude oil, which is affected by CO2 corrosion. Now a day, the computational approach and artificial neural network approach will be used to study the corrosion rate. Therefore, in this work, Computational Fluid Dynamics (CFD) and Artificial Neural Network (ANN) studies on piping systems were made to determine the corrosion rate induced byCO2 saturated aqueous solutions on carbon steel pipeline. In CFD study, corrosion rates were computed by modeling the electrochemical processes occurring at themetal substrate fromcathodic reductions of the carbonic acid and hydrogen ions, and the anodic oxidation of the metal component. Also, an artificial neural network study wasmade using a multilayer perceptron neural network method; and, computational fluid dynamics and artificial neural network simulations were validated with in-house built experiment set-up. The experimental study had been carried out for more than 200-h to find the corrosion rate on the pipeline, and satisfactory trendswere observed between computational fluid dynamics, artificial neural network, and experimental values. In the end, corroded pipes were observed under a scanning electron microscope and X-ray spectroscopy, and the corroded zones were viewed as against the non-corroded pipe. © 2020 IOP Publishing Ltd.
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    Influence of green inhibitor on flow-accelerated corrosion of API X70 line pipe steel in synthetic oilfield water
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Ajmal, T.S.; Arya, S.B.; Thippeswamy, L.R.; Quraishi, M.A.; Haque, J.
    Inhibition effect of oleic acid hydrazide (OAH), a green corrosion inhibitor on API X70 steel in an Indian oilfield produced water was investigated for the first time under flow condition. The test was carried out at a more critical location (90-degree pipe elbow) in a circulating loop system with the fixed flow velocity. This location is deliberately chosen because, at this location, catastrophic failure of a low alloy steel piping system usually takes place under highly corrosive turbulent flow with higher wall shear stress and flow velocity. The corrosion examination was carried out by varying the concentrations (0.05, 0.15, 0.30 g L?1) of the OAH inhibitor under flow condition. The maximum inhibitor efficiency is found 87.7% at 0.30 g L?1 concentration. The formation of protective film was confirmed by SEM, XPS, Raman spectroscopy and FTIR spectra. © 2020, © 2020 Institute of Materials, Minerals and Mining Published by Taylor & Francis on behalf of the Institute.
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    Effect of hydrodynamics and laser surface melting on erosion-corrosion of X70 steel pipe elbow in oilfield slurry
    (Elsevier Ltd, 2022) Ajmal, T.S.; Arya, S.B.; Maurya, P.; Shariff, S.M.
    Erosion-corrosion (EC) is a significant cause of pipeline failure in the petrochemical industry. The influence of laser surface melting (LSM) on the EC of API X70 steel was investigated with simulated oilfield slurry (1.5 wt% silica sand). The slurry was circulated continuously in a closed-loop apparatus at 3 m/s velocity and EC tests were performed using electrochemical corrosion and weight loss measurements for the untreated and LSM (2.5 kW) samples located at a 90⁰ pipe elbow. Since the erodent particle velocity and the flow rate are low, the EC was dominated by corrosion. LSM samples exhibited higher EC resistance and hardness due to the surface metallurgy alteration and the EC rate varies within the pipe elbow. The primary reasons for the severe EC rates of electrodes placed at the downstream side of the elbow's extrados (outer face) are the secondary flow effect and higher sand concentration. © 2022 Elsevier Ltd
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    Enhancing the Flow-Accelerated Corrosion Resistance of X70 API Steel Through Laser Surface Melting in Synthetic Oilfield Water
    (John Wiley and Sons Inc, 2025) Ajmal, T.S.; Singh, R.K.; Arya, S.B.; Kumar D, S.
    Hydrodynamic flow conditions play a critical role in piping failure due to sharp variations of the Reynolds number in process and petrochemical industries. The current study aims to enhance flow-accelerated corrosion (FAC) resistance using metallurgy of the surface by utilizing the laser surface melting (LSM) technique. The FAC behavior of API X70 steel in simulated Indian synthetic oilfield water was studied by utilizing a closed-loop corrosion apparatus to simulate the pipeline flow. Electrochemical corrosion experiments (AC and DC methods) were conducted at a constant fluid velocity of 3 m/s in untreated and LSM-treated samples (at 2.5 and 3.0 kW) placed at a 90° pipe elbow. Experimental results showed that LSM-treated samples displayed enhanced resistance to FAC, attributed to changes in surface metallurgy. Additionally, it was observed that the corrosion rate varied within the pipe elbow for the different samples at different locations. © 2024 Wiley-VCH GmbH.