• Corrosion Science and Technology
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• v.14 no.6
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• pp.253-260
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• 2015

The pitting behaviours of 304L and 316L stainless steels were investigated at $3^{\circ}C$ to $90^{\circ}C$ in 1 M solutions of NaCl, NaBr and NaI by potentiodynamic polarization. The temperature dependences of the pitting potential varied according to the anion, being near linear in bromide but exponential in chloride. As a result, at low temperatures grades 304L and 316L steel are most susceptible to pitting by bromide ions, while at high temperatures both stainless steels were more susceptible to pitting by small chloride anions than the larger bromide and iodide. Thus, increasing temperature appears to favour attack by smaller anions. This paper will attempt to rationalise both of the above findings in terms of the point defect model. Initial findings are that qualitatively this approach can be reasonably successful, but not at the quantitative level, possibly due to insufficient data on the mechanical properties of thin passive films.

• Corrosion Science and Technology
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• v.14 no.4
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• pp.195-199
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• 2015

Materials of choice for offshore structures and the marine industry have been increasingly favoring materials that offer high strength-to-weight ratios. One of the most promising families of light-weight materials is titanium alloys, but these do have two potential Achilles' heels: (i) the passive film may not form or may be unstable in low oxygen environments, leading to rapid corrosion; and (ii) titanium is a strong hydride former, making it vulnerable to hydrogen embrittlement (cracking) at high temperatures in low oxygen environments. Unfortunately, such environments exist at deep sea well-heads; temperatures can exceed $120^{\circ}C$, and oxygen levels can drop below 1 ppm. The present study demonstrates the results of investigations into the corrosion behavior of a range of titanium alloys, including newly developed alloys containing rare earth additions for refined microstructure and added strength, in artificial seawater over the temperature range of $25^{\circ}C$ to $200^{\circ}C$. Tests include potentiodynamic polarization, crevice corrosion, and U-bend stress corrosion cracking.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.3
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• pp.341-350
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• 2012

In this paper we observe the protective coatings carbon for steel, aluminium and titanium alloys were obtained by plasma electrolytic oxidation (PEO) under unipolar and bipolar conditions. The anticorrosion properties and the thermal stability of the surface layers were studied by electrochemical impedance spectroscopy and potentiodynamic polarization. It was found that the application of the bipolar PEO mode enables one to synthesize the surface layers that possess enhanced anticorrosion and mechanical properties. results of research of antiscale PEO - coatings for marine power equipment are presented. The combined method of prevention of corrosion and scale formation was tested at the industrial plants of Russian Shipyard "Zvezda".

• Journal of the Korean institute of surface engineering
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• v.47 no.1
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• pp.25-32
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• 2014

The effects of shot peening pressure on electrochemical and surface morphological characteristics of ALBC3 alloy were investigated in this work. The surface hardness of ALBC3 alloy was improved by shot peening process under all shot peening pressures between 2 and 5 bar, and the hight value of surface hardness was observed to be about 420 Hv at 4 bar of the shot peening pressure. The shot peened surface presented very rough surface due to shot ball collision. The result of anodic potentiodynamic polarization in seawater revealed that there is no significant difference between the shot peened and non-shot peened specimen in terms of corrosion characteristics. Therefore, the optimum projection pressure is determined to be 4 bar.

• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.115-131
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• 2016

Though battery chemistry and technology had been developed for over a hundred years back, increase in demand for storage energy, in the computer accessories, cell phones, automobile industries for future battery car and uninterrupted power supply, has made, the development of existing and new battery, as an emerging areas of research. With innovation of high energetic inexpensive Nano structure materials, a more energy efficient battery with lower cost can be competitive with the present primary and rechargeable batteries. Materials electrochemistry of electrode materials, their synthesis and testing have been explained in the present paper to find new high efficient battery materials. The paper discusses fundamental of electrochemistry in finding true cell potential, overvoltages, current, specific energy of various combinations of anode-cathode system. It also describes of finding the performance of new electrode materials by various experiments viz. i. Cyclic Voltammetry ii. Chronoamperometry iii. Potentiodynamic Polarization iv. Electrochemical Impedance Spectroscopy (EIS). Research works of different battery materials scientists are discussed for the development of existing battery materials and new nano materials for high energetic electrodes. Problems and prospects of a few promising future batteries are explained.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.625-630
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• 2003

Increasing environmental concerns require to solve the problem produced due to the use of heavy metals in coating formulations. Therefore, it is necessary to develop new coating strategy employing inherently conducting polymers such as Polyaniline(PANI). Polyaniline films were electrosynthesized by oxidation of aniline on cold rolled and weathering sheets using the potentiostatic mode from an aqueous oxalic acid medium. Potentiodynamic polarization curves were obtained for cold rolled and weathering sheets in the aqueous solution of 3% sodium chloride. The structure and properties of polyaniline film were elucidated using SEM, DSC, SST. A high corrosion resistance of polyaniline films were observed with a gain of the corrosion potential around 600-900 mV positive in the substrate covered with polyaniline than in the case without it.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.289-290
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• 2015

In this experiment, nitriding treatment has been performed at $400^{\circ}C$ with various $N_2$ content and with changing processing time on AISI 420 martensitic stainless steel to investigate the expanded martensite layer (${\alpha}^{\prime}_N$ layer) formation behavior. Nitriding was implemented with changing $N_2$ content from 10% to 25% for 15 hrs and processing time was changed from 4hr to 15hr at 25% $N_2$ content. After treatment, the behavior of the ${\alpha}^{\prime}_N$ layer was investigated by optical microscopy, X-ray diffraction, and micro-hardness testing. Potentiodynamic polarization test was also used to evaluate the corrosion resistance of the samples. It was found that the surface hardness and ${\alpha}^{\prime}_N$ layer thickness increases with increasing $N_2$ percentage and processing time. Although their corrosion behaviors are worse than the bare sample.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.175-177
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• 2012

A corrosion resistance and hard nitrocarburized layer was distinctly formed on 310 austenitic stainless steel substrate by DC plasma nitrocarburizing. Basically, 310L austenitic stainless steel has high chromium and nickel content which is applicable for high temperature applications. In this experiment, plasma nitrocarburizing was performed in a D.C. pulsed plasma ion nitriding system at different temperatures in $H_2-N_2-CH_4$ gas mixtures. After the experiment structural phases, micro-hardness and corrosion resistance were investigated by the optical microscopy, X-ray diffraction, scanning electron microscopy, micro-hardness testing and Potentiodynamic polarization tests. The hardness of the samples was measured by using a Vickers micro hardness tester with the load of 100 g. XRD indicated a single expanded austenite phase was formed at all treatment temperatures. Such a nitrogen and carbon supersaturated layer is precipitation free and possesses a high hardness and good corrosion resistance.

• Journal of Electrochemical Science and Technology
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• v.6 no.1
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• pp.7-15
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• 2015

3-(4-Iodophenyl)-2-imino-2,3-dihydrobenzo[d]oxazol-5-yl 4-methylbenzenesulfonate (4-IPhOXTs) was synthesized and its inhibiting action on the corrosion of stainless steel 316L (SS) in sulfuric acid was investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of the investigation show that this compound has excellent inhibiting properties for SS corrosion in sulfuric acid. Inhibition efficiency increases with increase in the concentration of the inhibitor. The adsorption of 4-IPhOXTs onto the SS surface followed the Langmuir adsorption model with the free energy of adsorption ΔG⁰_ads of −8.45 kJ mol⁻¹ . Quantum chemical calculations were employed to give further insight into the mechanism of inhibition action of 4-IPhOXTs.

• Journal of the Korean Ceramic Society
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• v.32 no.11
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• pp.1301-1307
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• 1995

Pitting corrosion of TiN film deposited on Inconel 600 by plasma assisted chemical vapor deposition (PACVD) was investigated. Cyclic potentiodynamic polarization (CPP) tests were conducted in order to determine the pit nucleation potentials, Enp, of the TiN-deposited sample and the bare Inconel 600 in deaerated NaCl solution at 25, 135 and 20$0^{\circ}C$. The effects of the TiN film thickness, the solution temperature and the Cl- concentration on Enp were studied. Enp of the TiN-deposited sample which had the film thickness above 1${\mu}{\textrm}{m}$ were higher than those of the bare Inconel 600 by 300~600mV at all the solution temperatures, implying the pitting resistance improvement of the TiN film. The morphologies of the pits generated after immersion test were examined with a scaning electron microscopy. The higher was the solution temperature, the more corrosion products, mainly composed of Cr and Ni oxides, were formed.