• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.31-32
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• 2001

Recently, many of the current development in surface modification engineering are focused on multilayered coatings. Multilayered coatings have the potential to improve the tribological and corrosion properties of tools and components. By using cathodic arc deposition, $WC-Ti_{1-x}Al_xN$ multilayers were deposited on steel substrates. Wear tests of four multiplayer coatings were performed using a ball-on-disc configuration with a linear sliding speed of 0.1m/s, 5N load. The tests were carried out at room temperature in airby employing AISI 52100 steel ball ($H_v=848N$) of 11mm in diameter. Electrochemical tests were performed using the potentiodynamic and electrochemical impedance spectroscopy (EIS) measurements. The surface morphology and topography of the wear scars of tribo-element and the corroded specimen have been determined by using scanning electron spectroscopy (SEM). Also, wear mechanism was determined by using SEM coupled with EDS. Results have showed an improved wear resistance and corrosion resistance of the $WC-Ti_{1-x}Al_xN$ coatings.

• Advances in materials Research
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• v.12 no.4
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• pp.263-271
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• 2023

In this study, AA1060/Alumina composites were fabricated by combined stir casting and accumulative press bonding (APB). The APB process was repeated up to six press bonding steps at 300Ċ. As the novelty, potential dynamic polarization in 3.5Wt% NaCl solution was used to study the corrosion properties of these composites. The corrosion behavior of these samples was compared and studied with that of the annealed aluminum alloy 1060 and versus the number of APB steps. So, as a result of enhancing influence on the number of APB process, this experimental investigation showed a significant enhancement in the main electrochemical parameters and the inert character of the Alumina particles. Together with Reducing the active zones of the material surfaces could delay the corrosion process. Also, at higher number of steps, the corrosion resistance of composites improved. The sample produced after six number of steps had a low corrosion density in comparison with high corrosion density of annealed specimens. Also, the scanning electron microscopy (SEM), was used to study the corrosion surface of samples.

• Corrosion Science and Technology
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• v.22 no.4
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• pp.242-251
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• 2023

The electrochemical corrosion behaviors of 304 stainless steels (STSs) with various coatings (organic coating and dry coating) were examined, and their applicability as bipolar plates in polymer electrolyte membrane fuel cells (PEMFCs) was validated. The results showed that the organic-coated samples had a significant decrease in anodic and cathodic current density compared to the uncoated sample. However, an increase in carbon black content in the organic coating or additional heat treatment at 700 ℃ resulted in a decrease in corrosion resistance. In addition, improvements in corrosion resistance achieved by adding TiO₂ powder to the organic coating were found to be limited. In contrast, dry coating with TiC and CrC exhibited higher corrosion potential, significantly lower current density, and reduced contact resistance compared to the organic coatings. Notably, the TiC-coated sample showed a comparatively lower current density and more stable behavior than the CrC-coated sample. Based on a series of experimental results, a thin TiC coating without defects is proposed as a promising surface treatment strategy for STS bipolar plates in PEMFC.

• Korean Journal of Materials Research
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• v.28 no.7
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• pp.428-434
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• 2018

Hydrogen evolution on a steel surface and subsequent hydrogen diffusion into the steel matrix are evaluated using an electrochemical permeation test with no applied cathodic current on the hydrogen charging side. In particular, cyclic operation in the permeation test is also conducted to clarify the corrosion-induced hydrogen evolution behavior. In contrast to the conventional perception that the cathodic reduction reaction on the steel in neutral aqueous environments is an oxygen reduction reaction, this study demonstrates that atomic hydrogen may be generated on the steel surface by the corrosion reaction, even in a neutral environment. Although a much lower permeation current density and significant slower diffusion kinetics of hydrogen are observed compared to the results measured in acidic environments, they contribute to the increase in the embrittlement index. This study suggests that the research on hydrogen embrittlement in ultra-strong steels should be approached from the viewpoint of corrosion reactions on the steel surface and subsequent hydrogen evolution/diffusion behavior.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.709-714
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• 2020

For zinc-air batteries, there are several limitations associated with zinc anodes. The self-discharge behavior of zinc-air batteries is a critical issue that is induced by corrosion reaction and hydrogen evolution reaction (HER) of zinc anodes. Aluminum and indium are effective additives for controlling the hydrogen evolution reaction as well as the corrosion reaction. To enhance the electrochemical performances of zinc-air batteries, mechanically alloyed Zn-Al and Zn-In materials with different compositions are successfully fabricated at 500rpm and 5h milling time. Investigated materials are characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), and energy dispersive spectrometer (EDS). Alloys are investigated for the application as novel anodes in zinc-air batteries. Especially, the material with 3 wt% of indium (ZI3) delivers 445.37 mAh/g and 408.52 mAh/g of specific discharge capacity with 1 h and 6 h storage, respectively. Also, it shows 91.72 % capacity retention and has the lowest value of corrosion current density among attempted materials.

• Corrosion Science and Technology
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• v.19 no.4
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• pp.203-210
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• 2020

The corrosion behavior of super austenitic stainless steel was studied by examining the characteristics of the sigma phase formed in the steel. A range of experimental and analytical methods was employed, including potentiodynamic polarization tests, critical pitting temperature tests, transmission electron microscopy, and energy-dispersive spectroscopy. Three steel samples with different sigma phase levels were obtained by intentionally adjusting the manufacturing process. The results showed that the corrosion resistance of the samples was strongly dependent upon the size and distribution of the sigma phase precipitated in the samples. The larger the size of the sigma phase, the higher the Mo content in the sigma phase and the higher the depletion level of Mo at the interface between the matrix/sigma phase, the more samples with a coarse-sized sigma phase were susceptible to localized pitting corrosion at the interface. These results suggest that various manufacturing processes, such as welding and the post-heat treatment of the steel, should be optimized so that both the size and fraction of the sigma phase precipitated in the steel are small to improve the resistance to localized corrosion.

• Analytical Science and Technology
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• v.5 no.1
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• pp.97-101
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• 1992

Potentiodynamic corrosion tests were conducted to know the corrosion characteristics of the NiTi intermetallic compound composed of pure Ni and Ti in artificial saline. Tafel extrapolation and linear polarization technique show similar results. Corrosion current Icorr and corrosion rate was increased in the order of NiTi

• Corrosion Science and Technology
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• v.6 no.5
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• pp.251-256
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• 2007

Plasma nitriding is a surface treatment process which is increasingly used to improve wear, fatigue and corrosion resistance of industrial parts. Active screen plasma nitriding (ASPN) has both the advantages of the classic cold wall and the hot wall conventional dc plasma nitriding (DCPN) method and the parts to be nitrided are no longer directly exposed to the plasma. In this study, AS plasma nitriding has been used to nitride the UNS S31803 duplex stainless steel, AISI 304 and AISI 316 austenitic stainless steel, and AISI 420 martensitic stainless steel. Treated specimenswere characterized by means of microstructural analysis, microhardness measurements and electrochemical tests in NaCl aerated solutions. Hardness of the nitride cases of AISI 420 stainless steel by Knoop test can get up to 1300 HK0.1. From polarization tests, the corrosion current densities of AISI 420 and UNS S31803specimens ASPN at $420^{\circ}C$ were generally lower than those of their untreated substrates. The corrosion resistance of UNS S31803 duplex stainless steel can be enhanced by plasma nitriding at $420^{\circ}C$ Cowing to the formation of the S-phase.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.315-323
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• 2021

In this study, we examined corrosion behaviors of two types of Pb alloys for a lead acid battery comparatively. One containing 6.6 wt% Sn, 36 mg/kg Bi, and 612.4 mg/kg Ca was prepared by twin-roll continuous casting. The other containing 5.2 wt% Sn, 30.5 mg/kg Ag, and 557 mg/kg Ca was made by twin-belt continuous casting. Potentiodynamic polarization tests were performed to evaluate corrosion resistance. Cyclic voltammetry was done to examine oxidation and reduction reactions occurring on the surface of each alloy in 4.8 M H₂SO₄ solution. Electrochemical test results implied that the Pb alloy prepared with the twin-belt casting method was less stable than that cast with the twin-roll method. Such results might be due to precipitations formed during the casting process. Rolling did not appear to affect the corrosion behavior of the twin-roll samples with Ag < 10 mg/kg, while it reduced the anodic reaction of Ag on the surface of the twin-belt sample with 30.5 mg/kg Ag.

• Corrosion Science and Technology
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• v.21 no.6
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• pp.487-494
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• 2022

Anodizing is a typical electrochemical surface treatment method that can improve the corrosion and insulating properties of aluminum alloys. The anodization process can obtain a dense structure. It can be used to artificially grow the thickness of an anodization film. Aluminum 3003 alloy used in this study is the most commonly used alloy for batteries due to its high strength and excellent formability as well as its weldability and corrosion resistance. Aluminum 3003 alloy was anodized at 0 ℃ with 0.3 M oxalic acid at 20 V, 40 V, or 60 V for 1 hour, 6 hours, or 12 hours. As a result of analyzing the composition of each specimen with an Energy Dispersive Spectrometer (EDS), aluminum was converted into an oxide film. The thickness of the formed anodization film increased when the applied voltage and anodization time increased. High corrosion potential values and low corrosion current density values were observed for the thickest oxide layer. The anodization film formed by anodization acted as a protective layer. The electrical resistance increased as the applied voltage and anodization time increased.