• International Journal of Precision Engineering and Manufacturing
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• v.6 no.3
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• pp.56-59
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• 2005

Aluminum alloy casting is gaining increased acceptance in automotive and electronic industries and especially, squeeze casting is the most efficient method of mass manufacturing of such parts. In this study, the microstructures and mechanical properties of Al-7.0Si-0.4Mg(AC4C) alloy fabricated by squeeze casting process for development of fuel system parts (fuel rail) are investigated. The microstructure of squeeze cast specimen was composed of eutectic structure aluminum solid solution and $Mg_2Si$ precipitates. The tensile strength of as-solid solution treatment Al-7.0Si-0.4Mg alloy was 298.5MPa. It was found that Al-7.0Si-0.4Mg alloy had good corrosion resistance in electrochemical polarization test.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.77-83
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• 2002

Magnesium alloys casting are gaining increased acceptance in the automotive and electronic industeries and die casting is the most efficient method of manufacturing such mass produced parts. This study has been investigated the microstructures and mechanical properties of Mg-9Al-lZn alloy fabricated by die casting process for development of air bag case. The microstructure of die casted specimen were composed of pro-eutectic magnesium solid solution and $\beta$(Mg17Al12) precipitates. The tensile strength of as-fabricated Mg-9Al-lZn alloy revealed 231.4MPa. It was found that Mg-9Al-lZn alloy have good corrosion resistance in electrochemical polarization test.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.12
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• pp.48-54
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• 2003

Alumium alloys casting are gaining increased acceptance in the automotive and electronic industeries and squeeze casting is the most efficient method of manufacturing such mass produced parts. This study has been investigated the microstructures and mechanical properties of Al-7.0Si-0.4Mg (AC4C) alloy fabricated by squeeze casting process for development of Fuel system Parts (Fuel rail). The microstructure of squeeze casted specimen were composed of eutectic structure Alumimim solid solution and $Mg_2$Si precipitates. The tensile strength of as-solid solution treatment Al-7.0Si-0.4Mg ahoy revealed 298.5MPa. It was found that Al-7.0Si-0.4Mg alloy have good corrosion resistance in electrochemical polarization test.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.277-282
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• 2003

Holographic interferometry, an electromagnetic method, was used to study corrosion of carbon steel, aluminum and copper nickel alloys in NaOH, KCI and $H_2SO_4$ solutions respectively. The technique, called electrochemical emission spectroscopy, consisted of in-situ monitoring of changes in the number of fringe evolutions during the corrosion process. It allowed a detailed picture of anodic dissolution rate changes of alloys. The results were compared to common corrosion measurement methods such as linear polarization resistance measurements and electrochemical impedance spectroscopy. A good agreement between both data was found, thus indicating that holographic interferometry can be a very powerful technique for in-situ corrosion monitoring.

• Ceramist
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• v.22 no.2
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• pp.110-121
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• 2019

Triboelectric nanogenerators and piezoelectric nanogenerators are a spotlighted energy harvesting method that converts the wasted mechanical energy from the environment into usable electrical energy. In the case of triboelectric nanogenerators, researches have been mainly focused on high permittivity and flexible polymer materials, and in the case of piezoelectric nanogenerators, researches have been focused on ceramic materials exhibiting high polarization characteristics. Recently, many researches have been conducted to improve durability and power in various environments by using composite materials which have flexible properties of polymer, high permittivity, thermal resistance and high polarization properties of ceramics. This article reviews the energy harvesting studies reported about composites materials using ceramics and polymers.

• Corrosion Science and Technology
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• v.3 no.6
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• pp.240-244
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• 2004

Recently a variety of electrochemical techniques have been used for the measurement of under-film corrosion of coated steel. Each method has its own characteristic and is suitable to determine some kinds of anti-corrosive mechanisms of coating film. We developed a new under-film corrosion tester (UFCT) which adoped current interrupter technique in principle. Electrochemical parameters can be measured by UFCT. It is possible for the novel under-film corrosion tester to evaluate under-film corrosion of steel covered with high electric resistance coating film which has no defect and is not easy to evaluate it by other methods. Finally some experimental results of protective coating performance obtained by UFCT were discussed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.153-154
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• 2007

Mg thin films were prepared by PVD method on electroplated Zn steel substrate. And the influence of gas pressure on their morphology and crystal orientation of the deposited films were investigated by scannig electron microscopy(SEM) and X-ray diffraction(XRD), respectively. In addition, the effect of corrosion resistance of these films as a funtion of morphology and crystal orientation was evaluated by anodic polarization test. From the measured results, it is investigated that the film of granular structure which deposited in condition of high gas pressure had the highest corrosion resistance.

• Corrosion Science and Technology
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• v.17 no.1
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• pp.20-29
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• 2018

Ti and its alloys show the excellent corrosion resistance to chloride environments, but they show less corrosion resistance in HCl, $H_2SO_4$, NaOH, $H_3PO_4$, and especially HF environments at high temperature and concentration. In this study, we used the commercially pure titanium and Ti-6Al-4V alloy, and evaluated the effect of the manufacturing process on the electrochemical properties. We used commercial products of rolled and forged materials, and made additive manufactured materials by DMT (Directed Metal Tooling) method. We annealed each specimen at $760^{\circ}C$ for one hour and then air cooled. We performed anodic polarization test, AC impedance measurement, and Mott-Schottky plot to evaluate the electrochemical properties. Despite of the difference of its microstructure of CP-Ti and Ti-6Al-4V alloys by the manufacturing process, the anodic polarization behavior was similar in 20% sulfuric acid. However, the addition of 0.1% hydrofluoric acid degraded the electrochemical properties. Among three kinds of the manufacturing process, the electrochemical properties of additive manufactured CP-Ti, and Ti-6Al-4V alloys were the lowest. It is noted that the test materials showed a Warburg impedance in HF acid environments.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.90.2-90.2
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• 2010

The coated metallic bipolar plates are getting attractive due to their good feasibility of mass production, low contact resistance, high electrical/thermal conductivity, low gas permeability and good mechanical strength comparing with graphite materials. Yet, metallic bipolar plates for polymer electrolyte membrane(PEM) fuel cells typically require coatings for corrosion protection. Other requirements for the corrosion protective coatings include low electrical contact resistance between metallic bipolar plate and gas diffusion layer, good mechanical robustness, low mechanical and fabrication cost. The authors have evaluated a number of protective coatings deposited on stainless steel substrate by electroplating. The coated metallic bipolar plates are investigated with an electrochemical polarization tests, salt dipping tests, adhesion tests for corrosion resistance and then the contact resistance was measured. The results showed that the selective samples electroplated with optimized method, satisfied the DOE target for corrosion resistance and contact resistance, and also were very stabilized in the typical fuel cell environments in the long-term.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.72-77
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• 2005

The materials used in a ship screw propeller are commonly made with brass. The seawater corrosion and seawater cavitation of the screw propeller reduces the propulsive performance of the ship. In screw manufacturing, the corrosion rust of the screw propeller is removed through a hand grinding method. The grinding process produces dust of the heavy metals from the brass. The dust creates a poor working environment that is harmful to the health of the workers. An automatic corrosionrust removing apparatus, using a blasting method, was developed for the improvement of screw polishing conditions and its working environment. The performance of this apparatus was investigated by surface roughness, weight loss rate, hardness, electrochemical corrosion resistance, and cavitation erosion, after removing of the corrosion rust under various blasting conditions. Two medias of alumina and emery were used in this experiment. The surface roughness and hardness of the screw were improved by this apparatus. The electrochemical corrosion potential (Ecorr) and current density (Icorr) were measured by the dynamic polarization method, using a potentiostat,under the conditions of surface polishing with grinding, blasting, wire brushing, and fine sand papering. The test results prove that the new corrosion rust-removing apparatus improves the surface performance of a screw propeller.