• Journal of the Korean institute of surface engineering
• /
• v.49 no.3
• /
• pp.280-285
• /
• 2016

In this study, we investigated the influences of potassium fluoride(KF) addition on the surface characteristics of plasma electrolytic oxidation(PEO) coating produced on Al alloy. The PEO of marine grade Al alloy(5083 grade) was conducted in KOH 1g/L solution adding different concentrations of KF(0, 1 and 2 g/L) under a galvanostatic regime. With KF addition, unusual behavior was observed on the voltage-time characteristic curves, which can be characterized by the following process: (i) initial rapid increase in voltage (ii) a short plateau after 1st breakdown (iii) gradual increase in voltage (iv) intermittent fluctuation of voltage after 2nd breakdown. The SEM observation revealed irregular surface morphology with KF addition, as compared with one formed without KF addition, which had a reticulate structure. The XRD analysis detected the formation of aluminium hydroxide fluoride hydrate($H_{4.76}Al_2F_{3.24}O_{3.76}$) on surface grown by PEO process with KF. Particularly, at very early stage of the process (~ 120 s), thin film was formed having nanoporous structure, and F element was confirmed on surface by EDS analysis. The thickness and surface roughness of the coating increased with increasing KF concentration. As a result, KF addition was found to be less beneficial influences on PEO of marine grade Al alloy, and therefore needs further research to improve its capability.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.5
• /
• pp.366-372
• /
• 2017

Plasma electrolytic oxidation(PEO) has attracted attention as a surface treatment which has high wear resistance and corrosion resistance. PEO is generally considered as cost-effective, environmentally friendly and superior in terms of coating performance. Most of studies about the PEO processes have been applied to light metals such as Al and Mg. Because the strength of Al and Mg is weaker than that of steel, there is a limit to the application. In this study, PEO process was used to form oxide coatings on Hot dipped aluminized(HDA) steel and the characteristics of the coating film according to the PEO current density were studied. The morphology was observed by SEM and component was analyzed by using EDS. The corrosion behaviors of PEO coating films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of PEO process current density, the pore size of the coating surface and the thickness of coating increased. It was confirmed that no Fe component was present on the coating surface. PEO coating films obviously showed good corrosion resistance compared with HDA. It is considered that the PEO coating acts as a barrier to protect the base material from external factors causing corrosion.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1995.10a
• /
• pp.82-85
• /
• 1995

Magnetic-electrolytic-abrasive polishign(MEAP) systemwas newly developed and the finishing characteristics of Cr-coated roller was analyzed. The paper describes the operational principle of MEAP system and magnetic field effect on the MEAP process by experimental results. The finishing characteristics and optimal finishing condition for Cr-coated roller were experimented and analyzed.

• Journal of the Korean Chemical Society
• /
• v.13 no.2
• /
• pp.165-169
• /
• 1969

On the electrolytic preparation of sodium chlorate, lead dioxide anode, instead of graphite was tested to find out the characteristics for current efficiency and life in various conditions. The results obtained are summerized as follows; 1. The current efficiency is slightly increased with the anode current density, until 25A/$dm^2$ 2. The higher the current concentrations. the lower current efficiencies are observed, particularly in case of both not-adding the potassium dichromate and large current concentration of more than 50A/l 3. The current efficiency may be improved linearly as the both temperature is raised.

• International Journal of Precision Engineering and Manufacturing
• /
• v.1 no.1
• /
• pp.127-132
• /
• 2000

A highly efficient mirror surface grinding technology has been developed for hard and brittle materials various metal materials, by employing the ELID (electrolytic in-process dressing) grinding method using metal bonded grinding wheels. In this research, some typical applications of ELID-grinding for cylindrical grinding are introduced and the mirror grinding characteristics are investigated. Good results are obtained in the grinding of ceramics and tungsten carbide.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1998.10a
• /
• pp.38-43
• /
• 1998

Magneto Electrolytic Polishing (MEP) is a process in which metal ions are removed from a abrasive through a combination of magnetic electric current and chemical solution. The substrate is immersed into the magnetic effect, chemical solution, and DC crunt is applied. Several factors affect the rate at which the metal ions are removed from the substrate. Three of the most significant are the amount of time in which the substrate is immersed I the solution, and the amount of direct current applied in magnetic field. In this study, the surface finishing characteristics and optical finishing condition for the stainless steel were experimented upon and analyzed.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.2 no.4
• /
• pp.25-32
• /
• 2003

In this study, the grinding characteristics of CBN wheels, such as grinding force and surface roughness, have been compared and analyzed from various working conditions of spindle speed and depth of cut. To actualize high efficient grinding at ceramic and silicon nitride material, electrolytic in-process dressing (ELID) method has been applied at metal bonded diamond and CBN wheels. Super precision grinding using ductile mode at difficult-ta-cut materials could be performed.

• Textile Coloration and Finishing
• /
• v.21 no.6
• /
• pp.56-63
• /
• 2009

In this study we have evaluated the separation characteristics and concentration of sericin using tubular type ultrafiltration membrane in silk degumming solution that extracted from electrolytic reduction water process. Ultrafiltration membranes have used in sericin separation performance and the separation characteristics of membrane satisfied typical Hagen-Poiseuille equation. It had the increase of flux according to the increase of feed pressure and temperature in occasion of pure water flux. And also the flux and solute rejection had about $25{\sim}60{\ell}/m^2{\cdot}h$ and more than 95% in sericin feed solution with concentration 1.00~1.89% at feed pressure force of $3{\sim}8kgf/cm^2$ respectively. In addition, the separation performance of tubular type ultrafiltration membrane for silk degumming solution was very steady-state with long experiment time.

• Journal of Radiation Protection and Research
• /
• v.27 no.2
• /
• pp.95-100
• /
• 2002

Conventional and modified electrolytic decontamination experiment were performed in the 1.7 M solution of sodium sulfate and sodium nitrate tot decontamination of carbon steel as the simulated metal wastes which have been produced in large amounts from nuclear power plants. Anode ant cathode were used as inconel and titanium respective. The reaction time and temperature were 1 hr and $25^{\circ}C$ The analyses were performed of the characteristics such as weight loss arid thickness change of metal waste. suspended solid in electrolyte and SEM observation. In modified electrolyte decontamination system with increased current density ranged from 0.1 to $0.6A/cm^2$, the metal waste showed thickness changes of $0.48{\pm}0.005$ to $67.7{\pm}0.02{\mu}m$ in 1.7 M sodium sulfate and those of $0.06{\pm}0.005$ to $17.7{\pm}0.05{\mu}m$ in sodium nitrate. Metal waste in modified electrolyte decontamination system showed the thickness change of $9.8{\pm}0.01{\mu}m$ while it reacted up to $3.7{\pm}0.03{\mu}m$ in conventional system with $0.3 A/cm^2$ of current density and 1.7 M sodium sulfate. Decontamination efficiencies of modified electrolytic process ate much hither than that of conventional electrolytic process when both are applied to metal waste.

• Korean Chemical Engineering Research
• /
• v.50 no.4
• /
• pp.696-701
• /
• 2012

Non-aqueous processes have been developed for stable management and reuse of spent fuels. Nowadays, a plan for the management of spent fuel is being sought focusing on a non-aqueous process in Korea. Named as pyroprocessing, it includes an electrolytic reduction process using molten salt at high temperature for the spent fuels, which provides metallic product for a following electro-refining process. The electrolytic reduction process utilizes electrochemical reaction producing Li to convert oxides into metals in high temperature LiCl medium. Various kinds of elements in the spent fuels would be distributed in the system according to their respective reactivity with the reductant, Li, and the medium, LiCl. This study elucidates the reactions of the elements to understand the behavior of composite elements on the spent fuels by thermodynamic calculations. Uranium and transuranic are reduced into their metallic forms while rare-earth oxides, except for Eu, are stable against the reaction at a process temperature. This study also covers the tendency of reactions with respect to the temperature and, finally, estimates radioactivity and heat load on the distributed phases based on the reference spent fuel characteristics.