• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
• /
• v.4 no.4
• /
• pp.255-261
• /
• 2000

Experiments were carried out to measure the corrosion potential and current density variations in the polarization curves of polypropylene. In particular, the results were examined to identify those influences affecting the corrosion potential, such as temperature, pH, salt, and oxygen. The Tafel slope for the anodic dissolution was determined based on the polarization effect under various conditions. Furthermore, the optimum conditions for the most rapid transformation were establish based on a variety of conditions, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(I(sub)r/I(sub)f). This I(sub)r/I(sub)f value was then used to measure the critical corrosion sensitivity of polypropylene. The potentiodynamic parameters of corrosion were obtained using a Tafel plot.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.8
• /
• pp.869-874
• /
• 1999

In this paper, electrochemical techniques are used to investigate hydrothermal-electrochemically formation of barium titanate (BT) ceramic films. For comparison, the electrochemical behaviors of anodic titanium oxide films formed in alkaline solution were also investigated both at room temperature and in hydrothermal condition at 150.0 ℃. Film structure and morphology were identified by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Titanium oxide films produced at different potentials exhibit different film morphology. The breakdown of titanium oxide films anodic growth on Ti electrode plays an important roles in the formation of BT films. BT films can grow on anodic oxide/metal substrate interface by short-circuit path, and the dissolution-precipitation processes on the ceramic film/solution interface control the film structure and morphology. Based upon the current experimental results and our previous work, extensively schematic proce-dures are proposed to model the mechanism of ceramic film formation by hydrothermal-electrochemical method.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1997.05a
• /
• pp.91-91
• /
• 1997

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.585-588
• /
• 2005

The dissolution characteristic of metal shows the different tendency according to the applied electrical potential, the kind of electrolyte and pH value, etc. In the micro electrochemical machining (ECM), unfavorable oxide/passive layer formation and overall corrosion of electrodes must be prevented. The anodic polarization curve of nickel has distinct three dissolution regions, i.e. two active regions and the transpassive dissolution region. In this paper, the stable electrode potentials of workpiece and tool were determined in sulfuric acid and hydrochloric acid solution, respectively. In each solution, different machining property was shown and possible electrochemical reactions were discussed. On the basis of this experiment, the methodology to obtain the proper electrode potential was suggested.

• International Journal of Precision Engineering and Manufacturing
• /
• v.2 no.1
• /
• pp.18-25
• /
• 2001

Electrolytic polishing is the anodic dissolution process in the transpassive state. It removes non-metallic inclusion and improves mechanical and corrosion resistance of stainless steel. If there is a Bailby layer, it will be removed and the true structure of the surface will be restored. Electrolytic polishing is normally used to remove a very thin layer of material from the surface of metal object. A new electrolyte composed of phosphoric, sulfuric and distilled water has been developed in this study. Two current density, high & low current density regions, have been applied in this study. In this study, In the region of high current density, there is no plateau region but excellent electrolytic polishing effect can be accomplished in short machining time because material removel process and leveling process occur simultaneously. In the low current density region, there can be found plateau region. The material removal process and leveling process occur successively. The aim of this work is to determine electrolytic polishing for stainless steel in terms of high & low current density and workpiece surface roughness.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.3
• /
• pp.163-168
• /
• 2010

Effects of Cetyl Trimethyl Ammonium Bromide (CTAB), which is a kind of cationic surfactants, and Sodium Dodecyl Sulfate (SDS), which is a kind of anionic surfactants on the anodic formation of nanoporous niobium oxide were compared. The addition of SDS could protect the surface from dissolution for long time, leading to the formation of niobium oxide with a double thickness (~400 nm) compared to that prepared without surfactant, whereas dissolution seriously occurred in the solution containing CTAB. The different behaviors were attributed to the interaction between the surfactants with positive (or negative) charge and positively charged niobium oxide.

• Journal of the Korean Electrochemical Society
• /
• v.18 no.3
• /
• pp.102-106
• /
• 2015

The performance of Li-B alloy as anode for molten salt electrolysis was firstly investigated. The crystalline phase of the prepared Li-B alloy was identified as $Li_7B_6$. The potential profile of Li-B alloy anode was monitored during the electrodeposition of $Nd^{3+}$ onto an LCC (liquid cadmium cathode) in molten LiCl-KCl salt at $500^{\circ}C$. The potential of Li-B alloy was increased from -2.0 V to -1.4 V vs. Ag/AgCl by increasing the applied current from 10 to $50mA{\cdot}cm^{-2}$. It was found that not only the anodic dissolution of Li to $Li^+$ but also the dissolution of the atomic lithium ($Li^0$) into the LiCl-KCl eutectic salt was observed, following the concomitant reduction of $Nd^{3+}$ by the $Li^0$ in Li-B alloy. It was expected that the direct reduction could be restrained by maintaining the anode potential higher that the deposition potential of neodymium.

• Journal of Electrochemical Science and Technology
• /
• v.3 no.2
• /
• pp.85-89
• /
• 2012

This study demonstrates the direct anodic electrodeposition of polypyrrole (PPy), poly(3,4-ethyl-enedioxythiophene) (PEDOT), and polythiophene (PTh) on Cu electrodes by employing a corrosion inhibitor, succinonitrile (SN). SN was found to suppress anodic Cu dissolution beyond the oxidation potential of the polymer monomers. It is also revealed that the Cu surface passivated by SN is still adequately conductive to allow the redox reaction of 1,4-difluoro-2,5-dimethoxybenzene (FMB) and the oxidation of the polymer monomers. Through both cyclic voltammetry and galvanostatic techniques, PPy, PEDOT, and PTh films were successfully synthesized on Cu electrodes in the presence of SN, and the redox behaviors of the films were evaluated.

• Journal of the Korean institute of surface engineering
• /
• v.12 no.3
• /
• pp.167-173
• /
• 1979

The structure of anodic aluminium oxide films formed in 2% oxalic asid at constant temperature was studied by the oid of the transmission and replica electron microscopy. Far the initial stage of oxidations, it is observed that pores are initiated from lattice defects as subgrain boundaries, and then spread radially. Some pores merge each other and the others cease to grow until the current density reaches to the steady state. The pore diameter and the cell size are proportional to the anodizing voltages, and it is considered that the pore initiation and growth are largely controlled by the field - assisted oxide dissolution.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2001.05a
• /
• pp.236-237
• /
• 2001

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves with amorphous $Fe_{70}Cr_5Si_{10}B_{15}$ and $Co_{70}Cr_5Si_{10}B_{15}$ alloy ribbon. The results were particularly examined to identify the influences of corrosion potential including various conditions such as hydrochloric acid, temperature, salt, pH, and oxygen. The optimum conditions were established with variations including temperature, salt, pH, oxygen, corrosion rate, and resistance of corrosion potential. The mass tranfer coefficient(${\alpha}$) value was determined with the Tafel's slope for the anodic dissolution based on the polarization effect with optimum conditions. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity($I_{r}/I_{f}$).