• Journal of the Korean institute of surface engineering
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• v.29 no.1
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• pp.60-72
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• 1996

A photoetching process is widely used for small and high precision parts in machinery, electronic and semi-conductor industries. One of the high precision parts, grid is very important part of digitron which use electron display, and it is fabricated by only photoetching process because of high precision. In this study, to develop high precision digitron grid, characteristics of etching solution were investigated with electrochemical test, that was potentiodynamic test and immersion test in the ferric chloride solution and added some additives. Based on the electrochemical etching test, grid was fabricated by continuous photoetching process at various etching condition. From the result of measured line width and etching depth under-cut and etching factor were calculated. For the fabrication of 25$\mu\textrm{m}$ line width, optimal etching condition was etching temperature 40~$45^{\circ}C$, spray pressure 1.5kg/$\textrm{cm}^2$ and etching time 3~4min.

• Journal of Power System Engineering
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• v.13 no.3
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• pp.33-39
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• 2009

The aim of this study is to analyze the welds characteristics of the 205 stainless steel pipe for application of street pole material. The welds corrosion behavior of STS 205 pipe in 0.1 N sulphuric acid solution and 5% NaCl solution at room temperature was studied using both salt spray test and potentiodynamic polarization experiment. The morphology and components of corrosion products on surface of STS 205 pipe welds were investigated using SEM/EDX. The tensile strength and yield strength values of STS 205 plate were 715 MPa and 369 MPa respectively. The microvickers hardness values of STS 205 pipe welds were slightly increased than that of STS 304 pipe welds. Corrosion current density($I_{corr.}$) and critical current density($I_{crit.}$) values of STS 205 pipe welds in 3.5% NaCl solution were $1.89{\times}10^{-6}$ $A/cm^2$ and $15.8{\times}10 ^{-6}$ $A/cm^2$. The corrosion resistance of SIS 205 pipe welds was similar to its STS 304 pipe welds. The STS 205 and 304 pipe welds passive films were chromium oxide. Especially, the STS 205 pipe welds showed good corrosion resistance in 0.1 N sulphuric acid. This is attributed to the forming of protective chromium oxide on the surface of STS 205 pipe welds.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.79-84
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• 2003

$WC-Ti_{1}$ -xA $l_{x}$ N multilayered coatings are performed by their periodically repeated structures of lamellae of WC-Ti/$WC-Ti_{1}$ -xA $l_{x}$ Nmaterials. The $WC-Ti_{1}$ -xA $l_{x}$ N coatings with variable Al content were deposited onto AISI D2 steel by cathodic arc deposition (CAD) method. The electrochemical behavior of multilayered $WC-Ti_{1}$ -xA $l_{x}$ N coatings with different phases (WC- Ti$0.6/Al_{0.4}$ N, $WC-Ti_{0.53}$$Al_{0.47}$N, $WC-Ti_{0.5}$ $Al_{0.5}$ N and $WC-Ti_{ 0.43}$$Al_{0.57}$ N) was investigated in deaerated 3.5% NaCl solution at room temperature. The corrosion behaviors for the multilayered coatings were investigated by electrochemical techniques (potentiodynamic polarization) and surface analyses (X-ray diffraction (XRD), scanning electron microscopy (SEM), and glow discharge optical emission spectroscopy (GDOES)). In the petentiodynamic polarization test, the corrosion current density of $WC-Ti_{0.5}$$Al_{0.5}$N was lower than others.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.801-808
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• 2012

TiAlCN coatings with various C contents were synthesized by unbalanced magnetron sputtering. The characteristics, the crystalline structure, surface morphology, hardness, and friction coefficient of the coatings as a function of the C content were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), a microhardness tester, and a wear test. In addition, their corrosion behaviors in a deaerated 3.5 wt% NaCl solution at $40^{\circ}C$ were investigated by potentiodynamic polarization tests. The results indicated that the $Ti_{14.9}Al_{15.5}C_{30.7}N_{38.9}$ coating had the highest hardness, elastic modulus, and a plastic deformation resistance of 39 GPa, 359 GPa, and 0.55, respectively, and it also had the lowest friction coefficient of approximately 0.26. Comparative evaluation of the TiAlCN coatings indicated that a wide range of coating properties, especially coating hardness, could be obtained by the synthesis methods and processing variables. The microhardness of the coatings was much higher than that from previously reported coating using similar magnetron sputtering processes. It was almost as high as the microhardness measured from the TiAlCN coatings (~41 GPa) synthesized using an arc ion plating process. The potentiodynamic test showed that the corrosion resistance of the TiAlCN coatings was significantly better than the TiAlN coatings, and their corrosion current density ($i_{corr}$), corrosion potentials ($E_{corr}$) and corrosion rate decreased with an increasing C content in the coatings. The much denser microstructure of the coatings due to the increased amount of amorphous phase with increasing C contents in the coatings could result in the the improved corrosion resistance of the coatings.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.370-374
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• 2008

In this study, we evaluated anti-corrosion properties of both commercial unleaded and lead epoxy primer for automotive substrate before applying to actual painting lines by salt spray test, and cyclic corrosion test, potentiodynamic test and electrochemical impedance spectroscopy. The difference in the corrosion resistance between automotive epoxy primers contained $Bi(OH)_{3}$ and leaded one was investigated. And it was also discussed the effect of zinc phosphate pretreatment to the epoxy primers. The specimen coated epoxy primer contained $Bi(OH)_{3}$ showed 0.5 V higher corrosion potential than that of bare steel. The result of salt spray test did not indicate remarkable difference of corrosion resistance in all specimens above $10{\mu}m$ thickness up to 1200 hours. In the cyclic corrosion test, epoxy primers contained $Bi(OH)_{3}$ on phosphated substrate performed good corrosion properties until 800 hours. The epoxy primer contained $Bi(OH)_{3}$ performed the equivalent corrosion resistance as leaded coating on phosphated steel, but slightly inferior to that of leaded on bare steel. These results show that the pre-treatment of zinc phosphate is effective as well as pigment changing in performing anti-corrosion properties in automotive bodies.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.628-641
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• 2006

Statement of problem: Dental magnetic materials have been applied to removable prosthetic appliances, maxillofacial prostheses, obturator and dental implant but they still have some problems such as low corrosion resistance in oral environments. Purpose: To increase the corrosion resistance of dental magnetic materials, surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels. Materials and methods : Surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels, and then three kinds of electrochemical corrosion test were performed in 0.9% NaCl solution; potentiodynamic, potentiostatic, and electrochemical impedance test. From this study, corrosion behavior, amount of elements released, mean average surface roughness values, the changing of retention force, and magnetic force values were measured comparing with control group of non-coated magnetic materials. Results: The values of surface roughness of TiN coated Sm-Co and TiN coated Nd-Fe-B based magnetic materials were lower than those of non coated Sm-Co and Nd-Fe-B alloy. From results of potentiodynamic test, the passive current density of TiN coated Sm-Co alloy were smaller than those of TiN coated Nd-Fe-B alloy and non coated alloys in 0.9% NaCl solution. From results of potentiostatic and electrochemical impedance test, the surface stability of the TiN coated Sm-Co alloy was more drastically increased than that of the TiN coated Nd-Fe-B alloy and non-coated alloy. The retention and magnetic force after and before corrosion test did not change in the case of TiN coated magnetic alloy sealed with stainless steel. Conclusion: It is considered that the corrosion problem and improvement for surface stability of dental magnetic materials could be solved by ion plating with TiN on the surface of dental magnetic materials and by sealing with stainless steels.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.576-584
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• 2020

The extruder screw material is mainly SKD11, but the recent development of synthetic resins have increased the occurrence of chemical corrosion and wear. To solve this issue, high chromium cast iron is needed because of its good abrasion resistance and corrosion resistance, but its use is avoided because of its poor machinability. In this study, to improve the machinability of high chrome cast iron, 0, 0.5, 1.0, 1.5% of nickel, which has excellent workability, was added to high chromium cast iron with a composition of Fe-23Cr-2.5C-1.2Si-1.08Mn-0.48Mo-0.3V, and annealed after casting. Subsequently, the effect of nickel on the machinability and corrosion resistance was analyzed using a turning test and coin polarization test, and compared with SKD11. After casting using a high-frequency vacuum induction furnace, the annealing treatment was performed at 750 ℃ for five hours and then reheated at 1100 ℃ for five hours. A turning test after annealing at 750 ℃ showed that the machinability was improved remarkably when the nickel content was over 1.0%. In the potentiodynamic polarization test in a 5% NaCl solution, the corrosion resistance decreased with increasing nickel content in the as-cast and annealing treatment. On the other hand, after reheating, the corrosion resistance was best with a 1.5% nickel content.

• Corrosion Science and Technology
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• v.17 no.2
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• pp.81-89
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• 2018

In this study, the effect of Nb alloying element on the corrosion fatigue properties of high strength steel is investigated by conducting fatigue experiments under corrosive condition and hydrogen induced condition, potentiodynamic polarization test, tensile test and surface analyses. Nb element is added to enhance the mechanical property of medium carbon steel. This element forms MX-type phases such as carbides and nitrides which are playing an important role in the grain refinement. The grain refinement is one of the effective way to improve mechanical property because both tensile strength and toughness can be improved at the same time. However, MX-type phase precipitates can be a susceptible site to localized corrosion in corrosive environment due to the potential difference between matrix and precipitate. The obtained results showed that Nb-added steel improved corrosion fatigue property by grain refinement. However, it is degraded for hydrogen-induced fatigue property due to Nb, Ti-inclusions acting as a stronger trap.

• Journal of Welding and Joining
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• v.4 no.3
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• pp.58-71
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• 1986

Mechanical and corrosion property of duplex stainless steel weldments made by the GTAW and SMAW process were studied. Fracture toughness, general and local corrosion resistance of GTAW and SMAW weldments were evaluated in terms of Charpy V notch impact test, anodic polarization diagram, pitting corrosion rate, respectively. SMA weld metal showed much lower impact toughness and higher ductile-brittle transition temperature than GTA weld metal. Fractographic and EDX analysis on fracture surface of SMA weld metal demonstrated the existence of (Si, Ti), oxide in large amounts. Potentiodynamic anodic polarization diagram of GMA weld metal showed much lower passive current density than SMA weld metal in 4% $H_2/SO_4$ solution. And pitting corrosion rate test showed the same tendency. Relating the microstructure, chemistry and property, it can be concluded that GTA weld metal gives better toughness due to lower oxygen content, i.e. lower inclusion content, and better corrosion resistance due to higher Pitting Index(PI) than SMA weld metal.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.269-272
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• 2000

The flow accelerated galvanic corrosion characteristics of a carbon steel coupled to stainless steel were investigated in deaerated alkaline-chloride solutions as a function of flow velocities(0, 0.2, 0.4 and 0.6 m/s), pH(8, 9, and 10) and temperature(25, 50 and $75^{\circ}C$). The electrochemical properties of specimens were investigated by potentiodynamic test and galvanic corrosion test using RCE(Rotating Cylinder Electrode). Carbon steel did not show passive behavior in the alkaline-chloride solution. The galvanic current density increases with increasing flow velocity and temperature, but decreased with increasing pH. Flow velocity had a small effect on the galvanic current density at $25^{\circ}C$, whereas the flow velocity increased galvanic current density significantly at $50^{\circ}C$ and $75^{\circ}C$. This might be due to the increased solubility of magnetite at the higher temperature.