• Korean Journal of Materials Research
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• v.20 no.4
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• pp.187-193
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• 2010

Chromium nitride (CrN) samples with two different layer structures (multilayer and single layer) were coated on bipolar plates of polymer electrolyte membrane fuel cells (PEMFC) using the reactive sputtering method. The effects with respect to layer structure on corrosion resistance and overall cell performance were investigated. A continuous and thin chromium nitride layer ($Cr_{0.48}\;N_{0.52}$) was formed on the surface of the SUS 316L when the nitrogen flow rate was 10 sccm. The electrochemical stability of the coated layers was examined using the potentiodynamic and potentiostatic methods in the simulated corrosive circumstances of the PEMFC under $80^{\circ}C$. Interfacial contact resistance (ICR) between the CrN coated sample and the gas diffusion layer was measured by using Wang's method. A single cell performance test was also conducted. The test results showed that CrN coated SUS316L with multilayer structure had excellent corrosion resistance compared to single layer structures and single cell performance results with $25\;cm^2$ in effective area also showed the same tendency. The difference of the electrochemical properties between the single and multilayer samples was attributed to the Cr interlayer layer, which improved the corrosion resistance. Because the coating layer was damaged by pinholes, the Cr layer prevented the penetration of corrosive media into the substrate. Therefore, the CrN with a multilayer structure is an effective coating method to increase the corrosion resistance and to decrease the ICR for metallic bipolar plates in PEMFC.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.587-592
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• 2002

Fiber reinforced concrete has been used for tunnel lining and rehabilitation of old structures. Recently, structural synthetic fiber was developed to overcome the corrosive properties of steel fibers. Fibers play a role to increase the tensile and cracking resistance of concrete structures. The Post cracking behavior must be clarified to predict cracking resistance of fiber reinforced concrete. The purpose of the present study is to develop a realistic analysis method for post cracking behavior of synthetic fiber reinforced concrete members.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.102-108
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• 2023

A Chloride-induced stress corrosion cracking (CISCC) of austenite stainless steel in dry cask storage system (DCSS) can occur with extending service time than originally designed. Cold spray coating (CSC) not only form a very dense microstructure that can protect from corrosive environments, but also can generate compressive stress on the surface. This characteristic of CSC process is very helpful to increase the resistance for CISCC. CSC with several powders, such as 304L, 316L and Ni can be optimized to form very dense coating layer. In addition, the impact energy generated as the CSC powder collides with the surface of base metal at a speed of Mach 2 or more can remove the residual tensile stress of welding area and serve the compress stress. CSC layers include no oxidation and no contamination with under 0.2% porosity, which is enough to protect from the penetration of corrosive chloride. Therefore, the CSC coating layer can be accompanied by a function that can be disconnected from the corrosive environment and an effect of improving the residual stress that causes CISCC, so the canister's CISCC resistance can be increased.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.365-369
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• 2004

Recently, Inconel 625 is used widely in offshore processing piping in order to extend the maintenance tenn and improve the quality of anti-corrosion. According to the resistance to attack in various corrosive media at temperatures from $200^{\circ}C$ to aver $1090^{\circ}C$, in combination with good low- and high-temperature mechanical strength. In general, High quality weldments for this material are readily produced by commonly used processes. in recent years, the flux cored arc welding(FCAW) process is becoming more popular due to higher deposition rate and a better weld quality as compared to the shielded metal arc welding (SMAW) process, at the same time, exhibiting equally good weld metal toughness similar to the SAW process. In this study, the weldability and weldment characteristics(mechanical properties and corrosive environment) of Inconel 625 are considered in FCAW weld associated with the several weld shielding gases($80\%Ar\;+\;20\%\;CO_2,\;50\%Ar\;+\;50\%\;CO_2,\;100\%\;CO_2$) in viewpoint of welding productivity.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.399-406
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• 2005

Alloy 625 is used widely in industrial applications such as aeronautical aerospace, chemical, petrochemical and marine applications. Because of a good combination of yield strength. tensile strength, creep strength, excellent fabricability, weldability and good resistance to high temperature corrosion on prolonged exposure to aggressive environments. High qualify weldments for this material are readily produced by commonly used processes. But all of processes are not applicable to this material by reason of unavailability of matching, position or suitable welding filler metals and fluxes may limit the choice of welding processes. Recently, the flux cored wire is developed and applied for the better productivity in several welding position including the vortical position. In this study. the weldability and weldment characteristics of Alloy 625 are evaluated in FCAW weld associated with the several shielding gases($80\%Ar+20\%\;CO_2,\;50\%Ar+50\%\;CO_2.\;100\%\;CO_2$) in viewpoint of welding productivity. The results of the experimental study on corrosive characteristics of Alloy 625 are as follows; There is no remarkable difference among shielding gases. however they has a striking difference among corrosive solutions by results of distinguished density and time of corrosive solution. Generally, the shielding gases($80\%Ar+20\%\;CO_2$) was superior to the other gases on high temperature tensile and a low temperature impact. but all of the shield gases were making satisfactory results on corrosion test.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.103-110
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• 2019

As an anti-corrosion method in seawater, cathodic protection is widely recognized as the most effective and technically appropriate corrosion prevention methodology for marine structures against harsh corrosive environment. When applying the cathodic protection in seawater, the surface of the metal facilities the formation of compounds of $CaCO_3$ and $Mg(OH)_2$. These mixed compounds are generally called 'calcareous deposits'. This layer functions as a barrier against the corrosive environment and functions to further inhibit the corrosion process and then leading to a decrease in current demand for cathodic protection. However, calcareous deposit films are partially formed on the surface of the cathode and there are some difficulties to maintain both a corrosion resistance for a long period of time and a strong adhesion between deposits and base metal. In this study, the pulse electrodeposition process was applied to improve adhesion and corrosion resistance of the calcareous deposit films, and to solve the problem of hydrogen embrittlement at high current density. The uniform and compact calcareous deposit films were prepared by pulse electrodeposition process, and their properties were characterized using various surface analytical techniques together with electrochemical methods.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.472-483
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• 1999

Hard coatings playa continuously increasing role in the field of tribology as well as for decorative applications. In both areas they are often also exposed to corrosive media. While especially hard nitride coatings show a high corrosion resistance for themselves, hard $coating_strate systems may suffer from a severe corrosion attack due to the defects in the coating structure (pores, pinholes) resulting from the PVD-typical film morphology. While a huge number of investigations cover the tribological properties, only limited studies deal with the corrosion behavjour of coating substrate systems and attempts are made to improve their corrosion resistance. The present paper shortly describes the corrosion mechanisms and repots characteristic examples of the system behaviour. Special emphasis is laid on recent investigations to improve the corrosion resistance by alloying, interlayers or multilayered coating structures.es.

• Journal of the Korean institute of surface engineering
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• v.30 no.2
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• pp.93-103
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• 1997

High temperature materials used in the elevated temperature and corrosive atmosphere must have the good oxidation resistance and preserve their own mechanical properties simultaneously. For the oxidation resistance, it is very important to form a protective oxide scale such as $Al_2O_3$ or $Cr_2O_3$ on the substrate. However, the additions of protective oxide forming elements such as Cr and Al in the alloy to enhance its oxidation resistance are limited due to the deleterious effects on their mechanical properties. PECVD(P1asma Enhanced Chemical Vapor Deposition) coating processes were employed to improve the oxidation resistance at high temperature. Cr and/or A1 were coated on the substrates of Ni and Inconel 600 at various temperatures of 400, 500, $600^{\circ}C$ and at different conditions of specimen surfaces. Then, coated specimens were exposed to isothermal and cyclic oxidation conditions in air at 1000 and $1100^{\circ}C$. In order to enhance the adhesion between the substrate and coated layer, heat treatments of the coated specimens were conducted in a vacuum. At isothermal oxidation experiments, Al-coated Ni specimen showed better oxidation resistance than pure Ni. At cyclic oxidation experiments at $1000^{\circ}C$. Cr and Al-coated specimen showed better oxidation resistance. Cr-coated Inconel 600 had also showed better oxidation resistance due to Cr in the substrate. By PECVD coating process, oxidation resistance could be improved, but it was not improved as expected due to the weakness of the adhesion between the substrate and the coated layer.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.2
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• pp.3749-3757
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• 1975

This study was conducted to investigate some effects of Cemesol on acidresistance and compressive strength of concrete. In mix design of concrete, the cemesol was used as an admixture of cement, and it was added to the mix in an amount equal to 0.1%, 0.2%, 0.3%, and 0.4% by weight of cement of the mix. Concrete specimens were made in accordance with the. Korean Standard Specification for concrete and they were tested for acid-resistance and compressive strength at 2 weeks intervals through 8 weeks. The tests were performed in two cases non-curing and curing for 28 days. The results obtained from the tests are summarized as follows. 1. Refering to acid-resistance test, the cemesol was comparatively effective at every cemesol content except 0.3% in case of non-curing and it was found that cemesol content of 0.4% was the optimum. On the other hand, the cemesol was ineffective in case of curing, but it was seen that cemesol content of 0.1% had some effect at 6 to 8 weeks curing only. 2. Refering to compressive strength test, the cemesol was remarkably effective at a content of 0.1% but it was also shown most inefiective at content of 0.3% in case of non-curing. On the other hand the cemesol was comparatively effective at every content of cemesol except a content of 0.2% in case of curing and it was determined that the cemesol content of 0.3% may be an optimum content. 3. Since optimum cemesol content varied according to acid-resistance, compressive strength and cases such as non-curing and curing, as indicated above may be desirable to choose an optimum cemesol content suitable for purposes and ciroumstances of construction works or conditions of location. 4. The corrosive rate was proportional to compressive strength in case of non-curing, but the relation was reversed in case of curing. It was found that corrosive rate for 8 weeks did not influence compressive strength in case of non-curing but compressive strength in case of curing begins to vary under the influence of corrosion. Thus, corrosion may be more serious to compressive strength in case of curing than that in case of non-curing.

• Journal of Technologic Dentistry
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• v.34 no.3
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• pp.237-245
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• 2012

Purpose: This study was conducted to evaluate the corrosion resistance of metal ions of alloys and use the results as the dental health data. These were performed by examining the corrosion levels of Co-Cr alloys for the full and removable partial denture metal frameworks and porcelain-fused-to-metal crown, among the dental casting nonprecious alloys. Methods: The alloy specimens (N = 10) were manufactured in $15mm{\times}10mm{\times}1.2mm$ and stored in two types of corrosive solutions at $37^{\circ}C$ for seven days. The metal ions were quantitatively analyzed using the Inductively Coupled Plasma-Atomic Emission Spectrometer. Results: Of the three Co-Cr alloys, the Co ion concentration of the porcelain-fused-to-metal alloy was 1.512 ${\mu}g/cm^2$, which indicated the highest metal ion dissolution. The metal corrosion was higher in the more acidic pH 2.2 solution compared with the pH 4.4 solution. In all three Co-Cr alloys, Co ion dissolution was predominant in the two corrosive solutions. Conclusion: The corrosion resistance of the three Co-Cr alloys was high, indicating a good biocompatibility.