• Journal of Surface Science and Engineering
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• v.53 no.5
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• pp.201-206
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• 2020

A SiOxCy(-H) thin film was synthesized by atmospheric pressure dielectric barrier discharge(APDBD), and a SiO₂-like layer was formed on the surface of the film by oxidation treatment using oxygen plasma. Hexamethylcyclotrisiloxane was used as a precursor for the SiOxCy(-H) synthesis, and He gas was used for stabilizing APDBD. Oxygen permeability was evaluated by forming an oxidized SiOxCy(-H) thin film on a PET film. When the single-layer oxidized SiOxCy(-H) film was coated on the PET, the oxygen gas permeability decreased by 46% compared with bare PET. In case of three-layer oxidized SiOxCy(-H) film, the oxygen gas permeability decreased by 73%. The oxygen permeability was affected by the thickness of the SiO₂-like layer formed by oxidation treatment rather than the thickness of the SiOxCy(-H) film. The excellent corrosion resistance was demonstrated by coating an oxidized SiOxCy(-H) thin film on the silver-coated aluminum PCB for light emitting diode (LED).

• Journal of Surface Science and Engineering
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• v.56 no.6
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• pp.443-450
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• 2023

SiC/SiC_f CMC is vulnerable to water vapor corrosion at a high temperature of 1500℃. So, EBC (Environmental Barrier Coating) materials are required to protect Si-based CMCs. Ytterbium silicates are reported to have coefficient of thermal expansion (CTE) similar to that of the base material, such as SiC/SiC_f CMC. When the EBC are materials exposed to high temperature environment, the interface between ytterbium silicates and SiC/SiC_f CMC is not separated, and the coating purpose can be safely achieved. For the perspective of EBC applications, thermally grown oxide (TGO) layer with different CTE is formed by the reaction with water vapor in EBC, which leads to a decrease in life time. In this study, we prepare two types of ytterbium silicates to observe the corrosion behavior during the expose to high temperature and water vapor. In order to observe this behavior, the steam-jet furnace is prepared. In addition, phase formation of these ytterbium silicates is analyzed with microstructures by the before/after steam-jet evaluation at 1500℃ for 100 h.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.895-900
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• 2013

Several plasma spray and metallurgical surface coatings such as $Al_2O_3$, $Cr_2O_3$, WC-Ni, and chromizing coating have been examined for their application in environments with high temperature, wear, and corrosion. The chromizing coating is different from others coatings in the manufacturing process the surface. These coatings' characteristics were tested experimentally, and the results were compared. WC-Ni shows good performance against thermal barrier, wear, and corrosion and is one of the best candidates for the environment considered herein. These coatings were studied for their application in the steel manufacturing industry. The most commonly required functions in this industry are thermal and wear resistance.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.105-105
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• 2016

Recently, high power impulse magnetron sputtering (HIPIMS) has attracted considerable attentions due to its high potential for industrial applications. By pulsing the sputtering target with high power density and short duration pulses, a high plasma density and high ionization of the sputtered species can be obtained. HIPIMS has exhibited several merits such as increased coating density, good adhesion, microparticle-free and smooth surface, which make the HIPIMS technique desirable for synthesizing hard coatings. However, hard coatings present intrinsic defects (columnar structures, pinholes, pores, discontinuities) which can affect the corrosion behavior, especially when substrates are active alloys like steel or in a wear-corrosion process. Atomic layer deposition (ALD), a CVD derived method with a broad spectrum of applications, has shown great potential for corrosion protection of high-precision metallic parts or systems. In ALD deposition, the growth proceeds through cyclic repetition of self-limiting surface reactions, which leads to the thin films possess high quality, low defect density, uniformity, low-temperature processing and exquisite thickness control. These merits make ALD an ideal candidate for the fabrication of excellent oxide barrier layer which can block the pinhole and other defects left in the coating structure to improve the corrosion protection of hard coatings. In this work, CrN/Al2O3/CrN multilayered coatings were synthesized by a hybrid process of HIPIMS and ALD techniques, aiming to improve the CrN hard coating properties. The influence of the Al2O3 interlayer addition, the thickness and intercalation position of the Al2O3 layer in the coatings on the microstructure, surface roughness, mechanical properties and corrosion behaviors were investigated. The results indicated that the dense Al2O3 interlayer addition by ALD lead to a significant decrease of the average grain size and surface roughness and greatly improved the mechanical properties and corrosion resistance of the CrN coatings. The thickness increase of the Al2O3 layer and intercalation position change to near the coating surface resulted in improved mechanical properties and corrosion resistance. The mechanism can be explained by that the dense Al2O3 interlayer acted as an excellent barrier for dislocation motion and diffusion of the corrosive substance.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.223-226
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• 2009

Polymer coatings are commonly applied to metal substrates to prevent corrosion in aggressive environments such as high humidity and under salt water. Once the polymer coating has been breached, for example due to cracking or scratches, it loses its effectiveness, and corrosion can rapidly propagate across the substrate. The self-healing system we will describe prevents corrosion by healing the damage through a healing reaction triggered by the actual damage event. This self-healing coating solution can be easily applied to most substrate materials, and our dual-capsule healing system provides a general approach to be compatible with most common polymer matrices. Specifically, we expect an excellent anti-corrosion property of the self-healing coatings in damaged parts coated on galvanized metal substrates.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.151-154
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• 2007

To build up the green roofs, it must not adverse effect to durability and structural safety. That is conducted by safety system which consist of waterproofing to form basically, root barrier to protect the waterproofing. The reason why root barrier form is to protect the penetration force of root growth and the root could penetrate concrete surface, move inward so far. It may cause shorten the life span on concrete structure. For this problem, government constantly demand the solution to form the root barrier for waterproofing and concrete structure before the building is service. However, the technical action is not fully prepared. Therefore, in this study, we would like to suggest the workability and suitability of the copper plate to solve not only the side of waterproofing but also root barrier for green roof system and exhibit the mechanism for root penetration resistance and corrosion resistance.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.1
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• pp.11-19
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• 2016

This paper focuses on the estimation of durability and service-life of reinforced concrete structures in Wolsong Low- and intermediate-level wastes Disposal Center (WLDC) in Korea. There are six disposal silos located in the saturated environment. The silo concrete is degraded due to reactions with groundwater and chemical attacks, and finally it will lose its properties as a transport barrier. The infiltration of sulfate and magnesium, leaching of potassium hydroxide, and chlorine induced corrosion are the most significant factors for degradation of reinforced concrete structure in underground environment. From the result of evaluation of the degradation time for each factor, the degradation rate of the reinforced concrete due to sulfate and magnesium is $1.308{\times}10^{-3}cm/yr$, and it is estimated to take 48,000 years for full degradation while potassium hydroxide is leached in depth of less than 1.5 cm at 1,000 years after the initiation of degradation. In case of chlorine induced corrosion, it takes 1,648 years to initiate corrosion in the main reinforced bar and 2,288 years to reach the lifetime limit of the structural integrity, and thus it is evaluated as the most significant factor.

• Corrosion Science and Technology
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• v.15 no.6
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• pp.314-319
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• 2016

Reduced activation ferritic-martensitic steels (RAFM) are envisaged in future fusion technology as structural material which will be in direct contact with a flowing liquid lead-lithium melt, serving as breeder material. Aluminium-based coatings had proven their ability to protect the structural material from corrosion attack in flowing Pb-15.7Li and to reduce tritium permeation into the coolant, significantly. Coming from scales produced by hot dipping aluminization (HDA), the development of electrochemical-based processes to produce well-defined aluminium-based coatings on RAFM steels gained increased attention in research during the last years. Two different electrochemical processes are described in this paper: The first one, referred to as ECA, is based on the electrodeposition of aluminium from volatile, metal-organic electrolytes. The other process called ECX is based on ionic liquids. All three processes exhibit specific characteristics, for example in the field of processability, control of coating thicknesses (low activation criteria) and heat treatment behavior. The aim of this article is to compare these different coating processes critically, whereby the focus is on the comparison of ECA and ECX processes. New results for ECX will be presented and occurring development needs for the future will be discussed.

• Corrosion Science and Technology
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• v.17 no.4
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• pp.147-153
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• 2018

Copper is used in various applications in environments favoring and enabling formation of biofilms by naturally occurring microbes. Copper is also the chosen corrosion barrier for nuclear waste in Finland. The copper canisters should have lifetimes of 100,000 years. Copper is commonly considered to be resistant to corrosion in oxygen-free water. This is an important argument for using copper as a corrosion protection in the planned canisters for spent nuclear-fuel encapsulation. However, microbial biofilm formation on metal surfaces can increase corrosion in various conditions and provide conditions where corrosion would not otherwise occur. Microbes can alter pH and redox potential, excrete corrosion-inducing metabolites, directly or indirectly reduce or oxidize the corrosion products, and form biofilms that create corrosive microenvironments. Microbial metabolites are known to initiate, facilitate, or accelerate general or localized corrosion, galvanic corrosion, and intergranular corrosion, as well as enable stress-corrosion cracking. Sulfate-reducing bacteria (SRB) are present in the repository environment. Sulfide is known to be a corrosive agent for copper. Here we show results from corrosion of copper in anoxic simulated ground water in the presence of SRB enriched from the planned disposal site.

• Korean Journal of Metals and Materials
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• v.46 no.10
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• pp.652-661
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• 2008

Reduction of NOx in emission gas, improvement of engine efficiency, and extension of warranty period has made demands for developing materials more corrosively resistant to the inner-muffler environments or predicting the lifetime of materials used in muffler more precisely. The corrosion inside muffler has been explained with condensate corrosion mainly though thermal oxidation experiences prior to condensate corrosion. Hence, the aim of this study is to describe how the thermal oxidation affects the corrosion of stainless steel exposed to the inner-muffler environments. Auger electron spectroscopy and electrochemical tests were employed to analyze oxide scale and to evaluate corrosion resistance, respectively. Thermal oxidation has different role of condensate corrosion depending on the temperature: inhibiting condensate corrosion below $380^{\circ}C$ and enhancing condensate corrosion above $380^{\circ}C$. The low temperature oxidation causes to form compact oxide layer functioning a barrier for penetrating condensate into a matrix. Although though thermal oxidation caused chromium-depleted layer between oxide layer and matrix, the enhancement of the condensate corrosion in high temperature oxidation resulted from corrosion-induced crevice formed by oxide scale rather than corrosion in chromium-depleted layer. It was proved by aids of anodic polarization tests and measurements of pitting corrosion potentials. By the study, the role of high temperature oxidation layer affecting the condensate corrosion of stainless steels used as muffler materials was well understood.