• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.84-89
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• 1998

Alloy 600 및 alloy 690과 Ni-8Cr-lOFe 합금 등의 응력부식(stress corrosion cracking, SCC) 거동을 고온의 염기성 분위기에서 C-ring 시편을 사용하여 연구하였다. Alloy 600과 alloy 690을 여러 조건에서 열처리하여 etching한 후 탄화물의 분포와 입계 주변의 Cr고갈 정도 등의 미세조직을 광학현미경과 주사 전자현미경(SEM)으로 관찰하였다. 이들 재료에 대한 SCC 시험을 315$^{\circ}C$의 40% NaOH 수용액에서 일정한 부하전위(부식전위 + 200㎷)를 가하면서 수행하였으며, 동일 조건에서의 분극거동도 측정하였다. Alloy 600 MA(mill anneal) 및 TT(thermal treatment)의 SCC 저항성은 alloy 690 TT와 Ni-8Cr-10Fe SA(solution anneal)보다 낮았다. Alloy 600 TT 재료는 alloy 600 MA 및 SA 재료에 비해 SCC 저항성이 더 컸다. 고용 탄소농도는 alloy 600의 SCC 저항성에 큰 영향을 주지 못했다. 대부분의 Alloy 600은 균열전파 입계균열을 보였으나, 일부에서는 입계 및 입내 혼합양상(mixed mode cracking)을 보였다. 염기성 분위기에서 Ni기 합금의 SCC 거동을 미세조직, 분극거동의 관점에서 고찰하였다.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.66-70
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• 1999

In order to investigate the quantitative behavior of galvanic corrosion in weld joints between stainless std이 and carbon steel, electrochemical polarization experiments were performed at pH4, pH7 and pH10 with boric acid concentration 4000ppm, and water temperature were selected as $35^{\circ}$C and $60^{\circ}$C. As the results, the galvanic corrosion phenomena of carbon steel weld material at $60^{\circ}$C was revealed $2{1\over2}$ times higher corrosion rate than that at $35^{\circ}$C condition. The corrosion rate of stainless steel was almost inedependent of the variation of pH. The significant corrosion rates of carbon steel and the weld joint of carbon-carbon steel were observed at pH 4.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1061-1062
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• 2012

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.295-301
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• 2010

Flow accelerated corrosion(FAC) of carbon steel pipes in nuclear power plants has been known as one of the major degradation mechanisms. It could have bad influence on the plant reliability and safety. Also detection of FAC is a significant cost to the nuclear power plant because of the need to remove and replace insulation. Recently, the interest of the guided wave testing(GWT) has grown because it allows long range inspection without removing insulation of the pipe except at the probe position. If GWT can be applied to detection of FAC damages, it will can significantly reduce the cost for the inspection of the pipes. The objective of this study was to determine the capability of GWT to identify location of FAC damages. In this paper, three kinds of techniques were used to measure the amplitude ratio between the first and the second welds at the elbow area of mock-ups that contain real FAC damages. As a result, optimal inspection technique and minimum detectability to detect FAC damages drew a conclusion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.451-460
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• 1989

This paper dealt with the effect of the ratios N2 to H2 gas on the corrosion fatigue failure behavior of ion-nitrided SM45C steel specimens. The specimens were water cooled after ion-nitriding at 500.deg. C for 3hrs in 5 Torr, 0.8N$_{2}$ and 0.5N$_{2}$ atmospheres. As the nitrogen concentration increases, the higher compressive residual stresses developed in the surface layer and the depth of nitrided layer increased, which in turn gave rise to increases in fatigue strength and corrosion fatigue life. In the region less than 1.5 * 10$^{5}$ cycles, fatigue failure initiated at the brittle nitrided case, whereas in the region higher than 1.5 * 10$^{5}$ cycles crack initiated from the non-metallic inclusions in the subsurface. The initiation of corrosion fatigue failure was mainly attributed to pitting of case hardened surface layer.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.653-658
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• 2021

Polyvinylidene fluoride (PVDF) is a promising coating material because of its outstanding processability. The PVDF coating, however, has limitations in anti-corrosion application due to its weak hydrophobicity compared to that of other fluoropolymers. In this study, plasma fluorination was performed using carbon tetrafluoride (CF₄) gas to improve anti-corrosion properties of PVDF. The fluorine content and hydrophobicity of PVDF were investigated in different CF₄ flow rates, followed by the determination of anti-corrosion properties. The fluorine content on the surface of the PVDF film increased by up to 46.70%, but the surface free energy was independent of CF₄ flow rate. Meanwhile, the surface roughness of the PDVF film tended to increase by up to 150% and then decrease with increasing CF₄ flow rate. It is considered that the plasma fluorination affects the surface free energy due to the introduction of fluorine functional groups and surface etching. In addition, the degree of corrosion of the PVDF-coated Fe plate was significantly reduced from 49.2% to 19.0% compared to that of the uncoated Fe plate. In particular, the degree of corrosion of the fluorinated PVDF-coated Fe plate was 13.6%, which was 28.4% lower than that of the PVDF-coated Fe plate, showing improved anti-corrosion protection.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.76.1-76.1
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• 2010

Recently, many efforts to solve the durability problem of PEM fuel cell are carried on constantly. However, despite this attention, durability researches of gas diffusion layer (GDL) are not much reported yet. Generally, GDL of PEM fuel cell experiences three external attacks, which are dissolution of water, erosion of gas flow, corrosion of electric potential. In this study, among these degradation factors, carbon corrosion of electric potential was focused and investigated with accelerated carbon corrosion test. Through the test, it is confirmed that carbon corrosion occurred at GDL, and corroded GDL decreased a performance of operating fuel cell. The property changes of GDL were measured with various methods such as air permeability meter, pore distribution analyzer, thermo gravimetric analyzer, and tensile stress test to discover the effects of carbon corrosion. Carbon corrosion caused not only loss of weight and thickness, but also degradation of mechanical strength of GDL. In addition, to analysis the reason of GDL property changes, a surface and a cross section of GDL were observed with scanning electron microscope. After 100 hours test, the GDL showed serious damage in center of layer.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.100-105
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• 2008

A106 Carbon Steel has recently been used as the material for pipes, nozzles, and tank shells in nuclear power plants. Its corrosion resistance gives the steel many advantages for use in structures under high temperature and high pressure. This steel is also expected to be used as a structural material in the shipbuilding industry for applications involving severe conditions, such as high temperature and pressure. In this study, the mechanical properties of A106 carbon steel were evaluated in regard to its corrosion times. The tensile and yielding strengths decreased as the corrosion time increased. In particular, the tensile strength was influenced by corrosion. In addition, an acoustic emission (AE) technique was used to clarify the microscopic damage to specimens that had undergone corrosion for a certain period. It was found that AE parameters, such as events, energy, duration time, and amplitude were useful for evaluating the degree of damage and remaining life of the corroded specimen. Various properties of the waveform and frequency range were also seen, based on the degree of damage to the specimen from the corrosion time.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.89.1-89.1
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• 2011

The influence of potential and humidity on the electrochemical carbon corrosion in high temperature polymer electrolyte membrane fuel cells(HT-PEMFCs) is investigated by measuring $CO_2$ emission at different potentials for 30 min using on-line mass spectrometry. These results are compared with low tempterature polymer electrolyte membrane fuel cells(LT-PEMFCs) operated at lower temperature and higher humidity condition. Although the HT-PEMFC is operated at non humidified condition, the emitted $CO_2$ in the condition of HT-PEMFC is more than LT-PEMFC at the same potential in carbon corrosion test. Thus, carbon corrosion shows a stronger positive correlation with the cell temperature. In addition, the presence of a little amount of water activate electrochemical carbon corrosion considerably in HT-PEMFC. With increased carbon corrosion, changes in fuel cell electrochemical characteristics become more noticeable and thereby indicate that such corrosion considerably affects fuel cell durability.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.124-126
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• 2011

본 연구에서는 가스온수기 사용 중에 발생하는 배기가스중의 일산화탄소 중독사고를 예방하기 위하여 사용자부주의, 설치불량 및 안전장치의 결함을 분석하고 문제점을 통해 사고예방대책을 강구하기 위한 것이다. 가스중독 사고 예방을 위해서는 목욕탕 또는 환기가 잘되지 아니하는 곳에 설치하지 않으며, 사용자는 창문 등으로 반드시 열어 사용하도록 한다. 열교환기 등의 부식이나 막힘 등에 대한 점검을 누락되지 않도록 하며, 전문 업체에 등록된 자가 시공하도록 한다. 안전 점검시 안전장치의 이상 유무 등을 점검한다. 즉, 가스온수기는 환기가 불량한 장소에 설치하는 경우 배기가스가 외부로 배출되지 못하고 실내에 체류하는 경우에 일산화탄소중독에 의한 사고로 이어지고 있기 때문에 예방대책에서 제시한 부분은 중독 사고를 예방하는데 기여할 수 있을 것으로 판단한다.