• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.349-355
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• 2005

The bolts used for the electronic parts of a car a is the important parts which carry out an electric and physical performance. At the time of storage, transportation and use, Corrosion occurs in bolts under the influence of environmental factor. During the period exported especially overseas the chemical corrosion by the chlorine ion contained in the atmosphere occurs frequency. Then, The failure mechanism over corrosion is investigated and we consider to the design procedure of a environmental examination. We are going to select the proper plating thickness of bolts through a salt spray test, for investigating the corrosion resistance of bolts.

• Journal of Acupuncture Research
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• 제24권5호
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• pp.105-111
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• 2007

Objectives : The electroacupuncture(EA) was often used in Oriental medicine clinic and basic researches. However, there have been neither any national standard of acupuncture needles in Korea nor many studies about the property of acupuncture needles for applying electrical stimulations. Therefore we investigated the electrical corrosion property of acupuncture needles used for EA stimulation in clinic. Methods : We observed the occurrence of electrical corrosion like changes in the surface of acupuncture needles after EA stimulation with various parameters(electrical stimulation intensity, treatment duration, diameter of needle) under a light microscope. We performed EA stimulation on Baekhoe($GV_{20}$) or Joksamli($ST_{36}$) of rats with intensity of 0.025, 0.05, 0.075, 0.1, 0.25 or 0.5mA at a 10Hz frequency. Results : The electrical corrosion-like changes were found on the surface of needles when the EA stimulation was given over 0.05mA of intensity. When electrical stimulation was treated for 10min, the electrical corrosion-like changes were low, but the electrical corrosion-like changes gradually increased by the treatment duration(20, 30min). We also found that acupuncture needles of 0.2mm diameter were produced more extensive electrical corrosion-like changes than acupuncture needles of 0.3 or 0.4mm diameter by electrical stimulation. Conclusions: These results suggested that EA stimulation could produce electrical corrosion-like changes of acupuncture needles through intensity of current, duration of electric stimulation and/or diameter of needle.

• 한국해양공학회지
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• 제6권2호
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• pp.85-93
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• 1992

The only hardness of 2nd phase of martensite in dual phase steel which was composed of the martensite and ferrite was changed. Fatigue test was conducted by cantilever type of self-made rotated bending fatigue testing machine. The corrosion fatigue fracture behaviors of dual phase steel were investigated in 3% NaCl solution at $N_f$ = $1.5\times$$10^5$ $N_f$=1.0 $\times$ $10^6$ cycles. The fatigue strength was increased with increasing the hardness of 2nd phase. The size and number of corrsion pits were influenced by the 2nd phase hardness and pits remain constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of $\Delta$K and da/dn has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the higher the corrosion fatigue life becomes. Corrosion fatigue fracture behavior was effected by mechanics in case of $N_f$=1.5$\times$10$^5$$N_f$=1.5$\times$10$^6$ cycles.

• Nuclear Engineering and Technology
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• 제44권3호
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• pp.343-354
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• 2012

Primary water stress corrosion cracking (PWSCC) is a major safety concern in the nuclear power industry worldwide. PWSCC is known to initiate only in the condition in which sufficiently high tensile stress is applied to alloy 600 tube material or alloy 82/182 weld material in pressurized water reactor operating environments. However, it is still uncertain how much tensile stress is re-quired to generate PWSCC or what causes such high tensile stress. This study was performed to pre-dict the magnitude of weld residual stress and operating stress and compare it with previous experi-mental results for PWSCC initiation. For the study, a pressurizer safety nozzle was selected because it is reported to be vulnerable to PWSCC in overseas plants. The assessment was conducted by nu-merical analysis. Before performing stress analysis for plant conditions, a preliminary mock-up ana-lysis was done. The result of the preliminary analysis was validated by residual stress measurement in the mock-up. After verification of the analysis methodology, an analysis under plant conditions was conducted. The analysis results show that the stress level is not high enough to initiate PWSCC. If a plant is properly welded and operated, PWSCC is not likely to occur in the pressurizer safety nozzle.

• 청정기술
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• 제20권2호
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• pp.136-140
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• 2014

본 연구에서 폴리프로필렌을 모재로 사용하여 Co/Ni/P/Mn 4가지 금속을 무전해도금 방법으로 코팅하였다. 이 때 도금욕의 시약의 양을 조절함으로써 폴리프로필렌 위에 도금된 금속의 조성을 다르게 조정하였다. 이러한 조건으로 만들어진 도금 금속에 대하여 두께, 전기적 표면 저항, 주사형 전자현미경을 사용한 표면상태, 에너지 분산형 분석기를 통한 금속조성을 측정하였다. 인 함량이 높을수록 전지저항이 커지는 것이 관찰되어 인 함량과 전지전도성간의 상관성이 있는 것이 관찰되었다. 또한 코팅 금속의 수용액에서의 부식성을 3.5 wt% 염화나트륨 용액과 5.0 wt% 황산용액에서 비교한 결과 인을 많이 포함할수록 내식성이 강함을 알 수 있었다.

• 공업화학
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• 제19권2호
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• pp.228-235
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• 2008

니켈 표면처리 공정에서 전류밀도에 따라 니켈의 전착두께가 증가되었으며, 증가폭은 $6{\sim}10A/dm^2$에서 저전류보다 높게 나타났다. 전류밀도를 측정하기 위해 Hull-cell 분석을 수행 하였다. 최적 공정온도는 $60^{\circ}C$, pH는 3.5~4.0이었고, 전해용액 중 니켈이온의 농도는 300 g/L 이상에서 농도에 따라 전착두께가 증가되었다. 전류밀도에 따라 용액 중 니켈이온 감소 속도가 증가되었는데, 이는 음극표면에서 니켈 전착 량에 따른 전착두께의 증가를 나타낸다. 그러나 전착속도가 빠를 경우 니켈 전착 층의 치밀성은 저하되며, 표면의 상태는 불규칙하게 변화된다. 니켈이온의 전착과정이 불규칙하게 일어나 조직의 pin hole 등을 야기해 표면특성을 저하시키는 것으로 확인되었다. 광택니켈 전착 후 25 h 내식을 유지한 결과, 낮은 전류밀도를 유지하는 것이 내식특성이 우수한 것으로 나타났다. 프로그램모사 결과, 전류밀도가 높아질수록 확산 층의 두께는 증가하며, 음극표면의 농도는 낮아진다. 농도분포는 낮은 전류밀도에서 고른 분포를 나타내었으며 이는 일정한 전착두께를 예측할 수 있다. 생산성 저하를 예방하기 위해 공정시간은 크게 변화시키지 않았으며, 전류밀도와 전착두께를 변화시키면서 공정변수를 조절하였다. 본 연구의 표면분석 결과 조직특성이나 내식성 등의 표면 물성이 낮은 전류밀도를 사용할 경우에 더욱 우수한 것으로 나타났다.

• Corrosion Science and Technology
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• 제6권3호
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• pp.96-102
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• 2007

The resistance of the linepipe steel to hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) is very important for steel to be used in sour oil/gas environments. Welding of steels is necessary to the construction of pipe-line transporting oil/gas. In this study, HIC and SSC resistance of an electric resistance welded (ERW) steel plate which belongs to API X70 grade was evaluated by using NACE TM0284-96A and NACE TM0177-96A methods. HIC and SSC fracturing behavior was investigated by observing fractured surfaces using optical microscopy (OM) and scanning electron microscopy (SEM). It was discussed in terms of metallurgical parameters such as the distribution of primary microstructure, second phases and inclusions. Results showed that the weld joint of ERW steel is more sensitive than base metal to HIC and SSC. This is due to difference in the contribution of metallurgical parameters to HIC and SSC nucleation and propagation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.597-600
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• 2006

In Marine Land underground reinforced concrete structures, such as electric box power structure, water and chloride ion penetrated into concrete through the cracks of concrete and its permeable property, cause the corrosion of reinforcing steel bar, which accelerates the expansive cracks and deterioration of concrete. The purpose of this paper is to evaluate on deterioration of durability concrete through instrumental analysis such as schmidt hammer and carbonation, chloride content. Under the reclaimed marine land, the main cause of deterioration of concrete structures is the steel corrosion due to the penetration of chlorides and the deterioration of outer concrete itself by chemical attack.

• 한국재료학회지
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• 제10권2호
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• pp.138-143
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• 2000

화력발전설비의 주요 손상 요인 중의 하나인 응력부식 균열 성장에 대한 확률론적 잔존 수명평가에 대하여 연구하였으며, 손상해석 및 수명평가에 확률해석 기법을 도입한 확률론적 수명평가 프로그램을 개발하였다. 확률론적 수명평가는 재료물성치, 형상, 하중조건, 운전조건 등과 같은 불확실성과 변동 가능성을 고려하여 해석을 수행하며, 일정 시간 운전후 구조물의 손상이 일어날 확률을 예측하는 것이다. 응력부식 균열 성장에 대한 확률론적 잔존 수명평가 연구를 통하여 확률론적 수명평가 기술의 기반을 구축하였으며, 다른 손상기구에 대한 확률론적 수명평가를 수행하여 발전설비에 발생하는 모든 손상에 대하여 확률론적 수명평가가 가능하도록 확대할 계획이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.1083-1084
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• 2006

The wide spread of DC electric railway systems such as urban rapid transits including heavy rail and light rail transits has significant ramification as the stray currents from return conductor rails can cause the electrochemical interference, that is, the electrolytic corrosion of both rails and outside underground metallic infrastructures. The immature understanding of either the railway authority who is responsible for establishing the necessary provisions at the design stage or the affected parties makes it difficult to prepare the optimum range of solutions for the long-pending interference problem. In Japan, however, numerous assessment studies have been carried out on the stray current interference, by which protective guidelines are provided by "Electrolysis Committee". In this paper, we review a guide book from "Tokyo Electrolysis Committee", namely, "Protective Methods for Stray Current Corrosion".