• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 추계학술논문요약집
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• pp.207-208
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• 2018

• Corrosion Science and Technology
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• 제19권4호
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• pp.189-195
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• 2020

Two air vents situated on a heat transport pipe in district heating system were exposed to the same environment for 10 years. However, one air vent was more corroded than the other. It also had a hole on the top of the front-end pipe. Comparative analysis was performed for these air vents to identify the cause of corrosion and establish countermeasures. Through experimental observation of the damaged part and analyses of powders sampled from air vents, it was found that corrosion was initiated at the top of the front-end pipe. It then spread to the bottom. Energy dispersive X-ray spectroscopy results showed that potassium and chlorine were measured from the corroded product in the damaged air vent derived from rainwater and insulation, respectively. The temperature of the damaged air vent was maintained at 75 ~ 120 ℃ by heating water. Rainwater-soaked insulation around the front-end pipe had been hydrolyzed. Therefore, the damaged air vent was exposed to an environment in which corrosion under insulation could be facilitated. In addition, ion chromatography and inductively coupled plasma measurements indicated that the matrix of the damaged front-end pipe contained a higher manganese content which might have promoted corrosion under insulation.

• Corrosion Science and Technology
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• 제19권6호
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• pp.296-301
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• 2020

Failure analysis on the welded type 304 pipe used for cooling water piping in the district heating primary side was conducted. Inorganic elements and bacteria in the cooling water and in corrosion products were analyzed, and the weldment was inspected by microscopy and a sensitization test. Corrosion damages were observed in the heat-affected zone, on weld defects such as incomplete fusion or excessive penetration caused by improper welding, or/and at the 6 o'clock position along the pipe axial direction. However, the level of concentration of chloride in the cooling water as low as 80 ppm has been reported to be not enough for even a sensitized type 304 steel, meaning that the additional corrosive factor was required for these corrosion damages. The factor leading to these corrosion damages was drawn to be the metabolisms of the types of bacteria, which is proved by the detection of proton, sulfur containing species, biofilms, and both bacteria and corrosion product analyses.

• 방사성폐기물학회지
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• 제1권1호
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• pp.73-79
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• 2003

가압경수형 원자력발전소 일차계통에서 발생되는 방사성 부식생성물(크러드)은 원자력발전소 작업종사자 피폭의 주요원인이다. 또한, 최근 원자력발전소의 장주기운전 추세에 따라 장기간 노심에 침적된 방사성 부식생성물은 hideout 현상으로 노심의 출력에 영향을 주는 축방향이상출력 (AOA) 현상의 원인이 되고 있다. 크러드의 주요 성분은 마그네타이트, 니켈 페라이트, 코발트 페라이트가 주를 이루며, 이러한 산화물 형태는 강자성의 자기적 성질을 가지고 있다. 따라서, 전자석과 영구자석의 적절한 배치를 통하여 자기장을 발생시켜 크러드를 제거하는 필터 개발을 위해 개념 설계를 하였다. 기존의 필터와 달리 유체의 흐름을 방해하지 않아 압력저하 현상이 발생하지 않고, 연속적으로 사용할 수 있는 장점이 있다. 크러드 제거 기술의 하나로써 활용될 수 있을 것으로 기대된다.

• 한국산학기술학회논문지
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• 제21권2호
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• pp.619-626
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• 2020

환경 보호까지 고려한 Non-amine계 부식 방지제를 포함하는 새로운 부동액 개발이 주요한 이슈가 되고 있다. 본 연구에서는 Non-amine계 부식 방지제 4종을 합성하고 이를 이용하여 새로운 자동차용 부동액 5종을 제조하여 무게 변화량, 표면 관찰, 거칠기 측정, 용액 중 구리 용출량 측정을 통해 구리의 부식 속도를 평가하였다. 평가 결과 부동액 5종중에서 Sample 4가 유도결합 플라즈마 광도계로 측정하였을 때 구리의 용출량이 적고 용출 속도가 매우 느렸다. Sample 4는 시험 후 금속 표면이 매끄러운 편이나 표면에 작은 국부 부식이 관찰됨에 따라 표면에 부식 생성물 층을 고르게 형성한 것으로 보여 구리의 부동태화에 따른 부식 억제 효과가 있으므로 가장 양호한 부식방지 성능을 보였다. Sample 4에 첨가된 주요 부식방지제는 1-Aminomethyl(N',N'-di(2-hydroxyethyl) benzotrazole로, 이 부식 억제 성분은 국부부식은 상대적으로 높으나 부동태화가 진행된 Sample 5에도 일정 함량 포함되었다. 따라서 본 연구에서 사용한 4종의 부식 방지제 중 1-Aminomethyl(N',N'-di(2-hydroxyethyl)benzotrazole이 가장 부식 억제 효과가 높았다. 이는 상기의 부식 방지제가 부동액상에서 구리의 부동태화를 촉진함으로써 부식을 방지하는 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.131-134
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• 1999

Microstructure modification and electrochemical properties are investigate to estimate the effects of internal chlorides on the steel corrosion in the blended cement systems. According to the test results, slag cement system showed high chloride binding capacity and low corrosion rate. The impedance data showed three distince arcs from lowest(mHz) frequency to highest (MHz) frequency due to product layer, interfacial reaction and bulk matrix. Through the microstructural investigation, fine steel-matrix interface of slag cement system was observed but rough steel-matrix interface of OPC system was observed. Friedel's salt was thought that the substantial material contributed to the chloride binding of slag cement system.

• 환경위생공학
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• 제17권1호
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• pp.57-62
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• 2002

Carbon cast iron and Zinc coated steel were the most widely used portable water of supply and distribution Pipeline system. The leaching of red water in portable water could produce sericus environmental sanitary problems. Due to the red water was the most alternative to inner scale of metal pipeline. So this study was conducted the impact of red water on scale products, and was evaluated by the corrosive metal contaminants of 20 fears over. Surface tests, metal surface composition measurements of samples XRF, XRD, and SEM(EDS), analysis were used to investigate the corrosion characteristies of carbon cast iron and Zinc coated steel. As the contaminants of Fe increased the red water of carbon castiron pipe increased due to the scale products amount of $Fe_2O_3$ (Hemite).

• 한국안전학회지
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• 제16권4호
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• pp.52-57
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• 2001

Fatigue crack growth behaviour of Ti-6A-4V alloy is investigated in air and salt solution environment at room temperature and $200^{\circ}C$. Fatigue crack growth rate is blown to be fast for the formation of corrosive product in hot salt environment. For the effect on corrosion fatigue crack growth behaviour of region II. fatigue crack growth rate in atmosphere had a little gap to both case, $200^{\circ}C$ and room temperature. However, it showed very fast tendency in salt corrosive atmosphere, and it was remarkably accelerated in $200^{\circ}C$ temperature salt environment. When $\Delta$K was approximately 30MPa(equation omitted), fatigue crack growth rate had a little difference between at room temperature and at $200^{\circ}C$ high temperature, however in case of salt corrosive environment the room temperature was 3.5 times Inter and $200^{\circ}C$ high temperature for 16 times than air environment respectively.

• 보존과학회지
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• 제33권3호
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• pp.167-179
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• 2017

서산 비경도 출수 상평통보를 대상으로 혐기성 수중 매장환경에서 형성되는 부식화합물 성분과 이에 따른 혐기성 부식 원인을 추정하였다. 미세조직 관찰, 원소 mapping, 층위별 주성분 분석, 부식화합물 동정을 실시하였다. 그 결과 표면의 고착물은 침상형 육면체형 팔면체형으로 분류되며, 그에 따른 분석 결과 Cu, Pb, S 등의 원소가 검출되었다. 원소 mapping에서는 최외곽에 Cu-S로 이루어진 뚜렷한 층이 확인되었다. 층위별 주성분은 Cu, S, Pb 등이 검출되었고, Zn은 검출되지 않았다. 부식화합물은 $PbCO_3$(고착물), $Cu_{1.96}S$(소지금속)이 나타났다. 따라서 서산 비경도 출수 상평통보의 혐기성 부식 특성은 탈아연, 황화동, 납화합물 세 가지로 요약할 수 있다.

• 한국재료학회지
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• 제29권1호
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• pp.11-15
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• 2019

Severe wall thinning is found on the tube of a low-pressure evaporator(LPEVA) module that is used for a heat recovery steam generator(HRSG) of a district heating system. Since wall thinning can lead to sudden failure or accidents that lead to shutdown of the operation, it is very important to investigate the main mechanism of the wall thinning. In this study, corrosion analysis associated with a typical flow-accelerated corrosion(FAC) is performed using the corroded tube connected to an upper header of the LPEVA. To investigate factors triggering the FAC, the morphology, composition, and phase of the corroded product of the tube are examined using optical microscopy, scanning electron microscopy combined with energy dispersive spectroscopy, and x-ray diffraction. The results show that the thinnest part of the tube is in the region where gas directly contacts, revealing the typical orange peel type of morphology frequently found in the FAC. The discovery of oxide scales containing phosphate indicates that phosphate corrosion is the main mechanism that weakens the stability of the protective magnetite film and the FAC accelerates the corrosion by generating the orange peel type of morphology.