• 제목/요약/키워드: cathodic potential

검색결과 268건 처리시간 0.023초

Mg 합금 유전양극에 의한 온수Boiler의 음극방식특성에 관한 연구(1) (Study on the Cathodic Protection Characteristics of Hot Water Boiler by Mg-Alloy Galvanic Anode(1))

  • 임우조;윤병두
    • 수산해양기술연구
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    • 제37권2호
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    • pp.147-152
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    • 2001
  • 본 연구에서는 수도수 중에서 Mg합금유전양극에 의한 연강재 온수보일러의 음극방식특성을 연구한 결과 다음과 같은 결론을 얻었다. 1) 온수보일러 관체의 개로전위에서나 전위가 높은 구간에서 모재의 부식전류밀도가 용접부위의 부식전류밀도보다 더 적게 배류된다. 2) 주조된 표면 그대로의 Mg합금 유전양극의 전류밀도는 주조된 표면을 연마한 상태의 Mg합금 유전양극의 전류밀도보다 더 많이 배류된다. 3) Mg합금 유전양극으로부터 거리가 멀어질수록 연강재 온수보일러의 음극방식전위는 높게 나타나고, 음극방식시간이 경과하면서 방식전위는 높게 나타나다가 6-10일 이후부터 방식전위는 안정되고 있다.

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매설가스배관의 음극방식이 배관의 파괴인성에 미치는 영향 (The Effects of cathodic protection on fracture toughness of buried gas pipeline)

  • 김철만;김우식
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.573-578
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    • 2001
  • For the corrosion protect ion of the natural gas transmission pipelines, two methods are used, cathodic protection and coating technique. In the case of cathodic protection, defects are embrittled by occurring hydrogen at the crack tip or material surface. It is however very important to evaluate whether cracks in the embrittled area can grow or not, especially in weld metal. In this work, on the basis of elastic plastic fracture mechanics, we performed CTOD test ing with varying test conditions, such as the potential and current density. The CTOD of the base steel and weld metal showed a strong dependence of the test conditions. The CTOD decreased with increasing cathodic potential and current density. The morphology of the fracture surface showed quasi-cleavage. Hydrogen introduced fractures, caused by cathodic overprotection.

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Fracture Toughness Evaluation of Natural Gas Pipeline under the Cathodic Protection

  • Kim, Cheol-Man;Baek, Jong-Hyun;Kim, Young-Pyo;Kim, Woo-Sik
    • Corrosion Science and Technology
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    • 제8권4호
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    • pp.133-138
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    • 2009
  • For the corrosion protection of the natural gas transmission pipelines, two methods are used, cathodic protection and coating technique. In the case of cathodic protection, defects are embrittled by occurring hydrogen at the crack tip or material surface. It is however very important to evaluate whether cracks in the embrittled area can grow or not, especially in weld metal. In this work, on the basis of elastic plastic fracture mechanics, we performed the CTOD testing with various test conditions, such as testing rate and potential. The CTOD of the base metal and the weld metal showed a strong dependence of the test conditions. The CTOD decreased with decreasing testing rate and with increasing cathodic potential. The morphology of the fracture surface showed the quasi-cleavage at low testing rate and cathodic overprotection. The low CTOD was caused by hydrogen embrittlement at crack tip.

정전위법에 의한 해상풍력 타워 구조물용 강재의 음극방식을 위한 최적방식전위 결정 (Determination of optimum protection potential for cathodic protection of offshore wind-turbine-tower steel substructure by using potentiostatic method)

  • 이정형;정광후;박재철;김성종
    • Journal of Advanced Marine Engineering and Technology
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    • 제41권3호
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    • pp.230-237
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    • 2017
  • 본 연구에서는 해상풍력 타워 지지구조물용 강재인 S355ML 강에 대하여 전기화학적 기법으로 전기방식 설계에 필요한 최적 방식전위를 규명하고자 하였다. 동전위분극 실험 결과, 양극분극 곡선 상에서는 부동태 구간은 존재하지 않으며, 음극분극 곡선 상에는 용존산소환원반응에 의한 농도분극 구간과 수소가스 발생에 의한 활성화분극 구간이 관찰되었다. 음극방식 시 방식전위에 해당하는 농도분극 구간은 약 - 0.72 V ~ - 1.0 V의 전위 구간인 것으로 확인되었다. 다양한 전위에서 정전위 실험을 실시한 결과 전류밀도 변화는 시간에 따라 안정화되는 경향을 나타냈다. 1200초 동안 정전위 실험 후 주사전자현미경과 3D 분석 현미경을 이용한 시험편 표면 분석 결과, 양극분극 전위에 해당하는 0 V ~ - 0.50 V의 전위구간에서는 양극용해반응에 의한 부식손상이 관찰되었다. 이에 반해 음극분극 전위 영역에서는 대체적으로 손상이 없는 양호한 표면을 유지하였으며 석회질 피막 형성을 확인할 수 있었다. 연구결과, 농도분극 영역에 해당하는 - 0.8 V ~ - 1.0 V의 전위영역이 S355ML 강의 외부전원법에 의한 음극방식 적용 시 최적 방식 전위 구간으로 사료된다.

Regional Cathodic Protection Design of a Natural Gas Distribution Station

  • Yabo, Hu;Feng, Zhang;Jun, Zhao
    • Corrosion Science and Technology
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    • 제16권5호
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    • pp.235-240
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    • 2017
  • Regional cathodic protection has significant impact on pipeline integrity management. After risk analyses of a newly built gas distribution station constructed in an area with large dwelling density, risk score was high because of potential threat caused by galvanic corrosion. Except reinforced steel in concrete, there are four kinds of metal buried under earth: carbon steel, galvanized flat steel, zinc rod and graphite module. To protect buried pipeline from external corrosion, design and construction of regional cathodic protection was proposed. Current density was measured with potential using potential dynamic test and boundary element method (BEM) was used to calculate current requirement and optimize best anode placement during design. From our calculation on the potential, optimized conditions for this area were that an applied current was 3A and anode was placed at 40 meters deep from the soil surface. It results in potential range between $-1.128V_{CSE}$ and $-0.863V_{CSE}$, meeting the $-0.85V_{CSE}$ criterion and the $-1.2V_{CSE}$ criterion that no potential was more negative than $-1.2V_{CSE}$ to cause hydrogen evolution at defects in coating of the pipeline.

토양 매설 배관의 음극방식과 환경인자 간의 상관관계 (Relationship between the Cathodic Protection of Pipe Buried in Soil and Environmental Factors)

  • 최승헌;원석연;유영란;김영식
    • Corrosion Science and Technology
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    • 제21권5호
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    • pp.372-380
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    • 2022
  • The external corrosion control of buried pipes can be achieved by a combination of coatings and cathodic protection to maximize effectiveness. One of the factors affecting cathodic protection is the environmental soil conditions. Because soil is a kind of electrolyte, the environmental conditions of soil may be changed by the atmospheric environment. Therefore, in this study, changes in environmental soil factors by atmospheric environmental factors were monitored. In cathodic protection, on-potential and off-potential were measured from December 2021 to July 2022. The effects of external environmental factors and soil environmental factors on cathodic protection were analyzed. Changes in outdoor temperature affected soil temperature, and soil conductivity had a proportional relationship with soil humidity, but outdoor humidity and precipitation did not significantly affect humidity and conductivity of the soil. In contrast, in cathodic protection, the on-potential was affected by temperature, humidity, the conductivity of the soil, and the anode used, but the off-potential was little affected by these factors.

해양환경중에서 A1-합금희생양극에 의한 음극방식특성 (A Study on the Characteristics of Cathodic Protection by Al-Alloy Sacrificial Anode in Marine Environment)

  • 이연호
    • 수산해양기술연구
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    • 제28권1호
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    • pp.53-60
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    • 1992
  • In this study, cathodic protection experiment was carried out by Al-alloy sacrificial anode in marine environments which have specific resistance($\rho$) if 25~7000$\Omega$.cm and investigated protection potential, current density and loss rate of Al-alloy sacrificial anode. The main results resistance($\rho$) of 400$\Omega$.cm, the cathodic protection potential appears high about-720 mV(SCE). But below specific resistance($\rho$) of 300$\Omega$.cm, the cathodic protection potential appears low about-770 mV(SCE) and simultaneously, cathode is protected sufficiently. 2) The loss rate of Al-Alloy sacrificial anode became large with decreasing specific resistance and increasing the ratio(A sub(c)/A sub(a) of bared surface area of anode and cathode. 3) The loss rate of Al-alloy sacrificial anode(w) to the mean current density of anode(i) is as follows. w=ai+b (a, b : experimental constants)

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EFFECT OF POST-WELD HEAT TREATMENT OF MARINE STRUCTURE STEEL DURING CATHODIC PROTECTION

  • Kim, Seong-Jong;Masazumi Okido;Kim, Jin-Gyeong;Moon, Kyung-Man
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.273-275
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    • 2002
  • The effect of post-weld heat treatment (PWHT) of marine structures steel was investigated at electrochemical viewpoint. In addition, slow strain rate test (SSRT) was carried out to investigate both electrochemical and mechanical properties by PWHT effect during impressed current cathodic protection. The optimum cathodic protection potential by SSRT was -770 mV(SCE). At the applied cathodic protection potential of -770 mV -850 mV(SCE), the fracture morphology was dimple pattern with ductile fracture, while it was transgranular pattern (Q.C: quasi cleavage) under -875 mV(SCE).

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Engineering Technology Far-end Telecontrol Cathodic Protection on the Structure of Jetty Bridge Cap Beams

  • Liu, Yi-Hsiung;Lim, Pau-Yee;Shih, Chien-Chis
    • Corrosion Science and Technology
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    • 제2권1호
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    • pp.47-52
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    • 2003
  • 23 cap beams on the 1 Km length jetty bridge in Shin-da power plant (Taipower co., Taiwan) utilize far-end telecontrol cathodic protection technology which is the first case ever used in Taiwan. The system comprises cathodic protection system and te1econtrol monitoring system. The control and monitoring such as protection current adjustment, protection potential and depolarization measurement of the 23 cap beams can be adjusted through system telecontrol operations. Thereby allows monitoring and control of the 23 anode zones in a convenient and cost effective way. This system is at present still in its best running condition since Sept. 1997 when it was completed. All the 23 cap beams can achieve the 100 mV depolarization potential criteria of protection. It meet the specifications of reinforced concrete cathodic protection standard and proved to be very excellent.

Distribution of Cathodic Protection Potential for Concrete Slab Specimens at Diverse Environmental Conditions

  • Jin, Chung-Kuk;Jeong, Jin-A
    • International Journal of Ocean System Engineering
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    • 제3권2호
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    • pp.90-94
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    • 2013
  • This study represents the recent laboratory results from cathodic protection (CP) system with the use of sacrificial anodes at different environmental conditions (temperature of $10^{\circ}C$ and $40^{\circ}C$). Specimens were slab type with a dimension of $500mm{\times}50mm{\times}100mm$, and concrete cover thickness were 25mm. Zinc mesh and/or bulk type anodes were installed at the center of specimen to confirm the distance that CP system has influences on the specimen to distribute uniform CP current to rebar. Two different kinds of temperature condition were applied to verify the effect of temperature. Experiments were conducted for 60 days, and the distribution of potential and current that supplied from anode to rebar was measured. From the results, CP potential was varied with time, and temperature played an important role in CP potential variations. Current was also changed with time, and current distribution could be improved by installing additional bulk type anode.