• 해양환경안전학회지
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• 제18권6호
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• pp.569-576
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• 2012

일반적으로 중성용액 하에서 알루미늄 합금은 부동태피막($Al_2O_3$나 $Al_2O_3{\cdot}3H_2O$)을 형성한다. 그러나, 해수 환경에서 염소이온이 표면에 생성된 부동태 피막을 파괴하여 부식이 발생하게 된다. 본 연구에서는 해수환경 하에서 부식 문제점을 해결하기 위해 Al-4.5%Mg-0.6%Mn 알루미늄 합금에 대하여 정전위 방식 기술을 적용하였다. 분극실험결과, 개로전위보다 귀한 전위에서는 활성 용해 반응이 나타났으며 개로전위 보다 비한 전위에서는 용존산소 환원에 의한 농도 분극과 활성화 분극이 관찰되었다. 정전위 실험결과, 농도 분극에서 활성화 분극으로 전환되는 전위부터 적용 시간이 증가할수록 전착물이 많이 생성되었으며, 부분적으로 전착물과 모재의 계면사이에서 틈부식이 관찰되었다. 전체적으로 정전위 양극분극실험시, 활성용해반응이 발생하여 정전위 방식 기술을 적용하기 어려운 반면, 정전위 음극분극 실험시 방식 전위인 농도분극 범위내에서 적용 시간을 고려하여 최적 방식 조건을 -1.1 V~-0.75 V로 규명하였다.

• Corrosion Science and Technology
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• 제9권1호
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• pp.48-55
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• 2010

The many vessels are built with FRP(Fiber-Reinforced Plastic) material for small boats and medium vessels. However, FRP is impossible to be used for recyclable material owing to environmental problems and causes large proportion of collision accidents because radar reflection wave is so weak that large vessels could not detect FRP ships during the sailing. Hence, Al alloy comes into the spotlight to solve these kinds of problems as a new-material for next generation instead of FRP. Al alloy ships are getting widely introduced for fish and leisure boats to save fuel consumption due to lightweight. In this study, it was selected 6061-T6 Al alloy which are mainly used for Al-ships and carried out various electrochemical experiment such as potential, anodic/cathodic polarization, Tafel analysis, potentiostatic experiment and surface morphologies observation after potentiostatic experiment for 1200 sec by using the SEM equipment to evaluate optimum corrosion protection potential in sea water. It is concluded that the optimum corrosion protection potential range is -1.4 V ~ -0.7 V(Ag/AgCl) for 6061-T6 Al alloy, in the case of application of ICCP(Impressed current cathodic protection), which was shown the lowest current density at the electrochemical experiment and good specimen surface morphologies after potentiostatic experiment for Al-Mg-Si(6061-T6) Al alloy in seawater environment.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.23-24
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• 2005

This paper investigated the mechanical and electrochemical properties of Al alloys in a slow strain rate test under various potential conditions. In general, Al and Al alloys do not corrode on formation of a film that has resistance to corrosion in neutral solutions. In seawater, however, $Cl^-$ ions lead to the formation and destruction of a passive film. In a potentiostatic experiment, the current density after 1200 sec in the potential range of $-0.68{\sim}-1.5 V$ was low. Comparison of the maximum tensile strength, elongation, and time to fracture indicated that the optimum protection potential range was from -1.5 to -0.7 V(SSCE).

• Journal of Advanced Marine Engineering and Technology
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• 제38권8호
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• pp.974-980
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• 2014

Aluminum acts as sacrificial anode and corrosion protection with Al2O3 formation. If the same current on material for Al ships with steel ships supplies, the more hydrogen would be occurred, that result is bring about over-protection. For this reason, the damage by hydrogen embrittlement leads to the serious accident. In this study, we evaluate electrochemical behavior with rotation speed of 5083-H116 Al alloy material for Al ship in seawater. To examine the electrochemical characteristics with rotation speed and its effects on performance, experiments were conducted at four rotation speed. Results of experiments, the corrosion current density and damage were increased by applying the rotation speed compared to static state.

• Corrosion Science and Technology
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• 제19권6호
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• pp.288-295
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• 2020

This study investigated the erosion-corrosion characteristics of 5038-H321 aluminum alloy in a natural seawater solution through various electrochemical experiments and flow rate parameters. Cathodic polarization experiments were conducted at flow rates ranging from 4 to 12 knots. Considering the concentration polarization section representing a relatively low current density, the range of the potentiostatic experiment was determined to be -1.6 to -1.0 V. The potentiostatic experiment was conducted at various potentials for 180 minutes in seawater. After the experiment, the corrosion characteristics were evaluated by observing surface morphology and measuring surface roughness. As a result, as the applied potential was lower, the amount of calcareous deposits increased and the roughness tended to increase. On the other hand, it was confirmed that the roughness was larger in the static condition than the flow rate condition due to the influence of the flow velocity. Variations in the chemical composition with flow rate variations were analyzed by energy-dispersive spectroscopy (EDS). In conclusion, the cathodic potential of AA5083-H321 in seawater was determined to be -1.0 V.

• 방사성폐기물학회지
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• 제8권3호
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• pp.247-260
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• 2010

한국원자력연구원 처분시스템개발과제에서는 처분용기 재료로 개발중인 저온분사코팅 구리에 대한 틈새부식(Crevice Corrosion) 시험을 실시하였다. 본 시험을 통하여 틈새에서의 부식의 발생여부와 발생되는 시점인 재부동태 전위(Repassivation Potential)를 측정하고자 하였다. 틈새부식 시험 방법으로 (1) ASTM G61-86 : Cyclic Potentiodynamic Polarization Measurements, (2) SWRI의 Potentiodynamic Polarization plus intermediate Potentiostatic Hold method, 그리고 (3) ASTM G192-08 (THE method) :Potentiodynamic- Galvanostatic -Potentiostatic Method 등의 3가지 방법을 소개하였다. 실제 저온분사 코팅구리의 부식시험에서는 ASTM G61-86에 따라서 틈새부식장치를 설치하고, 저온분사코팅구리가 KURT 지하수를 모사한 용액에서 어떻게 틈새부식이 일어나는지 살펴보았다. 전기적 부식조건으로는 Cyclic Polarization Test, Potentiostatic Polarization Test, 및 Electrochemical Impedance Spectroscopy 등을 사용하였다. 그리고 부식이 된 시편에 대해 Profilometer Measurement를 통해 실제 부식표면의 높낮이를 조사하여 틈새부식 유무를 관찰하였다. 최종적인 결론에서는 저온분사코팅구리는 틈새부식을 나타나지 않는다는 것을 확인할 수 있었다. 그리고 시험에 사용된 세종류의 구리에 대한 상대적인 부식평가를 한 결과, 부식전위를 나타내는 개방회로(Open Cell)에서의 전위는 구리의 제조방식과 상관없이 구리의 순도가 높을수록 높은 값을 보이는 것을 확인할 수 있었다. 결론적으로 KURT 심층지하수 조건에서는 구리는 틈새부식이 발생되지 않는다고 결론지었다.

• Corrosion Science and Technology
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• 제21권5호
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• pp.340-347
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• 2022

In this research, mixed metal oxide (TiO₂, RuO₂) coating was applied to grade 1 titanium as a bipolar plate for polymer electrolyte membrane fuel cell (PEMFC). Electrochemical experiments were carried out in an aqueous solution of pH 3 (H₂SO₄ + 0.1 ppm HF, 80 ℃) determined by DoE. The air was bubbled to simulate a cathode environment. Potentiodynamic polarization test revealed that corrosion current densities of the titanium substrate and MMO-coated specimen were 0.180 µA/cm² and 4.381 µA/cm², respectively. There was no active peak. After potentiostatic experiment, current densities of the titanium substrate and the MMO-coated specimen were 0.19 µA/cm² and 1.05 µA/cm², respectively. As a result of observing the surface before and after the potentiostatic experiment, cracked dried clay structures were observed without corrosion damage. Both the titanium substrate and the MMO-coated specimen could not satisfy the interfacial contact resistance suggested by the DoE. Thus, further research is needed before they could be applied as bipolar plates.

• 자원리싸이클링
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• 제10권4호
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• pp.18-23
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• 2001

페놀을 함유한 폐 활성탄의 가열 재생시 대기 오염물인 페놀이 생성되어 환경을 오염시키므로 발생하는 페놀 제거에 대한 검토가 필요하다 본 연구에서 실험에 사용하여 페놀을 함유한 S.회사 활성탄(WS-GAC), C.회사 활성탄(WC-GAC), L.회사 활성탄(UL-GAC)의 전해산화는 정전위 전해방식으로 실험하였다. 시료에 함유된 페놀농도는 100 rng/g, 지지 전해질은 1.0% 염화나트륨 용액, Ti-Ir(10$\times$10$ extrm{cm}^2$)전극 간격은 2 cm,전류밀도는 $1.25 A/dm^2$인 조건에서 실험이 이루워졌을 경우 전해 산화 실험에서 얻은 결과 페놀의 잔류물은 검출되지 않았다. 그러므로 전해산화 반응에서 빈응시간, 전류밀도, 지지전해질의 농도, 전극간의 거리가 60 minutes, 1.25 $A/dm^2$, 1.0%, 2 cm 임을 알 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.157-168
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• 2006

Recently, interest in using Al alloys in ship construction instead of fiber-reinforced plastic (FRP) has increased because of the advantages of A) alloy ships over FRP ships, including high speed, increased load capacity. and ease of recycling. This paper investigated the mechanical and electrochemical properties of Al alloys in a slow strain rate test under various potential conditions. These results will provide reference data for ship design by determining the optimum protection potential regarding hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys do not corrode on formation of a film that has resistance to corrosion in neutral solutions. In seawater, however, $Cl^-$ ions lead to the formation and destruction of a Passive film. In a potentiostatic experiment. the current density after 1200 sec in the Potential range of $-0.68\~-1.5\;V$ was low. This low current density indicates the protection potential range. Elongation at an applied potential of 0 V was high in this SSRT. However, corrosion protection under these conditions is impossible because the mechanical properties are worse owing to decreased strength resulting from the active dissolution reaction in parallel parts of the specimen. A film composed of $CaCO_3\;and\;Mg(OH)_2$ confers corrosion resistance. However, at potentials below -1.6 V forms non-uniform electrodeposition coating, since there is too little time to form a coating. Therefore, we concluded that the mechanical properties are poor because the effect of hydrogen gas generation exceeds that of electrodeposition. Comparison of the maximum tensile strength, elongation, and time to fracture indicated that the optimum protection potential range was from -1.45 to -0.9 V (SSCE).

• 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.