• Title/Summary/Keyword: Seawater corrosion

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Estimation of Chloride Corrosion Threshold Value in Concrete by Using Electrochemical and Cyclic Wet and Dry Seawater Method (전기화학적 및 해수 건습반복 방법에 의한 콘크리트 내의 임계 염화물량 평가)

  • Bae Su Ho;Lee Kwang Myong;Chung Young Soo;Kim Jee Sang
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.05b
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    • pp.245-248
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    • 2005
  • It should be noted that the critical chloride threshold level is not considered to be a unique value for all conditions. This value is dependent on concrete mixture proportions, cement type and constituents, presence of admixtures, environmental factors, steel reinforcement surface. conditions, and other factors. In this study, the accelerated corrosion test for reinforcing steel was conducted by electrochemical and cyclic wet and dry seawater method, respectively and during the test, corrosion monitoring by half cell potential method was carried out to estimate the chloride corrosion threshold value when corrosion for reinforcing steel in concrete was perceived. For this purpose, lollypop and right hexahedron test specimens were made for 31.4$\%$, 41.5$\%$ and 49.7$\%$ of w/c, respectively and then the accelerated corrosion test for reinforcing steel was executed. It was observed from the test that the time to initiation of corrosion was found to be different with water-cement ratio and accelerated corrosion test method, respectively and the chloride corrosion threshold value was found to range from 0.91 to 1.43 kg/$m^{3}$.

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Improvement of Seawater Corrosion Resistance of Concrete Reinforcing Steel Using by Conductive Photocatalyst (전도성 광촉매를 이용한 콘크리트 철근의 염해 내구성 향상에 관한 연구)

  • Bae, Geun-Guk;Bae, Geun-Woo;Ahn, Yong-Sik
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.2
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    • pp.152-159
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    • 2017
  • In marine environment, the durability of concrete and reinforcing steel is known to be deteriorate by the permeation of chloride ion into concrete. In this study the conductive photocatalyst was used to improve the seawater corrosion resistance of the concrete and steel. Mortar and concrete samples were prepared by mixing with various amounts of conductive active carbon and photocatalytic powder($TiO_2$). The compressive strength of concrete was decreased with the increase of the amount of conductive carbon powders. The samples containing conductive carbon and photocatalytic powders showed the superior seawater corrosion resistance compared with the ordinary sample, which was verified by XRF analysis showing the concentration of chloride ion($Cl^-$) of mortars and concretes. The inhibitive effect of photocatalyst against chloride attack was discussed with the diffusion coefficient of chloride ion into mortar and concrete.

Fatigue Strength Evaluation of Rusting Decayed Hull Steel Plate in Air and in Artificial Seawater Condition (선체의 부식쇠모강판의 대기중 및 해수중 피로강도평가에 관한 연구)

  • Kim, Won-Beom;Paik, Jeom-Kee;Iwata, Mitsumasa;Yajima, Hiroshi
    • Journal of the Society of Naval Architects of Korea
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    • v.43 no.4 s.148
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    • pp.467-475
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    • 2006
  • Fatigue strength of hull structural steel plate, extracted from longitudinal bulkhead of a 17-year-old ore/oil carrier for renewal, was investigated in air and in artificial seawater condition. The surface of the plate was covered with corrosion pits and they proved to be crack initiation sites by fractography using SEM. From this research, it was found that the evaluation method for fatigue strength of virgin mild steel plates in air and in artificial seawater can also be applied to the evaluation of the fatigue strength of mild steel plates those were long-term exposed to a corrosive environment and their surfaces had been rusted intensively.

Electrochemical Characteristics of Zn-mesh Cathodic Protection Systems in Concrete in Natural Seawater at Elevated Temperature

  • Kim, Ki-Joon;Jung, Jin-A;Lee, Woo-Cheol;Jang, Tae-Seub
    • Corrosion Science and Technology
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    • v.6 no.6
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    • pp.269-274
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    • 2007
  • The corrosion of steel in concrete is significant in marine environment. Salt damage is one of the most detrimental causes to concrete bridges and port structures. Especially, the splash and tidal zones around water line are comparatively important in terms of safety and life-time point of view. During the last several decades, cathodic protection (cp) has been commonly accepted as an effective technique for corrosion control in concrete structures. Zn-mesh sacrificial anode has been recently developed and started to apply to the bridge column cp in marine condition. The detailed parameters regarding Zn-mesh cp technique, however, have not well understood so far. This study is to investigate how much Zn-mesh cp influences along the concrete column at elevated temperature. About 100 cm column specimens with eight of 10 cm segment rebars have been used to measure the variation of cp potential with the distance from Zn-mesh anode at both $10^{\circ}C$ and $40^{\circ}C$ in natural seawater. The cp potential change and current diminishment along the column specimens have been discussed for the optimum design of cp by Zn-mesh sacrificial anode.

Development of Corrosion Rust Removing Unit for Small Ship Propeller (소형선박용 프로펠러의 부식 녹 제거장치 개발)

  • Kim, Gui-Shik;Han, Se-Woong;Hyun, Chang-Hae
    • Journal of Ocean Engineering and Technology
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    • v.19 no.6 s.67
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    • pp.72-77
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    • 2005
  • The materials used in a ship screw propeller are commonly made with brass. The seawater corrosion and seawater cavitation of the screw propeller reduces the propulsive performance of the ship. In screw manufacturing, the corrosion rust of the screw propeller is removed through a hand grinding method. The grinding process produces dust of the heavy metals from the brass. The dust creates a poor working environment that is harmful to the health of the workers. An automatic corrosionrust removing apparatus, using a blasting method, was developed for the improvement of screw polishing conditions and its working environment. The performance of this apparatus was investigated by surface roughness, weight loss rate, hardness, electrochemical corrosion resistance, and cavitation erosion, after removing of the corrosion rust under various blasting conditions. Two medias of alumina and emery were used in this experiment. The surface roughness and hardness of the screw were improved by this apparatus. The electrochemical corrosion potential (Ecorr) and current density (Icorr) were measured by the dynamic polarization method, using a potentiostat,under the conditions of surface polishing with grinding, blasting, wire brushing, and fine sand papering. The test results prove that the new corrosion rust-removing apparatus improves the surface performance of a screw propeller.

Investigation of Liquid Droplet Impingement Erosion Corrosion based on the Flow Rate of Anodized 5083-H321 Al Alloy in Seawater (경질양극산화된 5083-H321 알루미늄 합금의 해수 내 액적충격침식부식 손상 연구)

  • Shin, Dong-Ho;Kim, Seong-Jong
    • Corrosion Science and Technology
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    • v.19 no.6
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    • pp.310-317
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    • 2020
  • This study investigated the damage to the specimen due to liquid droplet impingement erosion corrosion, which improved the corrosion resistance and durability via hard anodization of 5083-H321 aluminum alloy, which is widely used for small ships and marine structures. The experiment combined liquid droplet impingement erosion and electrochemical equipment with the flow rates in natural seawater solution. Subsequently, Tafel extrapolation of polarization curves was performed to evaluate damage due to the liquid droplet impingement erosion corrosion. The damaged surface was observed using a 3D microscope and a scanning electron microscope. The degree of pitting damage was measured using the Image J program, and the surface hardness was measured using the micro-Vickers hardness tester. The corrosion current density, area, depth, and ratio of the damaged areas increased with the increase in flow rate. The grain size of the damaged area at a flow rate of 20 m s-1 showed fewer and minor differences in height, and a smooth curved shape. The hardness of the damaged surface tended to decrease with increase in flow rate.

Experimental Investigation of Properties for Corrosion resistance of Corrosion Inhibitors (방식재료의 내부식 성능에 관한 물성연구)

  • 이상엽;김양현;한만엽;엄주용
    • Proceedings of the Korea Concrete Institute Conference
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    • 1997.10a
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    • pp.257-262
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    • 1997
  • Reinforced concrete structures built on the seashore or in seawater are damaged from saltwater which cause to accelerate corrosion of reinforcing steel in concrete. Therefore, Corrosion of steel reinforcement of concrete structures become more and more serious, and prediction of service lives of concrete structures considering steel corrosion is needed much more. this research is to investigate basic physical properties of various corrosion inhibitors and to evaluate their corrosion resistance in concrete. The object of this study is develop appropriate corrosion protection systems so as to enhance the durability of concrete.

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High Nitrogen-Bearing Austenitic Stainless Steels Resistant to Marine Corrosion

  • Kodama, Toshiaki;Katada, Yasuyuki;Baba, Haruo;Sagara, Masayuki
    • Corrosion Science and Technology
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    • v.2 no.6
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    • pp.272-276
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    • 2003
  • High nitrogen-bearing stainless steel (HNS) containing more than Imass% N was successfully created by means of pressurized electro-slag remelting (P-ESR) without the addition of manganese. Excellent localized corrosion resistant properties of the HNS were confirmed in terms of pitting and crevice corrosion in artificial seawater. The repassivation kinetics proved higher repassivation rate for HNS.

Rapid Corrosion Test on Reinforcing Steels in Chloride-Penetrating Concrete Structures with Various Crack Patterns (염화물 침투 콘크리트의 균열 특성에 관한 철근부식에 관한 연구)

  • 류금성;정영수;유환구;김국한;조창백
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.693-696
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    • 1999
  • Reinforced concrete is, in general, known as high durability construction material under normal environments due to strong alkalinity of cement. It is , however, well known that moderate or minor cracks in reinforced concrete should be most serious causes to deteriorate the durability of RC structures. Furthermore, chloride contents penetrating through unexpected cracks in reinforced concrete bridges get to weaken corrosion resistance of reinforcement steel in concrete and than to accelerate the deterioration of concrete durability. The objective of this experimental research is 1) to evaluate the effect of various corrosion protection system for reinforced concrete specimens with moderate or minor cracks which are exposed to cyclic wet and dry seawater, and then 2) to develop effective corrosion protection system for reinforced concrete bridges under the exposure of various detrimental environments such as seawater, deicing and etc.

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Rapid Corrosion Test on Reinforcing Steels in Chlordie-Penetrating Structures with Various Crack Patterns (염화물 침투 콘크리트의 균열 특성에 따른 철근 부식에 관한 연구)

  • 류금성;유환구;김국환;이상국;정영수
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.04a
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    • pp.718-723
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    • 2000
  • Reinforced concrete is in general, known as high durability construction material under normal environments due to strong alkalinity of cement. It is, however, well known that moderate or minor cracks in reinforced concrete should be most serious causes to deteriorate the durability of RC structures. Futhermore, chloride contents penetrating through unexpected cracks in reinforced concrete bridges get to weaken corrosion resistance of reinforcement steel in concrete and then to accelerate the deterioration of concrete durability. The objective of this experimental research is 1) to evaluate the effect of various corrosion protection systems for reinforced concrete specimens with moderate or minor cracks which are exposed to cyclic wet and dry seawater, and then 2) to develop effective corrosion protection systems for reinforced concrete bridges under the exposure of various detrimental environments such as seawater, deicing and etc.

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