• 제목/요약/키워드: 부식율

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ELECTRO-CHEMICAL ASPECTS OF STRESS CORROSION OF MILD STEELS ( I ) (연강의 전기화학적인 응력부식에 관한 연구 (I))

  • KIM Suk-Ho
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.7 no.4
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    • pp.234-237
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    • 1974
  • Electro-chemical aspects of stress corrosion on the mild steels when immersed in the $5\%\;H_2SO_4$ solution and charged with 100mV and 100mA were discussed. The main results of the experiment are follows; 1. The weight loss by corrosion was concerned with the applied stress. and the larger the applied stress, the greater the weight loss. 2. Reduction of corrosion stress was a factor of inverse proportion to the applied stress. 3. Corrosion began at first on the parts of impurities concentrated and the grain boundaries, and gradually developed and spreaded out. 4. The materials of unsteady structure deformed of space lattice by the high stress or work-hardening showed less reduction of corrosion stress.

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Effect of Relative Humidity on the Atmospheric Corrosion of Mild Steel Using the Electrochemical Wet/Dry Method (전기화학적 wet/dry 법을 이용한 탄소강의 대기부식에 미치는 상대습도의 영향에 관한 연구)

  • Yeon Jei-Won;Pyun Su-Il;Lee Woo-Jin;Choi In-Kyu;Chun Kwan-Sik
    • Journal of the Korean Electrochemical Society
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    • v.3 no.1
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    • pp.5-10
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    • 2000
  • In the present work, corrosion rate W and corrosion potential tow were simultaneously measured as a function of relative humidity RH employing the electrochemical wet and dry method as an accelelated atmospheric corrosion method. The W versus (vs.) RH curve is classified into .three regions, namely, the first W plateau region, the second region of the linear relationship between logarithmic W and RH, finally, followed by an abrupt decay region. Based upon the atmospheric corrosion mechanism of mild steel, we introduced another diagram of $\varepsilon_{corr}$ vs. RH which is divided into three regions. In the first region, the corrosion scales are composed of single lepidocrocite-phase $(\gamma-FeOOH)$; in the second region, $\gamma-FeOOH$-phase coexists with magnetite-phase $(Fe_3O_4)$ in the scales and finally the oxide scales change into a single Fe304-phase in the third region. The three distinct regions of both representations share almost each other, which is validated by FT-IR (Fourier transform infra-red) analysis and surface observation. Both representations prove to be convenient and complementary for surveying the spectrum of the atmospheric corrosion of mild steel.

A Study on Local Conditions in Amine Solutions Influencing on Corrosion of Carbon Steel (탄소강의 부식에 미치는 아민계 용액의 조건에 관한 연구)

  • Gwon, Hyuk-Jun;Ahn, Hyun-Kyoung;Song, Chan-Ho;Park, Byung-Gi;Cho, Dae-Chul;Rhee, In-Hyoung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.6
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    • pp.2879-2887
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    • 2011
  • This research is aimed for the better understanding of corrosion behavior of carbon steel in ETA or $NH_3$ solution at high temperature. To minimize the corrosion it is important to select proper pH control agent(s), which also let it maintain basic or reductive environment inside the steel pipe. This work will provide the practical guideline which can be applied to the nuclear power plant for developing the life extension method of carbon steel. Experiments were carried out by measuring the corrosion rate using the potentiodynamic polarization curve of carbon steel in ETA and NH3 at different temperatures. The corrosion rate was estimated by using the Tafel curve measured under various test conditions: i) $NH_3$ is less than ETA as a pH agent. ii) the corrosion was reduced at high pH, and iii) the corrosion was maximum in the temperature range of $150\sim200^{\circ}C$.

Nonlinear Analysis of RC Beams Damaged by Corrosion of Tension Main Rebar (인장 주근이 부식된 RC보의 비선형 해석)

  • Shin, Sung-Woo;Lee, Han-Seung;Yoo, Suk-Hyeong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.9 no.2
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    • pp.191-198
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    • 2005
  • This study was carried out to investigate quantitatively the relationship between the degree of rebar corrosion and the strength of reinforced concrete beams. After producing equations for the relationship between both the tensile properties of rebars and bond properties and the corrosion percentage of rebars, finite element analysis and bending tests were conducted for RC beams damaged by corrosion of tension main rebar. As a result, it was made that the strength of RC beams damaged by corrosion could be practically simulated by FEM analysis using experimentally determined material properties representing the bond and the mechanical characteristics of corroded rebars.

Analysis of Crack characteristic on Concrete Cover for Subway Box Structure Due to Reinforcement Corrosion (철근부식으로 인한 지하철 박스구조물의 콘크리트 피복층 균열특성 분석)

  • Choi, Jung-Youl;Shin, Dong-Sub;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
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    • v.8 no.6
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    • pp.727-732
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    • 2022
  • Applying the calculated cross-sectional reduction due to the corroded rebar investigated in the field to the numerical analysis model, the damage pattern and delamination of concrete in the field showed a tendency relatively similar to the numerical analysis results. It was analyzed that when the expansion pressure due to corrosion of the reinforcing bar is greater than the tensile stress of the concrete, cracks are generated and the concrete cover can be fracture. As a result of this study, the correlation between the corrosion rate of reinforcing bars and the crack occurrence of the concrete cover of the subway box structure was verified based on the numerical analysis and field test results. To prevent rebar corrosion, the corrosion rate can be reduced by applying rust prevention to the reinforcing bar and changing the material. In the case of exposed to a corrosive environment, the tensile strength of the concrete is improved by adjusting the concrete compressive strength to secure durability against the expansion pressure caused by the corroded rebar.

A Study on The Corrosion Resistance of Concrete Containing Copper Slag (동제련 슬래그 혼입 콘크리트의 부식 저항성에 관한 연구)

  • Lee, Dong-Un;Jung, Yoo-Jin;Kim, Young-Su
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.5
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    • pp.189-196
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    • 2007
  • The purpose of this study was to analyze steel corrosion resistance of concrete containing copper slag. The specimens were made with normal portland cement and pozzolan materials with various replacement ratio and with W/B ratio ranging from 35% to 55%. Compressive strength, coefficient of chloride diffusion, corrosion area ratio and weight reduction ratio were determinated for the test. The results show that the concrete with pozzolan materials is superior resistant to chloride ions compared to the concrete without pozzolan materials. It was observed that blast furnace slag replacement ratio of 20% gives the best results with respect to chloride ion penetration and corrosion tests and observed that copper slag replacement ratio of 10% gives the seperior resistance compared to normal concrete.

Corrosion Resistance of Cr-bearing Rebar to Macrocell Corrosion Caused by Concrete with Crack (피복 콘크리트의 균열 발생에 기인한 매크로셀 부식 환경하에서의 Cr강방식철근의 방식성)

  • Tae, Sung-Ho
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.4
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    • pp.79-86
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    • 2006
  • This study was investigated to corrosion resistance of Cr-bearing rebars to macrocell corrosion caused by concrete with crack. Ten types of steel bars having different Cr contents were embedded in concretes with imitation crack. The corrosion resistance of the Cr-bearing rebar was examined by measuring half-cell potential, macrocell corrosion current, corrosion area and weight loss up to 105 cycles of salt spray testing. The results revealed that the Cr content required for corrosion resistance in a macrocell corrosion environment caused by chloride ion gap of $3kg/m^3$ was 9% or more. The corrosion-resisting performance of Cr-bearing rebar was particularly noticeable with a Cr content of 11% or more.

Characterization of Humic Acid in the Chemical Oxidation Technology(I) - Characteristics by Photocatalytic Oxidation Process - (화학적 산화법에 의한 부식산의 분해 처리기술에 관한 연구(I) - 광산화공정을 통한 부식산의 분해특성 분석 -)

  • Kim, Jong Boo;Rhee, Dong Seok
    • Analytical Science and Technology
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    • v.13 no.2
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    • pp.234-240
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    • 2000
  • The efficiency of Photocatalytic Oxidation Process were investigated for the treatment of Aquatic Humic Substances (AHS). In UV-only system, pH 7-9 was the optimum pH range for TOC removal, and alkali range was the optimum pH for absorbance decrease. In UV/$TiO_2$ system, the optimum $TiO_2$ dosage was 50ppm and over 50ppm of $TiO_2$ dosage was not effective for removal of AHS. In UV/$H_2O_2$ system, optimum $H_2O_2$ dosage was 20mM, when over 20mM dosage, removal of TOC (Total Organic Carbon) and absorbance was decreased. Radical scavenger affected on the photo-oxidation of AHS. Removal rate of TOC and absorbance was decreased by addition of carbonate ions and TOC removal was more effected than that of absorbance.

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Outdoor corrosion test와 Accelerated corrosion test의 상대적 비교

  • Jo, Ui-Yeol;Gwon, Gi-Bong;Jo, Dae-Hyeong
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2012.11a
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    • pp.124-124
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    • 2012
  • 부식 현상은 산업과 실생활에서 경제적, 인간의 생활과 안전에서 손실을 일으키는 요인이다. 자동차 부품, 선박 부품 및 전자 부품 산업 등 다양한 분야에서 수명 및 고장율 시험에 대한 관심이 증가하고 있다. 넓은 분야에서 염수분무시험을 적용하고 있지만, 실제 야외환경에서 발생하는 부식과의 상관관계가 확실하게 규명되어 있지 않다. 그리고 이렇게 넓은 산업전반에서 적용하고 있는 염수분부시험 방법은 시료의 부식 저항성을 판단하기 위한 시험시간이 오래 걸리고 이런 이유로 적정한 시험시간을 설정하기 어려울 뿐만 아니라 고내식성 시료의 부식평가가 어렵다는 단점을 가지고 있다. 본 연구에서는 부식의 형태에서 균일부식 현상을 이용하여 옥외 노출 부식시험과 염수분무시험, 가속부식시험 환경에 노출된 시료의 무게 감량을 측정하여 가속계수 도출과 함께 부식 정도를 예측할 수 있는 방법을 연구하였다.

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A Study on the Ozonation of Aquatic Humic Substances(AHS) Extracted from Soyang Lake Water (소양호에서 추출한 수중 부식질(AHS)의 오존처리에 대한 연구)

  • An, Bok-Yeop;Rhee, Dong-Seok;Shin, Hyun-Sang
    • Journal of Korean Society of Environmental Engineers
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    • v.22 no.3
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    • pp.453-461
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    • 2000
  • Aquatic humic substance (AHS) was extracted from Soyang lake water using XAD-8 resin. and its concentration distribution in the lake from May to October. 1997 was determined. Ozonation characteristics of the AHS were studied as factors of pH, carbonate ion concentration. and the biodegradability and structural changes of the AHS were also investigated after ozonaticn. DOC distribution in Soyang Lake water was 1~3 mg/L. and the concentrations of AHS ranged between 0.2~0.8 mg/L. which was corresponding to 20~30% of DOC. AHS was composed of around 20% of HA and 80% of FA. The optimum pH value for AHS ozonation was in range of pH 7~9. When carbonate ions were added for AHS ozonation as a ladical scavenger. it was found that DOC removals were decreased. and the absorbance decreases were increased slightly. Biodegradability of the ozonized AHS was 50% higher than that of unozonated AHS. $^{13}C-NMR$ analysis showed that the aromatic compounds of AHS, after ozonation, were decreased from 49% to 17%. and the aliphatic and carboxylic compounds were increased from 34% to 51% and from 17% to 32%. respectively.

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