• 제목/요약/키워드: Cr-resistance

검색결과 901건 처리시간 0.026초

미생물의 크롬내성과 크롬환원의 상호 비교 (A Comparison between Bacterial Cr(VI) Resistance and Cr(VI) Reduction among Environmental Isolates)

  • 오영숙;최성찬
    • 미생물학회지
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    • 제33권2호
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    • pp.125-130
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    • 1997
  • 미생물에 의한 6가이온 크롬의 3가이온으로의 환원은 세균에게 크롬내성을 제공할 수 있는 것으로 알려져 있다. 본 연구에서는 이러한 가설을 확인하기 위하여 크롬오염 토양과 오염되지 않은 토양으로부터 형태적으로 다른 20종의 세균을 순수분리하고 각각의 균주에서 크롬내성과 크롬환원능을 상호 비교하였다. 전자의 공여체로 glucose를 사용했을 때 세포현탁액에 의한 크롬의 환원은 시간당 0.014-0.305mM Cr(VI)의 범위로 관찰되었으며, 액체배지에서 2mM의 크롬에 대한 내성은 크롬을 첨가하지 않은 배지에서 배양한 경우와 혼탁도를 비교한 결과 전혀 저해를 받지 않는 경우부터 93.4%의 성장저해를 받는 경우까지 다양하게 관찰되었다. 이러한 결과로부터 상관관계를 분석한 결과 크롬내성과 크롬환원은 전혀 상관이 없는 것으로 계산되었다. 한편 군집수준에서의 크롬내성비교는 크롬오염 토양과 오염되지 않은 토양에서 각각 19.1%와 0.4%로 나타나 크롬의 존재는 내성균주의 선택적 성장을 유도하는 것으로 밝혀졌다. 그러나 이때 획득된 크롬에 대한 내성은 크롬의 환원에 의해서 제공되는 것이 아님을 상관관계 분석으로부터 알 수 있었다.

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탈기된 $3.5wt.\%$ NaCl 용액 환경에서의 스테인리스 강에 증착된 CrN 박막의 Si 첨가에 따른 영향 평가 (Effect of Si Addition on the Corrosion Resistance of CrN Coatings in a Deaerated $3.5wt.\%$ NaCl Solution)

  • 김우중;최윤석;김정구;이호영;한전건
    • 한국표면공학회지
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    • 제38권4호
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    • pp.137-143
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    • 2005
  • CrSiN coatings of stepwise changing Si concentration were deposited on stainless steel by closed field unbalanced magnetron sputtering (CFUBM) system. Microstructure of the films due to the Si concentration is measured by XRD. The corrosion behavior of CrSiN coatings in deaerated $3.5\%$ NaCl solution was investigated by potentiodynamic test, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of CrSiN film depends on the Si concentration. When Si/(Cr+si) was under $11.7\%$, preferred orientation is defined at CrN(220), CrN(311) and $Cr_2N(111).$ The results of potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr+si) ratio. EIS measurements showed that the corrosion resistance of Si-bearing CrN was improved by phase transformation of the film, which leads to increase of pore resistance and charge transfer resistance. At the Si(Cr+si) ratio of 20, the Si-bearing CrN possesses the best corrosion resistance due to the highest pore resistance and charge transfer resistance.

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

  • 태성호
    • 한국구조물진단유지관리공학회 논문집
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    • 제10권4호
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    • pp.79-86
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    • 2006
  • 피복 콘크리트의 균열 발생에 기인한 매크로셀 부식 환경하에서의 Cr강방식철근의 방식성을 평가하기 위하여 10종류의 Cr강방식철근을 콘크리트에 매입 후 피복 콘크리트에 모사 균열을 발생시킨 공시체를 제작하였다. 그 후 염수 분무 촉진 양생 105사이클까지의 매크로셀 부식전류밀도의 경시변화와 아노드 캐소드 철근의 자연전위, 부식면적률, 부식감량률을 측정함으로써 Cr강방식철근의 방식성에 대하여 검토하였다. 그 결과, 염화물 이온 농도차 $3kg/m^3$ 이하의 매크로셀 부식 환경에 대하여 Cr함유율 9% 이상의 Cr강재에서 방식성이 확인되었으며 특히, Cr함유율 11% 이상의 Cr강재에서 뛰어난 방식성이 입증되었다.

크롬계 이중도금층 제조 및 특성평가 (Fabrication of Chromium-based Double Layered Deposit)

  • 박상언;김동수;김만;장도연;권식철
    • 연구논문집
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    • 통권31호
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    • pp.127-133
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    • 2001
  • In chromium electrodeposition, crack is inevitably accompanied by chromium layer. Behavior of crack formation and crack density were different from the plating conditions such as current density, temperature, waveform of applied current and so on. And cracks have an influence on the corrosion resistance of chromium deposit, because corrosion occurs through the network of cracks between deposit and substrate. Therefore, many researches have been achieved in order to remove the cracks in chromium deposit. Formation of double layers, Cr/Cr and Ni/Cr were investigated to increase corrosion resistance of chromium deposit in this study. As pretreatment prior to outer chromium coating, acid pickling and current control method were examined. Cracks in cross-section of each sample were observed with SEM and CASS(Copper modified acetic acid salt spray) test was performed to evaluate corrosion resistance. It was found that corrosion resistance of Cr/Cr and Ni/Cr double layers were superior to Cr or Ni single layer from the results of CASS test.

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내열용 오버레이 12%Cr계 스테인레스강의 열피로 특성에 미치는 Cr 함량과 델타-페라이트의 영향 (Effects of Cr Content and Volume Fraction of δ-Ferrite on Thermal Cycling Fatigue Properties of Overlay Welded Heat-Resistant 12%Cr Stainless Steels)

  • 정재영
    • 소성∙가공
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    • 제26권6호
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    • pp.356-364
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    • 2017
  • In this study, submerged arc cladded Fe-Cr-Ni-Mo-CuWNbV-C stainless steels containing various Cr contents between 11.2 wt.% and 16.7 wt.% were prepared with fixed C content at about 0.14 wt.%. Using these alloys, changes in microstructure, tensile property, and thermal fatigue property were investigated. Phase fraction of delta-ferrite was increased gradually with increasing Cr content. However, tensile strength, hardness, and thermal fatigue resistance appeared to be decreased. When the microstructure of delta-ferrite was observed, it was revealed that the mesh structure retained up to about 15% Cr content. Although thermal fatigue resistance was almost the same for Cr contents between 11.0 and 14.5 wt.%, it was significantly decreased at higher Cr contents. This was evident from mean value of crack lengths of 10 largest ones. Evaluation of thermal fatigue resistance on alloys with various Cr contents revealed the following important results. First, the reproducibility of ranking test was excellent regardless of the number of cycles. Second, thermal fatigue resistance was increased in proportion to true tensile fracture strength values of overlay materials. Finally, the number of thermal fatigue cracks per unit length was increased with increasing true tensile fracture strength.

직접결합 마그네시아-크로미아질 내화벽돌의 특성에 미치는 $Cr_2O_3$ 함유량의 영향 (Effects of $Cr_2O_3$ Content on the Properties of Direct-Bonded Magnesia-Chromia Bricks)

  • 홍기곤;엄창중
    • 한국세라믹학회지
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    • 제34권1호
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    • pp.63-69
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    • 1997
  • 출발원료로서 소결마그네시아 클링커 및 천연크롬철광을 사용하여 Cr2O3의 함유량을 약 10-30 중량%의 범위에서 변화시켜 직접결합 마그네시아-크로미아질 내화벽돌의 특성에 미치는 Cr2O3의 영향을 고찰하였다. 상온 꺾임강도 및 고온 꺽임강도는 Cr2O3의 함유량 및 flux 성분의 함유량과는 상관관계가 성립하지 않았으며, 상온 꺾임강도 및 고온 꺾임강도가 가장 우수한 Cr2O3 함유량의 범위는 20중량% 전후였다. 내식성을 좌우하는 주된 요인은 flux성분의 함유량보다는 2차 spinel의 생성량이었으며, 내식성은 2차 spinel의 생성량 증가에 따라 선형적으로 증가하였다. 또한, 내spalling성은 주로 flux 성분의 함유량에 의존하였으며, flux 함유량이 적을수록 내spalling성이 우수하였다.

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코팅에 의한 고온재료의 내산화성 향상을 위한 연구 (A strudyon the improvement of the oxidation resistance for high temperature materials by coating process)

  • 강석철;민경안;안연상;김길무
    • 한국표면공학회지
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    • 제30권2호
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    • pp.93-103
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    • 1997
  • High temperature materials used in the elevated temperature and corrosive atmosphere must have the good oxidation resistance and preserve their own mechanical properties simultaneously. For the oxidation resistance, it is very important to form a protective oxide scale such as $Al_2O_3$ or $Cr_2O_3$ on the substrate. However, the additions of protective oxide forming elements such as Cr and Al in the alloy to enhance its oxidation resistance are limited due to the deleterious effects on their mechanical properties. PECVD(P1asma Enhanced Chemical Vapor Deposition) coating processes were employed to improve the oxidation resistance at high temperature. Cr and/or A1 were coated on the substrates of Ni and Inconel 600 at various temperatures of 400, 500, $600^{\circ}C$ and at different conditions of specimen surfaces. Then, coated specimens were exposed to isothermal and cyclic oxidation conditions in air at 1000 and $1100^{\circ}C$. In order to enhance the adhesion between the substrate and coated layer, heat treatments of the coated specimens were conducted in a vacuum. At isothermal oxidation experiments, Al-coated Ni specimen showed better oxidation resistance than pure Ni. At cyclic oxidation experiments at $1000^{\circ}C$. Cr and Al-coated specimen showed better oxidation resistance. Cr-coated Inconel 600 had also showed better oxidation resistance due to Cr in the substrate. By PECVD coating process, oxidation resistance could be improved, but it was not improved as expected due to the weakness of the adhesion between the substrate and the coated layer.

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고크롬 철계 오버레이용접층의 긁힘마모거동에 미치는 크롬탄화물 양의 영향 (Effect of Volume Fraction of Cr Carbide Phase on the Abrasive Wear Behavior of the High Cr White Iron Harcfacing Weld Deposits)

  • 백응률
    • Journal of Welding and Joining
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    • 제16권1호
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    • pp.125-133
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    • 1998
  • The effect of volume fraction of Cr carbide phase (Cr CVF) on the low stress abrasion resistance in the chromium-carbide-type high Cr white iron hardfacing weld deposits has been investigated. In order to examine Cr CVF, a series of alloys with varying Cr CVF by changing chromium and carbon contents and the ratio of Cr/C were employed. The alloys were deposited once or twice on a mild steel plate using the self-shielding flux cored arc welding process. The low stress abrasion resistance of the alloys against sands was measured by the Dry Sand/Rubber Wheel Abrasion Test (RWAT). It was shown that hardness and abrasion resistance increased with increasing Cr CVF within the whole test range (Cr CVF : 0.23-0.64). Both primary Cr carbide and eutectic Cr carbide were particularly effective in resisting wear due to their high hardness.

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Effect of Thermal History on Pitting Corrosion of High Nitrogen and Low Molybdenum Stainless Steels

  • Kim, Kwangsik;Chang, Hyunyoung;Kim, Youngsik
    • Corrosion Science and Technology
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    • 제2권2호
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    • pp.75-81
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    • 2003
  • Chromium, molybdenum. and nitrogen are very important alloying elements in stainless steels and its effect was approved in pitting resistance equivalent (PRE) equations and many experimental results. However, Cr can improve the corrosion resistance, but facilitate the formation of sigma phase. Also. Mo has the same effect in stainless steels. If Cr and Mo are added at high amount to increase the corrosion resistance of stainless steel, corrosion resistance in annealed alloys can be improved, but in case of welding or aging heat treatment. its resistance will be drastically decreased. In this work, increasing Cr and N contents but decreasing Mo than the commercial alloys made the experimental alloys. Typical alloys are 25Cr-4.5Mo-0.43N alloy, 27Cr-4.7Mo-0.4N alloy, 27Cr-5.3Mo-0.25N alloy, 32Cr-2.6Mo-0.36N alloy. After annealing and aging heat treatment, microstructures, anodic polarization test, and pitting corrosion test were performed. Annealed alloys showed $100^{\circ}C$ of CPT and aged alloys showed the different tendency depending upon Cr and Mo contents(SFI)

Al2O3 분산 Zn-Co-Cr 전기도금강판의 제조조건 및 내식성에 관한 연구 (A Study of Electroplating Conditions and Corrosion Resistance for Al2O3 Dispersed Zn-Co-Cr Electroplated Steel Sheets)

  • 김상범;서수정;박현순
    • 열처리공학회지
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    • 제6권2호
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    • pp.89-97
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    • 1993
  • An improvement in corrosion resistance of various types of Zn-coated steel sheets is thought to be possible with the addition of fine oxide powder to the coating. In this study the corrosion resistance of the $Al_2O_3$ dispersed Zn-Co-Cr electroplated steel sheet has been investigated and the results were as follows : The corrosion resistance of $Al_2O_3$ dispersed Zn-Co-Cr electroplated steel sheets was improved by increasing the contents of Co and Cr ions, and also $Al_2O_3$ powders in the bath because of the increased amount of Co, Cr and $Al_2O_3$ in deposits. In the $Al_2O_3$ dispersed Zn-Co-Cr electroplated steels sheet, the structure of deposits was changed from fine microstructure as observed in high Co containing deposits to coarse microstructure as in high Cr and $Al_2O_3$ containing deposits. By cold rolling of the $Al_2O_3$ dispersed Zn-Co-Cr electroplated steel sheets to about 2 percent, thr corrosion resistance was improved further.

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