• 제목/요약/키워드: exfoliation corrosion

검색결과 17건 처리시간 0.022초

Influence of Retrogression and Re-aging on the Exfoliation Corrosion Behavior of AA 7085 Sheets

  • Krishnan, Ajay;Raja, V.S.;Mukhopadhyay, A.K.
    • Corrosion Science and Technology
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    • 제15권4호
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    • pp.159-165
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    • 2016
  • An attempt has been made to understand the influence of retrogression and re-aging (RRA) on the exfoliation corrosion behaviour of AA 7085 alloy in comparison with the peak aged condition (PA). Immersion tests using ASTM G34 and studies involving electrochemical impedance spectroscopy showed that the RRA treated alloy provided higher resistance to exfoliation corrosion than the PA treated alloy. The improved resistance was attributed to the enhanced Cu content and the discontinuous nature of the grain boundary precipitate, which was revealed through transmission electron microscopy.

구리합금에 대한 WC-27NiCr 초고속화염용사 코팅층의 해수내 캐비테이션 특성 평가 (Evaluation of Cavitation Characteristics in Seawater on HVOF Spray Coated Layer with WC-27NiCr Material for Cu Alloy)

  • 한민수;김민성;장석기;김성종
    • Corrosion Science and Technology
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    • 제11권6호
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    • pp.263-269
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    • 2012
  • Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of $30{\mu}m$ with seawater temperature. The cavitation at $15^{\circ}C$ caused exfoliation of the coating layer in 17.5 hours while that of $25^{\circ}C$ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to $25^{\circ}C$ from $15^{\circ}C$, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.

Preparation and Characterization of Muscovite Mica/UV Coating Materials for Steel

  • Cheong, In-Woo;Kim, Hyeon-Seok;Hwang, Dong-Seop;Yoo, Hye-Jin;Kim, Jin-Tae;Lee, Jae-Ryung
    • Corrosion Science and Technology
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    • 제9권6호
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    • pp.265-269
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    • 2010
  • This paper describes the exfoliation and surface modification of muscovite mica for UV coating formulation. For the exfoliation of the mica, hydrothermal process was used in the presence of lithium nitrate ($LiNO_3$). After the cation exchange with $Li^+$ ions, the surface of the mica was modified with several amphiphilic substances to increase compatibility and storage stability in UV coating formulation. Such a hydrophobic surface modification affected colloidal stability as well as dispersibility of the exfoliated mica in UV coating solution. Anticorrosive property of mica/UV coated steel plates was tested by salt spray test (SST) and compared with sodium montmorillonite ($Na^+$-MMT)/UV coated steel plates.

잔류 염소가 포함된 해수에서의 Cu-Ni 합금의 부식 거동 연구 (A Study on the Corrosion of Cu-Ni Alloy in Chlorinated Seawater for Marine Applications)

  • 정근수;윤병영;임채선
    • Corrosion Science and Technology
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    • 제17권4호
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    • pp.176-182
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    • 2018
  • Corrosion of the Cu alloy with 10wt% Ni in stagnant seawater with residual free chlorine was investigated. Despite that fact that Cu alloys are widely used for seawater applications due to their stubborn resistance to chloride attack, not much is known as to how the residual free chlorine in seawater affects corrosion of Cu and its alloys. In this work, immersion tests were conducted in the presence of different levels of chlorine for 90-10 Cu-Ni samples, one of the most frequently used Cu alloys for seawater application, mostly in shipbuilding. The results revealed no evidence for accelerated corrosion of the Cu-Ni alloy even in the presence of 5 ppm residual chlorine in seawater, signifying that the Cu-Ni alloy can be more tolerant to residual chlorine that has been commonly cited by the shipbuilding industry. However, comparison of polarization behavior of the alloy samples in the presence of different electrolytes with different concentrations of residual chlorine suggests that higher concentration of chlorine could increase the corrosion rate of the Cu-Ni alloy. Furthermore, it is suggested that microorganisms in the seawater could increase the corrosion rate of the Cu-Ni alloy by encouraging exfoliation of the corrosion product off the metal surface.

목조 건축문화재의 훼손현황과 보수방안 연구 - 제천시 목조 건축문화재를 중심으로 - (A Study on the Repair Method and the Damage Status of Wooden Architectural Heritages - Focused on the wooden architectural heritages in Jecheon -)

  • 이완건
    • 한국실내디자인학회논문집
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    • 제25권3호
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    • pp.82-89
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    • 2016
  • This study investigated the preservation status of wooden architectural heritages, designated as Chungcheongbuk-do designated heritage in Jecheon. The purpose of this paper is to find the damage cause and the preservation method of wooden architectural heritages. It was conducted using the research methods of the existing literature and field survey to compare a current status of wooden architectural heritages. The result are as followings. Firstly, it was found the problems of a break, a damage, etc. in the platform and the problems of a cracking, an exfoliation, a corrosion, a warp, etc. in the wall. And, it was found a cracking of the beam(梁) and a roof tile(瓦), a falling of Angto(仰土), a sagging roof, etc. in the roof. Secondly, the damage causes of wooden architectural heritages were mostly caused by the physical limitations of the materials. And, it was caused by a rainwater, a subsidence of ground settlement, a destruction of waterproof membrane, etc. Lastly, the repair methods are making a quicklime layer in the soil mound on a cracking and an exfoliation part, a resin treatment or strut operation on a corrosion part of column, etc.

플라즈마용사 세라믹코팅 피막부식재의 음향방출 특성 (Acoustic Emission Characteristics of Plasma Sprayed Ceramic Coating Layer after Salt Spray)

  • 김귀식;박경석;홍용의
    • 한국해양공학회지
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    • 제15권3호
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    • pp.69-74
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    • 2001
  • This paper was to investigate of a adhesiveness for the plasma sprayed coating materials did salt spray by acoustic emission method in tensile loadings. The powders used for the coating were nickel aluminum composite powder Ni-4.5wt.%Al and titanium dioxide powder $TiO_2$. These powders were coated on a carbon steel S45C by plasma spray method. The result solution was a 5% NaCl and the slat spray times were 2, 5 and 10 hours respectively. The salt solution penetrated into the surface of the substrate through pore of the coating layer built in the process of plasma spay. Corrosion productions formed on the surface of substrate. The adhesiveness between the substrate and the coating layer is weaken by corrosion and the exfoliation initiated chiefly at the corrosion surface of the substrate. The AE events and energy of the corroded coating specimens decreased as the salt spray times increased.

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플라즈마용사 세라믹코팅 피막부식재의 음향방출 특성 (Acoustic Emission Characteristics of Plasma Sprayed Ceramic Coating Layer after Salt Spray)

  • 김귀식;박경석;홍용의
    • 한국해양공학회:학술대회논문집
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    • 한국해양공학회 2001년도 춘계학술대회 논문집
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    • pp.344-349
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    • 2001
  • This paper was to investigate of a adhesiveness for the plasma sprayed coating materials did salt spray by acoustic emission method in tensile loadings. The powders used for the coating were nickel aluminum composite powder Ni-4,5wt.%Al and titanium dioxide powder Ti02. These powders were coated on a carbon steel S45C by plasma spray method. The salt solution was a 5% NaCl and the salt spray times were 2, 5 and 10 hours respectively. The salt solution penetrated into the surface of the substrate through pore of the coating layer built in the process of plasma spay. Corrosion productions formed on the surface of substrate. The adhesiveness between the substrate and the coating layer is weaken by corrosion and the exfoliation initiated chiefly at the corrosion surface of the substrate. The AE events and energy of the corroded coating specimens decreased as the salt spray times increased.

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음향방출법에 의한 용사코팅 피막부식재의 파손 해석 (Failure Analysis of Corroded Coating Materials by Acoustic Emission)

  • 김귀식;현창해;홍용의;손창환
    • 한국해양공학회지
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    • 제19권5호
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    • pp.43-49
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    • 2005
  • This paper is to investigate the effect of corrosion by acoustic emission method in tensile loading and the adhesiveness between substrate and coating layer. The powders used are Zn and Amdry625, respectively. They are coated on brass alloy substrate. AE signals of Zn and Amdry625 coating layer increase drastically in strain $2\%$. However, those of Zn specimen have more than those of Amdry625 specimen. When the specimens executed the corrosion test under $3.5\%$ NaCl solution for 500, 1000 hours, the salt solution penetrated into the surface of the substrate through the pores of the coating layer. As a result, corrosion production formed on the surface of the substrate. The adhesiveness between coating layers is weakened by the polarization and corrosion itself. The AE event, count, and energy of corroded coating specimens decrease, compared to specimens without corrosion. The results are summarized as follows : 1. In the tensile tests, the time that it took to start and develop the cracks and exfoliations between the surface of the substrates and the plasma spray coatings were different according to the type of plasma sprayed material, which are Zn and Amdry625. These phenomena were obvious at the strain rate 1 to $5\%$, and few available data were found after that stage. 2. The specimens with Zn coating showed the characteristics of crack, according to the changes of the tensile strength applied on the substrates while those with Amdry625 showed exfoliation as a result of low adaptation to the tensile strength. 3. The anti-corrosion specimens showed that the adhesive properties between the substrate and the plasma spray coating were strong in the order of Zn, Amdry. It showed that Corroded specimens cracked or exfoliated easily, even with the small energy, because those had a comparatively weakened adhesive property, due to corrosion. 4. Zn specimen showed no corrosion phenomena on the surface of the substrates, because they had the function of sacrifice anode however, Amdry625 specimen showed the corrosion, because it did not have that function.

Evaluation of Dynamic Wettability of Liquid Zn with Steel Sheets Containing Si and Mn

  • Tanaka, Toshihiro
    • Corrosion Science and Technology
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    • 제9권2호
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    • pp.87-91
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    • 2010
  • It is pointed out that non-wetting behavior of liquid Zn alloy occurs on high-tensile strength steels, which usually contain Si and Mn. There have been a lot of investigations to improve the above wettability of liquid Zn alloy with steels containing Si and Mn. Although those studies evaluated the wettability qualitatively by observation of the surface of steels galvanized by Zn or exfoliation test of Zn with substrate steels and so on, it is required to evaluate the wettability of liquid Zn with steels by measuring contact angle, work of adhesion, spreading velocity etc. which are usually used to assessment of general wetting behavior. In the present work, we evaluated the wettability of liquid Zn with steels containing Si and Mn by applying a sessile drop method to measure the change in contact angle and diameter of liquid Zn droplet wetted on steels.

인히비터 첨가용액의 침지에 의한 용융아연도금 강판의 내식성 개선에 관한 전기화학적 연구 (An Electrochemical Study on the Corrosion Resistance Improvement of Galvanizing Steel by Dipping to Solution with Inhibitor)

  • 문경만;조황래;강태영;이명훈;김윤해
    • Journal of Advanced Marine Engineering and Technology
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    • 제31권2호
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    • pp.173-181
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    • 2007
  • Recently, galvanizing method is predominantly being used not only a economical point of view but also due to it s stability and long life. For example, guard rail of high way, all kinds of structures for ship etc. were protected with galvanizing and demand of galvanized structural materials was being increased with more and more. However, galvanized structures were inevitably being deteriorated with time eventually because they were corroded with solution of galvanizing film and exfoliation of it s film in the present severe corrosive environment. Therefore, it is necessary to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment. In this study, three test specimens such as pure galvanizing, galvarium, and chromate treatment were submerged at tap water with inhibitor addition. And the effect of their corrosion resistance improvement was comparatively investigated with electrochemical method. Corrosion current density of the galvanized steel was the largest among three specimens, however, the galvarium steel showed the lowest corrosion current density. Futhermore, these three kinds of test specimens indicated considerably excellent corrosion resistance by dipped at tap water with inhibitor addition. Especially, the galvanized steel showed the best effect of corrosion resistance improvement than other test specimens.