• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(3)
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• pp.145-150
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• 1996

Acoustic Emission (AE) technique was applied to stress corrosion cracking of Inconel 600 to investigate the AE capability of detecting crack growth and to obtain the relation between AE characteristics and crack mechanism. The specimens were heat-treated in two conditions (600$^{\circ}C$ for 30 hrs or 700 $^{\circ}C$ for 1 hr) and undergone CERT at two extension rates ( 2.5${\times}$10$^{-5}$ or 1.25${\times}$10$^{－4}$(mm/s)). It was found that the AE peak amplitude from plastic deformation was generally smaller than about 48dB (0.25mV), while Intergranular stress corrosion cracking (IGSCC) and ductile fracture produced higher values of 49 to 70dB (0.3mV to 3mV). The slopes of cumulative amplitude distribution (b-values) were linearly dependent on IGSCC susceptibility and the higher the susceptibility, the smaller the b-value. The monitoring of combined AE parameters such as event rate, amplitude, count and energy can provide effective means to clearly identify the transition from crack initiation and small crack growth to rapid growth of dominant cracks.

• Corrosion Science and Technology
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• 제17권1호
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• pp.6-11
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• 2018

Outdoor exposure tests using of 7B04 aluminium alloy samples including plate, tensile and various SCC samples were carried out in Tuandao station, Shandong province (East of China) and Wanning station, Hainan province (South of China). Corrosion characteristics including weight loss, microstructure, tensile strength and SCC susceptibility were investigated. The corrosion rates in Tuandao and Wanning showed high to low and the corrosion rates changed to the following equation of $w=at^b$ (b<1). The corrosion of 7B04 aluminium alloy in Wanning was more serious than that in Tuandao. Pitting appeared at early stage of expose test, and it can be changed to general corrosion with test time extension. The 7B04 aluminium alloy of which specimen shapes are forging and thick plate also showed SCC (Stress corrosion cracking) in the marine atmosphere. The higher SCC sensitivity was observed in Wanning station than in Tuandao station. The 7B04 aluminium alloy with a high stress level was more sensitive to SCC. Intergranular and transgranular or a mixed mode of cracking can be observed in different marine exposure.

• Corrosion Science and Technology
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• 제5권6호
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• pp.189-195
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• 2006

Effects of tungsten (W) on the precipitation kinetics of secondary phases and the associated resistance to pitting corrosion of 25%Cr duplex stainless steels were investigated through microstructural and electrochemical noise analyses. With the partial substitution of W for Mo in duplex stainless steel, the potential and current noises of the alloy were significantly decreased in chloride solution due to retardation of the ${\sigma}$ phase precipitation. The preferential precipitation of the $\chi$ phase in the W-containing alloy during the early period of aging contributed to retarding the precipitation of the $\sigma$ phase by depleting W and Mo along grain boundaries. In addition, the retardation of the nucleation and growth of the $\sigma$ phase in the W-containing alloy appears to be attributed to the inherently low diffusivity of W compared with that of Mo.

• Journal of Electrochemical Science and Technology
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• 제7권1호
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• pp.58-67
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• 2016

The corrosion behavior of duplex stainless steel AISI 2205 was investigated in ethylene glycol-water mixture in the presence of 50 W/V % LiBr at different concentrations and different temperatures. Cyclic polarization, impedance measurements and Mott-Schottky analysis were used to study the corrosion behavior the semi conductive properties of the passive films. The results showed that with increasing in the ethylene glycol concentration to 10 V/V%, the corrosion rate of the steel alloy substrate increased. In higher concentrations of ethylene glycol, corrosion current of steel decreased. The results of scanning electron microscopy of electrode surface confirmed the electrochemical tests. Electrochemical experiment showed that duplex steel was stable for pitting corrosion in this environment. The increase in the ethylene glycol concentration led to increasing the susceptibility to pitting corrosion. The corrosion current increased as the temperature rise and also pitting potentials and repassivation potentials shifted towards the less positive values as the temperature increased. According to Mott-Schottky analysis, passive films of stainless steel at the different temperatures showed both n-type and p-type semiconductor behavior in different potential.

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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• pp.460-469
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• 2000

A study on the corrosion behavior of RE36 steel for marine structure was investigated with parameters such as micro-Vickers hardness, corrosion potential and corrosion current density measurement of weld metal(WM), base metal (BM) and heat affected zone(HAZ), Al anode generating current and Al anode weight loss quantity in case of cathodic protection. And we carried out slow strain rate test(SSRT) in order to research mechanical properties such as stress at maximum load, percent strain, time to fracture and strain to failure ratio etc and to find out limiting cathodic polarization potential for hydrogen embrittlement with applied cathodic polarization potential. Hardness of HAZ part was the highest among those three parts and also galvanic corrosion susceptibility was the highest in HAZ part among those three parts due to the lowest corrosion potential than other parts. However corrosion current density was the highest in WM part among those three parts. And the optimum cathodic polarization potential showing the best mechanical properties obtained by SSRT method with applied constant cathodic potential was from - 770mV to - 875mV(SCE). However it is suggested that limiting cathodic polarization potential indicating hydrogen embrittlement on the mechanical properties was under - 900mV(SCE).

• Corrosion Science and Technology
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• 제22권6호
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• pp.399-407
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• 2023

This study investigated the formation of oxide films on 6061 aluminum (Al) alloy and their impacts on corrosion resistance efficiency by regulating anodization voltage. Despite advantageous properties inherent to Al alloys, their susceptibility to corrosion remains a significant limitation. Thus, enhancing corrosion resistance through developing protective oxide films on alloy surfaces is paramount. The first anodization was performed for 6 h with an applied voltage of 30, 50, or 70 V on the 6061 Al alloy. The second anodization was performed for 0.5 h by applying 40 V after removing the existing oxide film. Resulting oxide film's shape and roughness were analyzed using field emission-scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Wettability and corrosion resistance were compared before and after a self-assembled monolayer (SAM) using an FDTS (1H, 1H, 2H, 2H-Perfluorodecyltrichlorosilane) solution. As the first anodization voltage increased, the final oxide film's thickness and pore diameter also increased, resulting in higher surface roughness. Consequently, all samples exhibited superhydrophilic behavior before coating. However, contact angle after coating increased as the first anodization voltage increased. Notably, the sample anodized at 70 V with superhydrophobic characteristics after coating demonstrated the highest corrosion resistance performance.

• Corrosion Science and Technology
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• 제7권1호
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• pp.27-34
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• 2008

In industrial and fluid handling systems, frequently the protective film forming materials suffer from severe corrosion due to microbial effects. As an example, various micro-organisms, including bacteria, exist in seawater normally fed to power and desalination plants. Unless seawater intakes are properly disinfected to control these microbial organisms, biological fouling and microbial induced corrosion (MIC) will be developed. This problem could destroy metallic alloys used for plant construction. Seawater intakes of cogeneration plants are usually disinfected by chlorine gas or sodium hypochlorite solution. The dose of disinfectant is designed according to the level of contamination of the open seawater in the vicinity of the plant intake. Higher temperature levels, lower pH, reduced flow velocity and oxidation potential play an important role in the enhancement of microbial induced corrosion and bio-fouling. This paper describes, in brief, the different types of bacteria, mechanisms of microbiological induced corrosion, susceptibility of different metal alloys to MIC and possible solutions for mitigating this problem in industry. A case study is presented for the power plant steam condenser at Al-Taweelah B-station in Abu Dhabi. The study demonstrates resistance of Titanium tubes to MIC.

• Restorative Dentistry and Endodontics
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• 제30권2호
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• pp.121-127
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• 2005

근관 치료시 많이 사용되고 있는 $K-flex^{(R)}$ S-S 파일 (Maillefer, USA)과 $Profile^{(R)}$ Ni-Ti 파일 (Maillefer, USA), $K-3^{(R)}$ Ni-Ti파일 (SybronEndo, USA)의 부식 정도를 보기 위하여 총 360개의 20번 file을 1) 멸균소독 방법 (고압가열멸균소독, E-O gas 소독) ,2) 근관세척 액 ($5,25\%$ 차아염소산나트륨, 생리식염수) ,3) 멸균소독 횟수 (1, 5, 10회 ) 에 따라 36개 실험군으로 나누었다. 각각의 파일을 각 군별로 처리한 뒤, 세 명의 검사자가 광학 현미경 하에서 25배의 배율로 검사하여 0; 부식 없음, 1; 경도의 부식, 2; 중등도의 부식, 3; 심한 부식으로 점수화 하였다. 심한 부식을 보이는 파일의 표면은 SEM으로 관찰하였고 Kruskal-Wallis test (p < 0.05)를 이용하여 통계 분석 처리하여 차아염소산나트륨 접촉 여부와 멸균소독 방법의 차이에 의한 부식 정도를 평가하였다. 그 결과 고압가열멸균소독을 10회 시행한 파일은 통계적으로 유의한 차이를 보여 부식 정도가 심하였고, 1회나 5회 고압가열멸균소독을 시행한 파일과 E-O 가스로 소독한 파일들은 부식의 정도가 경미하여 통계적으로 유의하지 않았다. 차아염소산나트륨 접촉 여부와 제조사 혹은 파일 재료에 따른 유의성 있는 차이는 없었다

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.194.2-194.2
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• 2016

Magnesium has many desirable properties of which the high strength/weight ratio makes it extremely valuable in automobile and aerospace industry. However, the high corrosion susceptibility of magnesium and its alloys has greatly limited their large scale use for various applications. Organic coating is one of the most effective ways to prevent magnesium alloys from corrosion. An organic coating is normally used in the final stage of a coating process. It can enhance corrosion resistance of magnesium and its alloys. Organic coating involves a variety of process such as painting, powder coating, cathodic electrocoating (E-painting) and the application of lacquers, enamel and varnishes.

• Journal of Advanced Marine Engineering and Technology
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• 제13권4호
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• pp.54-62
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• 1989

When some kinds of inhibitors, i.e. $1{\times}10{-3}mol/l$ arsenic trioxide, 0.2 mol/l 2-mercaptoethanol, 0.2mol/l thiourea were added to 3% NaCl solution, there were some considererable effects to decrease corrosion current density in natural potential condition and the effect fo solution temperature increasing corrosion rate was smaller than that of no addition to 3% NaCl solution. However the susceptibility of hydrogen embrittlement due to over-protection in case of cathodic protection was much greater than that of no addition, especially was the greatest in case of addition of 2-mercaptoethanol. Therefore adding inhibitors for anti-corrosion effect, it is suggested that selection of the optimum protection potential is important from the view point of prevention against hydrogen embrittlement due to over-protection in case of cathodic protection.