• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 1994년도 특별강연 및 추계학술발표 개요집
• /
• pp.61-63
• /
• 1994

• Corrosion Science and Technology
• /
• 제6권4호
• /
• pp.170-176
• /
• 2007

Iodine-induced stress corrosion cracking (ISCC) properties and the associated ISCC process of Zircaloy-4 and an Nb-containing advanced nuclear fuel cladding were evaluated. An internal pressurization test with a pre-cracked specimen was performed with a stress-relieved (SR) or recrystallized (RX) microstructure at $350^{\circ}C$, in an iodine environment. The results showed that the $K_{ISCC}$ of the SR and RX Zircaloy-4 claddings were 3.3 and 4.8MPa\;m^{0.5}, respectively. And the crack propagation rate of the RX Zircaloy-4 was 10 times lower than that of the SR one. The chemical effect of iodine on the crack propagation rate was very high, which was increased $10^4$ times by iodine addition. Main factor affecting on the micro-crack nucleation was a pitting formation and its agglomeration along the grain boundary. However, this pitting formation on the grain-boundary was suppressed in the case of an Nb addition, which resulted in an increase of the ISCC resistance when compared to Zircaloy-4. Crack initiation and propagation mechanisms of fuel claddings were proposed by a grain boundary pitting model and a pitting assisted slip cleavage model and they showed reasonable results.

• The Plant Pathology Journal
• /
• 제33권1호
• /
• pp.9-20
• /
• 2017

Incidence of leaf blast on nursery plants and pitting disease on maturing banana bunches has been recorded in banana plantations during rainy season in Eastern India during 2014 to 2015. Taxonomical identification as well as DNA sequence analysis of the internal transcribed spacer region of fungus isolated from affected tissue culture derived plantlets and fruits confirmed the pathogen to be Pyricularia angulata Hashioka "in both the cases". Koch's postulates were proved on young plantlets as well as on maturing fruits of cv. Grand Naine under simulated conditions. Evolutionary history was inferred and presented for our P. angulata strain PG9001 with GenBank accession no. KU984740. The analysis indicated that the P. angulata is phylogenitically distinct from other related species related to both Pyricularia and Magnaporthe. Detailed symptoms of blast lesions on young leaves, transition leaves, mid rib, petioles, peduncle, maturing bunches, bunch stalks and cushions were documented. Notably, the distinct small pitting spots on maturing bunches reduced the visual appeal of mature fruits. Appearance of pitting symptoms on fruits in relation with age of fruits and their distribution pattern on bunch and fingers was also documented in detail. Further, the roles of transitory leaves, weed hosts, seasonality on disease occurrence have also been documented.

• 한국재료학회지
• /
• 제24권11호
• /
• pp.610-616
• /
• 2014

In this study, we investigated the precipitation behavior of the R-phase precipitated at the initial stage of aging and its effect on the pitting corrosion of 25%Cr-7%Ni-4%Mo super duplex stainless steel. The R-phase in super duplex stainless steel was mainly precipitated at the interface of ferrite/austenite phases and inside of the ferrite phase during the initial stage of aging, and it was transformed into the ${\sigma}$-phase with an increase in aging time. The ferrite phase was decomposed into a new austenite phase and ${\sigma}$-phase. The R phase was an intermetallic compound, which represented a lower Ni and higher Mo than the matrix, and also had a higher Mo and Cr concentration than the ${\sigma}$ phase. With an increasing aging time, the pitting potential $E_p$ was increased slowly by the precipitation of the R-phase, and it was then steeply decreased by the precipitation of the ${\sigma}$-phase. The R-phase was decreased the pitting potential, but its effect was smaller than effect of ${\sigma}$-phase.

• 한국가스학회지
• /
• 제9권4호
• /
• pp.6-10
• /
• 2005

이 논문은 비저항에 따른 가스보일러용 오스테나이트계 스테인리스강(STS304)재의 손상거동에 관해 연구하기 위하여, 비저항에 따른 전기화학적 분극시험을 수행하였다. 그리고 비저항에 따른 가스보일러용 STS304강의 양극분극특성 및 손상거동인 공식양상을 고찰하였다. 비저항이 감소할수록 STS304강의 부동태유지전류밀도는 증가하고 부동태영역은 작아지고 있으며, 관통전위는 낮아지고 있다 또한 비저항이 가장 높은 $74{\Omega}{\cdot}m$중에서 손상거동인 공식양상은 거의 나타나지 않고, 비저항이 낮아질수록 손상거동인 공식양상은 더욱 성장되고, 공식수가 점점 증가하는 경향을 보이고 있다.

• 열처리공학회지
• /
• 제9권2호
• /
• pp.103-111
• /
• 1996

In this paper, we studied on both electrochemical polarization behaviors and pitting characteristics of ultra high strength Al-Cu-Li-Mg-Ag-Zr alloys(named C1 and C2) and 2090 alloy according to their treatments in the deaerated 3.5% NaCl, using by the potentiodynamic and the potentiostatic method, SEM micrograph and surface roughness including depth of pitting attack. With the cyclic polarization curves, the hysteresis of the C1 and C2 alloys appeared more remarkably than that of the 2090 alloy, because of precipitation microstructural difference between C1, C2 alloys and 2090 alloy. In the pitting experiments, the correlations between pitting growth and aging conditions were analyzed with the SEM micrograph and measurement of the pit depth.

• Journal of the Korean Data and Information Science Society
• /
• 제11권2호
• /
• pp.157-172
• /
• 2000

Metal containers represent a situation where a specific metal is exposed to a wide variety of electrolytes of varying degrees of corrosivity. For example, hundreds, if not thousands of different products are packaged in an aluminum beverage can. These products vary in pH, chloride concentration and other natural or artificial ingredients which can effect the type and severity of potential corrosion. Both localized (perforation) and uniform corrosion (metal dissolution without the onset of pitting) may occur in the can. A quick test or series of tests which could predict the propensity towards both types of corrosion would be useful to the manufacturer. Electrochemical noise data is used to detect the onset and continuation of pitting corrosion. Specific noise parameters such as the noise resistance (the potential noise divided by the current noise) have been used to both detect pitting corrosion and also to estimate the pitting severity. The utility of noise resistance and other electrochemical parameters has been explored through the application of artificial neural networks. The versatility of artificial neural networks is further demonstrated by combing electrochemical data with electrolyte properties such as pH and chloride concentration to predict both the severity of both localized and uniform corrosion.

• 동력기계공학회지
• /
• 제18권2호
• /
• pp.70-76
• /
• 2014

A specimen of weld metal was prepared by GTA welding with weld wire of super duplex stainless steel. Aging treatment was conducted for the sample at the temperature range of 700 to $900^{\circ}C$ for 5 to 300 minutes. The effect of aging temperature and time to pitting corrosion of weld metal has been investigated and the results were derived as follows. The volume fraction of ${\sigma}$ phase tends to increase with an increase of aging temperature and time. Pitting potential Ep representing pitting corrosion was found to tend to decrease with an increase of aging time at 700 to $900^{\circ}C$. And most of the pits formed near the ${\sigma}$-phase in the ferrite and seemed to propagated to austenite.

• Corrosion Science and Technology
• /
• 제16권6호
• /
• pp.278-284
• /
• 2017

The effects of TIG welding and post-treatment procedures on the microstructure and the pitting corrosion resistance of welded lean duplex stainless steel S82441 were investigated. Autogenous TIG welding was used with different amounts of heat input and shielding gases such as Ar, and mixtures of $Ar-N_2$ and Ar-He. The addition of 5% to 15% of nitrogen to argon practically did not affect the level of the pitting corrosion resistance. However, the application of gas mixtures (50% Ar + 50% He) resulted in a significant decrease in pitting corrosion resistance. We found that increased current (200 A and 250 A) led to lower values of CPT of welds compared with welds obtained with 50 A, 100 A and 150 A. In addition, the removal of the weld surface layer (0.2 ~ 0.3 mm thickness) in most cases not only resulted in a significant increase in resistance to the pitting corrosion but also post-treatment of weld, implying that corrosion resistance depended on factors such as surface roughness or the presence of undesirable oxides.

• Corrosion Science and Technology
• /
• 제19권2호
• /
• pp.89-99
• /
• 2020

The inhibition of pitting corrosion failure of copper sprinkler tubes in wet sprinkler systems was studied. First, an apparatus and technology for removing air in the sprinkler tubes by vacuum pumping and then filling the tubes with water were developed. Using this apparatus and technology, three methods for inhibiting the pitting corrosion of the copper sprinkler tubes installed in several apartment complexes were tested. The first one was filling the sprinkler tubes with water bubbled by high-pressure nitrogen gas to reduce the dissolved oxygen concentration to lower than 2 ppm. In the second method, the dissolved oxygen concentration of water was further reduced to lower than 0.01 ppm by sodium sulfite. In the third method, the sprinkler tubes were filled with benzotriazole (BTAH) dissolved in water. The third method was the most effective, reducing the failure frequency of the sprinkler tubes due to pitting corrosion by more than 80%. X-ray photoelectron spectroscopy analyses confirmed that a Cu-BTA layer was well coated on the inside surface of the corrosion pit, protecting it from corrosion. A potentiodynamic polarization test showed that BTAH should be very effective in reducing the corrosion rate of copper in the acidic environment of the corrosion pit.