• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.271-272
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• 2006

Zinc confers high corrosion resistance by acting as a sacrificial anode, and a zinc coating improves the appearance of steel. Chromate conversion coating (CCC) films are still one of the most efficient surface treatments for steel. Although such films can self-repair via the dissolution of Cr(VI), dissolved Cr(VI) have adverse effects on humans, and the environment. Therefore, we examined the corrosion protection property and morphology of colloidal silica conversion films as an alternative to CCC films. The corrosion behavior was investigated in 3% NaCl solution using electrochemical techniques, including electrochemical impedance spectroscopy, open circuit potential, and the salt spray test(SST). Corrosion was implied by the appearance of red rust on the specimen surface. In corrosion resistance at 3% NaCl solution, red rust appeared at 15-20, 55-70, and 83-98 days on Zn-electroplated steel, colloidal silica conversion-coated specimens, and CCC-coated specimens, respectively. In the salt spray test, the colloidal silica film provided better corrosion protection than CCC films, i.e., red rust appeared at 96 hours on the Zn-electroplated steel sheet, at 432 hours with the CCC films, and at 888 hours with silica conversion coating.

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

• Corrosion Science and Technology
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• 제17권4호
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• pp.166-175
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• 2018

In this study, the electrochemical properties of CP-Ti (commercially pure titanium) and Ti-64 (Ti-6Al-4V) were evaluated and the effect of hydrofluoric acid on corrosion resistance and electrochemical properties was elucidated. Additive manufactured materials were made by DMT (Directed Metal Tooling) method. Samples were heat-treated for 1 hour at $760^{\circ}C$ and then air cooled. Surface morphologies were studied by optical microscope and SEM. Electrochemical properties were evaluated by anodic polarization method and AC-impedance measurement. The oxide film formed on the surface was analyzed using an XPS. The addition of HF led to an increase in the passive current density and critical current density and decreased the polarization resistance regardless of the alloys employed. Based on the composition of the oxide film, the compositional difference observed by the addition of HF was little, regardless of the nature of alloys. The Warburg impedance obtained by AC-impedance measurement indicates the dissolution of the constituents of CP-Ti and Ti-64 through a porous oxide film.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.1954-1961
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• 2022

Lead-based fast reactor (LFR) has become one of the most promising reactors for Generation IV nuclear systems. A developing trend of LFR is high efficiency, along with operation temperatures up to 800 ℃ or even higher. One of key issues in the high-efficiency LFR is corrosion of cladding materials with lead at high temperatures. In this study, corrosion behavior of some refractory metals (Nb, Nb521, and Mo-0.5La) was investigated in static lead at 1000 ℃ for 1000 h. The results showed that Nb and Nb521 exhibited an intense dissolution corrosion with obvious lead penetration after corrosion, and lead penetration extended along the grain boundaries of the specimens. Furthermore, Nb521 showed a better corrosion resistance than that of Nb as a result of the elements of W and Mo included in Nb521. Mo-0.5La showed much better corrosion resistance than that of Nb and Nb521, and no lead penetration could be observed. However, an etched morphology appeared on the surface of Mo-0.5La, indicating the occurrence of corrosion to a certain degree. The results indicate that Mo-0.5La is compatible with lead up to 1000 ℃. While Nb and Nb alloys might be not compatible with lead for high-efficiency LFR at such high temperatures.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.93-94
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• 2022

The presence of chloride (Cl-) ions in environments causes localized corrosion resulting decrease the durability of the structures. In this study, 5% Mg containing Al alloys (Al-5Mg) wire used vis-à-vis compared its corrosion resistance with pure Al in 3.5wt.% NaCl solution with exposure periods. Initially both wires exhibited identical open circuit potential (OCP) attributed to the presence of native oxide film on the surface but with the exposure periods it shifted towards active direction owing to the dissolution of oxide film. The pure Al continuously shifted the OCP towards active direction while Al-5Mg shows stabilization of OCP after 8 days of exposure. The OCP of Al-5Mg is slightly higher compared to pure Al wire owing to the activeness of Mg. The total impedance of the Al-5Mg alloy is almost three times greater than pure Al with exposure periods in 3.5 wt.% NaCl solution. It might be formation of Al-Mg LDH (layered double hydroxide) thin film onto the surface.

• Corrosion Science and Technology
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• 제23권2호
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• pp.166-178
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• 2024

The localized corrosion resistance of UNS N07718 alloy was investigated after solution heat treatment. When the alloy was heat-treated at 1050 ℃ for 2.5 hours, it experienced an increase in average grain diameter, a reduction in grain boundary area, and the dissolution of delta phases along grain boundaries. Additionally, primary metallic nitrides (MN) and metallic carbides (MC), enriched with either Ti or Nb, were identified and exhibited a random distribution within the microstructures. Despite the solution heat treatment, the composition, diameter, and abundance of MNs and MCs remained relatively consistent. The critical pitting temperature (CPT), as determined by the ASTM G48-C immersion test, revealed similar values of 45 ℃ for both treated and untreated alloys. However, a decrease in maximum pit depth and corrosion rate was observed after the solution heat treatment. The microstructural changes that occurred during the heat treatment and their potential implications were discussed to understand the influence of the solution heat treatment.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권4호
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• pp.255-261
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• 2000

Experiments were carried out to measure the corrosion potential and current density variations in the polarization curves of polypropylene. In particular, the results were examined to identify those influences affecting the corrosion potential, such as temperature, pH, salt, and oxygen. The Tafel slope for the anodic dissolution was determined based on the polarization effect under various conditions. Furthermore, the optimum conditions for the most rapid transformation were establish based on a variety of conditions, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(I(sub)r/I(sub)f). This I(sub)r/I(sub)f value was then used to measure the critical corrosion sensitivity of polypropylene. The potentiodynamic parameters of corrosion were obtained using a Tafel plot.

• Journal of Pharmaceutical Investigation
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• 제9권1호
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• pp.15-19
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• 1979

The absorption rate of lysino-methylene-ampicillin from the rat small intestine, compared with ampicillin, was determined in vitro and in situ to establish the biopharmaceutical properties of lysino-methylene-ampicillin which is one of the new penicillinase-resistance antibiotics. The half of administered dose was absorbed rapidly within thirty minutes. The water-oil distribution coefficient of lysino-methylene-ampicillin was 0.03 in chloroform versus buffer system with $Na_{2}HPO_{4}-citric$ acid of pH5.2 at $37^{\circ}C$, and its dissolution rate reached the plateau in an hour and then represented 0.6 percent of equilibrium solubility

• 한국재료학회지
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• 제16권1호
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• pp.5-10
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• 2006

This study was performed to investigate the characteristics of the synthesized powder type ferro materials for wear resistant hardfacing. The powder type filler materials were made from ferro Cr and ferro Mn. Those ferro materials are two types, such as high carbon and low carbon contained. The alloy composed of high carbon ferro Cr and high carbon ferro Mn exhibited the best properties in terms of microstructure and hardeness for wear characteristics. Further, the alloys produced by the synthesized powders and wire type filler, were also evaluated in terms of microstructures and microhardness measurements. The results indicated that the synthesized powders displayed reasonable properties compared to commercial grade materials. The hardness value of the alloy produced by the synthesized powders were approached about 90% of the commercial grade's hardness. The hardness values of the alloys closely depended on the amount of the dissolution of the ferro Cr, the hardness and the volume of the eutectic phase.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1995년도 춘계학술발표회 초록집
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• pp.41-44
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• 1995

The electrochromic WO$_3$ thin films were prepared by using an electron - beam evaporation technique. The influence of the electron - beam evaporation conditions. especially the vacuum pressure, and resistance of ITO substrate on the structural and electrochromic properties of the investigated film was presented. This films showed electrochromic behavior in an aqueous electrolyte of 1 M H$_2$SO$_4$. Among these WO$_3$ thin films, films prepared at a vacuum pressure of 10$^{-4}$ mbar were found to be most stable in terms of cycling durability. The chemical stability of film against dissolution in the aqueous solution was also shown to depend on the quantity of water in the film.