• 대한화학회지
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• 제51권1호
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• pp.14-20
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• 2007

금(Au) 전극 위에 전해 석출한 철족 원소(Fe, Co, Ni)를 전극으로 phthalate 완충 용액에서 철족 원소의 부식과정을 조사하였다. Phthalate 완충용액의 pH의 변화에 대한 부식전위와 부식전류를 측정하여 각 원소(Fe, Co, Ni)전극의 산화반응과 환원반응에 대한 Tafel 기울기를 구하였으며 Tafel 기울기를 포함한 정량적인 전기화학 인자를 측정하여 전극의 산화반응과 환원반응에 대한 반응 메커니즘을 제안하였다. Phthalate 완충 용액에 존재하는 화학 종의 흡착은 철족 원소 전극의 산화반응에 영향을 미치는 것으로 보인다.

• 한국재료학회지
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• 제11권4호
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• pp.266-271
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• 2001

Al-Cu-Mn 주조합금의 응력부식균열 저항성에 미치는 Cd첨가의 영향을 C-ring test와 전기전도도 시험을 통하여 조사하였다. Cd첨가량이 증가함에 따라 전기전도도가 증가하였고 SCC 저항성도 증가하였다. SCC 시험결과 균열이 입계를 따라 전파되는 입계파괴가 일어났으며, 파면은 취성파괴양상을 나타내었고, 입계를 따라 조대 석출물과 무석출대가 나타난 것으로 보아서 이 합금의 SCC 기구는 anodic dissolution model이라고 판단된다. Cd을 첨가하지 않은 경우 최대경도값은 127Hv였으나, Cd을 첨가한 경우 최대경도값은 138∼146Hv로 증가하였다.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2001년도 가을 학술발표회 발표논문집
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• pp.188-190
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• 2001

We carried out to measure the variations of potential with current density polymers. The results were particularly examined to identify the influences on corrosion potential and corrosion rate of various factors including temperature and pH. The Tafel slope for anodic dissolution was determined by the polarization effect depending on these conditions. The optimum conditions were established for each case. The second anodic current density peak and maximum passive current density were designated as the relative corrosion sensitivity($I_{r}I_{f}$). The mass transfer coefficient value (${\alpha}$) was determined with the Tafel slope for anodic dissolution based on the polarization effect with optimum conditions.

• Corrosion Science and Technology
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• 제15권6호
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• pp.311-313
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• 2016

The anodic dissolution behavior of copper and brass in an electrolyte solution of 0.5M NaCl containing 0.5 mM $NaHCO_3$ was investigated by electrochemical impedance spectroscopy. The Nyquist plots of the copper impedance described a small loop in the high-frequency range and a large locus in the low-frequency range. Additionally, the features of the impedance spectrum of the brass were similar to those of the copper. This indicates that the copper-enriched layer formed on the brass surface due to the selective dissolution of the zinc from the surface. In addition, the rest potential and the anodic polarization curve for each sample were measured in order to discuss the selective dissolution of the zinc from the brass surface.

• 한국해양공학회지
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• 제7권1호
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• pp.147-155
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• 1993

The effect of stress waveforms on corrosin fatigue and the role of dissolution mechanism in 3NilCr steel and 20Ni maraging steel have been investigated in aerated 3% NaCl solution and synthetic seawater under sinusoidal, triangular, square, positive sawtooth, negative sawtooth, and trapezoidal stress waveforms with open circuit at frequency of 1Hz and stress ratio of 0.1. The crack growth rates under square waveform were substantially lower than under sinusoidal and triangular waveforms, but the crack growth rates under sinusoidal waveform were slightly higher under triangular waveform. For a given frequency the growth rates under the positive sawtooth waveform are higher than those under the negative sawtooth waveform. The fatigue crack growth rates of most specimens were in good agreement with the values calculated by the model based on the dissoultion mechanism.

• 대한화학회지
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• 제46권1호
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• pp.19-25
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• 2002

우리는 고분자 물질들에 대해서 전위와 전류 밀도의 변화를 측정하였다. 온도와 pH를 포함하여 전위와 속도에 대한 영향을 주는 여러 요인들에 밝히기 위하여, 연구 결과들이 주위 깊게 조사되었다. 양극 해리에 대한 Tafel 기울기는 이들 조건 하에서 분극 효과로 결정되었다. 각 경우에 최적 조건들이 확립되었다. 두 번째 양극 전류 밀도 피크와 최대 전류 밀도는 상대적 분극 감도$(I_r/I_f)$로 지정되었다. 최적 조건에서의 분극 효과를 바탕으로, 질량 전달 계수$({\alpha})$는 양극 해리에 대한 Tafel 기울기에 의해서 결정되었다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권1호
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• pp.43-50
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• 2000

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves using polycarbonate. The results were particularly examined to identify the influences affecting the corrosion potential including various conditions such as temperature, pH, catalytic enzyme, and salt. The lines representing the active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme, and salt. The tafel slope for the anodic dissolution was determined based on the polarization effect with various conditions. The slope of the polarization curves describing the active-to-passive transition region were noticeably shifted in direction. Also, from the variation in the conditions, the optimum conditions were established for the most rapid transformation, 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(Ir/If). The value of Ir/If was then used in measuring the extent of the critical corrosion sensitivity of the polycarbonate. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3730-3734
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• 2011

The degree of self-assembly and the size variation of nanotubular structures in anodic titanium oxide prepared by the anodization of titanium in ethylene glycol containing 0.25 wt % $NH_4F$ at 40 V were investigated as a function of anodization time. We found that the degree of self-assembly and the size of the nanotubes were strongly dependent on thickness deviation and thus indirectly on anodization time, as the thickness deviation was caused by the dissolution of the topmost tubular structures at local areas during long anodization. A large deviation in thickness led to a large deviation in the size and number of nanotubes per unit area. The dissolution primarily occurred at the bottoms of the nanotubes ($D_{bottom}$) in the initial stage of anodization (up to 6 h), which led to the growth of nanotubes. Dissolution at the tops ($D_{top}$) was accompanied by $D_{bottom}$ after the formed structures contacted the electrolyte after 12 h, generating the thickness deviation. After extremely long anodization (here, 70 h), $D_{top}$ was the dominant mode due to increase in pH, meaning that there was insufficient driving force to overcome the size distribution of nanotubes at the bottom. Thus, the nanotube array became disorder in this regime.

• 전기화학회지
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• 제18권3호
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• pp.107-114
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• 2015

전기화학적인 방법으로 나노구조를 지니는 금 표면을 형성하는 방법에 관한 연구는 최근 많은 연구자들의 관심을 끌고 있다. 첨가된 금 전구체를 전기화학 석출에 의해 나노구조 금 표면을 형성하는 기존 연구와는 달리, 본 연구에서는 전구체를 외부에서 첨가하지 않고 금 표면을 전기 화학적으로 변형하여 표면에 나노구조체를 형성하는 방법을 제시하였다. $Br^-$이 존재하는 인산 완충용액 전해질 하에서 금 전극에 산화전위를 가해 주면 산화 용해된 금은 $Br^-$과 결합하여 전극 표면에 전구체를 형성하는데, 이렇게 형성된 표면상의 전구체를 연이어 환원시켜 주면 실시간으로 나노구조 금 표면을 형성하는 것이 가능함을 보였다. 전극에 가해주는 전위와 시간의 조절이 전극 표면에 형성되는 금 나노구조의 모양에 미치는 영향을 체계적으로 관찰한 결과 독특한 척추 모양의 금 나노구조가 형성이 되었다. 척추 모양의 금 나노구조는 표면증강 라만 분광 활성이 높은 것으로 나타났다. 본 연구에서 제시된 방법은 전구체 없이 전기화학적으로 금 전극 표면을 변형시키는 새로운 방법으로 금 나노구조 형성에 관한 연구에 도움이 될 것으로 기대한다.

• Corrosion Science and Technology
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• 제14권6호
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• pp.273-279
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• 2015

Effects of passive film quality by chemical passivation and solution flow on the corrosion behavior of 304 stainless steel in HCl solution were investigated using a coloration indicator, and by corrosion weight loss, electrochemical polarization and element dissolution measurements. A high redness degree suggests a low passive-film integrity for 304 stainless steel following air exposure, while the minimum redness degree for the samples after chemical passivation suggests a high passive-film integrity. In the static condition, samples subjected to air exposure exhibited a high corrosion rate and preferential dissolution of Fe. Chemical passivation inhibited the corrosion rate due to the intrinsically high structural integrity of the passive film and high concentrations of Cr-rich oxides and hydroxide. Solution flow accelerated corrosion by promoting both the anodic dissolution reaction and the cathodic reaction. Solution flow also altered the preferential dissolution to fast uniform dissolution of metal elements.