Effects of solution temperature and Mn Content on the passivity of active-passive metals = 용액의 온도 및 합금 원소 Mn이 금속의 부동태 특성에 미치는 영향

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Effects of solution temperature and Mn content on the passivity of pure metals and alloys were investigated by electrochemical impedance measurement and micro-electrochemical technique. To reveal why the corrosion resistance of Ni is degraded with increase in solution temperature, the effects of temperature on the kinetic nature of passive film on Ni were examined. Under the steady state condition, the current density of Ni is associated with cation vacancy flux $\It{I_{ss}}=$F\GammaJ_{V\rdquo_{Ni}}$ in the passive film. With increasing temperature, the cation vacancy generation rate at the film/solution (f/s) interface increases significantly, thereby increasing the cation vacancy flux at the f/s interface ($J^{f/s}_{N\rdquo_i}$). Because diffusivity of cation vacancy is significantly enhanced by solution temperature, the cation vacancy generated at the f/s interface moves to the metal/film (m/f) interfaces more rapidly. While the annihilation rate of cation vacancy decreases by solution temperature, the cation vacancy concentration at the m/f interface ($\C^{m/f}_{N\rdquo_i}$) increases abruptly, thereby increasing the cation vacancy flux at the m/f interface ($\J^{m/f}_{N\rdquo_i}$). The increase in cation vacancy flux in the passive film resulted in the increase of $\It{I_{SS}}$. According to the Point Defect Model (PDM), film breakdown is closely associated with cation vacancy condensation at the m/f interface. The cation vacancy concentration at the m/f interface increased drastically with solution temperature. Therefore, it is suggested that the possibility of formation of “vacancy condensate” increases with temperature and accordingly, the susceptibility to film breakdown increases with solution temperature. The effects of temperature on the film growth kinetics of Fe were examined by analyzing the potentiostatic current flowing during the growth of passive film based on the PDM. Standard rate constants for the oxide lattice formation ($\It{k^{0}_{...
Advisors
Kwon, Hyuk-Sangresearcher권혁상researcher
Description
한국과학기술원 : 신소재공학과,
Publisher
한국과학기술원
Issue Date
2010
Identifier
455400/325007  / 020055828
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 신소재공학과, 2010.08, [ viii, 113 p. ]

Keywords

passivity; manganese; temperature; licalized corrosion; 국부 부식; 부동태; 망간; 온도

URI
http://hdl.handle.net/10203/49877
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=455400&flag=dissertation
Appears in Collection
MS-Theses_Ph.D.(박사논문)
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