(A) study on the effects of various ion-additives on the localized corrosion of pure aluminium and Al-Zn-Mg alloy in aqueous chloride solutions = 염화이온 함유 수용액 내에서 순수한 알루미늄 및Al-Zn-Mg 합금의 국부부식에 미치는 이온첨가제의 영향에 관한 연구

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The present work involves the studies on the effects of various ion-additives on the localized corrosion of pure aluminium (Al) and Al-Zn-Mg alloy in aqueous chloride solutions. Part A is concerned with the studies on the effects of hydroxide ion ($OH^-$), electrolytical charged hydrogen, i.e., proton ($H^{+}$), sulphate ($SO_4^{2-}$) ion additives on pitting corrosion of pure Al by using electrochemical quartz microbalance (EQCM) technique. In chapter Ⅲ, effects of OH^- ion addition on the anodic dissolution of pure Al were investigated in chloride ion ($Cl^-$)-containing solution using potentiodynamic polarisation experiment, optical microscopy, ac impedance spectroscopy and EQCM technique combined with open circuit potential (OCP) transient technique. The addition of $OH^-$ ions to NaCl solution raised the anodic dissolution rate of pure Al in value and at the same time extended the constant anodic current density region in width on the polarisation curves. This implies that the pitting corrosion is preceded by uniform thinning of the Al oxide film due to the chemical dissolution by the attack of $OH^-$ ion additives, which is validated by optical microscopy. The mass change rate enhanced by the addition of 0.5 M $Cl^-$ ions during immersion in $OH^-$ ion-free 0.01 M NaCl solution indicates that $Cl^-$ ions incorporate into the growing Al oxide film even at steady-state OCP. From the lower fresh inner oxide film resistance $R_{inn,ox}$ values in $OH^-$ ion-containing chloride solution than those in $OH^-$ ion-free chloride solution below the pitting potential ($E_{pit}$), it is suggested that the chemical dissolution of the fresh inner oxide film accelerated by the attack of $OH^-$ ions inhibits the formation of the $Cl^-$ ion-incorporated outer film, what is responsible for the suppression of the pitting corrosion of pure Al. In chapter Ⅳ, effect of prior cathodic polarization in the pitting corrosion of pure Al has been investigated in aqueous 1 M...
Advisors
Pyun, Su-Il변수일
Description
한국과학기술원 : 재료공학과,
Publisher
한국과학기술원
Issue Date
2000
Identifier
157710/325007 / 000965295
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 재료공학과, 2000.2, [ xv, 178 p. ]

Keywords

Aluminium; Localized corrosion; Ion-additive; Chloride ion; 염화이온; 알루미늄; 국부부식; 이온첨가제

URI
http://hdl.handle.net/10203/50388
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=157710&flag=dissertation
Appears in Collection
MS-Theses_Ph.D.(박사논문)
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