Journal of the Korean institute of surface engineering (한국표면공학회지)

The Korean Institute of Surface Engineering (한국표면공학회)
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Effect of Al Addition on the Reaction Behavior of Pure Cobalt with Molten Zinc

용융 아연과 WC-Co 코팅층 내 코발트의 반응거동에 미치는 아연욕 중의 Al 첨가 영향

  • Seong, Byeong-Geun (New Metallic Materials Research team, RIST) ;
  • Kim, Kyoo-Young (Graduate Institute of Ferrous Technology, POSTECH) ;
  • Kwon, Sung-Hee (School of Advanced Materials Engineering, Andong National University) ;
  • Lee, Kee-Ahn (School of Advanced Materials Engineering, Andong National University)
  • 성병근 (포항산업과학연구원 부품신소재연구센터 신금속연구실) ;
  • 김규영 (포항공과대학교 철강대학원) ;
  • 권성희 (안동대학교 공과대학 신소재공학부) ;
  • 이기안 (안동대학교 공과대학 신소재공학부)
  • Published : 2007.02.28
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Abstract

The objective of this study is to investigate the effect of Al addition on the reaction behavior of cobalt with molten zinc. Pure cobalt specimen was immersion tested in the three kinds of molten zinc (pure, 0.12%Al added and 0.24%Al added) baths at $460^{\circ}C,\;490^{\circ}C\;and\;520^{\circ}C$. For the understanding of degradation processes, specimens were analyzed with scanning electron microscope (SEM) and energy dispersive spectrum (EDS), and electrochemical stripping method. When 0.12% and 0.24% Al was added in molten zinc baths, three intermetallic compounds layers of ${\gamma},\;{\gamma}_1,\;and\;{\gamma}_2$ were formed on the Co matrix and ${\beta}_1$ layer was not formed between the Co matrix and the ${\gamma}$ layer. Particles of CoAl intermetallic compound were formed at the interface between the ${\gamma}_2$ layer and zinc melt and they did not adhere to the Co-Zn intermetallic layer. Weight loss of the Co specimen increased as Al content in the molten zinc increased and the relationship of weight loss vs. immersion time followed parabolic rate law. Rate controlling process for the reaction rate of Co with Al added molten zinc was analyzed as the diffusion process of Al atom through a boundary layer between the ${\gamma}_2$ layer and the Al added zinc melt.

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References

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