Journal of the Korean institute of surface engineering (한국표면공학회지)

The Korean Institute of Surface Engineering (한국표면공학회)
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Magnetite film on iron

강재의 마그네타이트 피복에 관한 연구

  • Kim, H. G. (Seoul National University, Metal Eng.Sci.Dept.) ;
  • Kang, T. (Seoul National University, Metal Eng.Sci.Dept.)
  • 김헌규 (서울 대학교 금속 공학과) ;
  • 강탁 (서울 대학교 금속 공학과)
  • Published : 1992.04.01
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Abstract

Magnetite film on iron surface could be coated in strongly alkaline solution (12M NaH\OH) which contained additives such as NaHCO3, KCl and NaNO2, Iron plate was immersed in boiling solution ($130^{\circ}C$) contained above mentioned additives for 1 hour. There are some microcracks and these cracks proved to be the sites for the initiation of corrosion when immersed in 3% NaCl solution. To improve corrosion resistance of the coated steel plate, chromating was done as a post treatment. Chromate film was formed on magnetite oxide film potentiostatically at-918mV/SCE for five minutes at temperature of $70^{\circ}C$ in the alkaline solution containing 5g/l Na2Cr2O7.2H2O.Cr3O4 was electrodeposited on magnetite oxide film and Cr2O3 was electrodeposited on iron surface which was assumed as surface revealed due to microcracks. Increased corrosion resistance of chromated magnetite oxide film was proved in salt spray test & immersion test.

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