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Improvement in the Corrosion Resistance of Zinc-plated Steel by Electrodeposition of Magnesium from a Molten Salt.

1996; The Iron and Steel Institute of Japan; Volume: 36; Issue: 6 Linguagem: Inglês

10.2355/isijinternational.36.714

1347-5460

Masao Morishita, Koichiro Koyama, Momonori Murase, Yoshitaka Mori,

Metallurgy and Material Science

Electrodeposition of magnesium on zinc-plated steel from a molten salt electrolyte was investigated in order to improve its corrosion resistance. The 55 mol%LiCl-39 mol%KCl-5 mol%MgCl2-1 mol%CsCl molten salt was used for the electrodeposition of magnesium on zinc-plated steel. The primary crystallization temperature of the salt is 574 K, which is 119 K lower than the melting point of zinc. The molten salt gave homogeneous electrodeposition of magnesium on a zinc-plated steel at 653 K. The magnesium electrodeposited diffused into the zinc layer of the zinc-plated steel during electrolysis. In 5 mass%NaCl aqueous solution at room temperature, the magnesium-deposited zinc-plated steel did not form red rust for 41 days whereas the zinc-plated steel formed red rust after 10 days. The red rust, which was formed at 41 days on the magnesium deposited zinc-plated steel, had localized for further 21 days without expanding. This fact suggests that the magnesium-deposited zinc-plated steel have a self healing ability. Moreover, in a salt spray test at 308 K, the time of generation of red rust for the magnesium-deposited zinc-plated steel was 10 times longer than for the conventional zinc-plated steel.