Zn-Mn 合金めつき鋼板の耐食性と塗装性
1986 年 72 巻 8 号 p. 968-975
詳細
1986 年 72 巻 8 号 p. 968-975
Strong interest has been focussed on corrosion-resistant steel by automobile industries to protect auto bodies from corrosion.
To meet the requirements for corrosion-resistant steel, Zn-Mn alloy electroplated steel has been newly developed.
Zn-Mn alloys are electrodeposited on the steel sheet from a citric bath consisting of zinc sulfate, manganese sulfate and sodium citrate.
Corrosion resistance of steel plated with Zn-Mn alloy without painting increased prominently in the range above 20 wt% Mn content, and time to no red rust occurred on the steel plated with 20 g/m2 Zn-Mn alloy up to 1 000 h, when Mn content in deposit. was more than 40 wt% or more.
This behavior of corrosion resistance without painting are correlated with crystal structures of Zn-Mn alloy ; γ-Mn, manganese solid solution of tetragonal structure, enhances corrosion resistance without painting. The good corrosion resistance results from γ-Mn2O3, corrosion product of Mn, which acts as protective barrier.
Moreover, as steel plated with Zn-Mn alloy also affords good corrosion resistance after painting, wet adhesion of paint and anti-cratering property, it is possible to use this plated steel sheet for automotive body panels.
