ZINC-MAGNESIUM PLATED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE AND ITS PRODUCTION

摘要

PURPOSE: To produce a Zn-Mg plated steel sheet showing excellent resistance to the initial generation of red rust and white rust. ;CONSTITUTION: This plated steel sheet has a plated layer of a two-layer structure (a) in which the surface of a Zn-Mg alloy layer having ≥7% Mg concn. is applied with a Zn-Mg alloy layer having ≤1wt.% Mg concn. or a three-layer structure (b) in which the space between the both is applied with an intermediate layer having 2 to 7% Mg concn. There is an Mg-concentrated layer oxidized on the surface. The Mg-concentrated layer is formed by heating diffusion after vapor deposition plating and is brought into reaction with oxygen contained in the heating atmosphere or in the air to form an Mg oxide layer or an Mg-Zn multiple oxide layer on the surface. The Mg-concentrated layer on the surface improves its white rust resistance, and the high Mg alloy layer as the lower layer improves its red rust resistance and long term corrosion resistance.;COPYRIGHT: (C)1996,JPO