摘要：For the purpose of applying hot-dip Zn-6%Al-3%Mg alloycoated steel sheet (“Zn-Al-Mg”) to automotive parts, wecompared and investigated the corrosion resistance of Zn-Al-Mg and ordinary materials treated using a conventionalrustproofing method (“post-Zn-coated material”) exposedto accelerated corrosion test environments. We alsocollected automotive parts made from Zn-Al-Mg fromvehicles that had been driven for three to five years inCanada to examine corrosion resistance capabilities whenexposed to actual vehicle environment conditions. Wefound that Zn-Al-Mg exhibited better corrosion resistancethan post-Zn-coated material, even at portions where thesteel substrate was exposed (along cut edges and in bentor spot-welded portions). Such Portions of the Zn-Al-Mgwere observed as being covered by fine and dense Zncorrosion products containing Mg, which suppressescathode reactions (dissolved oxygen reduction reactions).As a result, elution of the coating layer around such portionswas suppressed and favorable corrosion resistancemaintained. The flat and bent portions of automotive partsmade of Zn-Al-Mg collected from actual vehicles werecovered by fine and smooth corrosion products, with onlylittle corrosion being observed. It was thus confirmed thatZn-Al-Mg also exhibits excellent corrosion resistance in anactual vehicle environment.
