Hot-Dipping of Steel Sheet into Al-Zn Eutectoid-Base Superplastic Alloy and the Properties of the Hot-Dip Coated Steel

Abstract

Steel sheet hot-dip coated with an Al-Zn eutectoid-base alloy having a fine-grained structure has been tested, and the proper coating condition and some properties of the coated steel have been studied. There exists a bath temperature (T_S) at which the thickness of the coating becomes minimum. The coating deposited from a bath containing only the Al-78 Zn alloy is very brittle, and this is believed to be due to a rapid growth of a brittle alloy-phase reacted with Fe diffused from the steel substrate. Coatings dipped at temperatures around T_S from an Al-78 Zn bath to which was added about 0.1 to 0.3wt. % Si showed good formability, coating adhesion and flaking behavior, corrosion resistance, and damping capacity. The film had a fine, equi-axial structure that has a favorable effect on superplasticity and damping of vibration.