Tailoring Model Surfaces and Zn Wetting Experimenst for a Fundamental Understanding of Hot-dip Galvanizing

Takashi Kawano and Frank Uwe Renner

Tailoring Model Surfaces and Zn Wetting Experimenst for a Fundamental Understanding of Hot-dip Galvanizing, submitted to ISIJ International

Hot-dip galvanizing processes are widely used for automotive applications of steel production. The wetting behavior of molten zinc containing small amount of aluminum on a steel substrate is one of the most important issues concerning this process. Especially, studies on degradation of wettability caused by surface oxides have been focused on during recent years. Such surface oxides often segregate on the surfaces of high strength steel sheets. However such wetting behavior and the effects of different oxides have not been well illustrated due to complexity of a surface of practical steel sheets.

For this, different authors have tailored simple model surfaces with well-defined surface oxides and conducted wetting measurements by a sessile drop method on the surfaces. In this report, wetting behavior of model surfaces with patterned aluminum oxide islands or with manganese oxide layers on iron will be presented. The initial contact angles on patterned aluminum oxides were revealed to follow the Cassie equation. This indicates that the wetting of zinc-aluminum on this system can be treated as if it is a static wetting in its initial stage, in spite of the system is originally experiencing reactive wetting. It was also revealed that the aluminum in molten zinc reacted with the manganese oxide layer during wetting.