Development of a Dross Build-Up Growth Process Model for Hot-Dip Galvanizing Considering Surface Reaction Kinetics

The minimization of unwanted dross build-up formation on the sink rolls in continuous hot-dip galvanizing lines is a key goal of the industry. In this study, the CFD multi-physics modeling of the surface reaction kinetics for dross build-up growth and the coupling to the mass transfer is the basis for the evaluation of relevant process parameters. The results of a virtual Design of Experiments were processed by neural network approaches, as well as linear regression modeling to build a surrogate process model. It was found that the bath Al concentration has the highest effect (> 80 pct) on the dross build-up rate on the sink rolls. Operating the zinc bath at higher Al concentrations decreases the dross build-up reaction rate. Furthermore, it was found by the CFD multi-physics model that the local dross build-up rate increases toward the edges of the roll grooves which might lead to the occurrence of strip surface defects.