Simulation experiments were conducted to identify the dominant factors that affect top
dross generation in metal coating baths. From the experiments and the microstructural
analyses of the top dross, it is proposed that top dross is generated through bath metal
entrainment by the oxide film and subsequent drainage during holding. A new concept,
taking into consideration the fresh area creation during the wiping process, is introduced
and a mathematical model is developed to quantify dross generation in the metal coating
process. From the proposed mechanism, a new metric is developed to quantify top dross
generation in the coating bath. The experimental results agree well with both theoretical
results and production data of galvanising (GI) baths based on this metric.