Due to economic and ecological aspects, weight reduction of automobile bodies plays an important role. Newly developed steels used in this field of application have to be protected against corrosion, for instance by using hot-dip galvanization, which is one of the most important processes for corrosion prevention. Prior dipping the steel strip into the liquid zinc bath in hot-dip galvanization, the strip surface must have specific properties to guarantee adherence of the zinc coating. Therefore, the steel strip has to pass through a continuous preheating process for thermal and chemical treatment. This process line includes a direct-fired furnace for heating up and cleaning the steel strip, an annealing furnace to recrystallize and reduce the strip surface and a snout for ensuring a protected atmosphere just before the steel strip is dipping into the liquid zinc bath. For a holistic consideration of the preheating process, all regions are simulated by using the commercial CFD-software ANSYS Fluent, in which the results are transferred to the following sections. This leads to an optimization of the total preheating process that includes thermal and chemical treatment of the steel strip through all sections.