Evaluation of the Effects of Different Process Parameters on the Corrosion Protection Provided by Cerium-Based Coatings on Galvanized Steels

To avoid the environmental problems caused by Cr⁺⁶, cerium-based conversion coatings have widely been studied to improve the corrosion resistance of galvanized steels. The purpose of this study was to evaluate the effects of different process parameters on the corrosion resistance of galvanized steels coated with cerium-based conversion layers. The samples were dipped into a cerium salt solution containing colloidal silica (SiO₂), silane (SiH₄), and hydrogen peroxide (H₂O₂) for two different times and then placed immediately in an oven for two different drying temperatures and drying times. The corrosion behavior of the different samples was evaluated using electrochemical impedance spectroscopy (EIS) after 24 h exposure to 0.1 N sodium chloride (NaCl). The 2³ factorial design experiments were applied to determine the optimum process parameters. The drying temperature was found to have the largest positive influence on the corrosion resistance of galvanized steel treated in the cerium-based solution.