Synergistic effect of Mentha longifolia and zinc cations in silane primer coating to improve protection properties of the subsequent epoxy coating

A water-based silane primer formulated through the addition of Mentha Longifolia (ML) plant extract and zinc cations was suggested as a pretreatment prior to application of the epoxy coating. According to the electrochemical data and results of SEM-EDS and XPS surface analysis, the behavior was found to arise from deposition of a protective layer consisting of zinc hydroxide, adsorbed organic molecules (from ML extract) and complexes of the released organic species with Zn and/or Fe cations at the primer/mild steel interface. Moreover, the inclusion of the inhibitors in the silane coating formulation had no disturbing effect on the film formation and network reticulation.