Surface evaluation and electrochemical behaviour of doped silane pre-treatments on galvanised steel substrates

The present work aims at evaluating the surface morphology and the corrosion resistance of galvanised steel substrates pre-treated with bis-[triethoxysilylpropyl] tetrasulfide silane (BTESPT) solutions doped with cerium nitrate or zirconium nitrate. The silane pre-treatment leads to the formation of a silane coating in the metallic surface. The surface morphology of this coating was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM).The corrosion behaviour of the pre-treated substrates during immersion in 0.05 M NaCl was assessed by the scanning vibrating electrode technique (SVET) and by electrochemical impedance spectroscopy (EIS).The results show that the presence of dopant improves the protective properties of the silane pre-treatment. Moreover, it was found that pre-treatments based on silanes doped with cerium nitrate are more resistant against corrosion development due to the corrosion inhibition properties of the cerium ions.