Corrosion electrochemical behavior of Zn-Al silane coating on carbon steel

The corrosion electrochemical behavior of a Zn-Al silane coating on carbon steel was studied in 3.5%NaCl solution using open circuit potential monitoring, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The results indicated that the action process of the coating during immersion presented three stages. At the initial stage, the baked zinc powder on the surface layer of the coating started to activate due to the attack of the electrolyte. In the middle stage, the coating exhibited electrochemical protection for the substrate. For the third stage, the barrier protection of the coating predominated. The middle stage lasted a longer period than the third stage, indicating a strong cathodic protection and a weak barrier mechanism of corrosion prevention of the Zn-Al silane coating.