Evaluation of corrosion resistance of galvanized steel by electrochemical methods

The corrosion resistance of galvanized steel was evaluated by electrochemical polarization and electrochemical impedance spectroscopy. The results confirmed the effect of zinc layer on the improvement of steel’s anticorrosive properties by cathodic protection and barrier effect. According to the polarization curves corrosion rate of normal steel and galvanized steel were calculate 180±5 μm/y and 85±5 μm/y respectively. Impedance resistances of galvanized samples were about 520±10 ohms, while it was 140±10 ohms for the normal samples. These results were within the results obtained by polarization curves. Also it was observed that the presences of a zinc layer can affect the cathodic reactions by reducing the cathodic slop of Tafel plots, so the corrosion protection mechanism of zinc layer can be the cathodic protection.