The inhibition effect of sour cherry gum on corrosion of mild steel in phosphoric acid solution

The effect of sour cherry gum on the corrosion behavior of mild steel in 0.5 M H3PO4 was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the inhibition efficiency increases with increase in concentration of inhibitor, up to a certain concentration and decreases with increase in temperature. The calculated inhibition efficiencies from the two investigated methods were in good agreement. Polarization curves indicate that sour cherry gum act as a mixed type inhibitor. The EIS measurements show that by addition of the inhibitor up to a certain concentration, the charge transfer resistance increases and the double layer capacitance (Cdl) decreases. The EIS experimental data Suggests a frequency distribution of the capacitance, simulated as constant phase element. The adsorption studies revealed that the adsorption of the inhibitor on the alloy surface follows Freundluich adsorption isotherm. The values of activation energy as well as thermodynamic parameters were calculated and discussed.

Keywords:

natural corrosion inhibitor , potentiodynamic polarization , electrochemical impedance spectroscopy , adsorption isother , mild steel