Corrosion Inhibition of Mild Steel in Seawater by 2,4,6-Triamino-3-Pentadecylphenyl Acetate Derived from Cashew Nut Shell Liquid

The corrosion inhibition performance of 2,4,6-triamino-3-pentadecylphenyl acetate on mild steel in seawater at stationary condition, 30 °C and pH 8 was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. The maximum inhibition efficiency of 93% was found in the presence of 300 ppm of 2,4,6-triamino-3-pentadecylphenyl acetate for both potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The potentiodynamic polarization curves show that 2,4,6-triamino-3-pentadecylphenyl acetate acts as a mixed type inhibitor which influences more the anodic processes. The Nyquist plots revealed that the polarization resistance (Rp) increases whereas the double-layer capacitance (Cdl) and corrosion current density (icorr) decrease as the concentrations of the inhibitors increase due to the formation of a protective layer of inhibitor over the mild steel surface. The results obtained from the two electrochemical techniques are in good agreement. The adsorption of 2,4,6-triamino-3-pentadecylphenyl acetate on the mild steel surface obeyed Langmuir adsorption isotherm. Keywords: Cashew nut shell liquid; 2,4,6-triamino-3-pentadecylphenyl acetate; corrosion inhibitor; mild steel; seawater