Camphor as an effective corrosion inhibitor for carbon steel in 1M HCl solution: electrochemical and quantum chemical investigation

The inhibition of corrosion of carbon steel by camphor in hydrochloric acid (1M HCl) was tested, using electrochemical techniques (impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) and quantum chemical calculations (QCC). Impedance measurements showed that the double-layer capacitance decreased and charge transfer resistance increased with the rise of the inhibitor concentration, which explains the increase in inhibition efficiency. Potentiodynamic polarization techniques reveal that the presence of the inhibitor does not change the mechanism of hydrogen evolution. The effect of temperature on the corrosion behavior of carbon steel in 1 M HCl with and without addition of camphor was studied in the temperature range between 303 and 333 K. Phenomenon of physical adsorption is proposed from the activation parameter obtained. Thermodynamic parameters show that the adsorption process is spontaneous. Quantum chemical calculations using DFT were used to calculate some electronic properties of the molecule in order to ascertain the correlation between the inhibitive effect and the molecular structure of the camphor molecule.