Evaluation of Paullinia Cupana as a green corrosion inhibitor for carbon steel utilizing gravimetric and electrochemical noise techniques
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In view of the damage caused by corrosion and constant concern for the environment, the antioxidant properties found in Paullinia Cupana make it possible to apply this plant as a green corrosion inhibitor. Extract of Paullinia Cupana shell was used as a green inhibitor for the inhibition of mild steel corrosion in 1.0 M HCl and 0.5 M H2SO4 solution. The corrosion performance of the extract was evaluated using gravimetric, electrochemical noise (ECN), metallographic and Fourier transform infrared spectroscopy (FTIR) analyses. The gravimetric measurements showed that Paullinia Cupana shell presents a strong inhibitive characteristic, showing an efficiency of about 76.8% and 57.4% for HCl and H2SO4 acidic mediums, respectively, and the mechanism of action is physisorption. ECN allowed to analyze the variation of the corrosion charge over time, and about 8.6 and 2.2 times less charge generated with the inhibitor was observed in HCl and H2SO4 acidic mediums, respectively, and the type of localized corrosion also decreased. Metallographic analysis showed the efficiency of the inhibitor from micrographs of the electrodes before and after the electrochemical tests. Also, FTIR analysis showed compounds being consumed in H2SO4 medium indicating that this medium oxidizes the Paullinia Cupana compounds. Therefore, the results suggest that the Paullinia Cupana extract exhibits good inhibition in HCl medium.