Aqueous Extract of Cumaru (Dipteryx odorata) Seeds as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Viviane Teixeira,Michelle Rezende,Eliane D’Elia,Gustavo De Oliveira

doi:10.21577/0103-5053.20200194

Viviane Teixeira, Michelle Rezende + Show 2 more

Open Access

https://doi.org/10.21577/0103-5053.20200194

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Abstract

The corrosion inhibition of mild steel by aqueous extract of cumaru (Dipteryx odorata) seeds and its high molecular weight fraction (HMWF) was investigated in 1 mol L-1 HCl solution. The study was carried out through gravimetric essays, open circuit potential measurements, anodic and cathodic polarization curves and electrochemical impedance analyses, as well as morphological analysis of the mild steel by scanning electron microscopy. Gravimetric tests showed that the inhibition efficiency (IE) increased with immersion time and inhibitor concentration, reaching 98% of IE using 100 mg L-1 of the HMWF, after 6 h immersion time. The activation energy (Ea) increased with the addition of both inhibitors which characterizes a physical adsorption of the constituents of the aqueous extract of cumaru on the metal surface. Polarization curves indicated that both aqueous cumaru seeds extract and its HMWF act as mixed-type inhibitor. Impedance results showed a decrease in double layer capacitance (Cdl) and an increase in charge transfer resistance (Rct) evidencing a typically screening effect. The adsorption of molecules present in the aqueous extract of cumaru followed the Langmuir isotherm. The aqueous cumaru seeds extract was characterized by Fourier transform infrared spectroscopy (FTIR), 1H, 13C and 2D nuclear magnetic resonance (NMR).

Highlights

Oil is the most important component of global energy and it is considered a key element for the good functioning of a country’s economy
It is observed that the corrosion rate of the mild steel in acid medium decreases with the addition of the dry extract of cumaru, showing that the compounds present in the aqueous extract of cumaru seeds inhibit the corrosion of the mild steel in acid solution
The following conclusions can be drawn from this work. (i) The aqueous extract of cumaru seeds and its high molecular weight fraction prevent the corrosion of mild steel in 1 mol L−1 HCl solution

Summary

Introduction

Oil is the most important component of global energy and it is considered a key element for the good functioning of a country’s economy. The specimens used in the surface analysis were previously treated They were abraded with 100, 320 and 600 mesh sandpapers and immersed in a 1 mol L−1 HCl solution in the absence and in the presence of 100 mg L−1 of the aqueous extract of cumaru seeds at room temperature for 2 h. After this period, the specimens were washed with double distilled water, acetone and dried in hot air. Chemical shifts (d) are given in parts per million (ppm)

Results and Discussion

Conclusions

36. ASTM G31-7