Extraction of flavonoids from Butterfly blue pea (Clitoria ternatea) flower as carbon steel corrosion inhibitor in CO₂ environment: Experimental and theoretical approaches

The present study emphasizes the extraction of flavonoids from the Butterfly blue pea (Clitoria ternatea), a flower containing very strong antioxidant properties. The extracts were prepared using solvents with different polarity namely chloroform (CTCH), ethanol (CTET), ethyl acetate (CTEA) and water (CTW). The phytochemical studies for all extracts were evaluated to screen the phenolic content, flavonoid content, reducing power assay and tannin content as potential source of antioxidant properties of the flower. The crude aqueous extract (CTW) had the maximum phenolic content (106.79 +/- 4.40 mg/GAE g) and the highest flavonoid content (85.05 +/- 5.01 mg QE/g). All of the extracts were then characterized using complementary analyses, including FTIR, TGA, DSC, 1 H and 13C NMR. CT extracts showed a substantial amount of phenols and flavonoids in comparison with standard quercetin. The performances of mild steel to prevent corrosion in 3.5 % NaCl medium doped with CT extracts (50, 100, 250, 500, 750, 1000 ppm) were ascertained by carrying out electrochemical measurements. It is apparent that CTW is superior in terms of corrosion inhibition of mild steel in NaCl medium under CO2 environment with respect to CTET extract (%IECTW = 89.91 % > %IECTET = 85.53 %). Adsorption of both inhibitors on the surface of MS obeyed Langmuir isotherm. Therefore, it can be inferred from the findings that CT extracts were adsorbed via both physical and chemical adsorption, hence showing excellent corrosion resistance behaviour, thus indicating its potential to be an alternative source of natural antioxidants potent CO2 corrosion inhibitor.