A correlation study on the phenolic profiles and corrosion inhibition properties of mangrove tannins (Rhizophora apiculata) as affected by extraction solvents

The objective of this study was to investigate the correlation of phenolic compositions and corrosion inhibition properties of Rhizophora apiculata bark extracts as affected by nine solvent systems. Several phenolic compositions, namely, total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC) were investigated. In addition, the inhibitive actions of tannin extracts on mild steel in 1 M HCl solution were studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that extraction solvents had significant effects on TPC, TFC, CTC and inhibition properties of extracts. A correlation between CTC and inhibition properties of R. apiculata bark extracts was revealed.

Research highlights
► Extraction solvent significantly affected the phenolic profiles of R. apiculata bark extracts.
► 70% acetone is most efficient solvent for tannin extraction; high yield and high tannin content.
► All mangrove bark extracts were found to have some degree of inhibition in acidic medium.
► A good correlation was obtained between corrosion inhibition properties and condensed tannin contents.