Possible improvement of catechin as corrosion inhibitor in acidic medium

► Tannin and catechin were modified to alter their corrosion inhibition activities. ► Modification has improved the inhibition performance of catechin significantly. ► The converse is true for mangrove tannin with the same modification. ► Difference could be attributed to catechin inertness towards complete methylation. This article describes studies on the modification of mangrove tannin (MT) and catechin (CT) to enhance their corrosion inhibition properties. The inhibitive effect of the starting materials and the chemically modified products on the corrosion of mild steel in 1M HCl solution was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). We demonstrated that the chemical modification has successfully enhanced the inhibition efficiency of CT; however reduced that of MT. The disparity in the corrosion inhibitory performances of the modified products was attributed to the inertness of CT towards a complete methylation as compared to MT.