Synergy between iodide ions and mangrove tannins as inhibitors of mild steel corrosion

Abstract

Corrosion of materials is a problem faced by many industries. One of the solutions to this problem is to apply corrosion inhibitors. In this study, the synergy between iodide ions and mangrove tannin extracted from mangrove bark (waste products of the charcoal industry) was tested on the inhibition of corrosion of mild steel in 0.5 M HCl and 0.25 M H2SO4. It was compared with the inhibition provided by mimosa and chestnut tannins. Potentiodynamic and electrochemical impedance were recorded under various temperatures from 30 to 60°C in order to obtain the activation energy (Ea), the activated enthalpy (ΔH) and the activated entropy (ΔS). The results showed that there was an increase in inhibition efficiency when iodide ions were added to corrosive media in the presence of mangrove tannin. The effect decreased when temperature increased. Mangrove tannins showed comparable inhibitive properties to those of commercial mimosa and chestnut tannins. Inhibition efficiency of tannins as inhibitors of corrosion for mild steel in acidic media was improved by the addition of iodide ions. Tannins extracted from mangrove bark were more efficient than those from mimosa and chestnuts.