Green Inhibitors for Copper Corrosion by Mangrove Tannin

Inhibition of copper corrosion by mangrove tannin has been investigated in aqueous 0.5 M hydrochloric acid solution using weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) along with energy dispersive (EDX), atomic absorption spectroscopy (AAS) and ion chromatography (IC). Inhibition efficiency of 82 % was achieved with the addition of 3.0 g L-1 mangrove tannin from potentiodynamic polarisation measurements. Potentiodynamic curves showed that the presence of mangrove tannin in 0.5 M hydrochloric acid solution predominantly affected the cathodic process, decreased the corrosion current density and shifted the corrosion potential towards more negative values. Results obtained from the gravimetric (weight loss), potentiodynamic polarisation and impedance measurements showed similar trends of inhibition efficiency. AAS and IC analysis results showed that the concentrations of copper (II) ions and chloride ions in the electrolyte solutions decreased and increased, respectively, after the corrosion process, when the concentrations of mangrove tannin increased. Adsorption of mangrove tannin on the copper surface in 0.5 M hydrochloric acid solution fitted well with the Langmuir adsorption isotherm model. A change of morphology was observed after the addition of mangrove tannin as shown from SEM analysis.