Lotus leaves coating on copper substrates and their corrosion performances in sodium chloride solutions

Abstract

In the present work, the chloroform extract of lotus leaves (CELL) has been prepared and one to three layers of it have been coated on copper (Cu) via drop casting in a layer-wise manner. Open circuit potential (OCP) and Tafel Polarization (TP) curves, as well as electrochemical impedance spectroscopy (EIS), were used to investigate the corrosion behaviors of pristine and different layers (1–3) coated Cu in 0.5 M NaCl. Cu substrates are also investigated with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The electrochemical analysis indicates that 2 layers coated Cu is giving better performance (more positive OCP, greater impedance, lower corrosion current) than 1 layer and 3 layers coated Cu. Around 80 % of Cu saving in 0.5 M NaCl has been achieved with 2 layers of CELL coated Cu. The reason for protection is noticed as the effective coverage of Cu by CELL layers. However, the protection is compromised beyond 2 layers because it is found that CELL molecules are leaching out from various places on the Cu surface. The SEM results have also confirmed this fact. The EDX analysis of the Cu and coated Cu after corrosion suggests that 2L coated Cu is less attacked by O, Na, and Cl with respect to others, which indicates that the 2L of CELL coated Cu is the best performer against corrosion. A schematic is also provided to explain the protection of Cu by CELL.