Thin-Film Coating of the Hydrophobic Lotus Leaf on Copper by the Floating Film Transfer Method and Investigation on the Corrosion Behavior of Coated Copper in Saline Water

Copper (Cu) is an important base material for many electrical, thermal, and home applications. However, corrosion of Cu is a serious concern in chloride-containing solutions. The present work reports lotus leaf coating on Cu as a successful preventive solution. After preparation of a lotus leaf chloroform extract (LLCE), an ultrathin (15 +/- 5 nm) film of LLCE is created by the floating film transfer method (FFTM) and transported on Cu through stamping. LLCE has been characterized by UV-visible spectroscopy (UVS), nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy (FTIRS) techniques, which disclose that LLCE meets the expectations of being rich in biomolecules. The LLCE coating on Cu was done in a layerwise manner (1-3) and analyzed with scanning electron microscopy (SEM) and a drop shape analyzer (DSA). The SEM images show that there are films on Cu, and DSA suggests that LLCE coatings have increased the hydrophobicity of Cu (contact angle 96) to greater than 100. Open circuit potential (OCP) curves, Tafel polarization (TP) curves, electrochemical impedance spectroscopy (EIS), SEM, energy dispersive X-ray (EDX) spectroscopy, and atomic force microscopy (AFM) have been deployed to investigate the LLCE-coated Cu corrosion in 0.5 M sodium chloride. The LLCE film of three layers (3L) on Cu is found to be the most efficient (97%, TP) against corrosion among the tested ones. SEM and AFM images evidently show that the 3L-coated Cu was the least damaged through corrosion. The reason for prevention can be recommended as blockage of the openings on the bare Cu surface by LLCE films.