Electrodeposition of Superhydrophobic Cu Film on Active Substrate from Deep Eutectic Solvent

Abstract

A hierarchical rough Cu film constructed by nanosheet-like clusters is electrodeposited on Fe and Mg alloy substrates from a deep eutectic solvent based electrolyte containing CuCl 2 and NaH 2 PO 2 at 75 • C (CuP-75 • C). After modifying by stearic acid for 5 min, the film turns from superhydrophilic to superhydrophobic with a water contact angle (CA) of 161 • and a sliding angle of ∼1.0 • . For comparison, the electrodeposited Cu film from the electrolyte only containing CuCl 2 (Cu-75 • C) exhibits more hydrophilic. Smaller CA value is obtained at lower deposition temperature due to the decrease in surface roughness. The CA value of the CuP-75 • C film increases with increase of the surface modification time. Amazingly, only 3 min of stearic acid modification at room temperature can make the CuP-75 • C film superhydrophobic with a CA of 155 • . Such a fast process is attributed to the chemical reactions of the native CuO formed on the film surface with stearic acid and physical absorptions caused by larger specific surface area. The superhydrophobic CuP-75 • C film exhibits a positively shifted E corr (−356 mV vs. Ag/AgCl) and a decreased i corr (7.07 μA cm −2 ) compared with the hydrophilic counterpart film, thus providing effective protections for active substrates.Superhydrophobic surface, defined as a solid surface with a large water contact angle (CA ≥ 150 • ) and a small sliding angle (SA ≤ 10 • ), has received significant attentions in both fundamental researches and practical applications in the past decades. 1 Inspired by the natural "lotus effect" originally explained by Neinhuis and Barthlott in 1997, 2,3 lots of efforts have been devoted to understand the structures and causes of a superhydrophobic surface. 4-8 Afterwards, novel superhydrophobic surfaces are imitated artificially for various applications, such as self-cleaning, 9,10 anticorrosion, 11-14 antipollution, 15 chemical shielding, 16 oil/water separation 17,18 and so on. Meanwhile, the theoretical researches for superhydrophobicity are further developed. Wenzel model 19 and Cassie-Baxter model 20 are the most widely accepted theories to explain the behavior of water droplet on a rough surface. Wenzel assumed that water can completely penetrate into the grooves when it contacted with the rough surface while Cassie claimed that water can sit on the grooves where air was trapped. Herein, a rough surface with low surface energy is necessary for a superhydrophobic surface. On the case that metals have high surface free energy, 21,22 a superhydrophobic metal surface is prepared by a conventional two-step procedure, i.e. obtaining a rough surface firstly and followed by lowering the surface energy. 23 Copper film, as an essential engineering material, plays a key role in industrial and decorative applications, especially in electronics and printing industry. 24 However, electrodeposition of Cu film for protecting active substrates, especially magnesium alloys, is a severe challenge due to the high micro-galvanic corrosion and hydrogen evolution in...

Microstructure and corrosion behavior of Cr and Cr–P alloy coatings electrodeposited from a Cr(iii) deep eutectic solvent

“…18 Meanwhile, great attention has also been focused on the electrodeposition of Cr(III) from ionic liquids, which have the nature of multicomponent ions and complex organic species, to facilitate coordination chemistry or proton transfer. 19,20 In other words, ionic liquids themselves could provide organic complexing agents for Cr(III) electrodeposition. Most investigations for non-aqueous Cr(III) electrodeposition have mainly focused on 1-butyl-3-methylimidazolium ([BMIM])-based ionic liquids.…”

A Smart Superhydrophobic Coating on AZ31B Magnesium Alloy with Self‐Healing Effect

“…The snapshots of the self‐healing behavior are shown in Figure . As shown in Figure a, a bright and complete silver‐like film on the Cr(III) CCC surface can be observed at the beginning, which results from the air pocket layer trapped between the coating and liquid . It suggests that the superhydrophobic Cr(III) CCC is initially in Cassie state or Cassie impregnating wetting state where the corrosive solution partially enters into the larger scale grooves but not into the smaller ones .…”

“…An obvious polarization increase can be achieved by covering the substrate with a hydrophilic Cr(III) CCC (with CA value of ≈56°). After hydrophobic modification, the polarization is further increased due to an isolation of the coating surface from the corrosive medium, i.e., the air pocket layer formed between the coating surface and the NaCl solution preventing Cl − and oxygen from reaching the Cr(III) CCC surface . For the superhydrophobic Cr(III) CCC (with CA value of ≈157°) exposed for 30 min to the NaCl solution, the air pocket layer and self‐assembled monolayer (SAM) lead to a tiny positive shift of the E corr .…”

Simultaneously Fabricating Multifunctional Superhydrophobic/Superoleophilic Coatings by One-Step Electrodeposition Method on Cathodic and Anodic Magnesium Surfaces

“…However, the peak at 1702 cm −1 ascribed to the carboxyl (−COO) group of MA is no longer present after the electrodeposition process. Instead, two new absorption bands at 1562 cm −1 and 1468 cm −1 appearing may stem from asymmetric and symmetric stretches of coordinated −COO moieties, 22,23,28 respectively. In addition, Fig.…”