Investigation of Effects of Acid, Alkali, and Salt Solutions on Fluorinated Superhydrophobic Surfaces

Abstract

Extensive studies have been carried out to investigate the stability of superhydrophobic surfaces under acid, alkali, and salt solutions. It is noted that previous literature studies just demonstrated a variety of experimental phenomena. However, very few works have focused on the protection mechanism or failure mechanism of fluorinated superhydrophobic surfaces from the perspective of chemical aspects. Herein, this paper aims to investigate the effects of acid, alkali, and salt solutions on the stability of fluorinated superhydrophobic surfaces, and the anticorrosion/corrosion mechanism will be further proposed. The superhydrophobic coating was obtained on silicon substrates by laser surface texturing followed by fluoroalkyl silane modification. The resultant surfaces presented a water contact angle (WCA) of 157.6 ± 0.4° with a small water sliding angle (WSA) of 1.3 ± 0.3°. The newly fabricated superhydrophobic surfaces were then immersed in different concentrations of corrosive solutions (acid, alkali, and salt solutions). The revolution of surface wettability and surface morphology on treated silicon surfaces was evaluated through WCAs, scanning electron microscopy, and white light confocal microscopy. The results indicate that the hydrogen ions (H+) played a positive role in the retention of superhydrophobicity. However, the hydroxyl (OH–) and chloride ions (Cl–) presented the negative influence. The protection mechanism or corrosion mechanism under different solutions was proposed based on the X-ray photoelectron spectroscopy results. In addition, the potentiodynamic polarization and electrochemical impedance spectroscopy measurements provided strong support in data and were conducted to verify the rationality of the proposed mechanism.

Stability Mechanism of Laser-induced Fluorinated Super-hydrophobic Coating in Alkaline Solution

“…This phenomenon implied that the strong alkaline solution had dramatically damaged the flat copper surface to generate rough micro/nano-structures, causing a huge change in surface wettability. Based on Wenzel theory, surface roughness has the amplifying effect on surface wettability, indicating that the increase of surface roughness results in smaller WCA on intrinsic hydrophilic surface or larger WCA on intrinsic hydrophobic surface [30,31].…”

The Study on the Anti-corrosion Performance of NiTi Alloy in Human Body Solution with the Fabricating Processes of Laser Irradiation and PDMS Modification

“…Noticeably, NiTi-I had the lowest impedance modulus |Z| at the low frequency of 0.01 Hz, while Ni-Ti-III possessed the biggest impedance modulus |Z|. Previous literature had verified that the larger value of impedance modulus |Z| at the low frequency in Bode diagrams implies the better corrosion resistance [42,43] . Hence, both the Nyquist plots and Bode diagrams confirmed the excellent corrosion resistance of NiTi-III.…”

“…As far as NiTi-II and NiTi-III, the better fitting results were obtained via the equivalent circuit displayed in Fig. 10b, where the electrolytic resistance is described by R s , the resistance between the passive film or the PDMS coating and corrosion solution is represented by R f , CPE f means the constant phase element and the corresponding value reflects the number of corrosion ions in contact with the film or coating [43] . CPE dl and R ct components represent the impedance of interface reaction between the NiTi substrate and the surface coating.…”

Novel Environmentally Friendly Waterborne Epoxy Coating with Long-Term Antiscaling and Anticorrosion Properties

“…These strategies may provide a significant improvement in the short term, but the performance of antiscaling rapidly declines with the loss of metal ions and scale inhibitors. Other researchers have shown that superhydrophobic coatings with low surface energy substances (such as F and Si) or with special structures constructed on the surface of the coating can effectively reduce fouling adhesion. − Although this technology of a superhydrophobic coating has achieved excellent scale inhibition effects in the short term, it cannot overcome the drawback of a short lifetime at present.…”