Sprayed superamphiphobic coatings on copper substrate with enhanced corrosive resistance
Graphical abstract
Introduction
There has recently been a significant amount of research directed toward producing superhydrophobic surfaces owing to their wide applicability in various fields, including the development of self-cleaning surfaces, anti-fogging films, and anticorrosion coatings [1], [2], [3], [4], [5]. Typically, surfaces are considered to be superhydrophobic if they display contact angles > 150° and contact angle hysteresis < 5° with water, and superamphiphobic if they display contact angles > 150° and contact angle hysteresis < 5° with water and oils. To maximize the self-cleaning effect, the coating should not only be able to repel water, but also have the ability to repel organic liquids. The three conventional wetting states described by the Wenzel, Cassie–Baxter, and Cassie-impregnating models are often cited to clarify the superhydrophobic surface. The Wenzel model means a complete wetting state. In the Cassie–Baxter model, liquid droplet only contacts the tips of the surface and trapped large fractions of airs, which generates the non-wetting and easily roll-off properties. Cassie-impregnating model is account for superhydrophobic surface with high adhesive force. Traditional superhydrophobic surfaces are easily fouled by oils and other organic matters, and this susceptibility to oil fouling severely hindered their use in practical applications. Our investigation focuses on the development of surfaces that simultaneously exhibit superhydrophobic and superoleophobic properties; such universally nonwetting surfaces are often referred to as superamphiphobic. However, creating superamphiphobic surfaces has proven to be much more difficult than creating superhydrophobic surfaces, owing to the similarity of the low surface tension of oils to that of the commonly used low energy materials. To address this problem, several studies systematically discussed the impact of surface texture on wettability and demonstrated that the overhang structure or the re-entrant surface curvature was essential to achieve superoleophobicity, besides the roughened texture and low surface energy materials [6], [7], [8], [9], [10], [11]. In addition, theoretical analysis has shown that surfaces with two scales of texture can enhance the stability of Cassie–Baxter state by producing re-entrant structure. The re-entrant structures produce the Laplace pressure force ( where γ is the surface tension of the liquid, θ is Youngʼs contact angle of the liquid on a flat surface, α is the inclination angle, R is the half-width between base edges of two adjacent inclined walls, P is the pressure on the liquid side of the meniscus), which can effectively prevent the liquids from penetrating into the texture [12]. The Laplace pressure is important in maintaining a composite interface. This understanding allowed for the possibility of constructing superamphiphobic surfaces, although the pristine surface was hydrophilic and oleophilic, and fabrication methods involved lithography [13], [14], [15], deposition [16], [17], [18], electrochemical polymerization [19], electrospun method [20], [21]. Although targeted superamphiphobic property has been achieved [22], [23], the fabrication process is usually substrates restricted and time consuming, which limits the application of the obtained surfaces. Thus, seeking a simple way to produce superamphiphobic surfaces became an urgent demand.
As a kind of important engineering materials, copper has widely used in industrial applications, such as aerospace, railway, and automobile. However, the naturally occurring corrosion and oil-fouling properties greatly restricted the scope of its applications. Endowing copper substrate with superamphiphobicity and corrosion resistance may be an alternative way to solve this problem. Here, we developed spraying method to fabricate superamphiphobic coatings based on fluorinated silica and fluoropolymer. Liquids with different surface tension remained spherical on the surface and could roll off the surface easily. The resulting superoleophobic surface also enhanced corrosion resistance, allowing it to exhibit a more positive corrosion potential and a more negative corrosion current density than pristine copper substrate. Tunable surface wettability can be achieved by varying the ratio of fluorinated silica and fluoropolymer.
Section snippets
Materials
Silicon dioxide nanopowder (10–20 nm particle size), poly(vinylidene fluoride-hexafluoro-propylene) (Mw ∼ 400,000), Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane, PFTS, were obtained from Aldrich and used as received. Water (18.2 MΩ cm) was purified with a millipore simplicity system and used for all experiments.
Preparation of fluorinated silica
0.5 g SiO2 was immersed in piranha solution in 50 °C for 12 h (H2SO4 and 30 wt% H2O2 in a 3:2 volume ratio) [24] and washed with distilled water and ethanol until the pH was near 7. After put
Results and discussion
Fig. 1a shows the dispersion property of pristine silica, piranha solution treated silica, and fluorinated silica in water. As shown in Fig. 1a, the sedimentation rate of pristine silica was fast in water. After being treated in piranha solution, the silica particle has a good dispersion in water. While for the fluorinated silica, it floats on the surface of water, indicating its repellence to water. The FTIR spectra of pristine silica and fluorinated silica are shown in Fig. 1b. In the spectra
Conclusion
Superamphiphobic surfaces were fabricated by spraying the mixture of fluorinated silica and fluoropolymer onto substrate. The resulting coating can resist water and hexadecane, allowing them to roll off the coating surface easily. Tunable surface wettability have achieved by varying the ratio of fluorinated silica and fluoropolymer. Potentiodynamic polarization tests demonstrated endowing copper substrate with superamphiphobic property enhanced its corrosion resistance significantly, when
Acknowledgements
The authors acknowledge the financial support of the National Science Foundation of China (Grant No. 51002162) and “Western Action Program”.
References (27)
- et al.
A modified Cassie–Baxter relationship to explain contact angle hysteresis and anisotropy on non-wetting textured surfaces
J. Colloid Inter. Sci.
(2009) - et al.
Superhydrophobicity and superoleophobicity from hierarchical silica sphere stacking layers
Mater. Chem. Phys.
(2010) - et al.
Super water-repellent poly (alkylpyrrole) films having environmental stability
J. Colloid Inter. Sci.
(2007) - et al.
Bioinspired super-antiwetting interfaces with special liquid–solid adhesion
Acc. Chem. Res.
(2010) - et al.
Progress in superhydrophobic surface development
Soft Matter
(2008) - et al.
Hierarchically sculptured plant surfaces and superhydrophobicity
Langmuir
(2009) - et al.
Design and creation of superwetting/antiwetting surfaces
Adv. Mater.
(2006) - et al.
Preparation of superhydrophobic coatings on zinc, silicon, and steel by a solution-immersion technique
ACS Appl. Mater. Inter.
(2009) - et al.
Fabrics with tunable oleophobicity
Adv. Mater.
(2009) - et al.
Scale dependence of omniphobic mesh surfaces
Langmuir
(2010)
From hygrophilic to superhygrophobic: theoretical conditions for making high-contact-angle surfaces from low-contact-angle materials
Langmuir
Super water- and oil-repellent surfaces on intrinsically hydrophilic and oleophilic porous silicon films
Langmuir
Nanonails: a simple geometrical approach to electrically tunable superlyophobic surfaces
Langmuir
Cited by (45)
Endowing versatility and antibacterial ability to composite coating via a spraying strategy
2023, Ceramics InternationalA durable superhydrophobic polyphenylene sulfide composite coating with high corrosion resistance and good self-cleaning ability
2023, Colloids and Surfaces A: Physicochemical and Engineering AspectsCitation Excerpt :Metal corrosion is a phenomenon in which chemical or electrochemical heterogeneous reactions occur on the metal surface, resulting in damage to metal materials [1,2].
A superhydrophobic polyphenylene sulfide composite coating with anti-corrosion and self-cleaning properties for metal protection
2022, Colloids and Surfaces A: Physicochemical and Engineering AspectsThe tribological properties and corrosion resistance of PPS/PTFE-bronze coatings deposited by electrohydrodynamic jet deposition
2022, Surface and Coatings TechnologyRecent progress in nano-oxides and CNTs based corrosion resistant superhydrophobic coatings: A critical review
2020, Progress in Organic Coatings