Superhydrophobic Stainless Steel Surfaces Research Articles

UV Resistance of Super-Hydrophobic Stainless Steel Surfaces Textured by Femtosecond Laser Pulses

The loss of spontaneous liquid repellency on the surface of AISI 304 stainless steel under UV irradiation has been investigated depending on the textures formed by femtosecond laser pulses using Owens–Wendt plot analysis. Laser-induced periodic surface structures (LIPSS) have shown less liquid repellency compared to microgrooves. The polarity of the super-hydrophobic non-polar layer increased under UV irradiation to a super-hydrophilic state. The rate of this transition is determined by the surface topography and was faster for LIPSS compared to the bihierarchical textures formed by LIPSS in combination with microgrooves. The applicability of the Owens–Wendt approach for the numerical comparison of the achievable liquid repellency of textured surfaces in the Cassie state and the degree of polarity reversal of the hydrophobic layer was shown.

Very simple method to produce superhydrophobic stainless steel surfaces at room temperature

The development of superhydrophobic (SHP) and self-cleaning surfaces has gained significant attention due to their potential applications in various fields. This study presents a rapid, simple, and environmentally friendly method for producing superhydrophobic and self-cleaning surfaces on AISI 347 stainless steel. The process involves mild chemical etching followed followed by Plasma Enhanced Chemical Vapor Deposition (PECVD) deposition of a fluorocarbon film using 1,1,1,2-tetrafluorethane (C2H2F4) as a precursor. The resulting surfaces exhibited contact angles (CA) of up to 164° and sliding angles (SA) as low as 3°. Characterization of the surfaces revealed favorable mechanical properties, including a maximum hardness of 1.1 GPa and an elastic modulus of 9.7 GPa. The method offers potential for large-scale applications and anti-fouling purposes, as demonstrated by initial fouling tests. The findings contribute to the development of cost-effective and durable superhydrophobic surfaces with enhanced mechanical strength and corrosion resistance.

Durable superhydrophobic coatings for stainless-steel: An effective defense against Escherichia coli and Listeria fouling in the post-harvest environment

Increasing concerns revolve around bacterial cross-contamination of leafy green vegetables via food-contact surfaces. Given that stainless-steel is among the commonly used food-contact surfaces, this study reports a coating strategy enhancing its hygiene and microbiological safety through an antifouling approach via superhydrophobicity. The developed method involves growing a nickel-nanodiamond nanocomposite film on 304 stainless-steel via electroplating and sequential functionalization of the outer surface layer with nonpolar organosilane molecules via polydopamine moieties. The resultant superhydrophobic stainless-steel surfaces had a static water contact angle of 156.3 ± 1.9° with only 2.3 ± 0.5° contact angle hysteresis. Application of the coating to stainless-steel was demonstrated to yield 2.3 ± 0.6 log10 and 2.0 ± 0.9 log10 reductions in the number of adherent gram-negative Escherichia coli O157:H7 and gram-positive Listeria innocua cells, respectively. These population reductions were shown to be statistically significant (α = 0.05). Coated stainless-steel also resisted fouling when contacted with contaminated romaine lettuce leaves and maintained significant non-wetting character when abraded with sand or contacted with high concentration surfactant solutions. The incorporation of superhydrophobic stainless-steel surfaces into food processing equipment used for washing and packaging leafy green vegetables has the potential to mitigate the transmission of pathogenic bacteria within food production facilities.

Chemical stability of superhydrophobic stainless steel surfaces realized by laser-texturing and chemical functionalization

The combined adjustment of the topography and of the chemical surface composition of stainless-steel surfaces allows the fabrication of super hydrophobic surfaces with manifold potential applications. However, the factual usability depends in many cases on the chemical stability of the modified surface. The chemical stability in correlation to Hydrogen peroxide (H2O2) of a two-step modified stainless steel surface was studied. For this purpose, the surface was nanostructured by means of ultrashort pulse lasers and then the laser-treated surface was chemically modified by means of a self-assembled monolayer (SAM). This approach enables the specification of nano/microstructure and chemical composition independent of each other. Various hierarchical micro- and nanostructures can be realized by laser texturing of stainless steel surfaces using infrared picosecond laser radiation. The modified surface with different surface topographies was then stored in 50% H2O2-water solution and the contact angle was determined as a function of the exposure time. The H2O2 treatment results in a transition from a super hydrophobic to a super hydrophilic surface where the temporal stability of the super hydrophobic properties is dependent on laser-induced surface topography. Surfaces were produced which exhibited super hydrophobic properties for more than 14 days when stored in 50% H2O2.

A one-step preparation of superhydrophobic stainless steel mesh and application in raffinate cleaning technology as a coalescer for contaminated organic-water separation

Improving raffinate oil-water separation efficiency and simplifying the production process of coalescing material are both in great demand but remain difficult. In this study, a superhydrophobic stainless steel surface was created using a simple one-step electrodeposition process in an electrolyte solution comprising nickel chloride (NiCl2·6H2O), stearic acid, and ethanol. The surface shape, chemical content, and superhydrophobic property were studied using a scanning electron microscope (SEM), Fourier-transform infrared (FT-IR) spectrometer, energy dispersive spectroscopy (EDS), and contact angle measurement. The cotton-like microstructure, comprised of crystals of Ni metal and Ni(CH3(CH2)16COO)2, demonstrated outstanding acid and alkaline resistance with a maximum surface contact angle of 166.8°. The oil-water separation performance of raffinate was tested in a mixer-settler, and the separation efficiency ranged from 75% to 80% in a P507 + Kerosene/water system, based on Chemical Oxygen Demand (COD) indicating its potential applicability in the solvent extraction process. A high-speed camera was also used to observe the coalescing behavior of oil droplets in water.

Ultrasonic assisted rapid preparation of superhydrophobic stainless steel surface and its application in oil/water separation

The preparation of superhydrophobic (SH) surface on stainless steel by chemical etching method is challenging due to the good corrosion resistance of the material. In this work, SH surface with water contact angle (WCA) as high as 163.21° was accomplished on 304 stainless steel surface by a rapid ultrasonic-assisted chemical etching method within 7 min and a low-cost fluorine-free modification treatment. The mechanism of ultrasonic field on the etching process was explored by detecting the cavitation and oscillation energy in the reactor. It is the first time to found that the ultrasonic cavitation effect enhanced the etching process by both chemical and physical facilitation resulting in hierarchical lamellar micro-structures, “mountain-like” micro-structure clusters and “coral-reef-like” nano-scale structures on the surface. With the ultrasonic power increasing, the ultrasonic cavitation effect not only enhanced the superhydrophobicity of sample surface, but also improved the uniformity of surface wettability. The samples also showed excellent performance of oil/water separation for various organics (all separation efficiencies up to 96%) and remarkable mechanical stability.

Ultrasonic Assisted Rapid Preparation of Superhydrophobic Stainless Steel Surface and its Application in Oil/Water Separation

Ultrasonic Assisted Rapid Preparation of Superhydrophobic Stainless Steel Surface and its Application in Oil/Water Separation

Directional sliding of water: biomimetic snake scale surfaces

Bioinspired superhydrophobic surfaces have attracted many industrial and academic interests in recent years. Inspired by unique superhydrophobicity and anisotropic friction properties of snake scale surfaces, this study explores the feasibility to produce a bionic superhydrophobic stainless steel surface via laser precision engineering, which allows the realization of directional superhydrophobicity and dynamic control of its water transportation. Dynamic mechanism of water sliding on hierarchical snake scale structures is studied, which is the key to reproduce artificially bioinspired multifunctional materials with great potentials to be used for water harvesting, droplet manipulation, pipeline transportation, and vehicle acceleration.

Fabrication and coating adhesion study of superhydrophobic stainless steel surfaces: The effect of substrate surface roughness

In this study, superhydrophobic 17–4 PH stainless steel surfaces were fabricated for applications in harsh marine environment. The impacts of the substrate's surface roughness on the fabrication and durability of the developed superhydrophobic coating, comprised of a Zn electrodeposited layer capped with 0.05 M stearic acid, were investigated for the first time in this study. Various micron and sub-micron scale finished surfaces with different surface roughness, namely as-received (Ra ~ 4.62 μm), sandblasted (Ra ~ 11.93 μm), and ground (Ra ~ 0.39 μm) surfaces, were fabricated, followed by applying Zn electrodeposited coating to improve the water-repellent properties of the stainless steel substrate. The adhesion durability of the coating and corrosion behavior of the electrodeposited Zn layer were deliberated by studying the combined impacts of the initial surface roughness, and super-hydrophobicity of the surfaces. The cyclic potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results measured in aerated 3.5 wt.% NaCl electrolyte at room temperature along with salt spray testing highlighted a significantly better uniformity and adhesion durability of the coating on the as-received substrate correlated to its optimum surface roughness. The best coating adhesion was obtained on surfaces with an initial surface roughness of 4.62 ± 0.15 µm. The coated 17–4 pH stainless steel surfaces were also found to be effective in preventing the aggressive chloride ions from approaching the substrate, leading to the improved corrosion performance of the material.

Controllable Superhydrophobic Stainless Steel Surfaces Fabrication by Femtosecond Laser

Abstract Ultrafast laser processing has emerged as important tool for micro- and nanoscale fabrications. It is also used to create self-organized microstructures with nanoscale features on surfaces. Fabrications of superhydrophobic surfaces induced by femtosecond laser have many applications that include anticorrosion, self-cleaning, and drag reduction. We created hydrophobic surfaces on stainless steel surfaces by producing a hierarchical nano–microstructure with ultrafast laser ablation. Periodic nano–microstructures with different topographies were fabricated on stainless steel AISI 304 surface using a femtosecond laser with a pulse duration of 100 fs and a wavelength of 800 nm. Ablation was performed in the open air with no subsequent treatment. In this study, a three-level Box–Behnken design of response surface method was used to investigate and optimize the process parameters for hydrophobic surfaces. The laser-machined hierarchical nano–microstructures were examined using a scanning electron microscope and an opto-digital 3D microscope. The wetting of surfaces was measured in terms of the contact angle of a water droplet using a digitized goniometer. The contact angle of laser-modified surfaces was changed from a hydrophilic behavior to a hydrophobic one without any surface coatings. The effect of pulse energy was found to be significant on the output characterization. The results revealed that the average pulse energy range of 0.035–0.05 mJ at 10,000 Hz with a scanning speed of 10–100 mm/s and line separation of 10–30 μm produced hydrophobic surfaces with the apparent contact angle of 110–135°. We demonstrated a simple way to tune hydrophobicity using femtosecond laser surface modification in a single step with no subsequent post treatment.

Analysis of Wetting Behavior and Solidification Process of Molten Urea on a Superhydrophobic Surface and Its Application in Large Granular Urea Production

The wetting behavior of polar high-temperature melt on superhydrophobic surfaces is rarely studied, although water wetting process under normal temperature has been widely investigated. In this work, molten urea was considered as the typical polar melt substance, and its wetting behavior and solidifying process on a polytetrafluoroethylene (PTFE)-coated superhydrophobic stainless steel surface (PSSSS) were investigated. The results confirm the super-repellency of PSSSS on molten urea droplets with a static angle of over 155° and a rolling angle of 3.5 ± 1°, which is consistent with the Cassie–Baxter state. Such a superurea-melt-phobic state is ascribed to the high roughness of the PTFE-coated surface and high cohesive energy density difference between the urea and PTFE. The solidification process of the urea melt on PSSSS occurred from the outside to inside in 44 s at 18 °C to form a compact urea granule of large size and high mechanical strength. This occurrence provides a feasible and promising granulat...

Biomimetic robust superhydrophobic stainless-steel surfaces with antimicrobial activity and molecular dynamics simulation

Wettability is an effective strategy to reduce the adhesion force between bacteria and a solid surface, also is favor to effectively overcome the limitation of the substrate materials and expand their practical applications. Herein, inspired by the special micro/nano structures of the creatures and the bioadhesion of marine mussels, a green and simple two-step method, the laser interference patterning and in-situ polymerization, was used to fabricate the superhydrophobic surface with antibacterial property on the stainless-steel (SS) substrate. As well, this patterned surface also has successfully realized the wettability transition from superhydrophilic to superhydrophobic. Meanwhile, the results of MD simulations directly suggested the PDA@ODA compounds how to adsorb on the SS substrate and interact with water molecules, which was consistent with the experimental. In addition, according to the agar plate assays and fluorescent microscope tests, the obtained specimens presented a certain antimicrobial activity. Moreover, the samples had good robustness in the heat resistance, physical performance and durability, which will expand the application fields and working life.

Preparation and Corrosion Resistance of 304 Super-hydrophobic Stainless-Steel Surface

Super-hydrophobic stainless-steel surface (SHSSS) was prepared by simple chemical etching method using ferric chloride ethanol solution and nutmeg acid ethanol solution as etching and modification solution respectively. Characterization analyses, including water contact angle (WCA) determination, Fourier-transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and electrochemical workstation were performed on SHSSS.The stainless steel etched with ferric chloride (20 wt%) ethanol solution for 1 h, modified with nutmeg acid, and obtained super-hydrophobic properties (WCA = 151.6 °). Furthermore, the SHSSS has satisfactory chemical stability and corrosion resistance. The surface can maintain super-hydrophobicity within 3.5 wt% NaCl solution of 2 days. The corrosion inhibition efficiency calculated by the fitting parameters of Tafel polarization curve is 81.8%.

The design of superhydrophobic stainless steel surfaces by controlling nanostructures: A key parameter to reduce the implantation of pathogenic bacteria

Reducing bacterial adhesion on substrates is fundamental for various industries. In this work, new superhydrophobic surfaces are created by electrodeposition of hydrophobic polymers (PEDOT-F4 or PEDOT-H8) on stainless steel with controlled topographical features, especially at a nano-scale. Results show that anti-bioadhesive and anti-biofilm properties require the control of the surface topographical features, and should be associated with a low adhesion of water onto the surface (Cassie-Baxter state) with limited crevice features at the scale of bacterial cells (nano-scale structures).

One‐Stage Method for Fabricating Superhydrophobic Stainless Steel Surface and Its Anti‐Corrosion Performance

One‐stage preparation of superhydrophobic stainless steel surface is achieved by combining chemical etching and assembly. The contact angle of the prepared surface reaches as high as 175°. The correlative mechanism between the contact angle and surface morphology is elucidated from the dynamics perspective by controlling reaction conditions. The optimum reaction conditions are then determined. Experimental results demonstrate that the stainless steel surface achieves optimal water contact angle upon the formation of the “honeycomb” 3D network structure. Electrochemical corrosion test shows that the prepared superhydrophobic stainless steel surface possesses 16 times higher corrosion resistance than common stainless steel surface.

A facile and scalable method to produce superhydrophic stainless steel surface

A superhydrophobic stainless steel surface was achieved by changing the morphology applying a sandblasting process and then modifying the surface energy with myristic acid. The effect of chemical etching with HCl and HF on surface morphology was studied; however, chemical etching induced surface morphology led to decrease of the contact angles. According to the Cassie–Baxter and Wenzel models, the effects of the different sizes of SiC powders used in sandblasting were evaluated. In addition, the influence of soaking time in the myristic acid solution on wettability was studied. With optimized surface modification parameters (roughness, myristic acid coating time), a maximum contact angle of 167° was achieved with an average value of 158.3°. A sliding angle over 180° was obtained, which can be explained with the Petal effect. The method presented is facile, low-cost and scalable, and hence with high potential for large-scale applications of stainless steel.

Creation of Superhydrophobic Stainless Steel Surfaces by Acid Treatments and Hydrophobic Film Deposition

In this work, we present a method to render stainless steel surfaces superhydrophobic while maintaining their corrosion resistance. Creation of surface roughness on 304 and 316 grade stainless steels was performed using a hydrofluoric acid bath. New insight into the etch process is developed through a detailed analysis of the chemical and physical changes that occur on the stainless steel surfaces. As a result of intergranular corrosion, along with metallic oxide and fluoride redeposition, surface roughness was generated on the nano- and microscales. Differences in alloy composition between 304 and 316 grades of stainless steel led to variations in etch rate and different levels of surface roughness for similar etch times. After fluorocarbon film deposition to lower the surface energy, etched samples of 304 and 316 stainless steel displayed maximum static water contact angles of 159.9 and 146.6°, respectively. However, etching in HF also caused both grades of stainless steel to be susceptible to corrosion. By passivating the HF-etched samples in a nitric acid bath, the corrosion resistant properties of stainless steels were recovered. When a three step process was used, consisting of etching, passivation and fluorocarbon deposition, 304 and 316 stainless steel samples exhibited maximum contact angles of 157.3 and 134.9°, respectively, while maintaining corrosion resistance.