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Editorial

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4 pages, 161 KiB

Open AccessEditorial

Special Issue on Superhydrophobic Coatings for Corrosion and Tribology

by Shuncai Wang and Guochen Zhao

Coatings 2019, 9(10), 668; https://doi.org/10.3390/coatings9100668 - 14 Oct 2019

Viewed by 1950

Abstract

Superhydrophobicity, showing strong water-repellency, has been widely investigated for many applications, especially in the fields of corrosion protection and antifouling [...] Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

Research

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16 pages, 5703 KiB

Open AccessFeature PaperArticle

Structure-Property Relationships in Suspension HVOF Nano-TiO₂ Coatings

by Feifei Zhang, Shuncai Wang, Ben W. Robinson, Heidi L. de Villiers Lovelock and Robert J.K. Wood

Coatings 2019, 9(8), 504; https://doi.org/10.3390/coatings9080504 - 9 Aug 2019

Cited by 4 | Viewed by 3673

Abstract

Hardness and tribological properties of microstructured coatings developed by conventional thermal spraying are significantly affected by the feedstock melting condition, however, their effect on the performance of nanostructured coatings by suspension high velocity oxy-fuel (HVOF) are inconclusive. In this work, nano-TiO₂ coatings [...] Read more.

Hardness and tribological properties of microstructured coatings developed by conventional thermal spraying are significantly affected by the feedstock melting condition, however, their effect on the performance of nanostructured coatings by suspension high velocity oxy-fuel (HVOF) are inconclusive. In this work, nano-TiO₂ coatings with different degrees of melting (12%, 51%, 81%) of nanosized feedstock were deposited via suspension HVOF spraying, using suspensions with a solid content of 5 wt.%. All the coatings produced had dense structures without visible pores and cracks. Two TiO₂ crystal structures were identified in which the rutile content of the coatings increased with increased feedstock melting. Their mechanical, friction and wear behaviours largely relied on the extent of melting of the feedstock. The coating composed of mostly agglomerate particles (12% melted particles) had the lowest coefficient of friction and wear rate due to the formation of a smooth tribo-film on the wearing surface, while the coating composed of mostly fully melted splats (81% melted particles) presented the highest coefficient of friction and low wear rate, whose wear mechanism was dominated by abrasive wear and accompanied by the formation of cracks. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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10 pages, 5475 KiB

Open AccessArticle

Preparation of Superhydrophobic Steel Surfaces with Chemical Stability and Corrosion

by Chongwei Du, Xiaoyan He, Feng Tian, Xiuqin Bai and Chengqing Yuan

Coatings 2019, 9(6), 398; https://doi.org/10.3390/coatings9060398 - 20 Jun 2019

Cited by 37 | Viewed by 3831

Abstract

Corrosion seriously limits the long-term application of Q235 carbon steel. Herein, a simple fabrication method was used to fabricate superhydrophobic surfaces on Q235 carbon steel for anticorrosion application. The combination of structure and the grafted low-surface-energy material contributed to the formation of superhydrophobic [...] Read more.

Corrosion seriously limits the long-term application of Q235 carbon steel. Herein, a simple fabrication method was used to fabricate superhydrophobic surfaces on Q235 carbon steel for anticorrosion application. The combination of structure and the grafted low-surface-energy material contributed to the formation of superhydrophobic steel surfaces, which exhibited a water contact angle of 161.6° and a contact angle hysteresis of 0.8°. Meanwhile, the as-prepared superhydrophobic surface showed repellent toward different solutions with pH ranging from 1 to 14, presenting excellent chemical stability. Moreover, the acid corrosive liquid (HCl solution with pH of 1) maintained sphere-like shape on the as-prepared superhydrophobic surface at room temperature, indicating superior corrosion resistance. This work provides a simple method to fabricate superhydrophobic steel surfaces with chemical stability and corrosion resistance. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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9 pages, 2272 KiB

Open AccessArticle

Oscillating Magnetic Drop: How to Grade Water-Repellent Surfaces

by Angelica Goncalves Dos Santos, Francisco Javier Montes-Ruiz Cabello, Fernando Vereda, Miguel A. Cabrerizo-Vilchez and Miguel A. Rodriguez-Valverde

Coatings 2019, 9(4), 270; https://doi.org/10.3390/coatings9040270 - 21 Apr 2019

Cited by 6 | Viewed by 3209

Abstract

Evaluation of superhydrophobic (SH) surfaces based on contact angle measurements is challenging due to the high mobility of drops and the resolution limits of optical goniometry. For this reason, some alternatives to drop-shape methods have been proposed such as the damped-oscillatory motion of [...] Read more.

Evaluation of superhydrophobic (SH) surfaces based on contact angle measurements is challenging due to the high mobility of drops and the resolution limits of optical goniometry. For this reason, some alternatives to drop-shape methods have been proposed such as the damped-oscillatory motion of ferrofluid sessile drops produced by an external magnetic field. This approach provides information on surface friction (lateral/shear adhesion) from the kinetic energy dissipation of the drop. In this work, we used this method to compare the low adhesion of four commercial SH coatings (Neverwet, WX2100, Ultraever dry, Hydrobead) formed on glass substrates. As ferrofluid, we used a maghemite aqueous suspension (2% v/v) synthesized ad hoc. The rolling magnetic drop is used as a probe to explore shear solid–liquid adhesion. Additionally, drop energy dissipates due to velocity-dependent viscous stresses developed close to the solid–liquid interface. By fitting the damped harmonic oscillations, we estimated the decay time on each coating. The SH coatings were statistically different by using the mean damping time. The differences found between SH coatings could be ascribed to surface–drop adhesion (contact angle hysteresis and apparent contact area). By using this methodology, we were able to grade meaningfully the liquid-repelling properties of superhydrophobic surfaces. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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14 pages, 8172 KiB

Open AccessArticle

Super-Hydrophobic Co–Ni Coating with High Abrasion Resistance Prepared by Electrodeposition

by Yanpeng Xue, Shuqiang Wang, Peng Bi, Guochen Zhao and Ying Jin

Coatings 2019, 9(4), 232; https://doi.org/10.3390/coatings9040232 - 2 Apr 2019

Cited by 23 | Viewed by 4140

Abstract

Although super-hydrophobic surfaces have great application prospects in industry, their preparation cost and mechanical durability have limited their practical utilization. In this work, we presented a new low-cost process preparation for super-hydrophobic Co–Ni coating on carbon steel substrate via an electrodeposition route. The [...] Read more.

Although super-hydrophobic surfaces have great application prospects in industry, their preparation cost and mechanical durability have limited their practical utilization. In this work, we presented a new low-cost process preparation for super-hydrophobic Co–Ni coating on carbon steel substrate via an electrodeposition route. The deposited Co–Ni coating with cauliflower-shaped micro-nano structures exhibited high super-hydrophobic properties with water contact angles over 161° after modification with 1H,1H,2H,2H-Perfluorooctyltrichlorosilane (PFTEOS). Evaluated by the linear abrasion methods, the super-hydrophobic coating can maintain super-hydrophobicity after abrasion distance of 12 m under the applied pressure of 5 kPa, which was attributed to the high cobalt content of the Co–Ni coating. Moreover, electrochemical tests showed that the super-hydrophobic Co–Ni coatings exhibited a good anti-corrosion performance thus providing an adequate protection to the carbon steel substrates. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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12 pages, 4786 KiB

Open AccessArticle

Synthesis and Properties of Electrodeposited Ni–Co/WS₂ Nanocomposite Coatings

by Yang He, Shuncai Wang, Wanting Sun, Philippa A.S. Reed and Frank C. Walsh

Coatings 2019, 9(2), 148; https://doi.org/10.3390/coatings9020148 - 25 Feb 2019

Cited by 10 | Viewed by 4429

Abstract

Ni–Co coatings have gained widespread attention due to their potential in replacing hard chromium deposits (which have traditionally utilized toxic and corrosive chromic acid baths). A major challenge is to lower the high coefficient of friction of coated surfaces against steel, under dry [...] Read more.

Ni–Co coatings have gained widespread attention due to their potential in replacing hard chromium deposits (which have traditionally utilized toxic and corrosive chromic acid baths). A major challenge is to lower the high coefficient of friction of coated surfaces against steel, under dry sliding conditions. In this research, low friction Ni–Co/WS₂ nanocomposite coatings have been prepared by a convenient, one-pot electrodeposition from aqueous Ni–Co plating baths containing WS₂ particles. The embedment of the WS₂ lubricants is found to reduce the friction coefficient of coating significantly, and an ultra-low friction coefficient of 0.16 is obtained for the coating having a WS₂ content of 7.1 wt.%. Morphology and composition characterization of wear tracks reveal that the formation of a WS₂-rich lubricating tribofilm on the contact surfaces is beneficial to a low friction coefficient and good oxidation resistance. The wettability of electrodeposited coatings was also investigated. Compared to pure Ni-Co coating, the Ni–Co/7.1 wt.% WS₂ coating has an excellent hydrophobicity with a high water contact angle (WCA) of 157°, due to a rough surface with dual scale protrusions and the low surface energy of WS₂. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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14 pages, 5187 KiB

Open AccessArticle

Surfactant-Free Electroless Codeposition of Ni–P–MoS₂/Al₂O₃ Composite Coatings

by Ping Liu, Yongwei Zhu, Qi Shen, Meifu Jin, Gaoyan Zhong, Zhiwei Hou, Xiao Zhao, Shuncai Wang and Shoufeng Yang

Coatings 2019, 9(2), 116; https://doi.org/10.3390/coatings9020116 - 13 Feb 2019

Cited by 11 | Viewed by 5500

Abstract

This paper presents the influence of an inorganic Al₂O₃ layer over MoS₂ particles on the tribological performance of electroless Ni–P–MoS₂/Al₂O₃ composite coatings fabricated without using surfactants. The Al₂O₃-coated MoS₂ [...] Read more.

This paper presents the influence of an inorganic Al₂O₃ layer over MoS₂ particles on the tribological performance of electroless Ni–P–MoS₂/Al₂O₃ composite coatings fabricated without using surfactants. The Al₂O₃-coated MoS₂ particles were prepared by a heterogeneous nucleation process. The dry sliding tests of the composite coatings were tested against a WC ball. SEM was used to observe the surface morphology of particles, composite coatings, and worn surfaces. The results indicate that the coverage of an Al₂O₃ coating on MoS₂ particles significantly affects the surface morphology, frictional coefficient and wear loss of the composite coatings. The incorporation of Al₂O₃-coated MoS₂ particles with lower coverage (up to 7% of Al₂O₃) could obtain compact surface structure of composite coatings, which contribute to reduced wear loss. However, higher coverage would lead to loose surface structure of the composite coatings, and thus increase their wear loss. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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17 pages, 3988 KiB

Open AccessArticle

Effects of Surface Microstructures on Superhydrophobic Properties and Oil-Water Separation Efficiency

by Yangyang Chen, Shengke Yang, Qian Zhang, Dan Zhang, Chunyan Yang, Zongzhou Wang, Runze Wang, Rong Song, Wenke Wang and Yaqian Zhao

Coatings 2019, 9(2), 69; https://doi.org/10.3390/coatings9020069 - 24 Jan 2019

Cited by 5 | Viewed by 3338

Abstract

In order to explore the effects of microstructures of membranes on superhydrophobic properties, it is critical, though, challenging, to study microstructures with different morphologies. In this work, a combination of chemical etching and oxidation was used and some copper meshes were selected for [...] Read more.

In order to explore the effects of microstructures of membranes on superhydrophobic properties, it is critical, though, challenging, to study microstructures with different morphologies. In this work, a combination of chemical etching and oxidation was used and some copper meshes were selected for grinding. Two superhydrophobic morphologies could be successfully prepared for oil-water separation: a parabolic morphology and a truncated cone morphology. The surface morphology, chemical composition, and wettability were characterized. The results indicated that the water contact angle and the advancing and receding contact angles of the parabolic morphology were 153.6°, 154.6° ± 1.1°, and 151.5° ± 1.8°, respectively. The water contact angle and the advancing and receding contact angles of the truncated cone morphology were 121.8°, 122.7° ± 1.6°, and 119.6° ± 2.7°, respectively. The separation efficiency of the parabolic morphology for different oil-water mixtures was 97.5%, 97.2%, and 91%. The separation efficiency of the truncated cone morphology was 93.2%, 92%, and 89%. In addition, the values of the deepest heights of pressure resistance of the parabolic and truncated cone morphologies were 21.4 cm of water and 19.6 cm of water, respectively. This shows that the parabolic morphology had good separation efficiency, pressure resistance, and superhydrophobic ability compared with the truncated cone morphology. It illustrates that microstructure is one of the main factors affecting superhydrophobic properties. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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20 pages, 9306 KiB

Open AccessArticle

Effect of Surface Topography and Structural Parameters on the Lubrication Performance of a Water-Lubricated Bearing: Theoretical and Experimental Study

by Zhongliang Xie, Zhushi Rao and Huanling Liu

Coatings 2019, 9(1), 23; https://doi.org/10.3390/coatings9010023 - 2 Jan 2019

Cited by 16 | Viewed by 4401

Abstract

This study explored the influence of the surface topography of a bushing on the lubrication performance of a water-lubricated bearing. Bushing deformations were considered in the mathematical model. Theoretical calculations and experiments were performed. The test data corresponded well with the simulation. The [...] Read more.

This study explored the influence of the surface topography of a bushing on the lubrication performance of a water-lubricated bearing. Bushing deformations were considered in the mathematical model. Theoretical calculations and experiments were performed. The test data corresponded well with the simulation. The main stiffness and cross stiffness coefficients were measured and compared with the theoretical values, and the empirical formula of friction coefficient was fitted based on the test data. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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11 pages, 3303 KiB

Open AccessArticle

Fabrication of Superhydrophobic AA5052 Aluminum Alloy Surface with Improved Corrosion Resistance and Self Cleaning Property

by Qian Zhao, Tiantian Tang and Fang Wang

Coatings 2018, 8(11), 390; https://doi.org/10.3390/coatings8110390 - 31 Oct 2018

Cited by 16 | Viewed by 4246

Abstract

The development of a self-cleaning and corrosion resistant superhydrophobic coating for aluminum alloy surfaces that is durable in aggressive conditions has attracted great interest in materials science. In the present study, a superphydrophobic film was fabricated on an AA5052 aluminum alloy surface by [...] Read more.

The development of a self-cleaning and corrosion resistant superhydrophobic coating for aluminum alloy surfaces that is durable in aggressive conditions has attracted great interest in materials science. In the present study, a superphydrophobic film was fabricated on an AA5052 aluminum alloy surface by the electrodeposition of Ni–Co alloy coating, followed by modification with 6-(N-allyl-1,1,2,2-tetrahydro-perfluorodecyl) amino-1,3,5-triazine-2,4-dithiol monosodium (AF17N). The surface morphology and characteristics of the composite coatings were investigated by means of scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), atomic force microscope (AFM) and contact angle (CA). The corrosion resistance of the coatings was assessed by electrochemical tests. The results showed that the surface exhibited excellent superhydrophobicity and self-cleaning performance with a contact angle maintained at 160° after exposed to the atmosphere for 240 days. Moreover, the superhydrophobic coatings significantly improved the corrosion resistant performance of AA5052 aluminum alloy substrate in 3.5 wt.% NaCl solution. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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Review

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28 pages, 8631 KiB

Open AccessReview

Robust Super-Hydrophobic Coating Prepared by Electrochemical Surface Engineering for Corrosion Protection

by Peng Bi, Hongliang Li, Guochen Zhao, Minrui Ran, Lili Cao, Hanjie Guo and Yanpeng Xue

Coatings 2019, 9(7), 452; https://doi.org/10.3390/coatings9070452 - 18 Jul 2019

Cited by 45 | Viewed by 11816

Abstract

Corrosion—reactions occuring between engineering materials and their environment—can cause material failure and catastrophic accidents, which have a serious impact on economic development and social stability. Recently, super-hydrophobic coatings have received much attention due to their effectiveness in preventing engineering materials from further corrosion. [...] Read more.

Corrosion—reactions occuring between engineering materials and their environment—can cause material failure and catastrophic accidents, which have a serious impact on economic development and social stability. Recently, super-hydrophobic coatings have received much attention due to their effectiveness in preventing engineering materials from further corrosion. In this paper, basic principles of wetting properties and corrosion protection mechanism of super-hydrophobic coatings are introduced firstly. Secondly, the fabrication methods by electrochemical surface engineering—including electrochemical anodization, micro-arc oxidation, electrochemical etching, and deposition—are presented. Finally, the stabilities and future directions of super-hydrophobic coatings are discussed in order to promote the movement of such coatings into real-world applications. The objective of this review is to bring a brief overview of the recent progress in the fabrication of super-hydrophobic coatings by electrochemical surface methods for corrosion protection of engineering materials. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)

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