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3 pages, 169 KiB

Open AccessEditorial

Special Issue: “Advanced Hybrid Coatings and Thin Films for Surface Functionalization”

by Flavio Deflorian

Coatings 2020, 10(11), 1020; https://doi.org/10.3390/coatings10111020 - 23 Oct 2020

Viewed by 1257

Abstract

Many technologically advanced materials and components are characterized by surfaces with special coatings. The role of the coatings is not only the traditional one (protection and aesthetics), but, in addition, new advanced functions are required, such as special mechanical, chemical, electrical, and optical [...] Read more.

Many technologically advanced materials and components are characterized by surfaces with special coatings. The role of the coatings is not only the traditional one (protection and aesthetics), but, in addition, new advanced functions are required, such as special mechanical, chemical, electrical, and optical functions. A wide range of coating technologies offer the possibility to produce advanced and selected surface properties, such as hydrophobic or hydrophilic coatings, non-stick and easy-to-clean coatings, anti-freeze or anti-fogging coatings, scratch-resistant coatings, and anti-microbial coatings, etc. In particular, organic–inorganic hybrid coatings are very promising materials for new coatings functionalization and applications in many different industrial fields. The aim of this Special Issue is to provide an update of the most advanced research in the design, synthesis, and development of hybrid coatings/thin films, and their applications for surface functionalization, showing the innovation trends and promoting further research in this area. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

Research

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13 pages, 3274 KiB

Open AccessArticle

Experimental Assessment of the Performance of Two Marine Coatings to Curb Biofilm Formation of Microfoulers

by Sara I. Faria, Rita Teixeira-Santos, Luciana C. Gomes, Elisabete R. Silva, João Morais, Vítor Vasconcelos and Filipe J. M. Mergulhão

Coatings 2020, 10(9), 893; https://doi.org/10.3390/coatings10090893 - 18 Sep 2020

Cited by 20 | Viewed by 3387

Abstract

Biofilms formed on submerged marine surfaces play a critical role in the fouling process, causing increased fuel consumption, corrosion, and high maintenance costs. Thus, marine biofouling is a major issue and motivates the development of antifouling coatings. In this study, the performance of [...] Read more.

Biofilms formed on submerged marine surfaces play a critical role in the fouling process, causing increased fuel consumption, corrosion, and high maintenance costs. Thus, marine biofouling is a major issue and motivates the development of antifouling coatings. In this study, the performance of two commercial marine coatings, a foul-release silicone-based paint (SilRef) and an epoxy resin (EpoRef), was evaluated regarding their abilities to prevent biofilm formation by Cyanobium sp. and Pseudoalteromonas tunicata (common microfoulers). Biofilms were developed under defined hydrodynamic conditions to simulate marine settings, and the number of biofilm cells, wet weight, and thickness were monitored for 7 weeks. The biofilm structure was analyzed by confocal laser scanning microscopy (CLSM) at the end-point. Results demonstrated that EpoRef surfaces were effective in inhibiting biofilm formation at initial stages (until day 28), while SilRef surfaces showed high efficacy in decreasing biofilm formation during maturation (from day 35 onwards). Wet weight and thickness analysis, as well as CLSM data, indicate that SilRef surfaces were less prone to biofilm formation than EpoRef surfaces. Furthermore, the efficacy of SilRef surfaces may be dependent on the fouling microorganism, while the performance of EpoRef was strongly influenced by a combined effect of surface and microorganism. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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23 pages, 10239 KiB

Open AccessArticle

Effects of Graphene-Based Fillers on Cathodic Delamination and Abrasion Resistance of Cataphoretic Organic Coatings

by Massimo Calovi, Stefano Rossi, Flavio Deflorian, Sandra Dirè, Riccardo Ceccato, Xiaolei Guo and Gerald S. Frankel

Coatings 2020, 10(6), 602; https://doi.org/10.3390/coatings10060602 - 26 Jun 2020

Cited by 19 | Viewed by 2872

Abstract

This study aims to demonstrate the excellent protective performance of functionalized graphene oxide (fGO) flakes in acrylic cataphoretic coatings. The filler content provides an important contribution in improving the chemical and mechanical resistance of the acrylic matrix. The morphology of the fillers was [...] Read more.

This study aims to demonstrate the excellent protective performance of functionalized graphene oxide (fGO) flakes in acrylic cataphoretic coatings. The filler content provides an important contribution in improving the chemical and mechanical resistance of the acrylic matrix. The morphology of the fillers was first investigated by optical and electron microscopy, analysing the distribution of the fGO flakes within the polymer matrix. After that, the flakes were added to the cataphoretic bath in different concentrations, resulting in four series of samples. The cathodic delamination of the coatings was assessed with cathodic polarization cycles and with measurements carried out with a scanning Kelvin probe. Finally, the abrasion resistance at the macroscopic and microscopic level was studied by scrub testing and scratching atomic force microscopy analysis, respectively. The incorporation of fGO at the optimized concentration of 0.2 wt.% greatly increases the cathodic delamination resistance of the acrylic matrix, resulting in an effective barrier against the effects of absorbed aggressive substances. Graphene-based fillers also enhance abrasion resistance, thanks to their high mechanical strength. Thus, this work demonstrates the great protective benefits that can be obtained when using fGO flakes as reinforcing fillers in cataphoretic coatings. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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16 pages, 5600 KiB

Open AccessArticle

Morphology, Hardness, and Wear Properties of Ni-Base Composite Coating Containing Al Particle

by Rouhollah Mousavi, Flavio Deflorian and Mohammad Ebrahim Bahrololoom

Coatings 2020, 10(4), 346; https://doi.org/10.3390/coatings10040346 - 02 Apr 2020

Cited by 11 | Viewed by 2606

Abstract

Ni–Mo/Al composite coatings were obtained by electrodeposition from a Ni–Mo plating bath containing suspended Al particles. The factors including temperature, current density, and stirring rate affecting coating composition, wear, roughness, and morphology have been studied. It was found that properties such as hardness, [...] Read more.

Ni–Mo/Al composite coatings were obtained by electrodeposition from a Ni–Mo plating bath containing suspended Al particles. The factors including temperature, current density, and stirring rate affecting coating composition, wear, roughness, and morphology have been studied. It was found that properties such as hardness, roughness, wear, and the Al particle content showed parabolic behavior when changing each parameter. That means that there is a critical value for the mentioned parameters at which the properties of coatings become maximal. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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13 pages, 10357 KiB

Open AccessArticle

Insulating Thermal and Water-Resistant Hybrid Coating for Fabrics

by Simona Ortelli and Anna Luisa Costa

Coatings 2020, 10(1), 72; https://doi.org/10.3390/coatings10010072 - 14 Jan 2020

Cited by 9 | Viewed by 3228

Abstract

Organic–inorganic hybrid (ceramer) coatings were synthesized and deposited on the polyester nonwoven fabrics through the sol–gel process. This promoted the formation of an insulating barrier that was able to enhance the thermal stability and the hydrophobicity of fabrics. The hybrid phase is made [...] Read more.

Organic–inorganic hybrid (ceramer) coatings were synthesized and deposited on the polyester nonwoven fabrics through the sol–gel process. This promoted the formation of an insulating barrier that was able to enhance the thermal stability and the hydrophobicity of fabrics. The hybrid phase is made of an organic network arising from different alkoxysilane precursors (trimethoxymethylalkoxysilane (TMEOS), 3-aminopropyl-trimethoxyalkoxysilane (APTMS), and tetraethylorthosilicate (TEOS)) and inorganic phase made of titanium dioxide TiO₂ nanoparticles (NPs) and, in some cases, coated by P-based compound. The characterization of hybrid phase at liquid (size distribution and zeta potential of dispersed nanoparticles), dried state (crystalline phase, thermogravimetric (TGA), and Fourier transform infrared spectroscopic (FTIR) analyses), and on deposited coatings (contact angle, burn-out tests) aimed to find a correlation between the physicochemical properties of ceramer and functional performances of coated fabrics (thermal stability and hydrophobicity). The results showed that all ceramer formulations were able to improve the char formation after burn-out, in particular the highest thermal stability was obtained in the presence of TMEOS precursor and TiO₂ NPs coated by P-based compound, which also provided the highest hydrophobicity. In conclusion, we presented an environmentally friendly and easily scalable process for the preparation of ceramer formulations capable of being formed into transparent, thermal-resistant, and hydrophobic fabric coatings, whose functions are extremely challenging for the textile market. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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14 pages, 3599 KiB

Open AccessArticle

Characterization of Polyorganosilazane-Derived Hybrid Coatings for the Corrosion Protection of Mild Steel in Chloride Solution

by Michele Fedel, Francisco Javier Rodríguez Gómez, Stefano Rossi and Flavio Deflorian

Coatings 2019, 9(10), 680; https://doi.org/10.3390/coatings9100680 - 19 Oct 2019

Cited by 19 | Viewed by 3589

Abstract

Polysilazane (PSZ) have been used for many years as precursors for the development of ceramic materials. Recently, hydrocarbon-substituted polysilazane, which is called organopolysilazane (OPSZ), has been proposed as possible alternative to silanes for the corrosion protection of metals by the sol gel route. [...] Read more.

Polysilazane (PSZ) have been used for many years as precursors for the development of ceramic materials. Recently, hydrocarbon-substituted polysilazane, which is called organopolysilazane (OPSZ), has been proposed as possible alternative to silanes for the corrosion protection of metals by the sol gel route. In this work, polymethyl(hydro)/polydimethylsilazane-derived coatings were deposited on low-carbon steel for corrosion protection purposes. The effect of the OPSZ precursor concentration (10–40 v/v %) in butyl-acetate on the final properties of the coatings was investigated. Coatings in the thickness range of 1 to 3.5 µm were obtained. The experimental results showed that the concentration of OPSZ in the solvent affects the structural properties as well as the dry film thickness of the hybrid layer. In particular, the network arrangement seems to be influenced by the dilution of the OPSZ precursors solution. The electrochemical characterization revealed that a minimum thickness of about 2 to 3 µm is needed to provide the mild steel substrate with enhanced corrosion protection properties compared to the bare substrate. Comparing the obtained results with literature data, it seems that OPSZs are a potential alternative to coatings derived from organisilicon precursors. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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32 pages, 9840 KiB

Open AccessFeature PaperArticle

Protection of Aluminum Alloy 3003 in Sodium Chloride and Simulated Acid Rain Solutions by Commercial Conversion Coatings Containing Zr and Cr

by Maja Mujdrica Kim, Barbara Kapun, Urša Tiringer, Gavrilo Šekularac and Ingrid Milošev

Coatings 2019, 9(9), 563; https://doi.org/10.3390/coatings9090563 - 03 Sep 2019

Cited by 16 | Viewed by 4746

Abstract

The morphology, composition and corrosion properties of commercial hexafluoro-zirconate trivalent chromium coatings (SurTec^® 650) deposited on chemically cleaned aluminum alloy 3003 were studied. The coatings were deposited at room temperature using different concentrations of SurTec^® 650 (10, 25 and 50 vol.%) [...] Read more.

The morphology, composition and corrosion properties of commercial hexafluoro-zirconate trivalent chromium coatings (SurTec^® 650) deposited on chemically cleaned aluminum alloy 3003 were studied. The coatings were deposited at room temperature using different concentrations of SurTec^® 650 (10, 25 and 50 vol.%) and different conversion times (90 s, 11 min and 18 min). Scanning electron microscopy with energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy and time-of-flight secondary ion spectrometry were employed to investigate the surface morphology, composition and thickness of uncoated and coated AA3003 samples. The morphology of the coating varied from uniform nodular to non-uniform and cracked; coatings were deposited at intermetallic particles and at the alloy matrix. The main constituents of conversion coatings were Zr(IV) and Cr(III) oxides; in addition to oxides, fluorides were also formed. The corrosion properties were investigated in two solutions: more aggressive sodium NaCl and less aggressive simulated acid rain. These commercial conversion coatings exhibited a good corrosion resistance but only after longer immersion in solution, i.e., 24 h. The results reveal an interesting behavior of zirconate-based coatings on aluminum-manganese alloy. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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13 pages, 11683 KiB

Open AccessEditor’s ChoiceArticle

Layered Double Hydroxide Clusters as Precursors of Novel Multifunctional Layers: A Bottom-Up Approach

by Cristina S. Neves, Alexandre C. Bastos, Andrei N. Salak, Maksim Starykevich, Daisy Rocha, Mikhail L. Zheludkevich, Angela Cunha, Adelaide Almeida, João Tedim and Mário G.S. Ferreira

Coatings 2019, 9(5), 328; https://doi.org/10.3390/coatings9050328 - 21 May 2019

Cited by 19 | Viewed by 4091

Abstract

The specific microstructure of aluminum alloys is herein explored to grow spatially-resolved layered double hydroxide (SR-LDH) clusters on their surface. Upon chemical modification of LDHs via intercalation, adsorption and grafting with different functional molecules, novel surface-engineered surfaces were obtained. Crystal structure and phase [...] Read more.

The specific microstructure of aluminum alloys is herein explored to grow spatially-resolved layered double hydroxide (SR-LDH) clusters on their surface. Upon chemical modification of LDHs via intercalation, adsorption and grafting with different functional molecules, novel surface-engineered surfaces were obtained. Crystal structure and phase composition were analyzed by X-ray diffraction (XRD) and surface morphology was observed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectrometry (GDOES) were used to correlate structural changes upon ion-exchange and interfacial modifications with chemical composition and surface profiles of the SR-LDH films, respectively. The protection conferred by these films against localized corrosion was investigated at microscale using the scanning vibrating electrode technique (SVET). LDH-NO₃ phase was obtained by direct growth onto AA2024 surface, as evidenced by (003) and (006) XRD diffraction reflections. After anion exchange of nitrate with 2-mercaptobenzothiazole (MBT) there was a decrease in the SR-LDH thickness inferred from GDOES profiles. The subsequent surface functionalization with HTMS was confirmed by the presence of Si signal in XPS and GDOES analyses, leading to an increase in the water contact angle (c.a 144° ± 3°). SVET measurements of the SR-LDH films revealed exceptional corrosion resistance, whereas the bioluminescent bacteria assay proved the anti-microbial character of the obtained films. Overall the results obtained show an effective corrosion protection of the SR-LDHs when compared to the bare substrate and the potential of these films for biofouling applications as new Cr-free pre-treatments. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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