Editorial

3 pages, 179 KiB

Open AccessEditorial

Special Issue “Recent Developments on Functional Coatings for Industrial Applications”

by Luigi Calabrese and Edoardo Proverbio

Coatings 2020, 10(11), 1017; https://doi.org/10.3390/coatings10111017 - 22 Oct 2020

Cited by 2 | Viewed by 1640

“Recent Developments on Functional Coatings for Industrial Applications” assessed some emerging aspects concerning the recent research progress in the designing, manufacturing and tailoring of new functional coatings for industrial applications. The purpose was to address the recent development in functional coatings synthesis, characterization [...] Read more.

“Recent Developments on Functional Coatings for Industrial Applications” assessed some emerging aspects concerning the recent research progress in the designing, manufacturing and tailoring of new functional coatings for industrial applications. The purpose was to address the recent development in functional coatings synthesis, characterization and optimization, highlighting its emerging industrial applicability in many industrial fields, such as self-healing, self-cleaning or sustainable energy technologies. The multidisciplinary nature of the issue represents an added value aimed at better enhancing the practical relevance and the technological versatility of the functional surface engineering design. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

Research

Jump to: Editorial, Review

11 pages, 3157 KiB

Open AccessArticle

Effect of Urethane Crosslinking by Blocked Isocyanates with Pyrazole-Based Blocking Agents on Rheological and Mechanical Performance of Clearcoats

by Young-Gun June, Kevin Injoe Jung, Moonhyun Choi, Tae Hee Lee, Seung Man Noh and Hyun Wook Jung

Coatings 2020, 10(10), 961; https://doi.org/10.3390/coatings10100961 - 07 Oct 2020

Cited by 14 | Viewed by 3904

Abstract

A novel blocked isocyanate crosslinker was synthesized, and its applicability was investigated for the low-temperature curing of automotive clearcoats. Various pyrazole derivatives were prepared as blocking agents in isocyanate crosslinkers, which strongly affect the deblocking and curing properties of the urethane-bonded coating systems. [...] Read more.

A novel blocked isocyanate crosslinker was synthesized, and its applicability was investigated for the low-temperature curing of automotive clearcoats. Various pyrazole derivatives were prepared as blocking agents in isocyanate crosslinkers, which strongly affect the deblocking and curing properties of the urethane-bonded coating systems. The thermal curing properties of clearcoat samples containing a pyrazole-based blocked isocyanate crosslinker and polyol resin were characterized under two different temperature conditions (120 and 150 °C). The decrease in the amount of hydroxyl groups in the polyol before and after curing was expressed by the change in OH stretching frequency in the Fourier transform infrared (FT-IR) spectra. The real-time rheological storage moduli of the bulk clearcoat mixtures were measured via a rotational rheometer to determine the effect of pyrazole-based blocking agents on the curing dynamics. In addition, a rigid-body pendulum tester (RPT) was employed to investigate the curing behavior in the thin film form. The nano-indentation and the nano-scratch tests were conducted to examine the surface hardness and scratch resistance characteristics of the cured clearcoat films. The results show that a low-temperature curing system of clearcoats can be realized by tuning the curing temperature and reactivity of isocyanate crosslinkers blocked with pyrazole-based substituents. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Figure 1

12 pages, 7484 KiB

Open AccessArticle

Anodic Protection Assessment Using Alumina-Forming Alloys in Chloride Molten Salt for CSP Plants

by Angel G. Fernández and Luisa F. Cabeza

Coatings 2020, 10(2), 138; https://doi.org/10.3390/coatings10020138 - 04 Feb 2020

Cited by 21 | Viewed by 2745

Abstract

The generation of a natural protective coating in alumina-forming alloys was analyzed using a ternary chloride molten salt as a thermal energy storage material for concentrated solar power (CSP) technology. The formation of the protective layer was monitored using electrochemical impedance spectroscopy (EIS). [...] Read more.

The generation of a natural protective coating in alumina-forming alloys was analyzed using a ternary chloride molten salt as a thermal energy storage material for concentrated solar power (CSP) technology. The formation of the protective layer was monitored using electrochemical impedance spectroscopy (EIS). A protective layer model for the OCT alloy and a localized corrosion model for the OCI and OC4 alloys were obtained after 5 h of immersion. The corrosion rates calculated using the linear polarization technique (LPR), were 8.03, 21.55, and 7.61 mm/year for OC4, OCI, and OCT alloys, respectively. These results were confirmed by scanning electron microscopy and X-ray diffraction. Our analysis showed that MgAl₂O₄ was the main protective coating generated by the alumina-forming alloys. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Figure 1

19 pages, 8133 KiB

Open AccessFeature PaperArticle

Effect of Pulse Current Mode on Microstructure, Composition and Corrosion Performance of the Coatings Produced by Plasma Electrolytic Oxidation on AZ31 Mg Alloy

by Maryam Rahmati, Keyvan Raeissi, Mohammad Reza Toroghinejad, Amin Hakimizad and Monica Santamaria

Coatings 2019, 9(10), 688; https://doi.org/10.3390/coatings9100688 - 22 Oct 2019

Cited by 33 | Viewed by 4203

Abstract

Plasma electrolytic oxidation (PEO) coatings were grown on AZ31 Mg alloy in a silicate-based electrolyte containing KF using unipolar and bipolar (usual and soft-sparking) waveforms. The coatings were dual-layered consisting of MgO, MgF₂ and Mg₂SiO₄ phases. Surface morphology of [...] Read more.

Plasma electrolytic oxidation (PEO) coatings were grown on AZ31 Mg alloy in a silicate-based electrolyte containing KF using unipolar and bipolar (usual and soft-sparking) waveforms. The coatings were dual-layered consisting of MgO, MgF₂ and Mg₂SiO₄ phases. Surface morphology of the coatings was a net-like (scaffold) containing a micro-pores network, micro-cracks and granules of oxide compounds. Deep pores were observed in the coating produced by unipolar and usual bipolar waveforms. The soft-sparking eliminated the deep pores and produced the lowest porosity in the coatings. It was found that the corrosion performance of the coatings evaluated using EIS in 3.5 wt. % NaCl solution is mostly determined by the inner layer resistance, because of its higher compactness. After 4 days of immersion, the inner layer resistances were almost the same for all coatings. However, the coatings produced by unipolar and usual bipolar waveforms showed sharp decays in inner layer resistances after 1 week and even the barrier effect of outer layer was lost for the unipolar-produced coating after 3 weeks. The low-frequency inductive loops appeared after a 3-week immersion for all coatings indicated that the substrate was under local corrosion attack. However, both coatings produced by soft-sparking waveforms provided the highest corrosion performance. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Graphical abstract

12 pages, 5849 KiB

Open AccessFeature PaperArticle

Manufacturing and Assessment of Electrospun PVP/TEOS Microfibres for Adsorptive Heat Transformers

by Patrizia Frontera, Mikio Kumita, Angela Malara, Junya Nishizawa and Lucio Bonaccorsi

Coatings 2019, 9(7), 443; https://doi.org/10.3390/coatings9070443 - 16 Jul 2019

Cited by 16 | Viewed by 3958

Abstract

A new adsorbent coating for the adsorber unit of an adsorption heat pump made of hybrid, organic–inorganic microfibres was prepared and characterized. Different coatings were obtained by the electrospinning of polyvinylpyrrolidone (PVP) solutions added with different quantities of tetraethyl orthosilicate (TEOS). PVP is [...] Read more.

A new adsorbent coating for the adsorber unit of an adsorption heat pump made of hybrid, organic–inorganic microfibres was prepared and characterized. Different coatings were obtained by the electrospinning of polyvinylpyrrolidone (PVP) solutions added with different quantities of tetraethyl orthosilicate (TEOS). PVP is a polymer with water adsorption capability and the TEOS addition allowed to increase the thermal stability of microfibres. The aim, indeed, was to preserve the polymeric structure of microfibres in order to obtain coatings with high flexibility and mechanical strength. The results demonstrated that TEOS concentrations in the range of 5–13 wt.% produced microfibre coatings of non-woven textile structure with both good water affinity and good thermal stability. SEM images of coatings showed that the deposited microfibre layers have both a high surface area and a high permeability representing a significant advantage in adsorption systems. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Figure 1

15 pages, 3684 KiB

Open AccessFeature PaperArticle

Assessment of Super-Hydrophobic Textured Coatings on AA6082 Aluminum Alloy

by Luigi Calabrese, Amani Khaskhoussi, Salvatore Patane and Edoardo Proverbio

Coatings 2019, 9(6), 352; https://doi.org/10.3390/coatings9060352 - 29 May 2019

Cited by 15 | Viewed by 4152

Abstract

Superhydrophobicity is one of the most required surface properties for a wide range of application such as self-cleaning, anti-corrosion, oil-water separation, anti-icing, and anti-bioadhesion. Recently, several methods have been developed to produce nature inspired super-hydrophobic surfaces. Nevertheless, these methods require a complicated process [...] Read more.

Superhydrophobicity is one of the most required surface properties for a wide range of application such as self-cleaning, anti-corrosion, oil-water separation, anti-icing, and anti-bioadhesion. Recently, several methods have been developed to produce nature inspired super-hydrophobic surfaces. Nevertheless, these methods require a complicated process and expensive equipment. In order to overcome these issues, we propose three different methods to obtain nature-inspired super-hydrophobic surfaces: short-term treatment with boiling water, HF/HCl and HNO₃/HCl concentrated solution etching. Afterwards, a thin layer of octadecylsilane was applied by in situ polymerization on all pre-treated surfaces. Eventually, all substrates were dried for 3 h at 100 °C to complete the silane curing. Scanning electron microscopy (SEM), contact angle measuring system and atomic force microscope (AFM) were used to characterize the surfaces. Surface morphology analysis showed that each method results in a specific dual hierarchical nano-/micro-structure. The corresponding water contact angles ranged from 160° to nearly 180°. The best results were observed for HF etched Al 6082 surface were water contact angle above 175° was achieved. Furthermore, a scheme able to assess the relationship between hydrophobic behavior and surface morphology was finally proposed. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Figure 1

16 pages, 4433 KiB

Open AccessFeature PaperArticle

PVB/ATO Nanocomposites for Glass Coating Applications: Effects of Nanoparticles on the PVB Matrix

by Silvia Pizzanelli, Claudia Forte, Simona Bronco, Tommaso Guazzini, Chiara Serraglini and Lucia Calucci

Coatings 2019, 9(4), 247; https://doi.org/10.3390/coatings9040247 - 12 Apr 2019

Cited by 9 | Viewed by 4649

Abstract

Films made of poly(vinyl butyral) (PVB) and antimony-doped tin oxide (ATO) nanoparticles (NPs), both uncoated and surface-modified with an alkoxysilane, were prepared by solution casting at filler volume fractions ranging from 0.08% to 4.5%. The films were characterized by standard techniques including transmission [...] Read more.

Films made of poly(vinyl butyral) (PVB) and antimony-doped tin oxide (ATO) nanoparticles (NPs), both uncoated and surface-modified with an alkoxysilane, were prepared by solution casting at filler volume fractions ranging from 0.08% to 4.5%. The films were characterized by standard techniques including transmission electron microscopy, thermogravimetric analysis and differential scanning calorimetry (DSC). In the polymeric matrix, the primary NPs (diameter ~10 nm) aggregate exhibiting different morphologies depending on the presence of the surface coating. Coated ATO NPs form spherical particles (with a diameter of 300–500 nm), whereas more elongated fractal structures (with a thickness of ~250 nm and length of tens of micrometers) are formed by uncoated NPs. The fraction of the polymer interacting with the NPs is always negligible. In agreement with this finding, DSC data did not reveal any rigid interface and ¹H time domain nuclear magnetic resonance (NMR) and fast field-cycling NMR did not show significant differences in polymer dynamics among the different samples. The ultraviolet-visible-near infrared (UV-Vis-NIR) transmittance of the films decreased compared to pure PVB, especially in the NIR range. The solar direct transmittance and the light transmittance were extracted from the spectra according to CEN EN 410/2011 in order to test the performance of our films as plastic layers in laminated glass for glazing. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Figure 1

Review

Jump to: Editorial, Research

27 pages, 3748 KiB

Open AccessReview

Coatings for Automotive Gray Cast Iron Brake Discs: A Review

by Omkar Aranke, Wael Algenaid, Samuel Awe and Shrikant Joshi

Coatings 2019, 9(9), 552; https://doi.org/10.3390/coatings9090552 - 27 Aug 2019

Cited by 59 | Viewed by 16070

Abstract

Gray cast iron (GCI) is a popular automotive brake disc material by virtue of its high melting point as well as excellent heat storage and damping capability. GCI is also attractive because of its good castability and machinability, combined with its cost-effectiveness. Although [...] Read more.

Gray cast iron (GCI) is a popular automotive brake disc material by virtue of its high melting point as well as excellent heat storage and damping capability. GCI is also attractive because of its good castability and machinability, combined with its cost-effectiveness. Although several lightweight alloys have been explored as alternatives in an attempt to achieve weight reduction, their widespread use has been limited by low melting point and high inherent costs. Therefore, GCI is still the preferred material for brake discs due to its robust performance. However, poor corrosion resistance and excessive wear of brake disc material during service continue to be areas of concern, with the latter leading to brake emissions in the form of dust and particulate matter that have adverse effects on human health. With the exhaust emission norms becoming increasingly stringent, it is important to address the problem of brake disc wear without compromising the braking performance of the material. Surface treatment of GCI brake discs in the form of a suitable coating represents a promising solution to this problem. This paper reviews the different coating technologies and materials that have been traditionally used and examines the prospects of some emergent thermal spray technologies, along with the industrial implications of adopting them for brake disc applications. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Figure 1

25 pages, 3716 KiB

Open AccessReview

A Brief Overview on the Anticorrosion Performances of Sol-Gel Zeolite Coatings

by Luigi Calabrese and Edoardo Proverbio

Coatings 2019, 9(6), 409; https://doi.org/10.3390/coatings9060409 - 24 Jun 2019

Cited by 24 | Viewed by 6046

Abstract

Research activity concerning nanoporous zeolites has grown considerably in recent decades. The structural porosity of zeolites provides versatile functional properties such as molecular selectivity, ion and molecule storage capacity, high surface area, and pore volume which combined with excellent thermal and chemical stability [...] Read more.

Research activity concerning nanoporous zeolites has grown considerably in recent decades. The structural porosity of zeolites provides versatile functional properties such as molecular selectivity, ion and molecule storage capacity, high surface area, and pore volume which combined with excellent thermal and chemical stability can extend its application fields in several industrial sectors. In such a context, anti-corrosion zeolite coatings are an emerging technology able to offer a reliable high performing and environmental friendly alternative to conventional chromate-based protective coatings. In this article, a focused overview on anti-corrosion performances of sol-gel composite zeolite coatings is provided. The topic of this review is addressed to assess the barrier and self-healing properties of composite zeolite coating. Based on results available in the literature, a property–structure relationship of this class of composites is proposed summarizing, furthermore, the competing anti-corrosion active and passive protective mechanisms involved during coating degradation. Eventually, a brief summary and a future trend evaluation is also reported. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Recent Developments on Functional Coatings for Industrial Applications

Share This Special Issue

Special Issue Editors

Special Issue Information

Related Special Issue

Published Papers (9 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI