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The aim of this work was to examine the advantages and disadvantages of using spirulina-derived pigment as a bio-based colorant for wood impregnators. It investigated the effects of three different quantities of spirulina granules on the aesthetic properties and durability of a water-based wood impregnator. The impact of this environmental friendly pigment on the overall appearance of the coatings was estimated through colorimetric measurements and observations using an optical microscope. The durability of the coatings with varying amounts of spirulina was assessed by subjecting the samples to UV-B radiation and cyclic thermal shocks and analyzing them using infrared spectroscopy and colorimetric inspections. Furthermore, the influence of additive concentration on the coating’s barrier efficiency was examined through liquid resistance and water uptake tests. Finally, the scrub test was carried out to assess the effect of the spirulina pigment on the abrasion resistance properties of the protective layers. Ultimately, this study emphasized the remarkable coloration achieved through the use of the spirulina-based additive. However, the pigment derived from natural sources exhibited significant concerns associated with deterioration caused by UV-B radiation or the fading of the phycocyanin component found in spirulina. Thus, the work underscores the importance of implementing appropriate measures to safeguard the bio-based pigment from external factors such as temperature, solar radiation, and liquids.

This study aims to assess the effect of hollow glass microspheres of different sizes derived from glass industry waste on the durability and thermal behavior of waterborne paint. The coatings were characterized by electron microscopy to investigate the distribution of the spheres and their influence on the layer morphology. The impact of the various glassy spheres on the mechanical feature of the coatings was assessed using the Buchholz hardness test and the Scrub abrasion test. The role of the spheres in altering the durability of the samples was analyzed by the salt spray exposure test and the electrochemical impedance spectroscopy measurements. Finally, a specific accelerated degradation test was carried out to explore the evolution of the thermal behavior of the composite coatings. Ultimately, this work revealed the pros and cons of using hollow glass spheres as a multifunctional paint filler, highlighting the size of the spheres as a key parameter. For example, spheres with adequate size (25–44 µm), totally embedded in the polymeric matrix, are able to reduce the thermal conductivity of the coating avoiding local heat accumulation phenomena.

Porcelain enamels are silica-based inorganic coatings, which are successfully applied to different kind of metallic substrates in applications where high chemical resistance and corrosion protection are needed. The main weakness of enamel coatings is represented by the glassy and brittle nature of the matrix: therefore, it is necessary to find some solutions to address this issue effectively and improve their resistance to abrasion. Some recent papers about the production of composite enamels with Al2O3 particles showed that a high concentration of corundum particles (10–20 wt%) could improve the abrasion resistance of these coatings. This work is focused on studying the influence of micro and macro sized corundum particles on the abrasion and chemical resistance of composite enamel coatings. The Al2O3 particles are added in 20 wt % concentration and the firing treatment is optimized for every sample type. The coatings topography and morphology are mainly characterized by scanning electron microscopy measurements and Energy Dispersive X-ray (EDX) microanalysis. The abrasion resistance of the coatings is evaluated by P.E.I. abrasion test. Mass loss and roughness measurements are used to assess the coatings surface properties during the mechanical damage; in addition, Electrochemical Impedance Spectroscopy (EIS) measurements and electron microscopy observations are carried out after 5000 P E.I. abrasion cycles to evaluate the decrease of the coatings protection properties due to mechanical damage. Finally, the coatings chemical resistance is evaluated by exposure to an aggressive fog with the presence of SO2 (Kesternich test), simulating an industrial environment. The addition of macro sized alumina particles leads to an improvement of the coating abrasion resistance, without a loss in the protection properties. Differently, the addition of micro sized alumina particles produces an increase of the coating surface roughness and results to have detrimental effects on the behaviour of the coating in aggressive environments.

Vitreous enamels represent a class of coatings with different technological properties, mainly appreciated for the protection they guarantee to the covered substrates. This review introduces enamel coatings, describing their production technologies and presenting the main properties affecting the enamel’s durability. Firstly, this review article introduces the most important studies regarding the improvement in abrasion resistance, highlighting both successes and failures. Afterward, the work reveals an outlook about the resistance to chemicals, underlining the good resistance of enamels toward acidic chemicals and discussing the results of studies aimed to improve their performances toward alkaline solutions. This review also considers the corrosion protection property of enamels, highlighting the high barrier effect they provide against the absorption of aggressive substances toward metal substrates. Finally, new perspectives and possible future research paths are presented, being aware that this kind of coating offers both good product protection and functional integrity over time.

Today, the use of silver in surfaces for public environments is very frequent, as it ensures high antimicrobial activities, avoiding the continuous disinfection of the surfaces themselves. Similarly, thanks to its interesting combination of technological properties, anodized aluminum is widely employed in the production of components for applications in public spaces. Therefore, this work describes a simple method of the codeposition of silver and anodized aluminum to combine the remarkable properties of Al

In this work, colloidal silver has been added into an acrylic clear cataphoretic bath, evaluating the effect of two different filler amounts on the durability of the composite coatings. The three series of samples were characterized by electron microscopy to assess the possible change in morphology introduced by the silver-based additive. The protective properties of the coatings were evaluated by a salt spray chamber exposure and electrochemical impedance spectroscopy measurements, evidencing the negative effect provided by high amount of silver, which introduced discontinuities in the acrylic matrix. Finally, the durability of composite coatings was studied by exposing them to UV-B radiation, observing a strong phenomenon of silver degradation. Although the coating containing high concentrations of silver demonstrated poor durability, this study revealed that small amounts of silver can be used to provide particular aesthetic features, but also to improve the protective performance of cataphoretic coatings.

This work aims to reveal the effect of a high amount of cellulose fibers on the durability and protective behavior of a bio-based wood paint. The influence of the filler on the morphology of the coatings was investigated by scanning electron microscopy observations, while the durability of the paint was evaluated by exposing the samples to UV-B radiation and continuous thermal shocks. Infrared spectroscopy analysis, colorimetric inspections, adhesion tests and scanning electron microscope observations were employed to assess the role of the high concentrations of fillers in affecting the resilience of the acrylic matrix. Moreover, the impact of the filler on the barrier performance of the coatings was estimated using a liquid resistance test and a water uptake test. Finally, the mechanical properties of hardness and abrasion resistance of the layers were evaluated by means of the Buchholz Hardness Indentation test and the Scrub test. Ultimately, this study demonstrates the pros and cons of using large amounts of cellulose fibers as filler in wood paint: the work warns against the excessive use of these fibers, which need a threshold limit so as not to significantly change the coating’s structure and thereby weaken its protective properties.

This study aims to validate an effective methodological analysis for the characterization of the adhesion values of antistick coatings employed in cooking systems. The morphology and chemistry of four different industrial products were investigated by roughness measurements, electron microscopy observations and infrared spectroscopy analysis. The adhesion of the coatings was evaluated comparing various techniques, such as the surface contact angle measurements, the pull-off test and the single lap-joint tensile shear method, in synergy with degradation phenomena simulated by P.E.I. abrasion and dishwashing tests. The single lap-joint tensile shear test was able to evaluate evident differences between all the proposed coatings, regardless of their state of deterioration, featuring the best selectivity among the used methods. However, the pull-off test proved to be a viable and more economical alternative for fast evaluation techniques, considering the overall instrument costs. While all the polytetrafluoroethylene-based systems turned out to be totally uninfluenced by the chemical attacks performed during the dishwasher cycles, the sol–gel coating exhibited lower performances of the applied releasing agent, before and after the mechanical degradation tests. Therefore, sol–gel coatings, despite being proposed as valid alternatives to PTFE ones, do not achieve the same quality standards in terms of releasing properties, being in addition much more sensible to degradation and loss in performances.

The emergence and spreading of the SARS-CoV-2 pandemic has forced the focus of attention on a significant issue: the realization of antimicrobial surfaces for public spaces, which do not require extensive use of disinfectants. Silver represents one of the most used elements in this context, thanks to its excellent biocidal performance. This work describes a simple method for the realization of anodized aluminum layers, whose antimicrobial features are ensured by the co-deposition with silver nitrate. The durability and the chemical resistance of the samples were evaluated by means of several accelerated degradation tests, such as the exposure in a salt spray chamber, the contact with synthetic sweat and the scrub test, highlighting the residual influence of silver in altering the protective behavior of the alumina layers. Furthermore, the ISO 22196:2011 standard was used as the reference protocol to set up an assay to measure the effective antibacterial activity of the alumina-Ag layers against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, even at low concentrations of silver. Finally, the Ag-containing aluminum oxide layers exhibited excellent antimicrobial performances also following the chemical–physical degradation processes, ensuring good durability over time of the antimicrobial surfaces. Overall, this work introduces a simple route for the realization of anodized aluminum surfaces with excellent antibacterial properties.

In this study, olive pit powders were added to a polyurethane-acrylate paint for examining the impact of two alternative functionalization processes in increasing the filler hydrophobicity in an effort to increase the durability of the paint. In order to look into potential changes in morphology and appearance owing to the surface conversion treatments of the two bio-based additives, the coatings were examined using electron microscopy and colorimetric tests. The coating’s resilience and the hydrophobic/hydrophilic role of the fillers were evaluated by salt spray chamber exposure, contact angle measurements, paint liquid resistance, UV-B exposure, and electrochemical impedance spectroscopy measurements, which highlighted the reduction in water absorption inclination of the filler made of lignocellulose due to the silane and wax functionalization. This study demonstrated that the bio-based filler, if properly functionalized, can actually be implemented as multifunctional pigment in waterborne paints, giving specific aesthetic characteristics, but also improving the barrier performance of the polymeric matrix and increasing the durability of the composite coating.

Frequently touched surfaces (FTS) that are contaminated with pathogens are one of the main sources of nosocomial infections, which commonly include hospital-acquired and healthcare-associated infections (HAIs). HAIs are considered the most common adverse event that has a significant burden on the public’s health worldwide currently. The persistence of pathogens on contaminated surfaces and the transmission of multi-drug resistant (MDR) pathogens by way of healthcare surfaces, which are frequently touched by healthcare workers, visitors, and patients increase the risk of acquiring infectious agents in hospital environments. Moreover, not only in hospitals but also in high-traffic public places, FTS play a major role in the spreading of pathogens. Consequently, attention has been devoted to developing novel and alternative methods to tackle this problem. This study planned to produce and characterize innovative functionalized enameled coated surfaces supplemented with 1% AgNO3 and 2% AgNO3. Thus, the antimicrobial properties of the enamels against relevant nosocomial pathogens including the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli and the yeast Candida albicans were assessed using the ISO:22196:2011 norm.

This study aims to demonstrate the remarkable features of graphene-based fillers, which are able to improve the protective performance of acrylic coatings. Furthermore, the joint application of a cataphoretic primer and a spray top coat, containing graphene and functionalized graphene oxide flakes, respectively, enables the deposition of a double-layer coating with high conductivity and abrasion resistance properties, capable of offering excellent corrosion resistance to the metal substrate. The surface morphology of the single- and double-layer coatings was investigated by optical and electron microscopies, analysing the defectiveness introduced in the polymer matrix due to the filler agglomeration. The behavior in aggressive environments was assessed by exposure of the samples in the salt spray chamber, evaluating the blister formation and the adhesion level of the coatings. Electrochemical impedance spectroscopy measurements were employed to study the corrosion protection properties of the coatings, whose conductivity and abrasion resistance features were analysed by conductivity assessment and scrub tests, respectively. The incorporation of graphene-based fillers in the cataphoretic primer improves the corrosion protection properties of the system, while the graphene flakes provide the top coat spray layer with high conductivity and excellent abrasion resistance features. Thus, this work demonstrates the possibility of employing different types of graphene-based fillers and deposition methods for the creation of multifunctional coatings.

The effect of over-heating in urban areas, called the urban heat island effect (UHI effect), is responsible for greater energy consumption for cooling buildings. Several reflective near-infrared (NIR) coatings, called cool coatings have proved to be effective for contrasting the UHI effect. The thermal and appearance properties of cool coatings depend on the color and they often have been studied only at the initial state, without undergoing atmospheric degradation and soiling. In this work, the thermal, visual and durability behaviors of red and brown polyester-based organic coatings for roof applications were studied. All samples were subjected to accelerated degradation cycles composed of UV-B and salt spray chamber exposure. The sample degradation was assessed by infrared spectroscopy, gloss and colorimetric analyses. Moreover, the thermal behavior was studied by means of a simplified experimental setup. Finally, a soiling and weathering test was conducted to simulate the soiling of three years&rsquo, external exposure. Despite the phenomena of chemical degradation and a decrease in aesthetic properties, the samples maintain their thermal performance, which is not even influenced by dirt products. In addition, NIR pigments significantly improve the thermal behavior of brown coatings.

The vitreous enamel coatings present very interesting properties for several industrial applications due to the glassy nature of the matter. Their chemical resistance and corrosion protection properties result very high due to the glassy nature of deposits. A good wear behavior is also requested in some applications. The use of composite layer obtained by the addition of hard particles to enamel could be a possible solution to increase the deposits hardness. In literature, there are some work about the chemical nature of the added particles, but the influence of the dimension and quantity of these particles are not well studied. The aim of this work is the study of composite enamel layers deposited on low carbon steel substrate with addition of Al2O3 particles characterized by macro and micro dimensions with different concentration (5, 10 and 20 wt.%). After the microstructure characterization, the abrasion resistance behavior is evaluated by Taber Test following ASTM C501 for 1500 cycles. Mass loss, gloss and roughness changes are collected. The protection properties change is evaluated by Electrochemical Impedance Spectroscopy measurements. The addition of micro dimension particles produces the best behavior. On the contrary, the presence of macro dimension particles reduces the abrasion resistance, probably caused by the increase of porosity level during firing treatment. Finally, the corrosion protection properties are evaluated by Kesternich test (aggressive fog with the presence of SO2), simulating an industrial environment. In this case the presence of the micro- particles shows a limited resistance. Probably the presence of the particles produces an increase of surface roughness and a presence of higher quantity of particles in surface, which favor the start of enamel degradation with a loss of protection properties. Increasing the quantity of particles, a reduction of chemical resistance is observed.

Graphene represents an innovative material, which possesses a unique combination of properties. The remarkable features of this material allow it to be often used as a reinforcing filler in organic based coatings. The excellent conductivity and mechanical strength properties of graphene produce a significant increase in the performance of the polymer matrix. Recently, however, scholars have focused on the barrier effect properties that can be provided by graphene flakes to obtain high corrosion resistance coatings. If well distributed in the polymeric matrix, in fact, the graphene-based sheets are able to provide a high resistance to the passage of aggressive ions, fundamental for the development of corrosion processes on the metal substrate. The distribution of graphene-based fillers, however, is a critical aspect, which can be improved by means of certain oxidation and functionalization processes of graphene flakes. Recent studies have shown the possibility of combining the excellent features of cataphoretic processes with the remarkable protective properties of graphene-based fillers in the creation of high-performance multifunctional composite coatings. The functionalized graphene oxide flakes, in the correct amount, can in fact increase the protective performance of cataphoretic coatings, as well as providing additional features such as mechanical strength and high conductivity.

This work aims to verify how the addition of graphene oxide into the cataphoretic bath goes to modify the properties of the obtained coating. Because a simple single-step deposition produced a strange morphology deposit, other combinations consisting of two deposition steps were done, in order to make the coating even more homogeneous and protective. Particular attention is therefore paid to the importance of the intermediate curing process, between the two deposition steps. The morphology of the coatings is analyzed by both optical and scanning electron microscopy, to measure the thickness of the protective layers and their defective properties. Finally, corrosion resistance properties of the coatings are evaluated by salt spray chamber exposure and electrochemical impedance spectroscopy measurements. It appears evident that the graphene oxide leads to the creation of defective layers, with the consequence of decreasing the durability of the coating. However, by depositing in two steps, with two different baths, it is possible to preserve the integrity of the coating, ensuring the protection of the substrate.

In many fields of application, the aluminium foam panels could undergo flexural loads or impact forces. The presence of a vitreous layer influences the foam's response. Four different enamel systems, deposited on aluminium closed-cell foam, are studied. The bending stiffness values are obtained using a 4-point bending test and then the Young's modulus and the strength are extrapolated using a transformed section method. To evaluate the cracking behavior an indentation test was performed. A better sintered filling increases the bending stiffness and strength, moreover the presence of a primer layer may cause an early fracture in the coating.

•Aluminum foams are a very interesting engineering materials.•The opened cells are critical for corrosion behavior.•Electrodeposited organic coating is a solution to guarantee corrosion protection properties.•The deposition parameters influence the protection performance of the paints.

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.

The functional properties displayed by graphene oxide (GO)-polymer nanocomposites are strongly affected by the dispersion ability of GO sheets in the polymeric matrix, which can be largely improved by functionalization with organosilanes. The grafting to GO of organosilanes with the general formula RSi(OCH3)3 is generally explained by the condensation reactions of silanols with GO reactive groups. In this study, the influence of the organic group on the RSi(OCH3)3 grafting ability was analyzed in depth, taking into account the interactions of the R end chain group with GO oxidized groups. Model systems composed of commercial graphene oxide reacted with 3-aminopropyltrimethoxysilane (APTMS), 3-mercaptopropyltrimethoxysilane (MPTMS), and 3-methacryloxypropyltrimethoxysilane, (MaPTMS), respectively, were characterized by natural abundance 13C, 15N and 29Si solid state nuclear magnetic resonance (NMR), x-ray diffraction (XRD), and electron spin resonance (ESR). The silane organic tail significantly impacts the grafting, both in terms of the degree of functionalization and direct interaction with GO reactive sites. Both the NMR and XRD proved that this is particularly relevant for APTMS and to a lower extent for MPTMS. Moreover, the epoxy functional groups on the GO sheets appeared to be the preferential anchoring sites for the silane condensation reaction. The characterization approach was applied to the GO samples prepared by the nitric acid etching of graphene and functionalized with the same organosilanes, which were used as a filler in acrylic coatings obtained by cataphoresis, making it possible to correlate the structural properties and the corrosion protection ability of the layers.

This study aims to assess the synergic effect of graphene-based filler and thermochromic pigments on the protective and aesthetical performances of cataphoretic acrylic coatings. The nature of the thermochromic pigments was investigated by electron microscopy observations and infrared spectroscopy analysis. The aesthetical features of the coatings were evaluated by colorimetric measurements, estimating the colour change with temperature due to the filler addition. The corrosion protection properties were assessed by means of salt spray chamber exposure and electrochemical impedance spectroscopy measurements, which evidenced a negative contribution of the combined presence of functionalized graphene oxide flakes and thermochromic pigments. Otherwise, the incorporation of both the two fillers improved the abrasion resistance of the cataphoretic coating, as observed thanks to scrub test, as well as its aesthetical performances after chemical degradation due to UV-B exposure. Thus, this work highlighted both the positive and the negative effects caused by the synergy of reinforcing graphene-based fillers and functional pigments on the properties of cataphoretic coatings.

Graphene is a particular type of material, made of a single crystal lattice layer of two dimensional honey-comb structure with excellent electrical, thermal and mechanical properties. Graphene oxide (GO) has been subjected to several studies in recent years. One of its possible applications concerns the production of composite coatings, to improve the protective properties of the coating itself together with other functional properties such as a remarkable conductivity. The cataphoretic electrodeposition process allows to obtain a coating with uniform thickness also with complex geometry, good adhesion properties, in a simple and economic way. To get good properties it is important to have a uniform distribution of graphene flakes, avoiding cluster formation, together with good adhesion between graphene particles and organic matrix. In this work, the effect of the graphene flakes addition in the organic coating was studied. The graphene flakes have been subjected to nitric acid oxidation treatment and functionalized with organosilane, to get a good dispersion in the acrylic cataphoretic bath. The deposits’ morphology was observed under optical and electronic microscope, to study the possible defectiveness of the coatings. The corrosion protection properties were evaluated by salt spray exposure test following the ASTM B117 standard and by electrochemical impedance spectroscopy measurements in chloride solution. The process parameters, as well as the concentration of functionalized graphene oxide inside the cataphoretic bath, have been optimized, obtaining composite coatings with excellent corrosion resistance properties. It has been verified that the presence of graphene in the cataphoretic coating allows to obtain a better behavior in an aggressive environment and corrosion protection of the metallic substrate. Finally, deposit conductivity was measured following ASTM D 257-07 standard.

In this work, functionalized graphene oxide (fGO) flakes have been added into an acrylic cataphoretic bath, studying the effect of fGO different concentration on the properties of the coatings deposited on carbon steel substrate. The samples were characterized by optical and electron microscopy, analyzing the distribution of the fGO flakes within the polymer matrix. The corrosion resistance properties were evaluated by salt spray chamber exposure and electrochemical impedance spectroscopy measurements. Finally, coatings’ conductivity was measured, in order to study the barrier effect performed by the flakes. The optimized fGO concentration, equal to 0.2 wt%, greatly increase the coating resistance in the aggressive environment.

The multiple properties of graphene can be exploited in the production of composite coatings to obtain multifunctional layers. To homogeneously disperse graphene in a polymer matrix, its sheets must be oxidised and properly functionalised. In this study, a fast, simple, and alternative method for the oxidation of graphene with nitric acid was studied. The obtained product was functionalised with three different organoalkoxysilanes. The obtained graphene flakes were subjected to infrared and X-ray analyses to study the oxidation grade and organosilane grafting. Several samples were produced by adding functionalised graphene oxide powder to an acrylic-based cataphoretic bath operating at four voltage values to evaluate the effective protective role of the powders. The morphology of the coatings was observed via optical and scanning electron microscopy (SEM) whereas their corrosion resistance properties were evaluated via salt spray chamber exposure and electrochemical impedance measurements. Although the oxidation level of graphene was low, the functionalisation was successful. The differences among the samples depended on the chemical properties of silane. By using (3-aminopropyl)trimethoxysilane (at sufficiently high voltages during the electrodeposition process), coatings with excellent properties, owing to the presence of functionalised graphene oxide sheets, were obtained.