Journal of Coatings Technology and Research最新文献

Intumescent fire-retardant coatings are widely applied as they combine designable aesthetics and fire protection without compromising substrate properties. When exposed to heat, intumescent fire-retardant coatings expand and build an insulating char. This study presents an investigation of the char by addition of kaolinite, barite, and titania as functional fillers in intumescent coatings. Expansion experiments at 400°C with custom build image analysis showed that kaolinite inhibited (0.03 mm/s, expansion factor ≈ 7), whereas barite acted synergistically on the expansion ability (0.59 mm/s, expansion factor ≈ 85). The resulting char density and the visual inspection showed that barite char was less compact, with cracks and voids. Evaluation of fire performance by single burning item tests resulted in Euroclass C for the barite system and Euroclass A2/B for the titania system. Post-heating chars demonstrated poor thermostability of barite char, and subsequent FTIR spectroscopy revealed that titania char formed the thermostable titanium pyrophosphate. Further inspection of the titania char revealed a uniform closed cell structure with mean bubble sizes of 26–56 µm. Titania coating expands rapidly (0.37 mm/s, expansion factor ≈ 60) and forms a structurally stable tumescent char with a compact and uniform porous structure exhibiting resistance to char oxidation at sustained heating.

Adhesion of bacteria and platelets on blood-contact implants and surgical devices is one of the causes of infections and thrombus. A superhydrophobic surface serving as a protective layer can minimize adhesion and contamination due to the low surface energy. The objective of this paper is to construct a superhydrophobic surface on a titanium implant by a combination of a topological structure and chemical coating. First, a micro/nano hierarchical morphology is obtained by sandblasting, acid-etching, and anodic oxidation. Then, a low surface energy coating material (fluoroalkylsilane, as the example case in this study) is used to modify the surface further. The effects of the morphology of micro and/or nanoscales and corresponding fluorination on the wettability are investigated. The results show that a hierarchical surface with microroughness and nanotubes is successfully constructed, and the contact angle (CA) is 44.9°, indicating good hydrophilicity. Interestingly, after being modified by fluoroalkylsilane, the surface converted from hydrophilic to superhydrophobic with a CA of 151.4°. In contrast, the fluorination modification of single micro or nanofeatures cannot achieve superhydrophobicity, indicating that the micro/nanostructures may show a synergistic effect for an efficient fluorination coating later on. Overall, our results demonstrate the feasibility of achieving a superhydrophobic surface via the micro/nano topological patterning and fluorination modification. The proposed method is expected to enrich the preparation technologies of superhydrophobic titanium surfaces.

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The goal of this research was to obtain a coating with low-infrared emissivity and both good hydrophobic and mechanical properties. Using nano-SiO₂ as the micro-nano structural modifier, a hydrogen-containing silicone oil (HCSO)-modified polyurethane (PU)/Al composite coating with super-hydrophobicity and low-infrared emissivity was prepared via a simple glass rod scraping method. Effects of the ratio of HCSO to PU, the total filler addition, and the ratio of Al powder and nano-SiO₂ on the coating properties are systematically discussed. The results show that as the ratio of HCSO to PU increases, the surface energy of the coating decreases, and this significantly increases the hydrophobicity of the coating. When the ratio is 2:8, the coating has outstanding hydrophobic properties, the adhesion strength of the coating reaches grade 1, and the water contact angle (WCA) reaches 152°. The total filler addition has a significant impact on the coating performance. With an increase in the filler addition, the emissivity of the coating increases, and the glossiness decreases. When the total filler addition is 50 wt%, the coating surface forms an obvious papillary micro-nano rough structure, so that the coating has outstanding hydrophobic properties. The ratio of Al powder to nano-SiO₂ obviously affects the emissivity and hydrophobic properties of the coating. When the ratio is 5.5:4.5, the coating has good overall performance. At this point, the emissivity of the coating is as low as 0.675; the glossiness and adhesion strength are 2.7 and grade 1, respectively; the WCA and sliding angle are 155° and 8°, respectively; and it has outstanding self-cleaning performance. Through the research in this paper, a low-infrared emissivity coating with outstanding super-hydrophobic properties and adhesion strength has been obtained and has important application value in the design and transformation of infrared stealth of various equipment.

An advanced long-term active corrosion protection coating for carbon steel was proposed using poly(aniline-aminosalicylic acid) nanofiber (PACA-f) covalently linked with cetyltrimethyl ammonium bromide (CTAB)-modified graphene oxide (CTGO). The proton-doped PACA-f functionalized CTGO (PACA-f/CTGO) exhibits excellent hydrophobicity and outstanding water resistance in waterborne epoxy polymer (WEP) coatings and better compatibility with WEP due to the formation of organic–inorganic networks. PACA-f/CTGO composite coating has a self-repairing function and shows superior corrosion resistance on Q235 steel. The surface-corrosion inhibition of PACA-f/CTGO on steel was investigated by molecular dynamics simulation(MD) which confirmed the chemical adsorption of the PACA-f/CTGO on the steel surface. The excellent water resistance and anticorrosion property of PACA-f/CTGO are ascribed to the high hydrophobicity of the hybrid coatings, the formation of intelligent passivation layer after the corrosive medium invading, and the barrier performance of CTGO.

An effective way to protect the steel surface from degradation is to develop a coating on top of the steel substrate. A wide variety of coating deposition processes are available to develop protective coatings on steel. To date, several processes like hot-dip galvanization (HDG), electrogalvanization (EG), and physical vapor deposition (PVD) have been investigated. Among them, the most commonly used methods are hot-dip galvanization and electrogalvanization. HDG is used extensively due to lower cost, shorter process time, the requirement of lesser maintenance, uniform protection, and ease of deposition at a larger scale. On the other hand, EG promises in providing advantages like versatility in the coating composition, good surface finish, uniformity in the coating, lower coating thickness, etc. Although both processes provide different advantages, there are always drawbacks limiting their applications. To overcome different limitations of conventional processes and for further advancement of protective coatings, PVD has received increased attention in recent years over hot dipping and electroplating. PVD process provides a more uniform deposit, higher accuracy, very low thickness, improved adhesion, a wider choice of materials, and no environmental pollution. In this paper, we review the scope and prospect of the PVD technique for the steel industry over HDG and EG. The paper focuses on different kinds of PVD techniques, their advantages, and disadvantages. An emphasis has been given to the recent development of Zn- and Al-based PVD coatings on steel substrates. The industrial competency of PVD in the steel industry has been discussed in this article. Challenges associated with the commercialization of the process and recommendations for further improvement have been discussed.

Free and microencapsulated thyme essential oils (Zataria multiflora Boiss) were incorporated into solvent and waterborne polyurethane coatings separately to enhance decay resistance of the biocide free coatings. The essential oil was extracted by hydro-distillation in a Clevenger-type apparatus for 4?h. Poly (methyl methacrylate) (PMMA) microcapsules containing thyme oil as an active ingredient were prepared through solvent evaporation method with oil in water emulsion system. Fungal resistance of the coated hornbeam wood (Carpinus?betulus) against white rot fungus Coriolus versicolor CTB 863 A and brown rot fungus Coniophora?puteana BAM Ebw. 15 was tested according to European EN?113 standard before and after six-cycle accelerated aging test (ASTM D1037). The results revealed that the core-shell capsules were formed properly, and their sizes were in the range of 5–50?μ. The encapsulation efficiency determined by UV–visible spectrophotometer at λ?=?275 nm was 67%. The free essential oil was not efficient enough to improve the fungal resistance, while the microencapsulated oil enhanced the resistance even after the accelerated aging via a controlled-release mechanism as well as protected the susceptible ingredients through the shielding effect of the polymeric shell.

Chitosan is an exciting alternative for the development of coating-surfaces due to its large action spectrum against pathogenic microorganisms. However, to produce a stable coating with effective antibacterial action, a compromise between deacetylation degree (DD) and molecular weight (MW) is essential. Four chitosan samples were characterized regarding Mw and DD and correlated with the minimum and bactericide concentrations against E. coli, P. aeruginosa, and S. aureus. CHI80MW (79.7% DD and 7.0 × 10⁵ Da) showed the best antibacterial effect and was selected to functionalize polytetrafluoroethylene (PTFE) surfaces by plasma. CHI80MW was grafted onto the PTFE surfaces using two different spacer molecules: poly(ethylene glycol) bis (carboxymethyl) ether (PEG) and poly(ethylene-alt-maleic anhydride) (PA). PTFE-Plasma-PA-CHI80MW exhibited a coating with more attached chitosan and better antibacterial action if compared to PTFE-Plasma-PEG-CHI80MW: after 8 h, PTFE-Plasma-PEG-CHI80MW presented a bacterial reduction of 25-30% for the three bacterial strains, and PTFE-Plasma-PA-CHI80MW reduced them to 77-90%. Moreover, cytotoxicity tests showed that PTFE-Plasma-PA-CHI80MW samples were compatible with human fibroblasts.

This paper investigates the gas jet wiping process, which is widely employed for controlling the final zinc-alloy coating thickness of a moving steel strip in the continuous hot-dip galvanizing process. In this study, large eddy simulation (LES) was employed to determine the effect of lower velocity symmetric auxiliary jets on main jet stabilization and coating thickness reduction during the gas jet wiping process. For validation purposes, experimental measurements of coating thickness were also carried out for the prediction of final coating thickness via a novel prototype multi-slot air knife used as the wiping actuator. Good agreement was found between the experimental measurements and model predictions for the coating weight, which also confirmed the applicability of the Elsaadawy et al.¹ model for the prediction of final coating weight for the multi-slot air knife geometry used. It was found that the jet flapping observed during single jet wiping could be prevented through use of the multi-slot air knife operating with lower velocity symmetric auxiliary jets (Re_a/Re_m =  0.45) situated on both sides of the main jet. The auxiliary jets modified the flow field in the main jet shear layer and diminished the formation of alternating vortices, which are the main cause of jet flow oscillations. As a result, a stabilized impinging flow with a longer potential core was found for the multi-slot jet configuration. This led to increased pressure gradient and increased shear stresses in the vicinity of the wiping region and, consequently, lower coating weights were obtained through use of the multi-slot air knife compared to the conventional single slot jet.

A manual scratch test to measure the scratch resistance of coatings applied to a certain substrate is usually used to test the adhesion of a coating. Despite its significant amount of subjectivity, the crosscut test is widely considered to be the most practical measuring method for adhesion strength with a good reliability. Intelligent software tools help to improve and optimize systems combining chemistry, engineering based on high-throughput formulation screening (HTFS) technologies and machine learning algorithms to open up novel solutions in material sciences. Nevertheless, automated testing often misses the link to quality control by the human eye that is sensitive in spotting and evaluating defects as it is the case in the crosscut test. In this paper, we present a method for the automated and objective characterization of coatings to drive and support Chemistry 4.0 solutions via semantic image segmentation using deep convolutional networks. The algorithm evaluated the adhesion strength based on the images of the crosscuts recognizing the delaminated area and the results were compared with the traditional classification rated by the human expert.

This article presents a concise review of different types of inhibitors for corrosion protection on metal surfaces. Corrosion inhibitors can be of different types, which include organic, inorganic and hybrid (organic/inorganic) materials. They are also classified as cathodic, anodic and/or mixed-type inhibitors, which are based on the active inhibitor molecules that retard the corrosion process. Silicate, nitrites, molybdates, phosphates, zinc salt and cerium salt are widely used as inorganic inhibitors. Many organic compounds have been widely utilized as inhibitors. Corrosion protection will be obtained by various mechanisms such as physisorption, chemisorption, barrier protection, thin-film formation and electrochemical processes. The type of inhibitors, inhibition mechanism and the evaluation methods have been explained in detail.