Degradation Of Coatings Research Articles

PREPARATION, CHARACTERIZATION, FUNCTION, AND DEGRADATION OF BIOPLASTICS FROM VEGETABLE WASTE COATING WITH POLYEUGENOL

This research aimed to prepare, characterize, function, and degrade bioplastics from vegetable waste via an ecofriendly method. The production of bioplastics using CH3COOH 1 M and blending with Polyvinyl Alcohol (PVA) in water, is easily saleable and does not involve the use of hazardous or organic chemicals, which raises environmental issues. Vegetable wastes like moringa (M), water spinach (WS), and green spinach (GS) blended with PVA were used to create free-standing, flexible bioplastic films. The result showed these bioplastics have tensile strength from 2.63- 6.70 MPa, elongation from 5.33-23.5 %, and modulus young from 13.67-51.30 MPa. Bioplastic's antioxidant properties belong to low antioxidants and coating bioplastic with polyeugenol can be increased antioxidant properties. Bioplastic from WS vegetable waste/PVA/Polyeugenol (PEU) can be used to increase the self-life of apple fruit. This research also examines the function and degradation of bioplastic from water spinach and its degradation. All these bioplastics were potentially applicable as active packaging material.

Thermal shock behavior and CMAS degradation of YSZ-Y2O3 and YSZ-Y2Zr2O7 double ceramic layered thermal barrier coatings

Thermal shock behavior and CMAS degradation of YSZ-Y2O3 and YSZ-Y2Zr2O7 double ceramic layered thermal barrier coatings

Data-driven AI for the automated classification of the isothermal heat-treated thermal barrier coatings using pulsed infrared thermography

Abstract Development of reliable age prediction models are crucial in monitoring the formation of oxide layer and degradation of TBC at regular intervals. This study proposes an automated classification of isothermal heat-treated TBC samples using temperature data, which helps in predicting the TBC life and monitoring the TBC degradation. TBC-coated samples are isothermal heat-treated at 1000 °C, and the initial growth of thermally grown oxide is monitored using a non-destructive thermal imaging technique. The proposed study integrates data-driven AI (DAI) models and feature extraction techniques to interpret complex thermal patterns measured from the TBC coating surface. The performance of the proposed classification framework is tested using deep learning and classical machine learning models with different types and window sizes of input data. Input data used for validation are raw experiment data, logarithmic of experiment data, polynomial fit data, and thermal signal reconstruction fit coefficients. The maximum classification performance is obtained with gated recurrent unit with accuracy and F1-score of 89.2% and 89.0%, respectively with raw temperature data as input of window 300. The study demonstrates that the proposed DAI approach effectively predicts the age of thermal barrier coatings under isothermal heat-treatment conditions by correlating the thermal response with coating degradation.

Natural Product-Based Pressure-Sensitive Adhesives via Carveol-Dithiothreitol Thiol-Ene Step-Growth Polymerization.

Pressure-sensitive adhesives occupy a large role in the commercial use of polymers; however, they are typically limited to nondegradable formulations using petroleum-based materials. As the plastic and environmental crises have intensified, the need for renewable starting materials and degradable designs has similarly deepened. With that goal, we endeavored to make adhesive films from renewable terpenes as a safer and more sustainable route to PSAs. Specifically, based on our previous report of the cross-linking ability of a carveol-based carbonate through thiol-ene chemistry, we report further exploration of the adhesive possibilities of this system. A carbonate monomer of dimerized carveol was linearly polymerized with dithiothreitol via UV-initiated thiol-ene chemistry and formed into adhesive coatings, with unmodified geraniol doped in as a tackifier. We obtained a range of adhesive properties based on the ratio of exo-methylene to thiol units and reported on the degradation of the adhesive coatings.

Machine Learning Approach to Investigate High Temperature Corrosion of Critical Infrastructure Materials

Degradation of coatings and structural materials due to high temperature corrosion in the presence of molten salt environment is a major concern for critical infrastructure applications to meet its commercial viability. The choice of high value coatings and structural (construction parts) materials comes with challenges, and therefore data centric approach may accelerate change in discovery and data practices. This research aims to use machine learning (ML) approach to estimate corrosion rates of materials when operated at high temperatures conditions (e.g., nuclear, geothermal, oxidation (dry/wet), solar applications) but geared towards nuclear thermochemical cycles. Published data related to materials (structural and coatings materials), their composition and manufacturing, including corrosion environment were gathered and analysed. Analysis demonstrated that random forest regression model is highly precise compared to other models. Assessment indicates that very limited sets of materials are likely to survive high temperature corrosive environment for extended period of exposure. While a higher quality and larger dataset are required to accurately predict the corrosion rate, the findings demonstrated the value of ML’s regression and data mining capabilities for corrosion data analysis. With the research gap in material selection strategies, proposed research will be critical to advancing data analytics approach exploiting their properties for high temperature corrosion applications.Graphical

Future Parabolic Trough Collector Absorber Coating Development and Service Lifetime Estimation

This work presents a study on the optical and mechanical degradation of parabolic trough collector absorber coatings produced through the spray coating application technique of in-house developed paint. The main aim of this investigation is to prepare, cure, load, and analyze the absorber coating on the substrate under conditions that mimic the on-field thermal properties. This research incorporates predicted isothermal and cyclic loads for parabolic trough systems as stresses. Biweekly inspections of loaded, identical samples monitored the degradation process. We further used the cascade of data from optical, oxide-thickening, crack length, and pull-off force measurements in mathematical modelling to predict the service life of the parabolic trough collector. The results collected and used in modelling suggested that cyclic load in combination with iso-thermal load is responsible for coating fatigue, influencing the solar absorber optical values and resulting in lower energy transformation efficiency. Finally, easy-to-apply coatings made out of spinel-structured black pigment and durable binder could serve as a low-cost absorber coating replacement for a new generation of parabolic trough collectors, making it possible to harvest solar energy to provide medium-temperature heat to decarbonize future food, tobacco, and paint production industrial processes.

Resistance and speed penalty of a naval ship with hull roughness

Hull roughness, attributed to factors such as corrosion, the degradation of marine coatings, and, notably, biofouling colonisation, leads to increased fuel consumption, thus entailing significant environmental and economic penalties. While this issue on commercial ships is well documented in recent studies, the specific impact on the speed of warships has received limited attention. To fill this gap, this research quantifies the resistance and power penalties, as well as the speed reduction under various fouling scenarios, and explores the resultant changes in flow characteristics around the hull. For this purpose, full-scale simulations of a naval ship, specifically the DTMB 5415, utilise the unsteady Reynolds Averaged Navier-Stokes (URANS) method. A modified wall function model was incorporated into the numerical model to accurately simulate the effects of surface roughness.

Degradation of LaPO4-8YSZ composite thick thermal barrier coatings by molten calcium-magnesium-aluminosilicate

The effect of LaPO4 content on the calcium-magnesium-aluminosilicates (CMAS) corrosion resistance of the plasma-sprayed LaPO4-8YSZ composite coatings at 1250 °C was investigated. The microstructure and corrosion products of the LaPO4-8YSZ composite coatings after CMAS attack was determined by using SEM/TEM/SAED. The results indicated that LaPO4 was segregated at the grain boundaries of the composite coatings and the addition of LaPO4 into 8YSZ coating increased their CMAS reactivity, which led to the formation of planar reaction zone while the CMAS infiltration depth decreased from ∼658 μm to ∼119 μm. The CMAS infiltration depth of the composite coatings firstly increased with LaPO4 addition, reaching its maximum for the composite coating with 5 wt% LaPO4, and then showed a downtrend. For the composite coating with 20 wt% LaPO4, a dense apatite layer formed in the corrosion front, which inhibited CMAS penetration and resulted in the shallowest CMAS infiltration depth among the test samples.

Corrosion Behavior of 3104 Aluminum Cans When Used as Packaging for Chinese Liquor.

Aluminum cans are commonly used for packaging soft drinks and low-alcohol beverages due to their good recyclability. To enhance the economic cycle and expand the packaging of liquors, the feasibility of commercial 3104 aluminum cans for packaging Chinese liquor was studied. The aluminum's migration into alcoholic solutions was studied using inductively coupled plasma emission spectroscopy (ICP-OES). Electrochemical impedance spectroscopy (EIS) was used to study the corrosion process of epoxy coatings on the aluminum cans. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), infrared attenuated total reflection (IR-ATR), and X-ray diffraction (XRD) were used to determine the inner coatings and adhering surfaces of the cans and the corrosion process. The results showed that the maximum aluminum migration in Chinese liquor was 4.3572 mg/kg at 60 °C for 30 days. The epoxy coating was corroded enough to decrease the coating impedance and expose the metal substrate after 25 days. Permeation and aging degradation of coatings are the main factors to consider when packaging liquor.

Enhanced effects of slowly co-released TGF-β3 and BMP-2 from biomimetic calcium phosphate-coated silk fibroin scaffolds in the repair of osteochondral defects

Bioactive agents have demonstrated regenerative potential for cell-free bone tissue engineering. Nevertheless, certain challenges persist, including ineffective delivery methods and confined therapeutic potency. Here, we demonstrated that the biomimetic calcium phosphate coating system (BioCaP) could effectively uptake and slowly release the incorporated bioactive agents compared to the surface absorption system via osteoclast-mediated degradation of BioCaP coatings. The release kinetics were determined as a function of time. The release rate was stable without remarkable burst release during the first 1 day, followed by a sustained release from day 7 to day 19. Then, we developed the bi-functional BioCaP-coated silk fibroin scaffolds enabling the effective co-delivery of TGF-β3 and BMP-2 (SFI-T/SFI-B) and the corresponding slow release of TGF-β3 and BMP-2 exhibited superior potential in promoting chondrogenesis and osteogenesis without impairing cell vitality in vitro. The SFI-T/SFI-B scaffolds could improve cartilage and bone regeneration in 5 × 4 mm rabbit osteochondral (OC) defect. These findings indicate that the biomimetic calcium-phosphate coated silk fibroin scaffolds with slowly co-released TGF-β3 and BMP-2 effectively promote the repair of OC defects, hence facilitating the future clinical translation of controlled drug delivery in tissue engineering.Graphic

A Dynamic Testing Approach for Particulate Erosion–Corrosion for Gas Turbine Coatings

Abstract Particle interactions in engines can be complex phenomena leading to degradation of thermal (TBCs) and environmental barrier coatings (EBCs) meant to protect engine components. Ingestion of particles into the engine can lead to recession of coatings due to particle erosion. Similarly, these particles can become molten, adhere to coatings, and result in thermochemical corrosion of coating materials. Erosion testing is often carried out where particles are injected into a gas stream, accelerated within a nozzle, and impinge on samples. Conversely, most molten particle corrosion testing is often done in static furnaces, which does not capture the dynamic nature of deposition. Nevertheless, these damage mechanisms are often tested separately, and no standard exists to test both erosive/corrosive particle interactions with coating materials under relevant turbine operating conditions. Understanding the synergies of particle interactions is crucial in determining operating lifetimes of potential coating materials. Such considerations emphasize the need for realistic approaches in standardizing particle interaction testing in combustion environments. This study outlines efforts at NASA Glenn's Erosion Burner Rig Facility in improving dynamic erosion/corrosion testing methods by assessing the durability of state-of-the-art (SOA) TBC 7 wt % yttria-stabilized zirconia (7YSZ) as a function of particle deposition rate, burner temperature, and particle size. Calibration data to determine particle deposition rate will be presented, and mass and optical profilometry measurements were utilized to estimate mass/volume loss versus deposition per increment of particulate used. Electron microscopy analyses were then carried out to assess coating damage after testing.

Thermochemical interaction of (Yb0.7Gd0.3)4Hf3O12 ceramic with CMAS melts

The molten calcium-magnesium alumino-silicate (CMAS) deposits degradation of thermal barrier coatings (TBCs) is increasingly severe in advanced turbine engines. In this study, the thermochemical interaction of a promising TBC candidate material, (Yb0.7Gd0.3)4Hf3O12, with CMAS melts at 1300 ℃ and 1500 ℃ was systematically investigated. The apatite and reprecipitated fluorite with high melting points were crystallized rapidly when the ceramic reacted with CMAS melts, resulting in the formation of a dense crystalline layer to suppress further infiltration of CMAS melts. Moreover, as the reaction proceeded, the formation of garnet and cuspidine occurred at 1300 ℃ and 1500 ℃, respectively. The CMAS resistance of (Yb0.7Gd0.3)4Hf3O12 was significantly higher compared to that of Yb4Hf3O12, which could be attributed to the greater volume fraction of apatite and reprecipitated fluorite in the reaction products. The (Yb0.7Gd0.3)4Hf3O12 exhibited high effectiveness in mitigating CMAS infiltration, making it a potential candidate material for thermal barrier coatings.

Post-service analysis of the degradation and protective mechanisms of chromate-based structural aircraft coatings

The substitution of chromate-containing structural coating systems in aviation with alternatives complying with nowadays strict environmental, health and safety regulations remains a formidable challenge. This complexity is partly due to the absence of a standardized from-test-to-market methodology, including a performance comparison between chromate-containing and alternative coating systems. To address this gap, the present study delves into the identification of crucial degradation factors that merit inclusion in such a methodology. Concurrently, it investigates the protective mechanisms inherent in chromate-containing coating systems and proposes improvements that can be applied to alternative coating systems. This study entails a comprehensive post-service examination of the degradation of paint applied to an aircraft component with over 35 years of service, employing electrochemical, microscopic and spectroscopic techniques. The findings underscore the role of thermo-oxidation as a significant degradation factor in the aging process of such coatings. Furthermore, the investigation elucidates a notable phenomenon in which aluminium ions within the coating pores form an aluminium hydroxide gel onto which chromate adsorbs. This process contributes to an increase in pore resistance upon exposure to electrolyte, leading to a self-healing barrier effect within the coating. Remarkably, this self-healing mechanism continues to offer long-term protection even when the coating matrix is sub-optimally cured due to application errors. Furthermore, this study reveals that the significant changes in capacitance during immersion testing result primarily from inhibitor leaching, emphasizing the effectiveness of combining Electrochemical Impedance Spectroscopy (EIS) with Scanning Electron Microscopy (SEM) analysis for studying coating degradation.

Durability of intumescent coatings and recommendations for test concepts for a working life of more than 10 years

It is an essential requirement for all building products to ensure durability of their fire safety. Throughout the working life of products, intumescent coatings are aged by certain climatic factors. To predict a lifetime of several years, generally the behaviour of the intumescent coating is extrapolated based on accelerated artificial ageing. The established German and European procedures to assess the durability assume a working life of at least 10 years. For a longer period, additional evidence is required; yet the procedure and the specifications to justify this are not described. In addition to addressing this formal lack, from a scientific point of view it is necessary to investigate the degradation of intumescent coatings in detail and to propose a reliable test concept to assess durability for more than 10 years. This paper summarises the existing knowledge about the ageing of intumescent coatings. The results of various demanding weathering approaches are presented for two intumescent coatings tested in a joint research project. Moreover, formulations with a reduced amount of functionally relevant components were analysed to gain insight into the associated effects. Derived from these research results and knowledge, recommendations are proposed to assess the durability of intumescent coatings for more than 10 years based on a combination of verifications.

Uniform and local degradation of epoxy-based powder coatings: Salt transport and accelerated exposure analysis

The barrier performance of epoxy-based powder coatings for pipelines was evaluated through salt transport measurements through free-standing coating films and via cyclic testing of coated steel panels. The permeability of salt through the free-standing coating films was measured using reverse osmosis techniques under hydraulic pressures relevant to industrial use. These tests showed that fusion bonded epoxy (FBE) and high-performance powder coating (HPPC) have low salt permeability. Accelerated exposure tests were then conducted on the coated steel panels, subjecting them to humidified environments, ultraviolet (UV) light, and salt/fog conditions, all in accordance with ASTM D5894. Some of the exposure conditions (e.g., intensity of UV light and humidity) were modified to examine the impact of each parameter on the relative performance of these coating systems. The reversibility of the coating properties was characterized by a thermal cycling protocol and adhesion performance analysis. Alternative exposure to dry- and wet-cycles (at 60 °C and 50 °C, respectively), salt/fog conditions and UV light results in irreversible damage to the coatings as early as two weeks. However, coated panels exposed to a lower UV intensity (one tenth of the value defined by the standard) showed minimal degradation of FBE, meaning that the most critical parameter was the UV radiation exposure. For one 336-h ageing sequence under UV exposure, the HPPC exhibited superior performance compared to FBE. More importantly, our extended exposure sequences showed that while the FBE coating structure undergoes a slow ablation process, indicating significant surface damage, it still retains its effectiveness as a barrier. However, the osmotic pressures around coated pipes and the pre-existing, unavoidable porosity throughout the coating thickness can facilitate local through-thickness pinholes, which could potentially serve as areas susceptible to cathodic disbondment.

High anti-corrosion barrier of poly (methyl methacrylate)-silica coatings explained: A thousand-days study

Poly (methyl methacrylate) (PMMA)-silica coatings form a few micrometers thick anti-corrosive barrier that blocks corrosive species when exposed to harsh environments. Their excellent anti-corrosive performance stands out for protecting metal alloys immersed in seawater for long periods (>2 years), making them compliant for applications in the marine, aeronautical, and automotive industries. A key approach to understanding the degradation of high-performance coatings over time consists of analyzing their water uptake-induced structural changes. This work examines in detail the uptake and structural modification of PMMA-silica coatings on Al alloys immersed for more than 1000 days in 3.5 wt% NaCl solution. Gravimetry, thermal analysis, infrared spectroscopy and electrochemical impedance spectroscopy (EIS) were employed to monitor the evolution of coated samples. Nuclear magnetic resonance, X-ray photoelectron spectroscopy, electron and atomic force microscopies before and after immersion indicate a slight leaching-induced surface roughening due to silica hydrolysis. These findings comply with the low uptake values (∼0.6 vol%) and a less-Fickian diffusion coefficient obtained from modelling of the EIS data. The high impedance modulus (>GΩ) is related to the highly cross-linked structure, resulting in a very low permeation rate of the electrolyte. The applied methodology is of crucial importance for establishing a standardized analysis for high-performance protective coatings.

Application of Secondary Ion Mass Spectrometry for Analysis of Decorative Coatings on Fancy Goods Accessories

The results of a secondary ion mass spectrometry (SIMS) study on Ag and ZrN decorative coatings on nickel and white bronze substrates for fancy goods accessories are presented. It was found that for Ag coatings, an intense diffusion of Cr from the adhesion layer between the coating and the substrate is observed, and corrosion testing in an acetic salt (CH3COOH+NaCl) atmosphere leads to the almost complete degradation of such coatings. ZrN coatings on white bronze turned out to be the most resistant to Cr diffusion and corrosion processes.

UV-durable self-cleaning coatings for autonomous driving

A key technology to ensure the safety and accuracy of autonomous driving for future transportation is the cleanliness of the sensor surfaces for accurate signal reading. This study focuses on hydrophobic coatings with self-cleaning performances and UV durability, their possible degradation mechanism of static water contact angle (sWCA), and the effect of the hydrophobic surface on camera image quality. The UV-durable hydrophobic coatings are applied by a spray process followed by a thermal curing. The UV-durable hydrophobic coatings are evaluated on a vision camera under lab-simulated weathering conditions such as rain, mud, fog, and bugs, on samples as-prepared and after various hours of Weather-Ometer® weathering. The results indicate that the sWCA degradation of the UV-durable hydrophobic coatings during accelerated weathering is corresponding to the loss of fluorine (F) atomic percentage in the coatings, and the vision camera imaging quality improves significantly with the UV-durable hydrophobic coatings in comparison to an uncoated surface. The self-cleaning performances of the UV-durable hydrophobic coatings, as measured by two metrics using signal-to-noise ratio and modulation transfer function 50 loss (MTF50loss), linearly correlate with sWCA of the coatings. The UV-durable hydrophobic coatings on the sensor surface will significantly benefit autonomous driving specifically for accurate signal reading under inclement weather.

Degradation of Various Organic Coatings via UV-Generated Sulfate Radicals.

Degradation of organic coatings is essential for recycling valuable substrates. Despite the development of strategies for this purpose, the resulting degradations are typically constrained by the composition of the coating. This paper presents a simple strategy utilizing radicals induced by UV for the degradation of diverse organic coatings. The sulfate radicals, generated from UV-exposed ammonium persulfates, induce the degradation of various organic coatings, including layer-by-layer assembled coating composed of alginate and chitosan polymers as well as polydopamine coating. This strategy also facilitates the separation of two adhered substrates by degrading the adhesive polymer layer positioned between them. This novel approach enables the complete degradation of various organic coatings in aqueous conditions without imposing restrictions on their composition, leading to the recovery of the original surface properties of the substrate.

Chemical and microbiological safety of drinking water in distribution networks made of plastic pipes

AbstractIn recent years, metal alloys used for drinking water distribution are gradually being replaced by PVC and HDPE pipes. In areas of distribution networks made of plastic, consumer complaints related to a significant deterioration of organoleptic parameters of water are frequently recorded. The decline in water quality is most likely the result of chemical and biological processes occurring on the inner walls of the transmission pipes coexisting with the disappearance of disinfectant residues. Plastic pipes are also characterized by high failure rates associated with aging of polymeric materials under operating conditions. Published reports indicate disturbing phenomena occurring in plastic pipes: oxidative aging of polymers, degradation of antioxidant coatings, release of organic compounds to water as well as surface damage and scaling, generating microplastic particles. PE and PVC networks are also susceptible to biofilm formation, characterized by a high phylogenetic diversity of microorganisms. Studies presented in the literature, indicating the risks resulting from the exploitation of PE and PVC pipes, are mainly based on model tests. There is a lack of works, which would complementarily explain all the phenomena occurring in working water pipes made of plastics. The aim of this review is to present the current state of knowledge regarding the phenomena and processes that can occur in PE and PVC pipes in service and their relevance to the safety and quality of drinking water in distribution networks, as well as to identify areas that require further analysis to enable water producers to deliver an appropriately high‐quality product to consumers.This article is categorized under: Engineering Water > Water, Health, and Sanitation Science of Water > Water Quality Water and Life > Conservation, Management, and Awareness