Degradation Of Coatings Research Articles

Solid particle erosion evaluation of automotive paint coatings under the influence of artificial weathering

Solid particle erosion (SPE) is one of the most critical tribological problems causing damage to automotive paint coatings. The correct characterization of SPE and resistance against it makes the possible extended service life of the coating, increasing the resale value of cars. Car manufacturers and paint industries have developed new techniques to apply coatings and coatings that improve the initial and long-term appearance, scratch performance, and durability of coatings. Several works have focused on studying the degradation and performance of paint coatings. However, there needs to be more understanding of wear progress under different environmental degradation conditions. This study investigates the mechanisms and resistance of erosive wear of actual automotive paint coatings before and after exposure to an accelerated weathering process. Steel substrate panels with a typical paint coating system were exposed to weathering degradation by UV and immersion in an artificial acid rain solution. The chemical changes induced in the coatings were analyzed by FT-IR spectroscopy. Then erosive tests were carried out using silica sand particles at two different angles of incidence (30° and 90°) and temperatures (25 °C and 60 °C) for both samples (unexposed and weathering conditions). The SPE rate was determined for each coating by mass loss estimation using an analytical balance; meanwhile, wear mechanisms were analyzed in detail by SEM. The results showed decreased SPE resistance promoted by chemical changes in samples exposed to both weathering processes.

Poly(l-lactide)/polycaprolactone based multifunctional coating to deliver paclitaxel/VEGF and control the degradation rate of magnesium alloy stent

Despite significant advancements made in cardiovascular stents, restenosis, thrombosis, biocompatibility, and clinical complications remain a matter of concern. Herein, we report a biodegradable Mg alloy stent with a dual effect of the drug (Paclitaxel) and growth factor (VEGF) release. To mitigate the fast degradation of Mg alloy, inorganic and organic coatings were formed on the alloy surface. The optimized hierarchal sequence of the coating was the first layer consisting of magnesium fluoride, followed by poly(l-lactide) and hydroxyapatite coating, and finally sealed by a polycaprolactone layer (MgC). PLLA and HAp were used to increase the adhesion strength and biocompatibility of the coating. Paclitaxel and VEGF were loaded in the final PCL layer (Mg-C/PTX-VEGF). As compared to bare Mg alloy (28 % weight loss), our MgC system showed (3.1 % weight loss) successful decrease in the degradation rate. Further, the in vitro biocompatibility illustrated the highly biocompatible nature of our drug and growth factor-loaded system. The in vivo results displayed that the drug loading decreased the inflammation and neointimal hyperplasia as indicated by the α-SMA and CD-68 antibody staining. The growth factor helped in the endothelialization which was established by the FLKI and ICAM antibody staining of the tissue.

Recent Development in Advance Ceramic Materials and Understanding the Mechanisms of Thermal Barrier Coatings Degradation

AbstractMetallic alloys' behavior at high temperatures, especially their response to corrosion and formation of protective surface layers, has long been a focus of scientific inquiry. Although certain alloy compositions require an initiation period before hot corrosion advances to the propagation stage, no combination of alloys can be considered impervious to hot corrosion indefinitely. The capacity of nickel-based materials to tolerate extreme circumstances such high temperatures, acidity, corrosion, and scratching is highly valued. However, they are unable to satisfy the strict demands of today's high-temperature applications. The durability of thermal barrier coatings (TBCs), which are prone to oxidation, rust, and degradation from sulphates and foreign object damage, has been the subject of recent study. For sophisticated ceramic materials exposed to high temperatures, hot rust degradation poses a considerable challenge. The main objective of this study is to investigate the effects of severe degradation on several advanced ceramic material types and their level of advancement. The purpose of the inquiry is to comprehend the deteriorating processes at the long term working condition, including the function of oxidation and liquid salts. Additionally, we investigate the effects of temperature, environment, and contact duration on the heated weathering behavior of earthenware. Finally, we discuss strategies for mitigating hot corrosion degradation in ceramics, such as protective coatings like new design of TBCs, doping, and composition optimization. This paper aims to offer a thorough understanding of the hot corrosion behavior of ceramics, which is crucial for developing durable materials suitable for high-temperature applications. Additionally, it explores the fabrication of protective coatings and addresses the challenges faced in this regard. The insights gained from this research can contribute to the advancement of resilient ceramic fabrics and the development of effective protective coatings.

The Combined Effect of Direct Current Polarization, Ultraviolet Radiation, and Saline Immersion on the Degradation of an Epoxy Coating

The Combined Effect of Direct Current Polarization, Ultraviolet Radiation, and Saline Immersion on the Degradation of an Epoxy Coating

Effect of potassium fluotitanate concentration on the corrosion resistance and degradation property of micro-arc oxidized ZM21 magnesium alloys

Magnesium (Mg) alloy is a focus biomaterial at present, while the rapid degradation rate in body fluid will hinder the practical clinical application. Therefore, surface modification of Mg alloy is essential. In the study, Mg–2Zn–Mn (ZM21) alloys and micro-arc oxidation (MAO) are used as the substrate and surface modification method. Then, the influence of potassium fluotitanate (K2TiF6) concentration in silicate basic electrolyte on the corrosion resistance and degradation of MAO coatings are studied. The results show that (1) TiF62− has obviously thickening effect, and adding 0.25 and 0.50 g/L K2TiF6 make the better corrosion resistance. (2) TiF62− concentration affects the coating quality, which is mainly attributed to F− generated by the reaction of TiF62− + 4OH− = TiO2 + 6F− + 2H2O. (3) Anatase TiO2 formed by ionization of TiF62− plays a role in sealing the micro-pores of MAO coating. (4) The hydrophilicity is improved, weight loss rate and pH value of MAO samples after immersion are obviously reduced, and available biological safety are improved, of which it is worth noting that the surface of K-0.75 sample has generated particles with a Ca/P ratio similar to hydroxyapatite (Ca10(PO4)6(OH)2, HA). (5) Cell adhesion test proves the available cytocompatibility.

Neutral salt spray aging effect on low emissivity coating

While Low-E coatings have already reached very good optical properties, their durability in a salt chemical environment has not been largely studied. Therefore the degradation of Low-E coatings deposited by magnetron sputtering with “AZO/Ti/Ag/AZO/substrate” structure has been investigated as a function of exposure time to a salt spray. A mechanism of degradation is proposed; the degradation step is initiated by the diffusion of water and salt through the top layer. We clearly show that those contaminants reach the metallic interfaces of Ag and Ti. During the delamination step, the AZO top layer reacts with contaminants, and Zn and O are evacuated in the environment by water droplets. Despite this delamination of the top layer, the Low-E coatings keep their optical properties with an emissivity of ∼0.08. At further delamination step, the silver layer agglomerates to form larger crystallite and the optical properties of Low-E coatings drastically deteriorate.

Problems of Masking and Anti-Reflective SiO2 in Silicon Technology

The article examines the problems of thermal oxidation of silicon. Oxidation plays an important role in planar technology, which in turn is the basis of the technology of silicon integrated circuits, photodetectors and other solid-state electronics. During our production of silicon p-i-n photodiodes, a number of systematic types of defects and deterioration of product parameters caused by the degradation of masking or anti-reflective coatings during the manufacturing process were observed. A decrease in the insulation resistance of responsive elements in multi-element photodiodes was observed, which contributed to the increase of dark currents. A decrease in the responsivity of the products due to the degradation of the thickness or structure of the anti-reflective coating during technological operations, etc., was also revealed. It was established that the reason for the decrease in insulation resistance is the formation of inversion layers at the Si-SiO2 interface, the presence of which can be detected when measuring CV-characteristics. It was also established that chemical treatment of substrates with SiO2 in boiling acid solutions helps to reduce the thickness of the oxide. To avoid deviation of the thickness of the film from the condition of minimum reflection, it is necessary to grow a thicker layer of anti-reflective coating. It is noted that when etching the oxide during photolithography or when removing the PSG/BSG in hydrofluoric acid, it is not permissible to remove the cassette with plates from the solution for a long time, as this leads to uneven etching of the film due to the flow of the herb on the surface of the substrate. The causes of defect formation in Si and SiO2 during oxidation are given. Thus, with improper mechanical and chemical processing of the plates, cristobalite inclusions may form in the film during oxidation. Cristobalite has a higher density than quartz glass, and the boundaries between amorphous regions and denser crystalline regions represent voids, which can be filled both by impurities from the surface and by the diffusant in the diffusion process. Also, during oxidation in silicon, packing defects are often formed. Centers of defect genesis can be mechanical damage to the plate surface or growth defects.

Synergistic acceleration effects of ultraviolet and salt spray on the degradation and failure of electromagnetic wave-absorbing coatings

There is an urgent need to reliably and rapidly evaluate the risk of failure of electromagnetic wave absorbing (EWA) coatings under the complex oceanic environment, which involves multiple weathering factors such as ultraviolet light, salt spray, etc. Unfortunately, conventional accelerated aging methods, which only consider single factor or apply multiple factors alternately, cannot adequately reproduce the failure modes and mechanisms of EWA coatings during real service. As a result, even though EWA coatings have passed existing qualification tests, their performance still could deteriorate much faster than expected. To this end, we investigated the synergistic acceleration effects of UV and salt spray on the degradation and failure of electromagnetic wave-absorbing coatings. Epoxy/flaky carbonyl iron (FCI) coating was prepared as the model sample. Effects of alternating- and combined-UV-salt spray (A-UV-SS and C-UV-SS) accelerated aging on the failure behaviors and underlying mechanisms of EWA coatings were investigated and compared thoroughly. It was found that EWA ability of coatings aged under C-UV-SS deteriorated much faster than that under A-UV-SS (more than two times). This additional acceleration aging effect was attributed to synergistic mechanisms with the coexistence of UV and salt spray: 1) acetic acid from the photo-oxidation of epoxy act synergistically with salt spray to accelerate the corrosion of Fe; 2) photovoltaic effect and salt spray synergistically promote the formation of iron oxides. This novel method has the potential to identify new failure mechanisms of EWA coatings and significantly reduce the test time, which is critical for their reliability evaluation and performance optimization.

Abrasion resistance of spray coated anti-soiling coatings during waterless cleaning of PV modules

Dust deposition on photovoltaic (PV) modules leads to remarkably high energy loss, which has an enormous economic impact on PV plants. Anti-soiling coatings have been extensively studied as a cost-effective dust mitigation strategy in the PV market. However, such coatings applied to the top surface of the PV modules should be resilient to environmental stressors. Coated modules would also need periodic cleaning; thus, such anti-soiling coating must be abrasion-resistant. This article investigated the abrasion-resistant property of 4 types of commercial hydrophobic anti-soiling coatings. The study emulates the effects of different brush designs on the degradation of anti-soiling coatings under low soiling conditions. The samples were subjected to dry brush cleaning. We tested the samples with 3 different brush designs (linear brush 1, linear brush 2 and rotary brush) with a varying packing density of brush bristles. Linear brush 1 had 3.5 times higher packing density of brush bristles than linear brush 2 and rotary brush. By increasing the packing density of brush bristles by 3.5 times, the degradation rates were enhanced by factors varying from 1.2 X to 4.4 X in coated samples when cleaned with linear brush 1, compared to linear brush 2 and rotary brush. Phenylsilicone based coating shows higher degradation rates (varying from 2.9 X to 11.2 X) than fluoropolymer-based coatings. The result indicates a decline of the anti-soiling property as we see an increase in roll-off angle (compared to Mumbai, India’s tilt angle = 19º) with the increase in number of cycles. The results also show that compared to the structural brush design, the packing density of the brush bristle has a strong impact on the coating life. However, the actual coating life in the field would also be dependent on other environmental factors like the amount of dust deposit, moisture etc.

Composite Nanocoatings of Biomedical Magnesium Alloy Implants: Advantages, Mechanisms, and Design Strategies.

The rapid degradation of magnesium (Mg) alloy implants erodes mechanical performance and interfacial bioactivity, thereby limiting their clinical utility. Surface modification is among the solutions to improve corrosion resistance and bioefficacy of Mg alloys. Novel composite coatings that incorporate nanostructures create new opportunities for their expanded use. Particle size dominance and impermeability may increase corrosion resistance and thereby prolong implant service time. Nanoparticles with specific biological effects may be released into the peri-implant microenvironment during the degradation of coatings to promote healing. Composite nanocoatings provide nanoscale surfaces to promote cell adhesion and proliferation. Nanoparticles may activate cellular signaling pathways, while those with porous or core-shell structures may carry antibacterial or immunomodulatory drugs. Composite nanocoatings may promote vascular reendothelialization and osteogenesis, attenuate inflammation, and inhibit bacterial growth, thus increasing their applicability in complex clinical microenvironments such as those of atherosclerosis and open fractures. This review combines the physicochemical properties and biological efficiency of Mg-based alloy biomedical implants to summarize the advantages of composite nanocoatings, analyzes their mechanisms of action, and proposes design and construction strategies, with the purpose of providing a reference for promoting the clinical application of Mg alloy implants and to further the design of nanocoatings.

Fabrication of robust and room-temperature curable superhydrophobic composite coatings with breathable and anti-icing performance

Superhydrophobic surfaces show great application prospects in various fields, yet the tedious preparation process, sophisticated equipment, and poor durability restrict their large-scale practical applications. In this study, we proposed a simple and efficient approach to fabricating room-temperature curable superhydrophobic composite coatings by spraying the suspension composed of fluorinated silicon-based acrylic copolymer (FSC), amino-terminated polydimethylsiloxane (PDMS) and fluorinated SiO2 nanoparticles (SiO2-F) on various substrates. Due to the special molecular design, our prepared coatings can be cured at room temperature. The resultant FSC15/PDMS/SiO2-F nanocomposite coating containing 40 wt% SiO2-F exhibited excellent superhydrophobicity with a high WCA of 160.4° and a low SA of 1.5°. The prepared coating also displayed satisfactory breathability, preventing structural degradation of the superhydrophobic coatings used in architecture. More impressively, the composite coating can sustain its superior water repellency even after being subjected to harsh mechanical durability damage, including sandpaper abrasion, water dripping, tape peeling tests, and rigorous working conditions, such as corrosive liquid environment, UV illumination, extreme temperatures, and ultrahigh humidity. Besides, the water-freezing time on the coated concrete sample can be postponed to 1860 s at −15 ℃, and the ice adhesion strength was reduced to 56.7 kPa. The facility and universality of the composite coating ensured that it could be applied on diverse material surfaces, including ceramics, tinplate, wood, glass, sponge, fabric filter paper, and cotton, which indicates the potential for large-scale application in industry.

Space Environment Effects on the Electron Yields of Thermal Control Coatings

Space-environment-induced degradation of white thermal control coatings from the Long Duration Exposure Facility (LDEF) was investigated. Much of the exterior of the LDEF was painted with a white thermal control coating, Aeroglaze A276; and most of the interior was coated with a black thermal control coating, Aeroglaze Z306. Outgassing from these coatings and other LDEF materials interacted with the white surface when exposed to sunlight after volatile materials condensed on the LDEF surfaces. Surface morphology was characterized by optical and scanning electron microscopies. Fourier-transform infrared spectroscopy and energy-dispersive x-ray spectroscopy were used to identify the chemical compounds and elements present in the contamination film. Many material properties were modified due to the prolonged approximately six year low-Earth-orbit exposure, but electron yield (EY) was the focus of this study due to its dominance in spacecraft charging. Measurements showed an increase in maximum EY with increased contamination, with the maximum EY more than doubling in some cases. The NASA Charging Analyzer Program simulations for simplified models of the LDEF showed the impact of the degradation on spacecraft charging under different environmental conditions; equilibrium surface potentials varied by more than 100% in some cases.

Study of abrasion tests for antireflective and antisoiling/antireflective coatings on glass solar tubes

The abrasion resistance of the antireflective coatings (ARC) applied on both sides of the parabolic-trough glass tubes is a key point to maintain throughout time the enhanced efficiency which produces the use of this film. The cleaning processes as well as the erosion produced by dust or sand in desert environments can damage the ARC, even removing it, affecting the system efficiency. The use of an antisoiling (AS) treatment on the antireflective (AR) coated solar glass envelopes are reaching increasing interest to reduce soiling and the water consumption associated to cleaning. RIOGLASS AR coated tubular samples were coated with a commercial hydrophobic treatment and the abrasion resistance of the AR + AS coatings combination against sole ARC were studied by carrying out two abrasion tests. Initial average solar transmittance values of 96.9 % and initial average static contact angle of 107° were obtained for the AR + AS samples. The results from the two abrasion tests have shown that the AR + AS coatings combination present a higher resistance to the abrasion. It has also been observed that two different abrasive media in the sand oscillating test produce different degradation mechanisms, (reflection losses versus absorptance losses). Additionally, the results have shown that solar transmittance values are not enough to characterize the abrasion degradation of AR coatings, being also important the haze value. Similar solar transmittance values (93.9 % and 94 %) but with different haze values (1.2 % against 3.2 %) and very different transmittance spectra indicating distinct degradation mechanism were obtained for samples abraded with two different sands.

Investigating Different Local Polyurethane Coatings Degradation Effects and Corrosion Behaivors by Talaromyces funiculosus via Wire Beam Electrodes.

The degradation effect of mold on the coating in a hot and humid environment is one of the important factors that cause layer failure. Combined with the wire beam electrode (WBE) and the traditional surface analysis technique, the local biodegradation of the coatings and the corrosion behaviors of metal substrates can be characterized accurately by a WBE. Herein, a WBE was used to study the degradation impact of Talaromyces funiculosus (T. funiculosus) isolated from a tropical rainforest environment on the corrosion of polyurethane (PU) coating. After immersion for 14 days, the local current density distribution of the WBE surface can reach ~10-3 A/cm2 in the fungal liquid mediums but maintains ~10-7 A/cm2 in sterile liquid mediums. The |Z|0.01Hz value of the high current densities area (#85 electrode) was 1.06 × 109 Ω cm2 in a fungal liquid medium after 14 days of immersion. After being attacked by T. funiculosus, the degradation of the PU was more severe, and there were wrinkles, cracks, blisters, and even micro-holes distributed randomly on the surface of electrodes. This resulted from the self-corrosion caused by the T. funiculosus degradation of the coating; the corrosion caused by the electric coupling effect of the coating was introduced. Energy dispersive spectroscopy (EDS) and Raman spectra results showed that the corrosion products were flakey and globular, which consisted of γ-FeOOH, γ-Fe2O3, and α-FeOOH.

Polypropylene sulphide coating on magnetic nanoparticles as a novel platform for excellent biocompatible, stimuli-responsive smart magnetic nanocarriers for cancer therapeutics.

Magnetic nanoparticle (MNP) delivery systems are promising for targeted drug delivery, imaging, and chemo-hyperthermia of cancer; however, their uses remain limited primarily due to their toxicity associated with reactive oxygen species (ROS) generation, targeted delivery, and biodegradation. Attempts employing polymer coatings to minimize the toxicity, along with other challenges, have had limited success. We designed a novel yet generic 'one-for-all' polypropylene sulphide (PPS) coated magnetic nano-delivery system (80 ± 15 nm) as a multi-faceted approach for significant biocompatibility improvement, loading of multiple drugs, ROS-responsive delivery, and combined chemo-hyperthermia therapy for biomedical applications. Three distinct MNP systems (15 ± 1 nm) were fabricated, coated with PPS polymer, and investigated to validate our hypothesis and design. Simultaneous degradation of MNPs and PPS coatings with ROS-scavenging characteristics boosted the biocompatibility of MNPs 2-3 times towards non-cancerous fibroblasts (NIH3T3) and human epithelial cells (HEK293). In an alternating magnetic field, PPS-MNPs (MnFe) had the strongest heating characteristics (SAR value of 240 W g-1). PPS-MNP drug-loaded NPs were efficiently internalised into cells and released 80% of the drugs under tumor microenvironment-mimicking (pH 5-7, ROS) conditions, and demonstrated effective chemo-hyperthermia (45 °C) application for breast cancer cells with 95% cell death in combined treatment vs. 55% and 30% cell death in only hyperthermia and chemotherapy respectively.

Abstract 1167: Bottom-up Approach to Rebuild Synergy in Biofilms to Stimulate the Degradation of Recalcitrant Polymer Coatings

Abstract 1167: Bottom-up Approach to Rebuild Synergy in Biofilms to Stimulate the Degradation of Recalcitrant Polymer Coatings

The Influence of Pd on the Structure and Oxidation Performance of β-NiAl Diffusion Coatings

Aluminized coatings on Ni based alloys greatly contribute to achieve process efficiency at higher operating temperatures. The present study characterized Pd-modified and unmodified aluminized coatings and compared with those of Pt-modified coatings regarding the mechanisms of formation and oxidation performance. The results show that Pd reduces the driving force for diffusion of Al during coating formation, increases outward diffusion of Ni and reduces diffusion of alloying elements (Cr and Ti) into the intermetallic layer. In contrast, Pt increases the driving force for diffusion of Al and the mobility of Al in the intermetallic layer of the aluminized coating. These characteristics have a direct impact on oxidation at 1000 °C that showed that Pd reduced the rate of θ-Al2O3 → α-Al2O3 transformation, accounting for higher density of voids at the interface β-(NiAl)/θ-Al2O3, diffusion of oxygen into the coating, spalling and faster degradation of coatings.

Chemical element variation in fungi-induced coating degradation using laser-induced breakdown spectroscopy combined with Raman spectroscopy, mass spectrometry, and multivariate analyses

Chemical element variation in fungi-induced coating degradation.

Evaluating the Electrochemical and In Vitro Degradation of an HA-Titania Nano-Channeled Coating for Effective Corrosion Resistance of Biodegradable Mg Alloy

Extensive research into magnesium (Mg) alloys highlights their possible applications in the field of biodegradable implants. As magnesium alloys are highly electronegative, it is imperative to tailor their degradation rate for clinical safety. Surface coatings have been widely used for the corrosion protection of Mg alloys, but the presence of spatial defects limits their effectiveness. An innovative and near-defect-free hydroxyapatite (HA)-TiO2 nano-channeled (TNC) coating architecture has been developed on ZM21 Mg alloy in the present study by combining anodization and the sol-gel dip coating technique. The HA-TNC coating positively shifted the Ecorr of ZM21 Mg alloy from −1.38 to −0.61 V. Accordingly, the corrosion current density (Icorr, 5.8 × 10−6 A/cm2) was suppressed by 53.4 times compared to uncoated ZM21 Mg alloy. The polarization resistance (Rp) and charge transfer resistance (Rct) values are the highest among all other samples, indicating the superior shielding ability of the coating. During in vitro immersion for up to 28 days in simulated body fluid (SBF), the HA−TNC coating maintained the lowest degradation rate and hydrogen evolution rate (HER) of 1.10 ± 0.22 mg/cm2/day and 1.83 ± 0.41 mL/cm2/day, respectively. A compact and structurally stable 2D plate-like HA (Ca/P:1.55), mineralized on HA-TNC-coated ZM21, provides effective shielding against the penetration of aggressive ions with prolonged SBF immersion. The findings of the present study provide a rational design for the development of bioactive ceramic coatings on Mg-based bioimplants.

Calcia-magnesia-alumino-silicate-induced degradation of (Gd0.9Yb0.1)2Zr2O7 thermal barrier coatings prepared by plasma spray-physical vapor deposition (PS-PVD)

(Gd0.9Yb0.1)2Zr2O7 (GYbZ) coatings with quasi-columnar structure prepared by PS-PVD were isothermally exposed to Calcia-magnesia-alumino-silicate (CMAS) at T = 1300 °C for t0 = 0.1 h, t1 = 1 h, t2 = 10 h, and t3 = 100 h. The resistance of GYbZ coatings against the CMAS melt penetration was investigated by wetting test and the reaction products were analyzed by energy-dispersive X-ray spectroscopy (EDS). The results show that a dense reaction layer was formed after isothermal exposure for t1 = 1 h, and the thickness of the reaction layers was almost the same from t1 = 1 h to t3 = 100 h, which indicated that the penetration of CMAS was basically suppressed. The particles between columns played a significant role in the rapid generation of a large amount of CMAS barrier apatite layer which prevented the penetration of the CMAS melt in the axial direction. The main reaction products were Gd-apatite, fluorite and spinel of which the Gd-apatite slowly grew from “free-island” to “net-frame”.