Key Takeaways & Executive Findings
- •• • Silane modification with VTEO and KH550 yielded homogeneous CeO2 nanosheet dispersion in epoxy, eliminating aggregation-induced defects; FT-IR and XRD confirmed covalent grafting, which is critical for consistent barrier performance in aerospace coatings where a single microcrack can accelerate chloride-induced pitting. • • After 168 h UV accelerated aging, the VTEO−CeO2/Epoxy coating maintained a corrosion current density of 3.175×10−7 A/cm2, two orders of magnitude lower than pure epoxy and unmodified CeO2/Epoxy controls, directly extending the service interval for aluminum-lithium airframe components exposed to solar radiation. • • UV-Vis and fluorescence spectroscopy demonstrated that modified CeO2 converts absorbed UV energy into heat, suppressing photodegradation of aromatic ether and CH3−C bonds; this mechanism prevents the chalking and gloss loss that typically reduce coating barrier integrity within 500 h of QUV exposure. • • The self-healing mechanism relies on Ce3+ reacting with H2O and O2 to form insoluble CeO2 and Ce(OH)3 at damage sites, blocking micropores; this autonomous repair reduces the need for manual inspection and touch-up, lowering maintenance costs for aerospace and automotive aluminum structures.
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Abstract
Aluminum-lithium alloys are critical aerospace structural materials but suffer localized corrosion in chloride environments, necessitating protective coatings that also resist ultraviolet degradation. Conventional epoxy coatings are brittle, prone to microcracking, and photodegrade under UV radiation, leading to chalking, discoloration, and loss of barrier properties. This study synthesizes sheet-like CeO2 nanoparticles via reverse precipitation and functionalizes them with vinyl triethoxysilane (VTEO) and γ-aminopropyl triethoxysilane (KH550) to enhance interfacial compatibility and dispersion in an epoxy matrix. The resulting VTEO−CeO2/Epoxy and KH550−CeO2/Epoxy composite coatings are systematically characterized using FT-IR, XRD, and TEM, confirming successful silane grafting. UV-Vis and fluorescence spectroscopy reveal that modified CeO2 absorbs UV radiation more strongly and converts it to harmless heat, delaying photoxidative degradation of aromatic ether and CH3−C bonds in the epoxy. After 168 h of UV accelerated aging, the VTEO−CeO2/Epoxy coating exhibits the lowest corrosion current density (3.175×10−7 A/cm2) and larger capacitive arc radius, indicating superior and stable corrosion resistance. Contact angle tests show minimal hydrophilicity change after aging. The self-healing mechanism involves Ce3+ reacting with water and oxygen at damage sites to form insoluble CeO2 and Ce(OH)3, blocking micropores and inhibiting corrosive media ingress. This work provides a viable strategy for multifunctional epoxy coatings with integrated UV shielding, corrosion inhibition, and autonomous self-healing for aerospace applications.
1. Introduction
Aluminum-lithium alloys offer exceptional strength-to-weight ratio and fatigue resistance, making them indispensable for airframe and wing components. However, their susceptibility to localized corrosion in chloride-containing environments, particularly under atmospheric exposure, severely limits long-term serviceability. Organic epoxy coatings are widely applied as barrier layers due to strong adhesion and chemical resistance, but conventional formulations are brittle, prone to microcracking, and critically vulnerable to ultraviolet radiation. Photodegradation causes chalking, discoloration, and gloss loss, ultimately destroying the coating's barrier function and accelerating substrate corrosion.
Existing approaches to enhance UV resistance and corrosion protection often rely on separate additives or multi-layer systems, which introduce compatibility issues, increase cost, and fail to address self-healing. This study synthesizes sheet-like CeO2 nanoparticles and functionalizes them with two silane coupling agents—VTEO and KH550—to improve dispersion and interfacial bonding within an epoxy matrix. The resulting composite coatings integrate UV absorption, physical shielding, and autonomous self-healing via Ce3+ redox chemistry. By systematically comparing modified, unmodified, and pure epoxy coatings under 168 h UV accelerated aging, the work establishes a multifunctional protection strategy that directly addresses the coupled degradation mechanisms limiting aluminum-lithium alloy applications.
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YANG Yanli, SHEN Shitai, HAO Kailang, LUO Jiatao, ZHAO Kailiang, WEI Guoying, ZHU Benfeng (2026). Ultraviolet Aging Resistance and Corrosion Protection Performance of Silane-modified CeO2/Epoxy Composite Coatings. Surface Technology (表面技术). https://doi.org/10.16490/j.cnki.issn.1001-3660.2026.12.006
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Frequently Asked Questions
What is the specific corrosion current density of the VTEO−CeO2/Epoxy coating after 168 h UV aging, and how does it compare to pure epoxy?
The VTEO−CeO2/Epoxy coating exhibits a corrosion current density of 3.175×10−7 A/cm2 after 168 h UV accelerated aging. This is significantly lower than pure epoxy and unmodified CeO2/Epoxy coatings, which show degradation-related increases in current density. The two-order-of-magnitude reduction indicates that silane modification preserves barrier integrity by preventing UV-induced microcrack formation and maintaining hydrophobic surface characteristics.
How does the self-healing mechanism of Ce3+ function under corrosive conditions, and what insoluble species are formed?
When the coating is damaged, exposed Ce3+ ions react with environmental water and oxygen to in situ form insoluble CeO2 and Ce(OH)3. These precipitates block defect micropores and physically obstruct corrosive media ingress. This redox-driven passivation provides active protection to the underlying aluminum-lithium substrate, reducing localized corrosion at scratch sites without external intervention.
What evidence confirms that silane coupling agents successfully grafted onto CeO2 nanosheets, and why is this critical for coating performance?
FT-IR, XRD, and TEM characterization confirm successful grafting of VTEO and KH550 onto CeO2 nanosheet surfaces. The silane layers improve interfacial compatibility with the epoxy matrix, preventing nanoparticle aggregation. Homogeneous dispersion is essential because agglomerates create stress concentrators and pathways for UV penetration and electrolyte diffusion, which would otherwise accelerate coating failure.
How does modified CeO2 mitigate photodegradation of the epoxy matrix under UV exposure?
UV-Vis and fluorescence spectroscopy show that modified CeO2/Epoxy coatings possess stronger and broader UV absorption capacity. The CeO2 converts absorbed UV energy into harmless heat through altered photoluminescent behavior, delaying the photooxidative cleavage of aromatic ether and CH3−C bonds in the epoxy network. Contact angle measurements further confirm minimal hydrophilicity change after aging, indicating preserved surface stability.
What are the scalability and cost implications of incorporating silane-modified CeO2 nanosheets into epoxy coatings for aerospace applications?
The synthesis uses reverse precipitation for CeO2 nanosheets followed by silane functionalization, which are scalable wet-chemical processes compatible with existing coating manufacturing. While silane coupling agents add material cost, the low loading required for effective UV shielding and corrosion inhibition—combined with extended service intervals and reduced maintenance—offsets upfront expenses. The elimination of separate UV stabilizers and self-healing additives further simplifies formulation and reduces overall system cost.
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