Structural investigations of sandwich coating system containing self-healing core-shell nanofibers resistant to corrosive environment.

The protection of metallic infrastructure against corrosion remains a significant and ongoing challenge across various industrial sectors. Conventional protective coatings often deteriorate over time, particularly when exposed to mechanical damage or harsh environments, compromising their barrier function. In response to this limitation, there is increasing interest in developing multifunctional “smart” coatings that combine long term corrosion resistance with inherent self-healing capabilities. Such systems, particularly those that incorporate nanomaterials and stimuli responsive architectures, show considerable promise for enhancing structural durability and extending service life. In this study, we engineered a corrosion resistance and self-healing coating by fabricating an epoxy matrix reinforced with silanized graphene oxide and embedded with polydimethylsiloxane (PDMS)-polyvinyl alcohol (PVA) core–shell nanofibers. The core–shell nanofibers were produced via coaxial electrospinning, utilizing PVA shell solutions at concentrations of 7, 10, and 15 wt%. The morphology and structural integrity of the nanofibers were characterized using field emission scanning electron microscopy (FE-SEM). Additionally, complementary analyses through transmission electron microscopy (TEM), fluorescence microscopy, and Fourier-transform infrared spectroscopy (FTIR) confirmed the successful coaxial configuration, with PDMS uniformly encapsulated within the PVA shell. We systematically evaluated the corrosion resistance and autonomous healing performance of the developed coatings through electrochemical impedance spectroscopy (EIS) under two experimental conditions: immersion of intact (unscratched) coatings for up to 148 days, and immersion of deliberately scratched coatings for up to 16 days. Accelerated corrosion testing was also conducted using the salt spray (fog) method. To assess the evolution of damage and healing at the microscale, we examined the scratch regions using FE-SEM coupled with energy dispersive X-ray spectroscopy (EDS). The self-healing functionality correlated strongly with the high areal density and homogeneous distribution of the core–shell nanofibers within the coating matrix, ensuring a consistent and adequate release of the PDMS based healing agent upon damage. Notably, FE-SEM micrographs acquired after 480 h of exposure demonstrated complete closure and restoration of the scratched region, confirming the effectiveness of the embedded self-healing mechanism.