Zinc- and sodium gluconate-modified carbon nanotubes enhance the barrier performance and provide effective self-healing properties for a new epoxy coating.

A research team led by Maryam Sanchuli has developed a novel smart nanocarrier system to enhance the corrosion resistance of epoxy coatings. Oxidised multi-walled carbon nanotubes (OMWCNTs) were functionalised with zinc ions and sodium gluconate (SG-OMWCNTs-Zn) and incorporated into an epoxy matrix.

Structural characterisation of the modified nanoparticles was conducted using X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), BET surface analysis and UV–Vis spectroscopy. Electrochemical tests (EIS, potentiodynamic polarisation) demonstrated that adding SG-OMWCNTs-Zn reduced steel corrosion by approximately 86 % in saline environments.

Enhanced adhesion and reduced cathodic disbondment

Embedding SG-OMWCNTs-Zn into epoxy led to an 83 % improvement in adhesion strength and a 75 % reduction in cathodic disbondment compared with unmodified epoxy coatings. In salt spray tests, SG-OMWCNTs-Zn containing samples exhibited a corrosion resistance of 57,008 Ω·cm² after 48 hours – around four times higher than neat epoxy. Additionally, intact coatings showed a 49 % increase in impedance.

Theoretical studies using DFT-D methodology confirmed the strong adsorption of zinc and gluconate complexes onto the carbon nanotube surfaces, supporting the experimental findings of enhanced self-healing and corrosion protection properties.

Source: Progress in Organic Coatings, Volume 200, March 2025, 109045