Enhancing the corrosion resistance of waterborne epoxy coatings using poly(sodium styrene sulfonate)-modified carbon nanotubes
Haoxuan Yang, Yang Sun, Junlong Ma, Zeyu GuoPurpose
Waterborne epoxy (WEP) coatings are environmentally friendly but exhibit limited long-term corrosion resistance. This study aims to improve the protective performance of WEP coatings by incorporating poly(sodium styrene sulfonate)-modified carbon nanotubes (CNT-PSS). The modification strategy is intended to enhance nanotube dispersion, suppress galvanic corrosion and inhibit chloride ion transport, addressing key drawbacks of CNT-filled epoxy coatings reported in recent anticorrosion studies.
Design/methodology/approach
CNT-PSS composites were synthesized by covalently grafting PSS onto carboxylated multi-walled carbon nanotubes and incorporated into WEP coatings at various loadings. The structure, composition and dispersion behavior of CNT-PSS were characterized using SEM, TEM, FT-IR, Raman spectroscopy, XPS, TGA, DLS and zeta potential analysis. Corrosion resistance was evaluated through electrochemical impedance spectroscopy, potentiodynamic polarization, salt spray testing and adhesion measurements.
Findings
PSS modification markedly improved CNT dispersion stability and introduced strong electrostatic repulsion toward chloride ions. The coating containing 0.2 Wt.% CNT-PSS exhibited optimal performance, maintaining an impedance modulus of 3.56 × 108 Ω·cm2 after 30 days of immersion, approximately four orders of magnitude higher than that of the neat WEP coating. Excessive CNT-PSS loading caused aggregation and ionic gel layer formation, accelerating localized corrosion.
Originality/value
This study proposes a dual-function CNT modification approach that simultaneously enhances dispersion and mitigates galvanic corrosion in WEP coatings. The results clarify the relationship between filler loading, electrostatic shielding and long-term corrosion stability, providing practical guidance for the design of environmentally friendly, high-performance anticorrosive coatings.