Multifunctional Epoxy Coatings with Gallic Acid-Functionalized Multi-Wall Carbon Nanotubes: Corrosion Resistance and Thermo-Mechanical Performance for Steel Protection

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Document Type : Original Article

Authors

1 Department of Nanomaterial and Nanocoatings, Institute for Color Science and Technology (ICST)

2 Department of Nanomaterials and Nanocoatings, Institute for Color Science and Technology, P.O. Box 16765-654, Tehran, Iran

3 Department of Surface Coatings and Corrosion, Institute for Color Science and Technology, P.O. Box 16765-654, Tehran, Iran

Abstract

Abstract

Amine-functionalized multi-wall carbon nanotubes (MWCNTs-NH₂) were employed as nanocarriers for gallic acid (GA), a green corrosion inhibitor, to develop multifunctional epoxy nanocomposites for steel protection in saline environments. GA was effectively immobilized onto MWCNTs-NH₂ to attain both active corrosion inhibition and enhanced barrier performance. Electrochemical impedance spectroscopy and polarization performed after 72 hours of immersion in saline solution indicated ~ 91% rise in total resistance and ~ 47% decrease in corrosion current density for the optimized MWCNT-NH₂/GA system, in comparison to uninhibited samples. Epoxy coatings incorporating 0.15 wt.% of the synthesized nanocomposites demonstrated active protection in damaged regions, as confirmed by EIS and salt spray testing. Following 24-hour exposure to saline solution, the total resistance of the epoxy coating with 50% GA-loading exhibited an increase of ~ 560% relative to the bare samples. Furthermore, the log|Z|10 mHz value, which acts as a suitable measure for evaluating the self-healing ability in the scratched region, increased to ~4.8 kΩ.cm2. While, it showed a notable decrease for uncoated epoxy, falling below 0.4 kΩ.cm2. These coatings also exhibited significantly improved adhesion under both dry and wet conditions. Adhesion loss for epoxy coating containing optimal 50% GA-loading was ~6%. Notably, cathodic disbondment were reduced by 50% and 42% relative to neat epoxy and MWCNTs-NH₂ contained epoxy coatings, respectively, in 50% GA-loaded formulation. Furthermore, Thermo-mechanical analysis confirmed enhanced toughness reinforcement. Overall, the synergistic barrier effect of MWCNTs-NH₂ and controlled release of gallate ions provide a promising strategy for durable, self-healing corrosion protection in harsh environments.

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Progress in Color, Colorants and Coatings

Articles in Press, Accepted Manuscript
Available Online from 12 November 2025

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