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<p>This study aims to elucidate how reduced graphene oxide (rGO) content influences the balance between cathodic protection and barrier performance in zinc-rich waterborne epoxy coatings. By systematically varying rGO mass fractions (0.3, 0.5 and 1.0%) in a bilayer coating system, the work seeks to identify the optimal filler loading for long-term corrosion resistance and to establish quantitative models for water and ion diffusion within the coating. Three bilayer coatings (DC-0.3, DC-0.5 and DC-1.0) were formulated, combining an inner rGO-reinforced zinc-rich epoxy layer with an outer rGO-modified epoxy layer. Their corrosion behavior was characterized through electrochemical impedance spectroscopy (EIS) and LCR capacitance measurements over extended immersion in 3.5&#xa0;wt.% NaCl. Equivalent circuit fitting yielded key resistive and capacitive parameters, while Fick’s second law and Brasher–Kingsbury analysis were employed to derive semi-infinite and finite-layer diffusion kinetics equations. The DC-0.5 coating delivered the best compromise between electron conductivity and barrier integrity, exhibiting the highest pore resistance, lowest water diffusion coefficient and stable zinc oxidation rate without observable steel corrosion. DC-0.3 suffered from insufficient conductive pathways and rapid water ingress, while DC-1.0 initially enhanced cathodic protection but developed excessive porosity that was later sealed by zinc corrosion products. Water uptake followed Fickian behavior in all systems, and kinetic models for both semi-infinite and finite-layer diffusion were successfully formulated. This work provides a comprehensive mechanistic framework that couples in-depth EIS analysis with diffusion kinetics modeling to optimize graphene content in zinc-rich epoxy coatings. The derivation of explicit semi-infinite and finite-layer diffusion equations represents a novel contribution, enabling predictive design of coating formulations. The findings offer actionable guidance for developing durable, environmentally friendly anticorrosive coatings with tailored sacrificial and barrier functionalities.</p>

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In-depth Analysis of Electrochemical Impedance Spectra and Diffusion Kinetics Modeling of Graphene-Reinforced Zinc-Rich Waterborne Epoxy Anticorrosive Coatings

  • 期刊论文

  • 发表日期：

    2026年3月9日

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  • Xiao Liu,
  • Rui Ding,
  • Bing Bai,
  • Jin-ying Li,
  • Yi-wen Zhang,
  • Hao-han Cao,
  • Yu-han Wang,
  • Yu-lin Zhang,
  • Ming-di Lei,
  • Jie Liu

摘要

This study aims to elucidate how reduced graphene oxide (rGO) content influences the balance between cathodic protection and barrier performance in zinc-rich waterborne epoxy coatings. By systematically varying rGO mass fractions (0.3, 0.5 and 1.0%) in a bilayer coating system, the work seeks to identify the optimal filler loading for long-term corrosion resistance and to establish quantitative models for water and ion diffusion within the coating. Three bilayer coatings (DC-0.3, DC-0.5 and DC-1.0) were formulated, combining an inner rGO-reinforced zinc-rich epoxy layer with an outer rGO-modified epoxy layer. Their corrosion behavior was characterized through electrochemical impedance spectroscopy (EIS) and LCR capacitance measurements over extended immersion in 3.5 wt.% NaCl. Equivalent circuit fitting yielded key resistive and capacitive parameters, while Fick’s second law and Brasher–Kingsbury analysis were employed to derive semi-infinite and finite-layer diffusion kinetics equations. The DC-0.5 coating delivered the best compromise between electron conductivity and barrier integrity, exhibiting the highest pore resistance, lowest water diffusion coefficient and stable zinc oxidation rate without observable steel corrosion. DC-0.3 suffered from insufficient conductive pathways and rapid water ingress, while DC-1.0 initially enhanced cathodic protection but developed excessive porosity that was later sealed by zinc corrosion products. Water uptake followed Fickian behavior in all systems, and kinetic models for both semi-infinite and finite-layer diffusion were successfully formulated. This work provides a comprehensive mechanistic framework that couples in-depth EIS analysis with diffusion kinetics modeling to optimize graphene content in zinc-rich epoxy coatings. The derivation of explicit semi-infinite and finite-layer diffusion equations represents a novel contribution, enabling predictive design of coating formulations. The findings offer actionable guidance for developing durable, environmentally friendly anticorrosive coatings with tailored sacrificial and barrier functionalities.