Corrosion resistance of functionalized carbon nanotubes enhanced epoxy coatings on sintered NdFeB magnets

Abstract

In this work, tannic acid (TA) was employed to modify the surface of multiwall carbon nanotubes (CNTs) to form TCNTs hybrids via noncovalent functionalization to enhance its dispersibility in water. Then, the TCNTs enhanced epoxy coatings were applied on sintered NdFeB magnets by cathodic electrophoretic deposition method for corrosion test. The corrosion resistance of prepared specimens was assessed by electrochemical experiments. The results show that TCNTs hybrids present a more homogeneous distribution in epoxy resin than pristine CNTs and could obviously promote anticorrosion properties of prepared specimens. Within 36-day soaking in 3.5 wt.% NaCl solution, the specimens maintain a high value of |Z|_0.01Hz (10⁸ Ω cm²) when the concentration of TCNTs is 2 g/L. When immersed in 3.5 wt.% NaCl solution for 40 days, the E_corr of specimens shifts to − 0.207 V and J_corr is about 5.281 × 10⁻¹¹ A cm⁻², which demonstrates superior corrosion resistance.