Preparation of poly(o-toluidine)/nano ZnO/epoxy composite coating and evaluation of its corrosion resistance properties

• Poly(o-toluidine)/nano ZnO composite was prepared by in situ polymerization method.
• The composition and structure of composite were characterized.
• Certain physicochemical interaction existed between poly(o-toluidine) and nano ZnO.
• Nano ZnO enhanced the barrier properties of the composite coating.
• Poly(o-toluidine)/nano ZnO/epoxy coating possessed excellent corrosion resistance.

Poly(o-toluidine)/nano ZnO composite was prepared by in situ polymerization of o-toluidine monomer in the presence of nano ZnO particles. Fourier transformation infrared spectroscopy (FT-IR), UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Thermogravimetric analysis (TGA) were used to characterize the composition and the structure of the composite. Poly(o-toluidine)/nano ZnO composite was mixed with epoxy resin through a solution blending method and the poly(o-toluidine)/nano ZnO/epoxy composite coating was coated onto the surface of steel sample, and its corrosion resistance properties were studied by potentiodynamic polarization, electrochemical impendence spectroscopy measurements and immersion test in 3.5% NaCl solution and also compared with that of poly(o-toluidine)/epoxy composite coating, pure epoxy coating and uncoated steel sample. The results showed that the composite coating containing poly(o-toluidine)/nano ZnO composite has higher corrosion resistance than that of poly(o-toluidine). The enhancement of corrosion protection ability of poly(o-toluidine)/nano ZnO composite containing coating may be due to the formation of more uniformly passive layer on steel surface and the addition of nano ZnO particles, which increases the tortuosity of the diffusion pathway of corrosive substances.

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