Comparative study on anti-corrosion behavior of granular polypyrrole and polypyrrole nanotube in waterborne epoxy coatings

Polypyrrole was utilized as nanofillers in waterborne coatings to enhance the anti-corrosion performance of the composite coatings. The morphology of the polypyrrole plays an important role in the performace of the composite coatings. It is of great significance to clarify how the morphology of polypyrrole affects the performance of water-based coatings. Herein, granular polypyrrole and polypyrrole nanotubes, namely GP and PNT, were prepared by chemical oxidation polymerization. The structure and morphology of GP and PNT were characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The different morphology of polypyrroles were incorporated into waterborne epoxy resin (WEP) to fabricate GP and PNT composite coatings, namely GP-WEP and PNT-WEP. The thermal performance, conductivity, physical and mechanical properties, and anti-corrosion properties of the composites and coatings were investigated. The effect of the morphology of polypyrrole on the thermal stability, conductivity, physical and mechanical properties, as well as the anti-corrosion performance of the composite coatings were discussed. Compared to GP-WEP, PNT-WEP significantly improved the anti-corrosion performance of composite coatings due to its higher conductivity and fiber reinforcement. The highest impedance at low frequency reached as high as 2.14 × 108 Ω·cm2 with a 1.5 % addition. The reinforcement of anti-corrosion mechanism of PNT-WEP was attributed to cathodic protection, anodic protection and shielding enhancement based on fiber increase mechanism.