Insight into the Impact of Conducting Polyaniline/Graphene Nanosheets on Corrosion Mechanism of Zinc-Rich Epoxy Primers on Low Alloy DH32 Steel in Artificial Sea Water

The mechanism of polyaniline-grafted Graphene (PANI-Gr) nanosheets on the corrosion performance of zinc-rich epoxy primer (ZRP) coatings was studied. Highly crystalline PANI nanosheets were chemically synthesized on the modified Gr nanosheets and analyzed using Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and high-resolution transmission electron microscopy (HR- TEM). Different from the whole coating measurements via the open circuit potential and electrochemical impedance spectroscopy (EIS) measurements, herein, we focused on the corrosive characteristics at defect areas. Potential changes of the artificial defect-included samples and localized EIS of the defect area were conducted, to investigate the impact of the PANI-Gr fragments on corrosion process. The electrochemical results indicated that a mixture of Gr at a content of 0.6% enhanced the sacrificial cathodic protection of ZRP coating due to extending its active sacrificial period. Further, the most pronounced improvement in the ZRP properties was obtained through PANI-Gr modification. A synergetic enhancement of the coating physical barrier and zinc sacrificial cathodic protection was obtained in the case of ZRP including PANI-Gr nanosheets. Thus, this study suggests a new strategy for simultaneously providing the enhanced cathodic and barrier protection activities for ZRP. (C) 2018 The Electrochemical Society.