Effect of Conducting Polyaniline/Graphene Nanosheet Content on the Corrosion Behavior of Zinc-Rich Epoxy Primers in 3.5% NaCl Solution.

Yanhua Lei,Dongdong Li,Yanhong Gu,Xueting Chang,Ning Tan,Yansheng Yin,Yuliang Zhang,Zhichao Qiu,Tao Liu,Jiurong Liu

doi:10.3390/polym11050850

Abstract

The corrosion behavior of zinc-rich epoxy primers or paints (ZRPs) with different conducting polyaniline-grafted graphene (PANI/Gr) contents was investigated. Conductivity of the formed PANI/Gr nanosheets was significantly improved by employing the Gr as the inner template to synthesize the PANI. The protective properties and electrochemical behavior of coatings with artificial defects were investigated by monitoring the free corrosion potential versus time and by using localized electrochemical impedance spectroscopy (LEIS). A synergetic enhancement of the physical barrier role of the coating and the zinc sacrificial cathodic protection was achieved in the case of ZRP including PANI/Gr nanosheets. In addition, the ZRP mixed with the PANI/Gr at a content of 0.6% exhibited the best anticorrosion performance across the range of investigated PANI/Gr contents.

Highlights

Organic coatings are applied to protect steel from corrosion due to their inhibition behavior, barrier function, and cathodic protection [1]
The conductivity of the PANI sample was evaluated at 5 S cm−1, which was comparable to the results of Stejskal and Gilbert [18]
Conductivity measurements indicate that the synthesized polyaniline-grafted graphene (PANI/Gr) shows higher conductivity compared to the PANI

Summary

Introduction

Organic coatings are applied to protect steel from corrosion due to their inhibition behavior, barrier function, and cathodic protection [1]. Zinc-rich epoxy primers or paints (ZRPs) are widely used as cathodic protection in a variety of severe environments via two protective mechanisms. Sufficient electrical contact between coating and substrate is established because of the high zinc content. After the electrolyte diffuses into the coating, the zinc particles provide cathodic protection via the sacrificial anodic dissolution, thereby promoting the electrochemical process of a Zn–Fe microcell. As the organic and inorganic binders which are commonly used in ZRPs are naturally non-conductive, the electrical contact between the spherical zinc particles and steel substrates could not be maintained for a long time. High zinc content (normally higher than 65 wt %) is necessary to ensure electrical conductivity [3]. The utilization ratio of the zinc particles is very low [4], which is a waste of resources and results in environmental pollution

Methods

Results

Conclusion