The influence of graphene on the cathodic protection performance of zinc-rich epoxy coatings

Abstract

Graphene has been proved to benefit the corrosion protection of zinc-rich epoxy coatings (ZREs) in 3.5 wt% NaCl solution. However, galvanic corrosion between graphene and zinc powders and its influence on the cathodic protection is still unknown. In this paper, ZREs with different graphene contents were prepared, and open-circuit potential and electrochemical impedance spectroscopy techniques were employed to evaluate the cathodic protection of the coatings. To further investigate the influence mechanism of graphene content on ZRE, the porosity of the coatings was measured with mercury intrusion porosimetry, and the corrosion rate of zinc was measured with the H2 evolution technique. The results from these experiments reveal that the graphene content exhibits an optimum of 0.3 wt%. With a graphene content lower than 0.3 wt%, the porosity of the coating decreases with increasing graphene content, which will decrease the corrosion rate of zinc and prolong the cathodic protection duration of the coating. With a graphene content higher than 0.3 wt%, the galvanic corrosion between graphene and zinc powders increases the corrosion rate of zinc, leading to a shortened cathodic protection duration. Exploring the galvanic corrosion process between graphene and zinc content can offer insights for the development of the ZRE with graphene, which facilitates solving the problems associated with the high zinc content.