Nacre-mimetic Strategy to Fabricate Waterborne FrGO/Zn/Epoxy Coatings with Dual Corrosion Protection.

Abstract

The service life of metal and other infrastructure requires extending through eco-friendly, low-carbon technology. Here, a nacre-mimetic γ-Fe2O3/reduced graphene oxide (FrGO)/zinc-containing epoxy coating (FrGO/Zn/epoxy coating) was fabricated by spraying a mixture of waterborne epoxy resin, zinc flakes, and magnetic conductive FrGO under a magnetic field. The FrGO, which was synthesized by in situ redox and precipitation, was aligned in the zinc-containing coatings (ZCC), and it oriented the zinc flakes in the direction of the magnetic field to mimic the lamellar structure of nacre. The obtained anti-corrosion coating showed enhanced barrier protection and cathodic protection, which was confirmed by the electrochemical tests and salt spray test results. The waterborne coatings less than 50 μm thick with parallelly aligned FrGO and 30 wt % zinc flakes exhibited a long cathodic period lasting more than 99 days and excellent barrier performance with a high initial coating resistance of 5.31 × 109 Ω·cm2, which was superior to that of the conventional zinc-rich coating containing 80 wt % zinc (80 days, 3.74 × 103 Ω·cm2). The dual anti-corrosion mechanism of the waterborne FrGO/Zn/epoxy coating was investigated. The integrity and long-term cathodic protection of the coatings were derived from the compactness achieved by the nacre-mimetic structure and the interface chemical and hydrogen bonding crosslinking interactions and the high, uniform zinc utilization achieved by the aligned FrGO-Zn charge transmission network. This work provides a feasible nacre-inspired strategy to fabricate a lightweight anti-corrosion waterborne ZCC that is resource-efficient and promising in creating compact materials with other functional properties, such as electromagnetic shielding and conductive networks.