Bilayer Zn-primer/Cu2O-topcoat ethyl silicate coating: a promising approach for combined marine corrosion and fouling resistance.

Abstract

Protecting marine metallic structures requires coatings that provide both corrosion resistance and antifouling. This research investigated multifunctional ethyl silicate coatings combining zinc (Zn) and copper(I) oxide (Cu2O). We compared four systems: Zn-only, Cu2O-only, a single-layer Zn/Cu composite, and a bilayer Zn+Cu structure (Zn primer/Cu2O topcoat). Comprehensive evaluations included electrochemical corrosion behavior (DC polarization, 60-day EIS in 3.5 wt% NaCl), ion release kinetics, and long-term antifouling efficacy via 12-month natural marine exposure. Results revealed distinct performance profiles. The Zn coating provided excellent short-term corrosion protection but failed antifouling tests. Conversely, the Cu2O coating showed good initial antifouling via effective Cu release (~ 12–14 µg/cm2.day) but had poor corrosion resistance. The composite Zn/Cu coating exhibited intermediate properties. Significantly, the bilayer Zn+Cu system demonstrated the most favorable synergy, offering the best long-term corrosion resistance (highest impedance via EIS after 60 days), superior adhesion, sustained effective copper release (3.41 µg/cm2.day), and outstanding antifouling performance over 12 months. This study underscores the decisive role of coating architecture, identifying the bilayer Zn+Cu structure as a highly promising configuration for developing durable, multifunctional protective coatings for maritime applications.