The effect of spherical Zn of Cu₂O/ZnAl embedded into ethyl silicate coatings for corrosion and fouling protection of steel

Traditional antifouling coatings for metal substrates typically involve three layers including an anticorrosion primer, a midcoat, and an antifouling paint. However, the limited bonding capacity between these layers restricts their effectiveness in industrial metal corrosion protection. In this work, we developed a single coating by dipping method on steel substrate that combines the anticorrosion properties of zinc and the antifouling properties of copper, using an ethyl silicate binder. This pigment mixture, containing flake ZnAl (5 wt%) and Cu₂O (10 wt%) with varying spherical Zn content (30, 40, and 50 wt%), was created and tested for its anticorrosion capabilities. Electrical properties were characterized using electrochemical impedance spectroscopy and the polarization curve method. Results showed that after 60 days of immersion in 3.5 wt% NaCl solution, the low-frequency impedance modulus of the coatings increased with higher Zn content, with the 40 wt% Zn content achieving the highest efficiency, showing an impedance modulus value of 56.43 kΩ cm². Stability evaluations revealed an increased release of Zn and Cu content in samples with higher Zn content. Antifouling assessments in natural seawater demonstrated that the Zn40 integrated coating had the lowest fouling density among the tested samples, with hard fouling surface coverage (FR ≥ 40) at 9.31% after three months. These findings highlight the effectiveness of the integrated coating utilizing Zn and Cu in providing robust corrosion protection, preventing settlement, and inhibiting fouling marine growth.