Zn-Mn composite coating codeposited with two-dimensional carbon nanoplatelets for improving corrosion resistance

Zn coating is a typical anti-corrosion coating for carbon steel. Considering the sacrificial nature of Zn coating, it is essential to enhance the corrosion resistance for the long-term performance in the practical application. In this work, two-dimensional carbon nanoplatelets (2D-CNs) with nanometer thickness (∼100 nm) and ultra-large lateral size (10–40 μm) and Mn element have been successfully co-deposited with Zn onto low carbon steel by a simple electrodeposition method. Results show that the Zn-Mn/2D-CNs composite coating is composed of Zn phase, ZnMn₃ phase and a small number of 2D-CNs. The Zn-Mn/2D-CNs composite coating exhibits a modified surface quality with ultrafine grains and smaller roughness (Ra = 176 nm, Rq = 131 nm) when compared with that of Zn coatings (Ra = 798 nm, Rq = 684 nm). Besides, the inert 2D-CNs within the composite coating can act as the corrosion barriers. Therefore, the Zn-Mn/2D-CNs composite coating has excellent anti-corrosion performance, owning the lowest corrosion current densities i_corr (9.2 μA cm⁻²) and maximum coating resistance R_coat (1.2 kΩ·cm⁻²) and charge transfer resistance R_ct (3.5 kΩ·cm⁻²), associated with its modified microstructure, Mn element with passivation property, and 2D-CNs barriers. These results demonstrate the desirable potentiality of inert 2D carbon materials in the electrodeposition of Zn-based coating for improving the corrosion resistance.