Fabrication of superhydrophobic Co/Ag composite coating via one-step electrodeposition for enhanced corrosion resistance and anti-biofouling performances

Corrosion and biofouling are common problems for metallic materials in the marine environment. There is a desire to develop new protection technologies to address these issues and promote the development of the marine economy. The preparation of superhydrophobic coatings on substrates is currently becoming an attractive method in the field of metal protection. In this study, a novel approach for fabricating superhydrophobic Co/Ag composite coating using a simplified one-step electrodeposition technique was developed. The superhydrophobicity was achieved through the codeposition of stearic acid, Co^{2 +} ions, and Ag nanoparticles. A cauliflower-like rough structure was observed on the carbon steel substrate. Wettability testing revealed that the resultant composite coating exhibited excellent superhydrophobic performance, with a water contact angle (CA) of 163.8° and a sliding angle (SA) as low as 3.5°. The dynamic behavior of water droplets on the surface of the coating was studied, and the surface adhesion work was measured. The extraordinary hydrophobic property of the coating resulted in a significant delay in the freezing time of the droplets on the surface, with a value of 344 s observed at a temperature of –10 ℃. Through testing using the cross-cut tape peeling and sandpaper abrasion, the produced coating's mechanical robustness was confirmed. Meanwhile, the superhydrophobic coating was proven to possess excellent chemical resistance and thermal stability. The mechanisms of anti-corrosion and anti-biofouling for the resulting coating were discussed. The corrosion current density of the superhydrophobic coating was two orders of magnitude lower than that of bare steel, thereby significantly improving corrosion resistance. Moreover, This Co/Ag composite coating exhibited an effective anti-biofouling capability towards Bacillus sp. and P. tricornutum because of its remarkable water repellency and the inherent anti-bacterial properties of Ag nanoparticles. Thus, the resulting coating can provide reliable protection for metal materials used in marine environments.