Multifunctional rGO–ZnO Composite Coatings with Enhanced Mechanical, Anticorrosion, and Antibacterial Characteristics for Practical Applications

This paper reports the development of multifunctional rGO–ZnO composite (RGZ) coatings with enhanced mechanical, anticorrosion, and antibacterial characteristics for practical marine applications. The structure and composition of the RGZ composite coatings are tuned to achieve distinct and compact intermetallic alloy layers, leading to improved hardness, wear resistance, friction resistance, electrochemical stability, and antibacterial activity. 0.3 wt %-RGZ composite coating with the highest Rct value (367.8 Ω cm2) exhibits the least corrosion rate (0.75 mmpy) as compared to the other compositions of the developed coatings. All the RGZ composite coatings exhibit enhanced antibacterial activity in different bacterial suspensions selected for the present study (Escherichia coli, Bacillus subtilis, and seawater consortium), and the 0.3 wt %-RGZ composite coating is demonstrated to be suitable for marine applications with the lowest bacterial survivability (20.3%) in the seawater consortium. The electrochemical stability and anticorrosion performance of the 0.3 wt %-RGZ composite coating even after long-term exposure (28 days) to seawater consortium confirmed from the largest Rct value (1154.7 Ω cm2) and the least icorr value (223.4 μA/cm2) indicate its suitability for practical application with excellent reusability. The enhanced antibacterial activity of the 0.3 wt %-RGZ composite coating as compared to other compositions of RGZ coatings and bare-Zn coating is attributed to its three-level bacterial destruction capability by inducing damage to the bacterial cell wall through physical damage, penetration of Zn2+ ions, and the activity of the photogenerated reactive oxygen species (ROS). The enhanced antibacterial activity and excellent electrochemical stability with attractive anticorrosion performance of 0.3 wt %-RGZ composite coating even after long-term exposure (28 days) in different bacterial suspensions, especially in seawater consortium, confirm its suitability for practical applications.