HE Hao, FAN Qixiang, WANG Tiegang, LIU Yanmei, CAO Fengting
Marine biofouling poses a persistent challenge for submerged mechanical equipment, leading to accelerated corrosion, operational inefficiencies, and significant economic losses. The accumulation of microbial communities on marine surfaces not only damages equipment but also substantially increases maintenance costs, creating a critical bottleneck for sustainable marine resource development. Addressing this issue through effective antifouling solutions has become a global research priority in marine engineering. Current antifouling technologies primarily encompass mechanical removal, ultrasonic cleaning, and protective coatings, with antifouling coatings emerging as the most widely adopted solution due to their cost-effectiveness, ease of application, and superior performance. There is a wide variety of antifouling coatings, each with distinct antifouling mechanisms. However, comprehensive reviews on the antifouling performance, advantages, and disadvantages of both traditional and novel antifouling coatings remain scarce. Thus, a comprehensive review is conducted on the research advancements of both traditional and novel antifouling coatings, such as natural antifoulant coatings, biomimetic coatings, self-healing coatings, etc. Their research status, antifouling mechanisms, and remaining challenges are discussed. Traditional antifouling coatings can be categorized into matrix-insoluble and matrix-soluble types. The former operate through the gradual release of embedded biocidal compounds that deter or eliminate fouling organisms. However, these coatings exhibit significant limitations, including short service lifetimes and complex application requirements, which restrict their widespread adoption in marine applications. Self-polishing antifouling coatings (SPCs), the most currently commercially successful matrix-soluble system, dominating 90% of the global market, utilize hydrolyzable polymer side chains to enable controlled antifoulant release. However, their uneven release kinetics (initial excess followed by insufficiency) compromises long-term performance, and their dependence on toxic biocides raises environmental concerns. In contrast to these traditional coatings that rely on biocidal agents, fouling-release coatings achieve antifouling effects solely through their low surface energy, preventing fouling organisms from firmly adhering. Under water flow, fouling organisms detach easily, providing excellent antifouling performance without harming the marine environment. However, these coatings perform poorly under static conditions, and their adhesion to substrate needs improvement. Natural antifoulant coatings derive their active substances from antifouling compounds secreted by plants and animals or their synthetic analogs. They reduce marine biofouling by inhibiting adhesion processes and interfering with microbial signaling systems. Compared to traditional antifoulants, natural antifoulants are less toxic and significantly reduce environmental impact. However, challenges such as broad-spectrum efficacy and long-term durability remain unresolved. Biomimetic coatings utilize micro- and nanostructures from self-cleaning natural surfaces (via 3D printing, laser etching, or transfer techniques) to achieve efficient and eco-friendly antifouling effects, showing high application potential. However, these coatings often suffer from low mechanical strength, poor adaptability, and high production costs. Self-healing marine coatings integrate specialized repair agents that autonomously mend surface damage, overcoming key limitations of conventional systems by extending service life and maintaining antifouling efficacy. Despite their potential for significant economic and performance benefits, commercialization challenges persist, including complex fabrication, high costs, and difficulties in scaling beyond laboratory prototypes. Photocatalytic coatings rely on photocatalysts to undergo redox reactions under specific light wavelengths, decomposing seawater and dissolved oxygen to generate reactive oxygen species (ROS). These ROS penetrate cell membranes, damage microbial DNA, and cause cell rupture, achieving antifouling through microbial inactivation. These coatings are safe, efficient, non-toxic, and pollution-free. However, their performance is highly dependent on UV intensity and light energy utilization, requiring further improvements in stability. Hydrogel coatings contain high water content (typically >70%, even >90%), forming a dense and dynamic hydration layer through hydrogen bonding between polymer chains and water molecules. This layer effectively blocks fouling organism attachment. However, their poor mechanical properties and weak adhesion limit broader applications. Despite the variety of marine antifouling coatings available, single mechanism approaches generally fail to meet the complex demands of marine environments, particularly regarding long-term efficacy, broad-spectrum performance, and environmental safety. To overcome these limitations, we propose the strategic integration of multiple antifouling mechanisms within hybrid coating systems. This synergistic approach aims to combine the advantages of different technologies while mitigating their individual weaknesses, paving the way for next-generation antifouling solutions that balance performance, durability, and ecological sustainability. The findings provide valuable insights for developing advanced marine coatings.
