1. The role of antifouling coatings
Essentially, antifouling coatings are meant to provide a coated surface that is free of biofouling for a specified period of validity. It can adopt different antifouling principles, but the most practical one is to use antifouling agent to effectively control the concentration of poisonous materials and inhibit biological adhesion. This requires that the antifouling coating can meet the requirement of controlled and slow release of antifouling agent, that is, there is a stable and effective antifouling agent exudation rate—the exudation amount of antifouling agent per square centimeter per day. Its antifouling effect is mainly determined by the exudation amount (exudation rate) of antifouling agent in the paint film. After the poison dissolves , it oozes into the seawater and forms a thin layer of toxic solution on the surface of the paint film to resist or kill the spores or larvae of marine organisms that try to stay on the paint film. The minimum exudation rate of the poison material required to prevent marine organisms from attaching is the critical exudation rate. If the exudation rate is too high, it will cause food costs and shorten the life of the coating. If the exudation rate is low, it will not be enough play an antifouling role.
Anti-fouling coatings also require: good adhesion with the anti-rust paint film on the lower layer, and incompatible ; the paint film has good seawater impact resistance and long-term immersion resistance
2. Types of antifouling agents
The antifouling agent should meet the following requirements: ①It has a broad anti-biological spectrum and can prevent the growth of attached organisms at a sufficiently low concentration; ②The solubility in seawater is low enough to ensure its effective seepage concentration , but avoid too fast ③ It meets the environmental requirements and is not only harmless to the production and construction personnel of the paint, but more importantly, it is harmless to marine organisms.
Antifouling agents are divided into inorganic and organic antifouling agents. Inorganic antifouling agents include copper powder and cuprous oxide; organic antifouling agents include organotin and the like.
