PURPOSE: To obtain a coating composition which can form a cured film within a short time, can be handled without any danger and can prevent the deposition of, for example, marine life for a long time, by mixing a paint with a reaction product of a hydroxylated liquid diene polymer with maleic acid (anhydride).

CONSTITUTION: A coating composition is obtained by kneading a paint with a reaction product of a hydroxylated liquid diene polymer (e.g., hydroxylterminated polybutadiene) with maleic acid or maleic anhydride. This composition as such or mixed with a solvent is applied to an object and is heated for a short time to form a cured film, and the cured film is excellent in an effect of preventing the deposition of marine life and can retain its effect for a long time. Further, this paint composition can be handled without any danger and is excellent in safety. Further because of its excellent waterproofness and rust-preventive property, it can be effectively used as a marine paint, a paint for underwater and submarine pipes, alga-repelling paint, etc.