Compositions suitable for forming marine anti-fouling surface coatings comprise a polymer (e.g. maleinized polybutadiene) capable of cross-linking with amines, a hydrocarbyl polyisocyanate and a hydrocarbyl tin oxide or sulphide. The composition is preferably in two packs, which are combined on the surface to be coated, one pack containing the polymer and tin oxide or sulphide, and the other the polyisocyanate. A (thio) carbamate is formed as an intermediate which then hydrolyzes to an amine. A method of coating surfaces and surface coatings so produced are also claimed.
