TBT free coating

A TBT-free coating is a hull anti-fouling paint that contains no tributyltin or other organotin biocides, the substances banned by the AFS Convention. Since 1 January 2008 no ship may apply or re-apply organotin anti-fouling systems, and existing TBT coatings must be removed or sealed under an overcoat. Modern alternatives use copper-based biocides, booster biocides, or biocide-free silicone and fluoropolymer foul-release coatings. Ships of 400 GT and above carry an International Anti-fouling System Certificate confirming the system complies; surveyors and port state control verify the coating type. The ban followed evidence that TBT caused imposex in marine gastropods at very low concentrations.