Cybutryne banned in anti-fouling systems from 1 January 2023


( In July 2021, at the 76th session of the Marine Environment Protection Committee (MEPC 76), the IMO adopted an amendment to the International Convention on the Control of Harmful Anti-fouling Systems on Ships (AFS Convention). This statutory news describes this requirement in more detail and provides recommendations for a smooth process towards compliance.

In addition to the already prohibited organotin compounds which act as biocides (try butyl tin, TBT) in anti-fouling systems, the ingredient cybutryne (CAS No. 28159-98-0) will be prohibited as per the amendments to the AFS Convention entering into force on 1 January 2023. The affected ship types and effective dates are listed in the table below:

Anti-fouling systemControl measuresApplicationEffective date
Cybutryne CAS No. 28159-98-0Ships shall not apply or re-apply anti-fouling systems containing this substance.All ships1 January 2023
Cybutryne CAS No. 28159-98-0Ships bearing an anti-fouling system that contains this substance in the external coating layer of their hulls or external parts or surfaces on 1 January 2023 shall either: (1) remove the anti-fouling system; or (2) apply a coating that forms a barrier to this substance leaching from the underlying non-compliant anti-fouling system.All ships except: (1) fixed and floating platforms, FSUs and FPSOs that have been constructed prior to 1 January 2023 and that have not been in dry-dock on or after 1 January 2023; (2) ships not engaged in international voyages; and (3) ships of less than 400 gross tonnage engaged in international voyages, if accepted by the coastal state(s).At the next scheduled renewal of the anti-fouling system after 1 January 2023, but no later than 60 months following the last application to the ship of an anti-fouling system containing cybutryne.


The International AFS certificate will change as of 1 January 2023 to include extra cybutryne tick boxes for the compliance options on controlled anti-fouling systems.

Ships in operation will need to comply with the requirement within the first anti-fouling renewal survey after 1 January 2023 and will be issued a new International AFS certificate which includes cybutryne-free compliance.

Ships under construction, which will be delivered after 1 January 2023, will need to be delivered as both TBT and cybutryne-free, and will be issued with an AFS certificate at the initial survey.


Owners/Managers to remain aware of vessel and fleet survey and docking schedules for both newbuildings and fleets in service for anti-fouling purchases. These should be accompanied by cybutryne-free statements from the manufacturers in order to obtain an AFS certificate from the attending surveyor.

Source: IMO







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