Anti-Fouling Systems (AFS Convention)

AFS Convention: TBT and cybutryne controls, treatment of existing coatings and ship-specific documentation.

Operational Explanation

The AFS Convention covers anti-fouling coatings, treatments, surfaces and devices, not just paints below the waterline. Articles 2–3 define systems and scope; Annex 1 controls substances; Annex 4 governs surveys and documents.

Organotin compounds acting as biocides, including TBT, must not be applied or reapplied. For old layers, verify absence of the prohibited system or a compliant barrier preventing leaching, supported by evidence: historical presence and new application are different situations.

From 1 January 2023 systems containing cybutryne must not be applied or reapplied. Ships with cybutryne in the external coating on 1 January 2023 must remove it or provide a barrier at the next scheduled renewal, no later than 60 months after its last application. Exceptions to this second obligation concern fixed/floating platforms, FSUs and FPSOs constructed before 2023 and not dry-docked since 1 January 2023; ships not on international voyages; and international ships below 400 GT if accepted by the relevant coastal States. No exception permits new cybutryne applications.

Regulatory Reference

AFS Convention, articles 2–3 and Annexes 1/4: Convention text, UK Treaty Series. Cybutryne controls and updated documents: MEPC.331(76).

IAFS validity (Annex 4, regulation 4): there is no automatic five-year renewal. The certificate ceases to be valid if the system is changed or replaced without the required endorsement, or upon a flag transfer; the latter requires a new certificate from the competent Administration.

The AFS Convention is separate from MARPOL; its placement in this module is thematic.

Scope of Application

Separate three checks: Convention applicability through flag/authority and entry to Parties’ ports, shipyards or terminals, subject to article 3 exclusions; the controlled substance/system; and the required document. International service is not a general exemption from prohibitions. International ships ≥400 GT require surveys and an IAFS, excluding fixed/floating platforms, FSUs and FPSOs; international ships ≥24 m and <400 GT require a Declaration signed by the owner or authorized agent with supporting documentation, also excluding fixed/floating platforms, FSUs and FPSOs (Annex 4, regulation 5). Being below a documentary threshold does not authorize prohibited biocides.

Procedure / How to Complete It

1. Establish scope and the IAFS/Declaration route or relevant national requirements.
2. Check composition and layer history: no TBT or a compliantly isolated old layer; no prohibited new application.
3. For cybutryne check the external coating on 1 January 2023, category and any exception conditions before calculating renewal/60 months.
4. After work subject to survey, arrange inspection and certificate endorsement/update with the Record of Anti-fouling Systems. An internal log does not replace them. Follow the separate Declaration route where applicable.
5. Keep product sheets, declarations and yard documents. The two-year certification transition expired on 1 January 2025 and is no longer open in 2026.

Practical Example

Scenario: a 20,000 GT international containership, cybutryne applied in March 2021 and still in the external coating on 1 January 2023, with no applicable exception. Removal or a barrier is due at the scheduled autumn 2025 renewal; the March 2026 maximum does not allow that renewal to be bypassed. A yard delay to June 2026 is not cured merely by notifying the flag: meet the deadline or establish a genuinely applicable, verified alternative legal basis.

What Typically Goes Wrong

Common Mistakes Mistake Library

Avoid equating “no dry-docking since 2023” with an exception for an ordinary ship, confusing documentary thresholds with freedom of use, renewing a system with only an internal entry, or treating flag notification as an automatic extension.

What the PSCO Checks

A PSCO may examine the document required for the ship, its attached Record, correspondence with the system and product/work evidence. Not all ships carry the same certificate, but absence of an IAFS requirement does not remove applicable substantive controls.

Operational Tips

• Check composition and earlier layers before booking renewal.
• Link work, survey and statutory document updates where required.
• Calculate cybutryne deadlines only after checking all conditions and exceptions.

Preparation checklist

Educational checklist. This summary supports learning and preparation only. It does not replace the vessel’s approved procedures, manuals, statutory documents, company SMS, or applicable official requirements. Completing it demonstrates neither compliance nor readiness for an inspection: it shows that a list has been read, not that the ship is in order. Always verify the current documents carried on board.

• Convention scope distinguished from documentary threshold
• No TBT or compliantly isolated old layer
• Cybutryne: no new application; external layer, exceptions and deadlines checked
• Survey/endorsement and Record or Declaration updated where required
• Product and yard evidence retained

FAQ

Related Topics

Last substantive revision of this page: 15 September 2026 · page fingerprint 1f1ac13d23f3