AFS Convention · MEPC.331(76) · MEPC.405(83) · MEPC.378(80)
AFS Convention, Cybutryne Ban and Biofouling Records Checklist
Updated · Written by SeaReady in our own words. Not affiliated with OCIMF, RightShip, CDI, any MoU or any administration — always check the current official documents.
1. Anti-fouling certificate, declaration and the cybutryne ban
The AFS Convention controls harmful anti-fouling systems on ships. Which document a ship carries depends on its size, and the record attached to the certificate must follow every change of hull coating. Drydock coating inspection itself is covered in the hull survey and coating guide, and the survey cycle in the flag and class survey checklist.
| Certificate or rule | What it requires | What to check on board |
|---|---|---|
| International Anti-fouling System Certificate (AFS Convention) | Ships of 400 GT and above on international voyages hold an International Anti-fouling System Certificate with its attached Record of Anti-fouling Systems. The record names the coating on the hull and is updated whenever the anti-fouling system is changed or replaced. | Compare the coating named on the record with the paint specification from the last drydock. A record still showing the previous scheme after a re-coat is a common finding. |
| Declaration on Anti-fouling Systems (AFS Convention) | Ships of 24 m or more in length but under 400 GT on international voyages carry a declaration signed by the owner or the owner’s authorised agent, with supporting documents such as the paint receipt or contractor invoice. | Check the declaration is signed and that the paint documents on board match the coating actually applied. |
| Cybutryne ban (IMO Res. MEPC.331(76), in force 1 January 2023) | Anti-fouling systems containing cybutryne may no longer be applied or re-applied. A ship that still carries such a coating has it removed or covered with a sealer coat at the next scheduled renewal of the anti-fouling system, and no later than 60 months after it was last applied. Organotin compounds acting as biocides have been banned under the Convention for much longer. | Check the record shows a cybutryne-free system, or a sealer coat, and that the date of the last cybutryne application (if any) is known. |
| Port State Control (IMO Res. A.1206(34)) | No valid anti-fouling certificate or declaration, or a banned anti-fouling system on the hull, is listed among the detention grounds in the PSC procedures. | Keep the certificate or declaration with the other statutory certificates and the drydock coating report ready for the boarding officer. |
2. IHM cybutryne thresholds and the 2023 biofouling guidelines
The Inventory of Hazardous Materials as a whole is covered in our IHM and ship recycling guide. Biofouling sits beside ballast water as an invasive species risk (see the ballast water management guide), and a fouled hull and propeller also burn more fuel, which shows in the ship’s CII rating.
| Instrument | What it says | What to check on board |
|---|---|---|
| IHM cybutryne thresholds (IMO Res. MEPC.405(83), amending MEPC.379(80)) | Adopted 11 April 2025 and effective no later than 26 June 2025, when the Hong Kong Convention entered into force. Table A row A-4 now gives two cybutryne values: 1,000 mg/kg for a dry coating sample taken from the hull and 200 mg/kg for a wet paint sample taken from the container. The organotin threshold stays at 2,500 mg total tin/kg. | For ships that keep an Inventory of Hazardous Materials, check the supplier Material Declarations for new hull paint use these thresholds and are filed in IHM Part I. |
| 2023 Biofouling Guidelines (IMO Res. MEPC.378(80)) | Adopted 7 July 2023, replacing MEPC.207(62). The guidelines describe a ship-specific Biofouling Management Plan, a Biofouling Record Book, a contingency action plan, inspection of niche areas, and in-water cleaning with capture of debris where required. They are IMO guidance, not a convention requirement. | Check the plan matches the ship’s coating, marine growth prevention system and trading pattern, and that the record book holds drydock, inspection and cleaning entries. |
| Australia (DAFF biofouling requirements, from 15 June 2022) | International commercial vessels arriving in Australia answer biofouling questions in the pre-arrival report made under section 193 of the Biosecurity Act 2015, and show how biofouling has been managed. | Have the plan, the record book and the latest hull inspection or cleaning report ready before the pre-arrival report is made. |
| New Zealand (MPI Craft Risk Management Standard: Biofouling, from 15 May 2018) | Vessels arriving in New Zealand must meet the standard, for example through continual hull maintenance or an MPI-approved hull maintenance plan. | Check the evidence the agent or MPI will ask for: cleaning certificates, inspection reports and the record book. |
3. Chief Officer's post-drydock and pre-arrival checks
- Check the Record of Anti-fouling Systems (or the signed declaration for ships of 24 m to under 400 GT) names the coating applied at this drydock.
- Keep the paint specification, batch details and the coating contractor’s report with the certificate.
- On ships that keep an IHM, file the new paint Material Declarations in IHM Part I and check they use the MEPC.405(83) cybutryne thresholds.
- Update the Biofouling Record Book with the drydock work, and record later hull and niche-area inspections, propeller polishing and any in-water cleaning, with the port’s permission where it is required.
- Record the operation of the marine growth prevention system for sea chests and cooling-water pipes as the plan sets out.
- Before calling in Australia or New Zealand, check their current biofouling requirements with the agent and have the plan, record book and latest inspection or cleaning report ready.
- For CDI-vetted ships, the anti-fouling certificate question (CDI ref 1.1.38) compares the record with the last drydock; see the CDI inspection guide. Commercial vetting is an industry inspection, not law.
Port State checks are summarised in the PSC inspection checklist and chemical and gas tanker vetting in the CDI inspection guide.
Questions seafarers ask
Which ships need an International Anti-fouling System Certificate and which need a declaration?
Under the AFS Convention, ships of 400 GT and above on international voyages hold an International Anti-fouling System Certificate with its attached Record of Anti-fouling Systems. Ships of 24 m or more in length but under 400 GT on international voyages carry a declaration signed by the owner or authorised agent, supported by paint documents.
What did MEPC.405(83) change about cybutryne in the Inventory of Hazardous Materials?
It amended the 2023 IHM guidelines (MEPC.379(80)) so that Table A row A-4 gives two cybutryne thresholds: 1,000 mg/kg for a dry coating sample taken from the hull and 200 mg/kg for a wet paint sample taken from the container. It was adopted on 11 April 2025 and applies from no later than 26 June 2025.
Is a Biofouling Management Plan mandatory?
Not under an IMO convention: the 2023 Biofouling Guidelines (MEPC.378(80)) are guidance. Some coastal States, such as Australia and New Zealand, set their own biofouling rules for arriving ships, and commercial vetting schemes may ask to see the plan and record book. Vetting is an industry inspection, not law.
What do inspectors check about anti-fouling after a drydock?
That the Record of Anti-fouling Systems was updated to the coating actually applied, that the coating contains no banned biocide, and, on ships that keep an Inventory of Hazardous Materials, that the new paint Material Declarations were added to IHM Part I.
Run the anti-fouling checks in SeaReady
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Related guides
- IHM Inventory of Hazardous Materials & ship recycling guideHong Kong Convention & EU SRR IHM Part I/II/III, MEPC.379(80)/405(83) Table A/B thresholds and MD/SDoC logs.
- Ballast Water Management (D-2, BWRB & BWMS) guideBWM D-2 compliance, MEPC.369(80) BWRB codes A–H, MEPC.387(81) challenging water quality and USCG 33 CFR 151.
- CII calculator & rating guideAttained vs required CII, the A–E boundaries, Z factors 2023–2030 and a worked example.
- ESP Code hull survey, UTM & PSPC coating guide2011 ESP Code (A.1049(27)/MSC.461(101)) bulk/tanker hull surveys, UTM pitting/grooving and PSPC 320 µm coatings.
- PSC inspection checklistThe inspection start to finish, every deficiency area, risk windows and the CIC.
- CDI inspection guideThe 10th edition report, gradings, the 14-day window and AEPS chapters.
- Flag-state & Class survey checklistHSSC windows, IACS UR Z1/Z7/Z10 class surveys and Flag-state ASI preparation.