By Capt. Neeraj Bharti, Founder, Master Mariner · Published · 2 min read
How in-water cleaning damages coatings, and how to prevent it
The fear that stops many superintendents booking in-water cleaning is simple: "they'll strip my coating." It is a fair fear. A clean that removes the antifouling along with the fouling leaves a hull that fouls faster next time, and a damaged foul-release coating can be expensive to put right. But coating damage is not inevitable. It comes from specific, avoidable choices.
How cleaning damages coatings
Brushes too hard for the coating. Stiff brushes or aggressive heads on soft antifouling or silicone foul-release coatings scratch and strip the surface.
Too many passes. Even a suitable brush wears a coating if it goes over the same area repeatedly to chase stubborn growth.
Wrong method for heavy fouling. Barnacles bonded firmly to the coating can tear pieces of coating away when removed carelessly.
Cleaning a coating that is already failing. Where the antifouling is breaking down, cleaning can expose bare primer or steel.
Cleaning too soon after application. New coatings need time to cure before they can take cleaning.
Warning signs in a report
- Colour change in the cleaned area (often the underlying coat showing through)
- Visible scratches or tracks from the brush cart
- Bare patches, especially on edges, welds and bilge keels
- Paint particles visible in the water during cleaning
A good report flags these. If the contractor's report never mentions coating condition, ask why.
How to prevent it
- Know the coating. Type (self-polishing, foul-release or hard), product and age. Give this to the contractor.
- Inspect before cleaning. Rate the fouling and check coating condition so the method can be chosen properly.
- Use the least aggressive method that works. Soft brushes and light passes for slime; patient hand work on heavy growth on delicate coatings.
- Clean more often, more gently. Light, frequent cleaning of slime is kinder to the coating than occasional heavy cleaning of barnacles.
- Stop and report. A contractor should stop and tell you if the coating is coming off, not carry on to finish the job.
- Check the manufacturer's advice. Many coating makers give guidance on in-water cleaning of their products.
Our approach
Cleanship selects brush hardness and method against the vessel's coating, with a pre-clean assessment of fouling and coating condition, and records coating condition before and after in the report. See our underwater hull cleaning service, how to choose a hull cleaning contractor, and the complete guide to ship hull cleaning.
If you are worried about your coating, request information about our cleaning method and reporting.
Sources & further reading
Frequently asked questions
Can in-water hull cleaning damage antifouling?
Yes, if the method is too aggressive for the coating, the same area is cleaned repeatedly, heavy growth is removed carelessly, or the coating is already failing. With the right method these risks are largely avoidable.
How can coating damage during cleaning be prevented?
Know the coating, inspect before cleaning, use the least aggressive method that works, clean more often and more gently, stop and report if coating is coming off, and follow the coating manufacturer's advice.
Are foul-release coatings safe to clean in the water?
They can be, with gentle methods. Silicone foul-release coatings scratch easily, so hard brushes and repeated passes must be avoided.
What should a report say about coating condition?
It should record coating condition before and after cleaning, note any damage, scratches or bare areas, and flag any areas where cleaning was stopped to protect the coating.
- hull cleaning coating damage
- antifouling damage divers
- coating wear hull cleaning
- gentle hull cleaning
- foul release coating cleaning damage
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