Washing and Polishing a Yacht Without Degrading the Coating
Published by Yacht IQ, Dubai Maritime City — part of the Silver Yachts group of companies.
A two-component polyurethane topcoat goes on at a typical dry film thickness of 100 microns per coat, with a specified maximum of 160 and a minimum of 50 (Jotun Hardtop XP data sheet). Gelcoat is typically 500 to 800 microns — a general reference figure rather than a manufacturer specification.
Same crew, same pads, same weekly routine — and one of those surfaces has five to sixteen times more material to give away than the other.
That single asymmetry explains most of the coating complaints we hear in Dubai Maritime City. A wash-and-polish regime that a production GRP hull tolerated for a decade will run a painted superyacht out of film in a few seasons, and nothing about the process looks wrong while it is happening.
Why continual cleaning shortens coating life
Every wash is mildly abrasive. Every polish is definitively abrasive — that is the mechanism, it is how gloss is restored. The question is never whether material is being removed but how much, how often, and from a budget of what size.
No coating manufacturer publishes a permissible number of polish cycles, and none publishes a minimum residual dry film thickness below which a topcoat is considered compromised. We looked for both and found neither. Rather than invent a figure, note how the manufacturers themselves answer the question — because one of them answers it very directly indeed.
Boero Yacht Coatings, in its own care leaflet:
“Polishing should not be considered a regular maintenance procedure, but a localized repair process.”
That is a coating maker reclassifying an operation that most crews run on a schedule. Alexseal (Mankiewicz) arrives in the same place by a different route, cautioning against “aggressive buffing which could remove excessive coating from the surface and reduce durability.”
Neither gives you a cycle count. Both tell you the activity belongs in the repair column, not the maintenance column. If polishing appears as a recurring line item in your maintenance schedule, the schedule is consuming the asset.
Wash water, pads and pressure
There is no published pressure limit for a yacht topcoat. We could not find a maximum PSI or bar figure from any coating manufacturer. Boero says only “wet the painted surface with a low-pressure freshwater jet.” Alexseal's topcoat care guidance gives no pressure figure at all.
The only hard number in Gulf waters comes from a port authority, not a paint company: the Port of Fujairah permits a maximum of 200 bar for high-pressure washing — and that rule governs underwater hull cleaning, not topside paint. Do not read it across. Treat it as evidence that even for a hull, somebody thought a ceiling was necessary.
Where the manufacturers are specific is consumables, and Boero is unusually quotable:
| Item | Manufacturer position |
|---|---|
| Soft-texture brushes (yellow) | “suitable for use on painted surfaces” |
| Coarse-texture brushes (white) | “should not be used on painted surfaces” |
| Abrasive household products | “Never use abrasive materials such as Vim, Cif, ScotchBrite” |
| Detergent | “Use a biodegradable and pH neutral detergent for heavy surface dirt” |
| Solvents and acids | “Never clean surfaces with solvents, non pH neutral products” |
A single wrong brush, used once by a contractor who does not know which yacht he is standing on, is a scratch pattern that will need a repair pass to remove. Colour-code the locker and brief the crew.
The vinegar problem
Here two topcoat manufacturers give directly opposing advice on the same task.
- Boero: “Do not use vinegar or other acidic materials in washing water.”
- Alexseal: remove “dried salt residue by washing the surface with a warm water and white vinegar solution.”
Both are legitimate technical positions from serious companies. They are not reconcilable, and there is no neutral authority above them to appeal to. The operational rule is therefore simple and worth writing into the vessel's standing orders: follow the chemistry statement of the coating that is actually on the boat, and never apply a competitor's care sheet to it. If nobody on board knows which system was sprayed, that is the first thing to establish — before the next wash, not after.
The rule that matters most in a Dubai August
Boero again: “Do not wash surfaces when hot (for example after long exposure to sunlight) to avoid alteration of gloss.” And for protective wax, “Do not apply on hot surfaces or in direct sunlight.”
On a Gulf summer afternoon a white topside is well above ambient and a dark hull considerably more so. The practical consequence is that the middle of the day is unavailable for exterior work — not inconvenient, unavailable. Wash early, wash late, or wash in shade. Dry with chamois leather or microfibre, and take Boero's escalation rule seriously: “In cases of abrasion or deep scratches, an immediate repair is recommended.” Deferring a scratch through a summer means water and salt sitting in the breach for months.
What to do instead of polishing
Boero's positive recommendation is not a compound. It is a sacrificial layer:
“Apply periodically (every three or four months) a non-abrasive silicon and teflon free protective wax.”
Three or four applications a year of something that adds material rather than removing it. That is the maintenance operation. Polishing is what you do when protection has already failed locally.
When a spot repair genuinely is required, Alexseal specifies 1500 to 2000 grit for blending, and names its compound and polish pairings explicitly — 3M 06085/06086 for buffing, 06064/06065 for polishing, and 06068/06069 for dark colours. Use the named system for the coating you have; mixing an unrelated compound into a manufacturer's blending sequence is how a small repair becomes a panel.
And if the film is already thin across whole areas — chalking, dieback, colour drift that a polish only masks for a fortnight — the answer is refinishing, not more compounding. That is yard work, and it is a different conversation from the one in this article. Our group company Silver Yachts works on repair and refit for vessels in the region.
Ceramic and graphene coatings: reading the claims properly
We looked for independent durability testing of marine ceramic and graphene coatings. We found none. Every source was vendor marketing. We also found no cost-per-square-metre figure from any source. Say what you like about the products; there is currently no published evidence base to argue from, and anyone claiming otherwise should be asked for the paper.
Two technical points, however, are solid and useful.
First, “9H” is not what most buyers think it is. It is the top of the pencil-hardness scale in ASTM D3363, a paint-industry test method — not Mohs hardness, and not a mineral property. The scale “runs from 6B, softest, to 9H, hardest,” so 9H is the ceiling of the scale, not a position on an open-ended one. Worse for comparison purposes, the result is method-dependent. A technical note from Tekra is blunt about it: “the biggest pitfall of the pencil hardness test is the variety of test procedures used,” and “the less pressure that is put on the pencil, there is a smaller chance that the lead will scratch the film, thus yielding a 'higher pencil hardness value'.” Their conclusion — “ALWAYS check the test procedures to make sure you are comparing 'apples to apples'” — is the correct response to a 9H claim quoted without a protocol. Without the method, the number is unfalsifiable.
Second, at least one topcoat manufacturer explicitly advises against them. Boero: “Avoid applying agressive products such as SiO2 based ceramic coatings.” That is a rare, citable, on-the-record position from the company that made the paint, and it sits directly against the ceramic vendors' warranty pitch.
Then set the durability claim against a ceramic specialist's own published maintenance programme: fresh-water rinse “weekly or bi-weekly,” pH-neutral wash monthly, an SiO₂ booster spray “every 2–3 months,” and “once a year, schedule a professional inspection and refresh service.” A product requiring a booster every eight to twelve weeks is not a multi-year set-and-forget treatment, on the vendor's own account.
None of that makes ceramic coatings useless. It does mean the honest way to evaluate one is as a sealant with a maintenance contract attached — and to check the paint manufacturer's position before it goes on a warranted topcoat.
Dust, salt and sunscreen are three different problems
They get treated as one “cleaning” problem and they are not.
Airborne dust and salt aerosol. This is the dominant load in a Gulf berth, and it is a physical problem: fine particulate sitting on a surface, then being dragged across it by a brush. Removal sequence matters far more than chemistry — flood first, agitate second. Our article on what shamal dust actually damages covers the timing and the cover strategy in detail.
Water spotting. The only mitigation we found with a source behind it is removing the dissolved solids from the rinse water rather than trying to outrun evaporation: “use a deionized rinse system or RO system to avoid water spots.” On a Dubai afternoon a panel dries before a chamois can reach the far end of it, so the practical fix is upstream of the drying, not in it. One honest gap: we could not obtain an authoritative DEWA water-quality report, so we are not going to tell you what your dockside TDS actually is. Have it tested — it is a cheap test and it decides whether a DI system is worth the money.
Sunscreen, DEET and cosmetics. Here we have to be straight with you: no coating manufacturer we could find publishes any statement at all about sunscreen, insect repellent or cosmetics. Neither Boero nor Alexseal mentions them. The EPA's DEET reregistration decision contains no claim that DEET damages paints or coatings; what it does say is that DEET is “miscible with several organic solvents.” That miscibility is a legitimate mechanistic reason to treat repellent as a solvent-like contact risk on a susceptible polymer — it is not evidence of coating damage, and we will not present it as such. On sunscreen there is real chemistry behind the orange staining crews report, but the documented cases concern fabric: avobenzone reacting with iron in the water to produce a rust-coloured oxidation stain.
The field practice that follows is unglamorous and does not depend on any of the above being resolved: wipe transfer immediately, keep repellent away from painted surfaces and varnish, and put towels on sunpads. If a manufacturer ever does publish a chemical-resistance statement for these, it will be worth reading. Nobody has.
Interior surfaces are a separate chemistry again — marine-grade leather and interior materials have their own care requirements, and exterior products do not belong anywhere near them.
A routine you can actually hand to a crew
| Interval | Operation | Notes |
|---|---|---|
| After every use, and after dust events | Fresh-water flood rinse | Low pressure. Cool surface only. No agitation until the dust is off. |
| Weekly | Wash with pH-neutral biodegradable detergent, soft (yellow) brush | Early morning or evening. Chamois or microfibre dry. DI or RO rinse if spotting is an issue. |
| Every 3–4 months | Non-abrasive protective wax, silicone and PTFE free | Not on hot surfaces or in direct sun. This is the maintenance step. |
| As required, not scheduled | Localised polish or compound repair | Manufacturer's named system only. 1500–2000 grit for blending. Log every pass. |
| Immediately | Repair abrasion and deep scratches | Do not carry a breach through a summer. |
| Annually | Film thickness survey on repair-prone areas | Cheap, and the only way to know how much budget is left. |
That last row is the one most operations skip. If polishing is a repair process, then repairs should be logged and the remaining film should be measured — otherwise the first hard evidence that the topcoat is finished arrives as a refinishing quotation.
Contact Yacht IQ about maintenance products and consumables for Gulf conditions.
Tell us which coating system is on the vessel and we will quote pH-neutral washes, correct-grade brushes and waxes that match the manufacturer's chemistry. Visit our showroom or get in touch.
📍 Showroom: Dubai Maritime City, F1B W223
📧 info@theyachtsolutions.com
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