Independent commentary, news and working tools on marine coatings - specifications, fouling control, application practice and the economics underneath. Spec'd in mils. Checked in microns.
Essays, market surveys and field notes for people who spec, buy and manage paint for a living. New pieces every few weeks.
Twelve manufacturers, three operating models, no clear winner yet. Where each robot actually lives, how it's controlled, and which one fits how you run your fleet.
Biocide-free hard coatings reframe the problem: solve for mechanical integrity, groom the rest. What that suddenly lets you optimize for - and the discipline it demands.
Coatings are roughly 1% of the total fuel bill over a drydock cycle. A mid-size bulk carrier case study on why getting that 1% wrong moves the other 99%.
Every underwater hull system starts the same way - blasted steel, anticorrosive epoxy. What goes on top is the strategic decision: deplete it, make it slippery, or make it hard and groom it. Pick one and watch the spec build, coat by coat.
2 × 150 EPOXY · 1 × 75 TIE COAT · 3 × 120 AF - 735 µm DFT
First-order models you can sanity-check a meeting with. Assumptions are printed on the panel. No login, no lead form, no vendor thumb on the scale.
Dial in the fouling rating, vessel class and hull regime. Outputs are first-order estimates from an admiralty-style resistance model and typical SFOC figures - directionally honest, not a class deliverable.
Area, DFT, volume solids, loss factor. The gap between theoretical and practical consumption is where jobs go over budget - so dial in the loss factor honestly, not optimistically.
Northwind - Coastal Charters is a full three-dimensional fleet simulator built in three.js: contracts, drydock scheduling, hull care and the economics of keeping ships on charter instead of idle. It plays in the browser, free, with the same first-order fouling and fuel-penalty logic behind CALC 01 above.
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Mils & Microns is written by Adam Stuchlik, a coatings industry lifer with extensive experience through R&D, sales and marketing. The commentary here is grounded in reality, driven by log reports and crawling ballast tanks, not press releases and brochures.
Everything published here is independent. No sponsorships, no affiliate links, no manufacturer slant - if a product is named, it is because the public record supports it.
This site exists because coating decisions are made with too little independent analysis. If you want that analysis on your side of the table, get in touch.
Get in touch →Hull coatings are roughly 1% of the total fuel bill over a drydock cycle. The range is roughly 0.7% to 1.3% of the fuel bill. One thing to note is that the bigger the vessel, the stronger the asymmetry gets, because fuel spend scales faster than coating cost.
What’s for sure is that the wrong specification decision on that 1% can easily cost seven figures in excess fuel consumption alone (making the 1% lower, but you get my point) before you even factor in unscheduled drydocking, warranty disputes, cleaning or the operational headaches that come with a hull that is not performing. I don’t know how common unscheduled dockings are - I do know it’s a last resort for an owner, and because of that they will try to manage a bad situation, and with that comes a massive organizational cost of money and time.
This is the asymmetry that almost nobody in the maritime industry talks about honestly: coatings are a small part of total cost, but the impact is asymmetrically good or bad.
Take a mid-size bulk carrier vessel on a standard trade route:
Now look at the coating. A full hull recoat material only runs somewhere around $150K-$350K depending on the vessel and the system. Call it $300K.
That is 1.25% of your fuel spend over the interval between drydockings.
Here is where it gets expensive.
A coating system that is not optimized for your vessel’s actual operating profile - wrong technology choice, wrong surface prep standard, wrong recoat specification - does not announce itself. There is no alarm (unless, as you sail away, the paint stays in drydock).
What happens is a gradual increase in roughness that shows up as excess fuel consumption. If that roughness is from the application quality, surface prep or the coating’s flow/wetting characteristics, the efficiency is gone (unless you break out the 3,000 grit sandpaper). At least with fouling you can do something about it in service.
The famous study to quote is Schultz, stating light slime is around 10% drag (I think that one surprised a lot of people at the time). Side note: I remember scratching my head when I read the term “hydraulically smooth” for the first time.
At 5% drag/efficiency loss, excess on a $4.8M annual fuel bill, you are burning an extra $1.2 million over 5 years. See how it mounts up?
At today’s bunker prices closer to $1,000/tonne, those numbers roughly double.
And that is just the fuel penalty. To focus on fouling, the cost cascade looks like this:
Three reasons, and they all compound each other:
1. The people specifying the coating are often not coating specialists and don’t have time to be. Superintendent gets a recommendation from the manufacturer rep, the yard has a preferred product, and the spec decision gets made on relationships and convenience rather than a rigorous analysis of what the vessel actually needs.
2. Nobody is doing the total cost of ownership math. The decision is framed as “which coating costs less per liter” instead of “which system delivers the lowest cost per tonne-mile over 60 months.” These are completely different questions and they often produce completely different answers.
3. The performance data stays siloed. The coating manufacturer has their test data. The hull cleaning company has their roughness measurements. The vessel has its fuel consumption logs. Nobody is connecting the dots across the ecosystem to evaluate whether the spec is actually performing.
This problem is solvable. The data exists. The analytical frameworks exist. What has been missing is an independent party with no product to sell who can look at the full picture: your vessel, your routes, your operational profile, your actual in-service performance, and tell you whether your current spec is costing you money or saving it.
The coating is 1% of your cost. But getting that 1% right or wrong moves the needle on the other 99%.
That is the asymmetry. And most are on the wrong side of it without knowing.
Independent. No manufacturer affiliation, no sponsorships.
This is a fundamentally different design philosophy. You are not solving for fouling. You are solving for mechanical integrity and then whatever else you want.
Every antifouling on the market is trying to solve the same problem: keep things from growing on your hull. The approach for decades has been chemical - from copper cladding in the past up to modern biocides that target specific critters. It works. It also means your hull is a continuous source of leachates, and whatever else the formulator decided to put in there.
Foul release took a different approach - if I oversimplify it, make the surface too slippery for organisms to stick. Silicone-based systems from Hempel and International dominate that category. They work well on a section of the market but they are soft, damage-prone, can be tricky to apply and cannot tolerate aggressive cleaning. If something does attach and harden, you are in a difficult position.
Pretty much everything in life is a trade-off and in this case the reduction of emissions to air via fuel consumption control has tended to outweigh the emissions to sea.
Another path that I think is the most intellectually interesting one in the coatings space right now: biocide-free hard coatings designed for proactive grooming.
The idea is simple but hard to execute. Instead of focusing on keeping the fouling off through a mastery of chemistry, you apply a hard coating and you clean it regularly before fouling has a chance to establish. Light, frequent grooming through whatever means (watch out for this article) - removes slime and early-stage biofilm while it is still soft and weakly bonded. The coating is engineered to survive this repeated contact without degrading.
This is a fundamentally different design philosophy. You are not solving for fouling. You are solving for mechanical integrity and then whatever else you want. And once you reframe the problem that way, a set of optimization targets opens up that SPC/FRC chemistry cannot touch.
Smoothness. Some of these coatings - particularly the silane/siloxane nano systems - cure to surface roughness profiles under 5 microns. That is glass-smooth. Others, like the glass-flake vinyl ester systems, start considerably rougher out of the gate but reportedly improve with repeated cleaning as the grooming action polishes the surface. There are reports of SPCs self smoothing although I couldn’t find any published studies. Someone independent should run a controlled comparison of FRC and SPC vs hard coatings.
Surface architecture. This is the really exciting one. When the coating does not have to concern itself with certain fouling related properties, the surface itself becomes a design variable. You are no longer constrained by the chemistry of polishing - you can engineer the surface for hydrodynamics.
Think sharkskin. Biomimetic riblet structures that reduce turbulent drag have been studied for decades in aerospace, but conventional antifouling chemistry makes them impractical on a hull - the surface is constantly changing as the coating depletes or fouls. A hard, stable, groomable surface is a different starting point. It holds its geometry. It can be textured at the micro scale and maintained there. GIT's graphene platelet technology is already working in this direction - orienting nanoscale structures to create specific surface energy profiles and flow characteristics that go beyond just "smooth."
The implication is that these coatings are not just passive protection. They are the beginning of engineered hull surfaces - where the coating is designed to hydrodynamically interact with the water, not just survive in it. That is a fundamentally different ambition than anything a biocidal or self-polishing system can offer, because those systems are, by definition, consuming themselves.
Emissions to sea. Near zero or zero. These coatings are inert. No biocides or oils leaching, no microplastic shedding, no copper discharge. Independent lab verification exists for some of the products below. As IMO’s biofouling guidelines tighten and port states move toward stricter discharge regulations - California’s copper limits are already forcing the conversation in the US - this becomes a compliance advantage, not just an environmental talking point. The February 2026 copper re-evaluation bill is a worry for those using it.
VOC emissions to air. High-solids formulations in this category are pushing 95%+ volume solids, which means very low VOC at application. For yards in regions with strict air quality regulations - or for owners who care about Scope 3 reporting - this matters. It also means better coverage per gallon and less waste. And note that I selected volume solids as the metric and not VOC content. The HAPS nonsense in the US is extraordinarily misleading.
Cosmetics. This one sounds trivial until you talk to a cruise operator or a yacht manager. A glossy, hard, cleanable surface stays visually clean between groomings. No streaking, no patchwork erosion, no visible polishing pattern. The hull looks like it was just painted, consistently, for years. For vessels where appearance is part of the brand - and that includes a growing number of commercial operators - this has real value. I remember talking to a container ship owner in the US whose vessels were often idle off the coast of Long Beach. They valued hull appearance very much because their name was plastered all along the topsides in giant letters.
The biocide-free hard coating space is still small enough that you can map the serious commercial players on one hand. Here is what is on the market today, with verified characteristics:
| Product | Manufacturer | Chemistry | DFT | Track Record | Grooming | Differentiator |
|---|---|---|---|---|---|---|
| XGIT-FORCE | GIT Coatings (Canada) | Graphene-reinforced amphiphilic hard foul release (DPET technology) | Single coat over primer (detailed spec not published in public TDS) | XGIT-FUEL predecessor on cruise vessels (Coral Expeditions), propellers on Stolt Tankers (25 vessels), Pacific Basin (40 vessels) | Only biocide-free coating with LR Enhanced Type Approval for grooming (XGIT-FUEL 2024, XGIT-FORCE 2026). Robotic grooming; 1–4 month intervals | Guaranteed 6% out-of-dock power gain vs. premium biocidal AF. Up to 10% fuel savings claimed. Ice/fender impact resistant |
| Ecospeed | Subsea Industries (Belgium) | Glass flake reinforced vinyl ester resin | 2 x 500 µm (1,000 µm total). High initial surface roughness - not a smooth-out-of-dock system | 20+ years in market. RRS Shackleton: coating intact after 12 years in Antarctic ice. Verified non-toxic (independent labs, NL & Canada). 10-year warranty | Proprietary cleaning tools. Manufacturer claims hull smoothness improves with each clean (starts rough, gets smoother - the inverse of most coatings). 10-year drydock interval achievable | Longest track record in category. Ice-rated variant. Life-of-vessel design intent. Extremely abrasion/cavitation resistant. Note: if you ever need to remove it and go in a different direction, blasting off a glass-flake vinyl ester matrix is a serious undertaking. This is a commitment |
| SEA-SPEED V 10 X | Seacoat SCT (USA) | Silane/siloxane nano coating | 2 x 125 µm epoxy + 1 x 150 µm finish coat | 4–12% fuel reduction claimed (manufacturer data). 10-year warranty. No independently verified case studies published to date | Withstands 1,000+ grooming operations without damage. Surface roughness < 5 µm | 95% volume solids, very low VOC. Glass-smooth finish. No heavy metals. Single-coat finish application |
| F2 EcoHull | F2 Eco (EU) | Hybrid polymer with Zeronic™ inorganic resin additive | Multi-coat system (detailed TDS not publicly available) | Primarily yacht/workboat scale to date. 5+ year durability with top-coat refresh (no full rebuild required) | Superhydrophobic surface, ultra-smooth. Fouling removal by light cleaning | Zero PFAS/PTFE. Zero solvents. Compatible with FRP, carbon, aluminum, steel, wood. Emerging technology - watch for commercial vessel scaling |
But let’s not forget, this will not work out so well without a grooming program. A biocide-free hard coating without regular cleaning will foul. You are trading chemical intervention for mechanical maintenance, and if you do not hold up your end, there will be trouble.
This is the single biggest reason the category has not grown faster. It requires operational discipline. It requires either a robotics partner, a reliable diving contractor, or in-house capability for regular hull maintenance. It requires scheduling, tracking, and accountability. For operators who struggle to keep up with basic planned maintenance, adding hull grooming to the rotation is a real ask.
But for operators who can commit to it - and particularly for operators who are already doing regular in-water inspections or cleaning - the numbers shift dramatically. You eliminate biocide complexity and environmental liability. You extend drydock intervals. You maintain out-of-dock smoothness through the entire service period. And you never have to worry about whether your antifouling is compatible with your cleaning method, because the coating was designed to be cleaned from day one.
The regulatory environment is moving in one direction. IMO’s 2023 Biofouling Guidelines and the 2025 in-water cleaning guidance are pushing the industry toward proactive hull management and away from “apply and forget” antifouling models. Port states are tightening discharge limits. Classification societies are beginning to certify grooming compatibility - Lloyd’s Register’s Enhanced Antifouling Type Approval, currently held only by GIT Coatings among biocide-free products, is the first formal recognition that a coating and grooming regime can be validated as a system. It will not be the last. Jotun has already secured a similar approval for their SeaQuantum Skate paired with the HullSkater robot, albeit for a biocidal system - the classification framework is being built in real time.
The biocide-free hard coating market is small - probably in the range of $50 million today, or roughly half a percent of the ~$8 billion global hull coatings market. The broader biocide-free /low biocide category, including foul release and self-polishing systems, is approaching $500 million and projected to more than double by 2035. As robotic grooming technology matures and becomes more accessible, the operational barrier drops. As regulations tighten, the compliance advantage grows. And as more vessels build track records with these systems, the performance data will either validate or challenge the claims being made today.
The elephants in the room are the technical complexity of hard coating + robotics combined with cost. But to achieve near zero efficiency loss, its likely worth looking into.
I do not think biocide-free hard coatings are the right answer for every vessel. They require a level of operational commitment that not every fleet is set up for. But for the operators who are willing to think differently about hull performance - who see the hull as a maintained system rather than a painted surface - this category deserves serious evaluation.
The coatings that do not emit anything (or very little) might be the ones that perform the best. You just have to be willing to take care of them.
I’m tracking the full hull performance ecosystem - coatings, robotics, cleaning systems, and everything in between. Follow along if you want the independent analysis.
As a marine coating chemist, my initial reaction to the widening use of robotics (for want of a better word) was annoyance - annoyance from a position of pride, in that chemistry could not solve fouling and needed some draconian million-dollar toothbrush. It just seemed inelegant.
After I got over that stupid thought I saw the opportunities. If we don’t need to worry about the drag that comes from fouling, we can look at the drag that comes from pushing anything through water at speed. That’s the cool thing about underwater cleaning robotics to me - you solve fouling and can then look at optimizing the surface, and maybe achieve a speed gain.
This article is an overview of the different robotics technologies on the market. It’s not exhaustive, so apologies if yours didn’t make it in here.
If we go back to what we’re trying to achieve with hull performance, it’s zero (or better) speed loss, complete operational flexibility and 100% reliability. At the same time, we should also have excellent HSEQ in terms of harmful content and solvent emissions. If you could solve all that, I don’t think any owner would be upset when you present a seven-figure invoice.
I do need to mention the coating aspect briefly. As a sign of how important coating compatibility with grooming is, in 2025 Lloyd’s Register handed out the industry’s first full antifouling type approval to GIT and Jotun. Those endorsements, from a class society and a coating maker, are noteworthy, and I imagine more will follow. Class approval is a sign of confidence from experts in the field. But let’s not forget that just because LR says something is OK doesn’t mean there aren’t other approaches that are also OK; that’s part of what this article is trying to communicate.
It would be tempting to group these robots either by brand or by cleaning mechanism. Neither helps an owner decide. I think it’s more relevant to do it by the operating model: where the robot lives and when it cleans. That determines port logistics, how often you intervene, whether you need a support vessel, and how much the cleaning depends on autonomy that has not been proven at sea. Mechanism still matters, but it is a property of each approach, not the organizing principle.
If we do it that way, the market splits into three families.
I think what everyone wants is an autonomous in-transit system that just takes care of everything on a proactive basis. Seems like an ideal scenario to me. Not even a sniff of being delayed because of cleaning - it just happens while underway, when we have all the time in the world.
Here we have tethered systems like Shipshave’s ITCH, which use a deck winch and hydrodynamic forces: no magnets, no autonomy, just the crew deploying and recovering the unit at service speed. Then there are autonomous systems like NakAI, which self-deploys from an onboard dock while the ship is under way, and Nautica, a self-organizing swarm, both chasing the same goal of cleaning with zero crew involvement. Right now, the tethered version is commercial. The autonomous version looks like it’s coming, just not quite here yet.
The device lives on the vessel and cleans early, at the slime stage (FR20-ish), before macrofouling takes hold. It is triggered by a shore operations center using fouling-risk data. Greensea and Jotun chose this approach, with Jotun’s HullSkater sold inside the HSS coating-plus-robot-plus-monitoring bundle. Greensea IQ’s EverClean pursues the same proactive thesis but as a port-based subscription rather than onboard hardware. The argument is that cleaning little and often beats cleaning hard and rarely. Who would want to brush their teeth quarterly?
This is the one everyone already knows - the robot comes to the ship in harbor, usually an ROV run off a service vessel or the pier. It’s the largest, most mature family by far, and it splits up by mechanism. High-pressure magnetic crawlers (Fleet Cleaner, VertiDrive) go for raw throughput on steel. Brushless, variable-pressure waterjets (HullWiper, ECOsubsea) skip contact entirely to protect the coating. Cavitation systems (Neptune, CLIIN) fracture fouling at low pressure. And small high-frequency units (Hullbot) clean gently, but often. Whatever the mechanism, they all share the same constraint: you only clean when you’ve got a port call, and you’re competing with everyone else for the slot.
There is more to it than where the robot lives and when it cleans. Three questions decide how a system fits your operation: does the crew have to operate it, is it autonomous, and is it run from a control center on the other side of the world? None of those is automatically better. Satellite links like Starlink now make remote operation feasible almost anywhere - a real step up from systems that leaned on shore-side 5G - and handing control to a remote center also lets the owner decide where and when to clean. The control and connectivity column below is where each system lands on that.
Twelve manufacturers, grouped by operating model (in-transit, stationary, or port-based):
| Manufacturer (product) | Origin & founded | Cleaning technology | Control & connectivity | Weight & size | Maturity |
|---|---|---|---|---|---|
| IN-TRANSIT (LIVES ONBOARD) | |||||
| Shipshave (ITCH) | Norway · 2019 | Tethered hydrodynamic drift; soft brush | Crew-operated from deck winch | ~50 kg (two-part, crew-portable); dimensions not disclosed | Commercial; multiple fleet deployments |
| NakAI Robotics (PLECOS) | Israel · ~2020 | Cable-free; UV + soft brush | Fully autonomous; no crew after install | Not publicly disclosed | Paid trials underway |
| STATIONARY (LIVES ONBOARD) | |||||
| Jotun HullSkater (HSS) | Norway · 1926 (HullSkater 2020) | Magnetic-wheel crawler; cleaning head | Remote ops center (4G / satellite); no crew cleaning role | ~200 kg; ~1.6 × 1.0 m | Commercial; LR type approval 2025 |
| PORT-BASED | |||||
| Fleet Cleaner (now Fleet Robotics) | Netherlands · 2011 | Magnetic crawler; high-pressure waterjet | Remote ops center (Delft); operator-run, support vessel | ~2.0 × 1.8 × 0.6 m; weight not disclosed | Commercial; 4 service vessels |
| VertiDrive | Netherlands · 2008 | Magnetic crawler; interchangeable heads (waterjet / UHP / abrasive) | Operator, on-site remote control | ~62 kg; 0.75 × 0.52 × 0.72 m (V700) | Commercial |
| CLIIN Robotics | Denmark · 2016 | Magnetic crawler; interchangeable brush / cavitation heads | Operator-run, on-site | ~89 kg (35 kg hull tool) | Commercial; hull & cargo-hold lines |
| HullWiper | UAE (dev. Norway) · 2013 | Brushless variable-pressure waterjet; debris capture | Operator-run ROV, on-site | ~1,275 kg; 3.3 × 1.7 × 0.85 m | Commercial; dozens of ports |
| ECOsubsea | Norway / UK · 2008 | Soft waterjet ROV; ~97% debris capture | Operator-run ROV, on-site | Not publicly disclosed | Commercial; approved for restricted ports |
| Neptune Robotics | Singapore · 2018 (founded Hong Kong) | Cavitation waterjet; AI-guided | AI-guided, operator-supervised, on-site | ~300 kg; dimensions not disclosed | Commercial; ~60 Asian ports |
| Greensea IQ / Armach (EverClean) | USA · Greensea 2006; Armach 2021 | Non-magnetic (suction); soft-brush grooming | Operator-run subscription; autonomous grooming, no crew | <30 kg; ~0.86 m long | Commercial; GIT coating approval 2025 |
| Hullbot | Australia · 2015 | Small free-swimming; soft brush | Autonomous, operator-supervised | ~10 kg; dimensions not disclosed | Commercial; high-frequency |
| Nautica Technologies (HYDRA) | Switzerland · 2024 | Autonomous swarm; soft brush | Fully autonomous swarm; no crew | Not publicly disclosed | Pilot; $4M seed 2025 |
Here is how the different families play out against the three things owners ask and care about most.
Reliability at sea. Proven port-based ROVs and crew-operated tethered systems are the safe bets today, because a person can recover the unit if conditions change and the operating envelope is well understood. The fully autonomous in-transit concepts are the most exciting and the least proven. Given that it’s a fully mappable substrate, full autonomy is possible and surely coming soon.
Clean capacity (m²/hr). If raw area per hour is the metric, high-pressure magnetic crawlers lead, in the range of roughly 1,000 to 2,000 m²/hr. Brushless waterjet systems can match that on speed, but the ones built for full debris capture trade throughput for containment and run closer to 300 to 600 m²/hr. Cavitation and soft-brush systems are slower still, often 200 to 400 m²/hr, and they buy coating safety with that lost speed. In-transit cleaning does not really belong on the same scale: a tethered unit can do a full mid-size hull in a single voyage leg with zero port time, which can beat a faster robot you have to wait in line for.
Size, weight, access, and cost. Lighter is more flexible. Man-portable units in the 10 to 90 kg range can be carried aboard and deployed by crew, while the high-throughput crawlers need a dedicated support vessel and a remote operations center, which makes them a port-only proposition. On commercial model, you are choosing among three structures: capital purchase, pay-per-visit subscription where the operator carries the equipment risk, and the bundled coating-plus-robot contract that buys integration at the cost of lock-in. None is cheapest in every case. The subscription model lowers the entry barrier; the bundle removes the coating-versus-cleaning warranty argument; owning the hardware makes sense only at fleet scale.
Net read: for most owners today, a proven port-based or tethered in-transit system is the dependable choice, and the right mechanism follows from your hull material and your coating. The proactive and autonomous categories are where the upside is, and they are worth piloting, but they are not yet where the reliability is.
The real winners here will be the ones who land high-profile references and deliver a decent result at a sensible cost. Owners adopt on proof, not promises. In a business where a bad clean can cost you a coating warranty or a hull, nobody wants to go first; everybody wants to go second. I do think that integrated solutions where coating and cleaning come together are strong - this can be through Jotun’s approach or a JV type like GIT. For an owner, having one point of contact and liability is beneficial.
The vendor who gets a respected operator to put a real fleet on the line, and then reports real savings, hands every other owner the evidence they were waiting for. That does more than any amount of marketing.
Winning looks like a good result at a sensible cost, not best in class. Fleets do not run on the best available technology; they run on the option that’s reliable and user friendly, with acceptable performance, acceptable risk, and an acceptable price. A system that saves a decent amount of fuel, leaves the coating intact, and does not wreck the maintenance budget will beat a technically superior one that is harder to buy, schedule, or trust.
A note on sources: every claim here comes from public manufacturer disclosures, class-society announcements, and trade-press coverage, current as of mid-2026. Throughput figures and capabilities are vendor-reported and should be verified against the most recent technical data when applied to a specific specification.