Hull coatings for decarbonisation: solutions, challenges, and next steps

Navigator Gas provided a detailed operator case study. Mr Manniche explained the company instrumented its gas carriers with high‑frequency sensors, including mass‑flow, torsion and power meters, plus draught, speed, wind and other inputs, to robustly measure coating effects.

Testing silicone‑based antifoulings on sister ships created a clean comparison and, “after less than a year”, the owner changed strategy and “decided to go full blown on silicone”, despite the need to manage softness near locks and when docking alongside berths.

Over a full five‑year docking cycle the firm observed strong performance from the silicone coating for roughly three‑and‑a‑half years, before a decline that might require cleaning; averaged across trades and seasons the company saw “a benefit of at least 10-12%”, especially valuable where Energy Efficiency Existing Ship Index (EEXI) engine‑power limits capped available speed margins.

Solutions for hull coatings for decarbonisation fell into three strands: selecting the right coating for the trade; validating performance claims; and embedding data‑led in‑service management.

Actual hydrodynamic performance depended on the operating profile — speeds, idle days, port routines and market volatility — and on how a coating interacted with the boundary layer around the hull in real water, not just its nominal smoothness.

“Low friction is a good starting point, but it does not equal hydrodynamic performance,” said Mr Skaret.

Jotun’s prescription was “tailored to trade”: combine an operational understanding of where and how the vessel would work with a commercial view of future uncertainty (lay‑ups, recharters, acquired ships with existing systems), then select for in‑service and out‑of‑dock performance, backed by proactive monitoring and, where needed, guarantees.

DNV independently validated Hempel’s claims and found a 6% efficiency gain compared with top-tier self-polishing antifouling coatings, with a speed loss of 1.4% over time. He also pointed to RightShip guidance recognising low-friction coatings in vessel-efficiency ratings.; Hempel reported more than 30 vessels with verified greenhouse‑gas rating upgrades after coating changes.

Mr Skaret said proactive monitoring of fouling risk and speed loss was essential, using vessel and open‑source data to trigger inspections or cleaning before performance degraded.

Ms Escobar added that Jotun’s HullKeeper platform linked trade‑driven fouling risk to speed deviation and achieved “close to 80% accuracy” when its predictions were checked against physical condition, allowing operators to act early, especially when vessels switched from predictable liner trades to volatile spot markets.

Jotun summarised the approach as “intelligent hull condition management”, emphasising continuous risk tracking across the docking cycle.

“The economics were shifting further in favour of premium systems as carbon costs rose”

Compliance and cost ran through the discussion and it was highlighted that coating selection and documentation were increasingly scrutinised by IMO instruments, such as CII, which scored how much CO2 a ship emitted per unit of transport work, and by EU ETS, which priced a portion of voyages touching European ports.

Owners therefore needed audit‑ready evidence of hull performance, integrated into dry‑dock plans and maintenance budgets, and should expect coating choice to feature in charterparty conversations. Mr Malmberg argued that the economics were shifting further in favour of premium systems as carbon costs rose and rating frameworks integrated hull friction explicitly.

The webinar audience probed practical limits in the question‑and‑answer session, and Mr Manniche advised protecting areas prone to mechanical damage in case of higher frequency port calls with a harder belt above the waterline to mitigate scuffing, even if it slightly reduced frictional benefit.

He cautioned that cleaning silicone surfaces was “not necessarily easy”, so methods had to be planned with suppliers, and he noted that some yards or jurisdictions restricted certain silicon-based products.

On modelling return on investment for slow vessels (for example, offshore support or dredging units), both coating manufacturers said the business case depended strongly on activity level and idle days; high‑activity ships recovered investment faster, but low‑activity vessels could still justify upgrades where port‑state requirements or carbon costs were material.

A recurring concern from the webinar audience was whether compliance rhetoric was crowding out performance reality.

Mr Manniche’s response was direct: discussions with charterers were “way beyond technical”, now including who benefited from EU allowances; however, he said, “We first need to demonstrate that we can measure” and agree baselines before sharing value.

From left to right: Carsten Manniche (Navigator Gas), Nikolaj Malmberg (Hempel), Habibe Escobar (Jotun), Jon Magnus Skaret (Jotun)