Hempel Silic One Topcoat Paint

Hempel’s Silic One 77450 is a biocide-free, high-solids fouling-release topcoat for glass fibre (GRP), steel, aluminium and plywood boats below the waterline. Its silicone and hydrogel technology creates a smooth, low-friction surface that makes it difficult for fouling organisms to attach and easier for growth to release when the boat is in motion. The theoretical spreading rate is 10m²/L at the recommended 80µm dry film thickness.

Hempel’s Silic One is the final topcoat within Hempel’s multi-stage Silic One system. It must be applied over Hempel’s Silic One Tiecoat and must not be applied directly to a bare hull, Hempel’s Light Primer or Hempel’s Conversion Primer. The correct system order is primer, Silic One Tiecoat, then Silic One.

Hempel states a service life of two years on the hull when the system is correctly applied and maintained. For the initial application, two coats of Silic One are required. Seasonal maintenance can be completed with one full Silic One recoat every two years, or with Hempel’s Infinity recharger for an additional season where the existing silicone coating remains in suitable condition.

Suitable Substrates and Intended Use

• Glass fibre (GRP)
• Steel
• Aluminium
• Plywood
• Marine hulls and propellers
• Exterior areas below the waterline

The current Hempel Product Data Sheet specifically lists glass fibre, steel, aluminium and plywood. It does not support the broader description “all substrates except wood”; solid timber is not listed, while plywood is explicitly included.

Required Silic One System

For a boat without antifouling: clean the surface with a suitable detergent, abrade with dry P120 abrasive paper, clean with fresh water and allow it to dry. Apply the specified Hempel Light Primer system, followed by one complete coat of Hempel’s Silic One Tiecoat and two coats of Hempel’s Silic One. New gelcoat must be epoxy primed to a minimum 300µm dry film thickness.

For sound existing antifouling: remove loose or brittle material, abrade the remaining coating, rinse carefully with fresh water and allow it to dry. Apply Hempel’s Conversion Primer, followed by one complete coat of Hempel’s Silic One Tiecoat and two coats of Hempel’s Silic One.

Where the existing coating system is damaged or incompatible, remove it back to a sound substrate or suitable two-component primer and rebuild the Hempel system specified for that substrate.

Application

Stir well before use. Apply by brush or short-haired or felt roller using soft, even strokes. Fully load the application tool and apply the maximum specified film thickness without creating runs or sagging. Pour the paint into a tray and replace the lid during application because the product is sensitive to humidity.

Do not thin Hempel’s Silic One. Hempel’s Thinner 808, product code 08081, is specified for cleaning tools only. Pot life is approximately 60 minutes at 20°C, and Hempel advises using an opened tin within one hour rather than storing it for later use.

The surface temperature must remain above 10°C during application and curing. Relative humidity must remain between 30% and 85%. Avoid application where rain is expected, provide adequate ventilation and prevent condensation on the freshly applied coating.

Film Thickness and Coverage

The recommended dry film thickness is 80µm and the corresponding wet film thickness is 102µm. The theoretical spreading rate is 10m²/L. This equals approximately 3.75m² per 375ml tin or 7.5m² per 750ml tin under theoretical conditions. Practical coverage will be lower where surface profile, hull shape and application losses increase consumption.

Overcoating and Immersion

Apply Hempel’s Silic One Tiecoat over Hempel’s Light Primer or Conversion Primer within 4–8 hours at 10°C, 2–4 hours at 20°C or 1–2 hours at 30°C. Apply the first Silic One coat over the Tiecoat within 16–48 hours at 10°C, 8–48 hours at 20°C or 4–24 hours at 30°C. If the maximum Tiecoat interval is exceeded, apply a fresh Tiecoat before continuing.

For the second Silic One coat during the initial application, Hempel’s 2026 system guide gives minimum intervals of 16 hours at 10°C, 16 hours at 20°C and 8 hours at 30°C, with no stated maximum. If more than 48 hours has elapsed, clean with a suitable detergent, rinse with fresh water, allow the surface to dry and overcoat as soon as possible.

The November 2025 Product Data Sheet lists a 16-hour minimum self-overcoating interval at all three temperatures, while the 2026 system guide lists eight hours at 30°C. Follow the current label, project specification or application instructions supplied with the product where the documents differ.

After the final coat, allow at least 36 hours before immersion at 10°C or 24 hours at 20°C and 30°C. Launch within one month.

Cleaning, Maintenance and Repair

High-speed motor boats can benefit from self-cleaning while under way. Slow-speed boats and sailing boats may require manual cleaning to keep the surface free from fouling and maintain low friction. Use a dense sponge or cloth followed by a fresh-water rinse, or pressure wash with fresh water at no more than 200 bar. Do not use a hard brush, stiff bristles or similarly aggressive tools.

For seasonal maintenance, clean with a soft sponge and soap, rinse with fresh water and allow the surface to dry. Apply one full coat of Silic One to the entire underwater area when recoating. If minor damage exposes the yellow Tiecoat, apply one Silic One coat over an area slightly larger than the damage. Deeper damage requires the affected primer, Tiecoat and topcoat stages to be rebuilt.

Traditional antifouling will not adhere directly to Silic One. Remove the silicone system before changing back to a conventional antifouling coating.

Key Features

• Official Hempel product code 77450
• Biocide-free, high-solids fouling-release topcoat
• Silicone and hydrogel technology
• Smooth, glossy, low-friction coating surface
• Suitable for glass fibre, steel, aluminium and plywood
• Suitable for hulls and propellers
• For exterior use below the waterline
• Must be applied over Hempel’s Silic One Tiecoat
• Compatible system primers: Hempel’s Light Primer or Conversion Primer
• Two Silic One coats required for initial application
• One full Silic One recoat every two years for routine system maintenance
• Hempel’s Infinity may be used as an alternative seasonal recharge where suitable
• Standard Product Data Sheet shade: Jet Black / Black 19990
• Additional current UK options: Red 59151 and True Blue 30390
• Glossy finish
• Volume solids: 78 ± 2%
• Specific gravity: 1kg/L
• Recommended dry film thickness: 80µm
• Recommended wet film thickness: 102µm
• Theoretical spreading rate: 10m²/L
• Apply by brush or short-haired or felt roller
• No thinning permitted
• Tool cleaner: Hempel’s Thinner 808, 08081
• Pot life: approximately 60 minutes at 20°C
• Hard dry in approximately two hours at 20°C
• Fully cured in approximately three days at 20°C
• Minimum immersion time: 24 hours at 20°C
• Maximum time before immersion: one month
• Flash point: 47°C
• EU VOC content: 117g/L; value may vary by shade
• Shelf life: 18 months at 25°C in original unopened containers

Frequently Asked Questions

What is Hempel’s Silic One 77450?
It is the biocide-free fouling-release topcoat in Hempel’s Silic One system. Silicone and hydrogel technology create a smooth, low-friction surface that reduces the ability of fouling organisms to attach firmly.

Is Silic One the Tiecoat?
No. Hempel’s Silic One 77450 is the final fouling-release topcoat. Hempel’s Silic One Tiecoat 27450 is a separate intermediate product applied between Light Primer or Conversion Primer and Silic One.

Can Silic One be applied directly over Light Primer?
No. The correct sequence is Hempel’s Light Primer or Conversion Primer, then Hempel’s Silic One Tiecoat, then Hempel’s Silic One.

Can it be applied directly to bare GRP, steel, aluminium or plywood?
No. The Product Data Sheet states that it is not for uncoated surfaces. Prepare and prime the substrate with the specified Hempel primer system before applying Silic One Tiecoat and Silic One.

Which substrates are suitable?
Hempel specifies glass fibre, steel, aluminium and plywood below the waterline. Solid timber is not listed in the current Product Data Sheet.

Is Hempel Silic One copper-free?
The current Hempel Product Data Sheet verifies that Silic One is biocide-free, but it does not separately state a copper-free claim. The verified product wording should therefore use “biocide-free”.

How many coats are required?
Apply two coats when installing Silic One for the first time. For routine full maintenance, Hempel specifies one Silic One coat every two years, subject to the condition and operating environment of the existing system.

How much area does one litre cover?
The theoretical spreading rate is 10m²/L at 80µm dry film thickness. A 375ml tin covers approximately 3.75m² and a 750ml tin approximately 7.5m² theoretically.

Can Hempel Silic One be thinned?
No. Thinning is not permitted. Use Hempel’s Thinner 808, product code 08081, for cleaning tools only.

How long can an opened tin be used?
The pot life is approximately 60 minutes at 20°C. Hempel advises opening the tin immediately before use, using it within one hour and not storing an opened tin for later application.

How long does Silic One take to dry?
At the recommended film thickness, it is hard dry in approximately four hours at 10°C, two hours at 20°C or one hour at 30°C. Full cure is approximately five, three or two days respectively.

When can the boat be launched?
Wait at least 36 hours after the final coat at 10°C or 24 hours at 20°C and 30°C. Launch within one month.

Does Silic One self-clean at low speed?
Self-cleaning is most effective at higher speed. Hempel states that it can also occur at lower speed with constant use, but slow-speed boats and sailing boats may require regular gentle cleaning.

Can a clean Silic One coating reduce drag?
Hempel states that keeping the surface free from fouling reduces friction, which can support increased speed and lower fuel or energy use compared with a fouled hull. Actual results depend on the vessel, operating profile and condition of the coating.

How should the coating be cleaned?
Use a dense sponge or cloth and rinse with fresh water, or use a fresh-water pressure washer at no more than 200 bar. Do not use hard brushes or stiff bristles.

Can traditional antifouling be applied over Silic One?
No. Conventional antifouling will not adhere directly to the silicone surface. Remove the Silic One system before changing to a traditional antifouling coating.

How is damaged Silic One repaired?
If only the black, red or blue topcoat is damaged and the yellow Tiecoat remains visible, apply one Silic One coat over an area slightly larger than the damage. If the damage penetrates deeper, rebuild the required primer, Tiecoat and topcoat stages.

What maintenance choices are available after the first application?
Hempel specifies either a full one-coat Silic One reapplication every two years or a Hempel’s Infinity recharge for an additional season where the existing system is in good condition. More frequent maintenance may be needed in severe fouling conditions or after prolonged storage ashore.

How should the product be stored?
Store unopened tins at a minimum of 5°C in a dry, shaded, cool and well-ventilated place, protected from direct sunlight, rain, snow, heat and ignition sources. Keep containers tightly closed.