Hempel Silic One Tiecoat Undercoat

Hempel’s Silic One Tiecoat 27450 is a high-solids, silicone-based intermediate tiecoat that secures adhesion between Hempel’s Light Primer or Hempel’s Conversion Primer and the Hempel Silic One or Silic Pro fouling-release topcoat. Designed for glass fibre, steel, aluminium and plywood boats below the waterline, it provides a theoretical spreading rate of 10m²/L at the recommended 70µm dry film thickness.

Important product distinction: Silic One Tiecoat is not the final antifouling or fouling-release topcoat. The hydrogel, low-friction fouling-release surface is created by the subsequent Hempel Silic One topcoat. The Tiecoat forms the adhesion layer within the multi-stage system.

Hempel’s Silic One Tiecoat is used as the bonding stage between the specified primer and Hempel’s Silic One or Hempel’s Silic Pro. Its Yellow/Cream 23410 semi-gloss coating must be applied as one complete, uniform coat before the selected silicone fouling-release topcoat.

The product has 67% volume solids, a specific gravity of 1.2kg/L and a recommended wet film thickness of 105µm. It is available in 375ml and 750ml pack sizes, providing calculated theoretical coverage of approximately 3.75m² and 7.5m² respectively at the specified film thickness.

Intended Applications and System Compatibility

Use Hempel’s Silic One Tiecoat on correctly prepared and primed glass fibre, steel, aluminium and plywood hulls for exterior areas below the waterline. Recommended previous coats are Hempel’s Light Primer and Hempel’s Conversion Primer. Recommended subsequent coats are Hempel’s Silic One and Hempel’s Silic Pro.

For new or bare substrates, prepare and prime the surface in accordance with the applicable Hempel primer specification. Do not apply Silic One Tiecoat directly to an unprimed hull. Hempel’s current Silic One guide states that new gelcoat must be epoxy primed to a minimum dry film thickness of 300µm.

Surface Preparation

Remove oil, grease and other contaminants with a suitable detergent. Bare substrates must be prepared according to Hempel’s primer instructions.

Where an existing antifouling coating remains in sound condition, apply one coat of Hempel’s Conversion Primer before the Tiecoat. On deteriorated surfaces, remove the old antifouling down to the sound two-component primer, then abrade, clean and dry the surface before applying one coat of Hempel’s Light Primer.

If the hull already has a sound two-component primer, abrade it and apply one coat of Hempel’s Light Primer. If the existing primer is non-epoxy or single-component, remove it and apply four to five coats of Hempel’s Light Primer before continuing with the Silic One system.

Application

Stir thoroughly before use. Apply one coat by brush or roller without thinning. Pour the product into a paint tray, replace the tin lid and fully load the brush or roller. Apply with soft, even strokes to achieve complete coverage, levelling any runs before the coating dries.

The recommended film build is 70µm dry and 105µm wet, giving a theoretical spreading rate of 10m²/L. Hempel’s Thinner 808, product code 08081, is specified for cleaning tools; thinning is not permitted.

At 20°C, the stated pot life is 60 minutes. Hempel’s current system guide advises using an opened tin within one hour and not storing it for later use. Surface temperature must remain above 10°C during application and curing, with relative humidity maintained between 30% and 85%. Provide adequate ventilation and prevent condensation on the fresh coating.

Drying and Overcoating

At the recommended 70µm dry film thickness, Silic One Tiecoat is hard dry after approximately three hours at 10°C, 1½ hours at 20°C or one hour at 30°C. Full cure is reached after approximately four days at 10°C, two days at 20°C or one day at 30°C.

Apply the 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. If this interval is exceeded, apply a fresh coat of the specified primer before continuing.

Overcoat the Tiecoat with Hempel’s Silic One or Silic Pro within 16–48 hours at 10°C, 8–48 hours at 20°C or 4–24 hours at 30°C. The surface must be clean before overcoating. Where the maximum Tiecoat-to-topcoat interval is exceeded, rebuild the applicable system stage in accordance with Hempel’s current Silic One instructions.

Launching time is determined by the final Silic One topcoat rather than the Tiecoat alone. Hempel’s current system guide specifies a minimum of 36 hours after the final coat at 10°C or 24 hours at 20°C and 30°C, with launch required within one month.

Key Features

• Official Hempel product code 27450
• High-solids, silicone-based intermediate tiecoat
• Secures adhesion between the specified primer and Silic One or Silic Pro
• Part of Hempel’s biocide-free fouling-release coating system
• Suitable for glass fibre, steel, aluminium and plywood
• For exterior use below the waterline
• Recommended previous coats: Hempel’s Light Primer or Conversion Primer
• New gelcoat requires epoxy priming to a minimum 300µm dry film thickness
• Recommended subsequent coats: Hempel’s Silic One or Silic Pro
• Standard shade: Yellow/Cream 23410
• Semi-gloss finish
• Volume solids: 67%
• Specific gravity: 1.2kg/L
• Recommended dry film thickness: 70µm
• Recommended wet film thickness: 105µm
• Theoretical spreading rate: 10m²/L
• Calculated theoretical coverage: 3.75m² per 375ml
• Calculated theoretical coverage: 7.5m² per 750ml
• Apply one coat by brush or roller
• No thinning permitted
• Tool cleaner: Hempel’s Thinner 808, 08081
• Pot life: 60 minutes at 20°C
• Minimum surface temperature: above 10°C
• Application and curing humidity: 30–85%
• Hard dry in approximately 1½ hours at 20°C
• Fully cured in approximately two days at 20°C
• Flash point: 33°C
• EU VOC content: 232g/L
• Shelf life: 18 months at 25°C in original unopened containers

Frequently Asked Questions

What is Hempel’s Silic One Tiecoat 27450 used for?
It is the intermediate adhesion coat between Hempel’s Light Primer or Conversion Primer and Hempel’s Silic One or Silic Pro fouling-release topcoat.

Is Silic One Tiecoat an antifouling topcoat?
No. It is a tiecoat within the Silic One system. It does not replace the final Silic One or Silic Pro fouling-release coating.

Does the Tiecoat itself create the hydrogel surface?
No. Hempel attributes the hydrogel, low-friction fouling-release surface to the Silic One topcoat. The Tiecoat provides adhesion between the primer and that topcoat.

Which hull materials are compatible?
Hempel specifies glass fibre, steel, aluminium and plywood, provided the substrate is correctly prepared and primed.

Can it be used above the waterline?
Hempel specifies Silic One Tiecoat for exterior use below the waterline as part of the Silic One fouling-release system.

Can it be applied directly to a bare hull or new gelcoat?
No. Bare substrates must be prepared and coated with the applicable Hempel primer system before the Tiecoat is applied. Hempel states that new gelcoat requires epoxy priming to a minimum 300µm dry film thickness.

What should be applied over sound existing antifouling?
For old antifouling in good condition, Hempel specifies one coat of Conversion Primer before Silic One Tiecoat.

What if the existing primer is single-component or non-epoxy?
Remove the incompatible primer and apply four to five coats of Hempel’s Light Primer before continuing with the Tiecoat.

How many Tiecoat coats are required?
Apply one complete coat at the recommended 70µm dry film thickness. Full, uniform coverage is required for adhesion.

Can the product be thinned?
No. Hempel states that thinning is not allowed. Use Hempel’s Thinner 808 only for cleaning tools.

How much area does it cover?
The theoretical spreading rate is 10m²/L. A 375ml tin therefore covers approximately 3.75m² and a 750ml tin approximately 7.5m² under theoretical conditions. Practical coverage will be lower where surface profile and application losses increase consumption.

How long is the product usable after opening?
The stated pot life is 60 minutes at 20°C. Hempel’s system guide advises using an opened tin within one hour and not storing it for later use.

When should it be applied over Light Primer or Conversion Primer?
Apply within 4–8 hours at 10°C, 2–4 hours at 20°C or 1–2 hours at 30°C. Apply a fresh primer coat if the maximum interval is exceeded.

When can Silic One be applied over the Tiecoat?
Apply Silic One or Silic Pro within 16–48 hours at 10°C, 8–48 hours at 20°C or 4–24 hours at 30°C.

How long does Silic One Tiecoat take to dry?
At 20°C it is hard dry in approximately 1½ hours and fully cured in approximately two days at the recommended film thickness.

Can it be used to repair damaged Silic One areas?
Yes. Where the coating system has been damaged, rebuild the required primer, Tiecoat and topcoat stages over the affected area according to the depth of damage and Hempel’s repair instructions.

When can the boat be launched?
Launching is governed by the final topcoat. Hempel’s Silic One system guide states at least 36 hours after the final coat at 10°C or 24 hours at 20°C and 30°C, with launch within one month.

How should the product be stored?
Store unopened containers at a minimum of 5°C in a dry, shaded, cool and well-ventilated area, protected from direct sunlight, rain, snow, heat and ignition sources. The stated shelf life is 18 months at 25°C.