Hempel Silic Seal Conversion Primer

Hempel’s Conversion Primer 45441, also supplied under the Hempel Silic Seal name, is a low-viscosity, two-component epoxy conversion primer for applying Hempel’s advanced biocide-free fouling-protection systems over sound existing antifouling. It mixes 3:1 by volume and has a theoretical spreading rate of 15m²/L at the recommended 25µm dry film thickness.

Hempel’s Conversion Primer is designed to form the adhesion stage between an existing antifouling coating in good condition and Hempel’s Silic One Tiecoat 27450. This allows a suitable existing antifouling system to be converted without automatically stripping the entire hull back to the bare substrate.

The existing antifouling must still be firmly adhered. Loose, brittle or poorly bonded layers must be removed before application. Hempel also specifies Conversion Primer as a tiecoat between an epoxy-primed surface and Hempaspeed TF.

Depending on the packaging generation supplied, the tin may be labelled Hempel’s Silic Seal or Hempel’s Conversion Primer. Both names refer to Hempel product code 45441. The standard mixed shade is Light Pink 50711 with a flat finish.

Silic One System Position

Conversion Primer is not the final fouling-release coating and does not replace Hempel’s Silic One Tiecoat. When converting sound existing antifouling to the Silic One system, the coating sequence is:

• Sound, correctly prepared existing antifouling
• One full coat of Hempel’s Conversion Primer 45441
• One full coat of Hempel’s Silic One Tiecoat 27450
• Two coats of Hempel’s Silic One 77450 for the initial application

Compatibility and Intended Use

Use Hempel’s Conversion Primer as a sealer over sound existing antifouling to secure adhesion to Hempel’s Silic One Tiecoat, or as a tiecoat between a suitable epoxy-primed surface and Hempaspeed TF. Hempel specifies the conversion-primer use for substrates excluding wood and for exterior coating systems below the waterline.

The product is not intended for direct application to an uncoated surface. Bare substrates must first be prepared and primed in accordance with the relevant Hempel primer specification.

Surface Preparation

Remove oil, grease and other contaminants with a suitable detergent. Test the adhesion of the aged antifouling with a metal scraper. Where adhesion is poor, remove all loose or brittle layers. Wet abrade the remaining sound coating, rinse thoroughly with fresh water and allow the surface to become clean and dry.

Areas containing filler must be sealed with a suitable primer or sealer before Conversion Primer is applied. The ability to retain an existing antifouling coating applies only where that coating remains sound and securely bonded.

Mixing and Application

Mix Base 45445 and Curing Agent 95441 in a 3:1 ratio by volume. Stir thoroughly until the mixture is uniform. Do not dilute the separate components and do not thin the mixed product.

Apply one full undiluted coat by brush or roller. Hempel’s Silic One guide identifies a long-haired roller as suitable for Conversion Primer. The coating has very low viscosity, so brush out runs and sags immediately.

Hempel’s Thinner 845, product code 08451, is specified for cleaning tools only. It is not specified for thinning Conversion Primer. Pot life is approximately eight hours at a product temperature of 20°C.

The recommended film build is 25µm dry and 69µm wet, providing a theoretical spreading rate of 15m²/L. This equals approximately 11.25m² per 750ml pack or 37.5m² per 2.5L pack under theoretical conditions. Practical coverage will be lower where surface profile and application losses increase consumption.

Keep the surface temperature above 10°C during application and curing. Relative humidity must remain below 85%. Maintain sufficient ventilation and avoid condensation on the freshly applied coating.

Drying and Overcoating

At the recommended 25µm dry film thickness, Hempel’s Conversion Primer is hard dry after approximately 2½ hours at 10°C, 1¼ hours at 20°C or 30 minutes at 30°C. At 20°C, it is ready to sand after approximately two hours. Full cure is reached after approximately 14 days at 10°C, seven days at 20°C or four days at 30°C.

Apply Hempel’s Silic One Tiecoat 27450 within 4–8 hours at 10°C, 2–4 hours at 20°C or 60 minutes to two hours at 30°C.

When Conversion Primer is used as the tiecoat beneath Hempaspeed TF, the stated overcoating interval is 30–65 minutes at 10°C, 20°C or 30°C. Hempel’s project specification takes precedence over the general overcoating table.

If the maximum overcoating interval is exceeded, roughen the surface to support intercoat adhesion. The surface must be clean before the next coating is applied.

Key Features

• Official Hempel product code 45441
• Also supplied under the Hempel Silic Seal name
• Two-component epoxy conversion primer
• Enables conversion from sound existing antifouling to Hempel’s biocide-free fouling-protection systems
• Forms the adhesion stage before Hempel’s Silic One Tiecoat 27450
• Also suitable as a tiecoat between an epoxy-primed surface and Hempaspeed TF
• For exterior coating systems below the waterline
• Hempel specifies conversion-primer use on substrates excluding wood
• Not for direct application to uncoated surfaces
• Base 45445 and Curing Agent 95441
• Mixing ratio: 3:1 by volume
• Standard shade: Light Pink 50711
• Flat finish
• Volume solids: 36 ± 2%
• Specific gravity: 1.2kg/L
• Recommended dry film thickness: 25µm
• Recommended wet film thickness: 69µm
• Theoretical spreading rate: 15m²/L
• Apply one full coat by brush or roller
• No thinning permitted
• Tool cleaner: Hempel’s Thinner 845, 08451
• Pot life: approximately eight hours at 20°C
• Hard dry in approximately 1¼ hours at 20°C
• Ready to sand in approximately two hours at 20°C
• Fully cured in approximately seven days at 20°C
• Flash point: 31°C
• EU VOC content of mixed product: 541g/L
• Base and curing-agent shelf life: 36 months at 25°C in original unopened containers
• Available in 750ml and 2.5L pack sizes

Frequently Asked Questions

What is Hempel’s Conversion Primer 45441 used for?
It is used over sound existing antifouling to create the adhesion stage for Hempel’s Silic One Tiecoat and subsequent Silic One fouling-release topcoat. It can also be used between an epoxy-primed surface and Hempaspeed TF.

Are Hempel Silic Seal and Hempel Conversion Primer the same product?
Yes. Depending on the packaging supplied, the tin may carry either name. Product code 45441 identifies the same two-component epoxy conversion primer.

Can it be applied over existing antifouling?
Yes, provided the antifouling is in good condition and remains firmly adhered. Test it with a metal scraper, remove loose or brittle material, wet abrade, rinse with fresh water and allow the surface to dry.

Does it eliminate the need to remove all old antifouling?
It can avoid full removal where the existing antifouling is sound. It does not allow loose, brittle or poorly bonded coating to remain; defective layers must be removed.

Can Conversion Primer be applied directly to a bare hull?
No. Hempel states that it is not for uncoated surfaces. Bare substrates must be prepared and primed according to the applicable Hempel primer instructions.

Can it be used on wood?
Hempel’s product page specifies the conversion-primer use for substrates excluding wood. Confirm an alternative Hempel system for timber or plywood substrates.

What is the correct Silic One coating sequence over existing antifouling?
Prepare the sound antifouling, apply one coat of Conversion Primer, apply one coat of Silic One Tiecoat and then apply two Silic One topcoats for the initial installation.

Does Conversion Primer replace Silic One Tiecoat?
No. Conversion Primer bonds to the existing antifouling. Silic One Tiecoat is then applied between Conversion Primer and the Silic One topcoat.

Can it be used with Hempaspeed TF?
Yes. Hempel specifies it as a tiecoat between an epoxy-primed surface and Hempaspeed TF.

What is the mixing ratio?
Mix Base 45445 and Curing Agent 95441 in a 3:1 ratio by volume.

Can Hempel Conversion Primer be thinned?
No. Hempel specifies no thinning. Hempel’s Thinner 845, product code 08451, is for cleaning application tools.

How should it be applied?
Apply one full undiluted coat by brush or roller. Because the coating has very low viscosity, brush out runs and sags immediately.

How much area does it cover?
The theoretical spreading rate is 15m²/L at 25µm dry film thickness. A 750ml pack covers approximately 11.25m² and a 2.5L pack approximately 37.5m² theoretically.

How long is the mixed product usable?
The stated pot life is approximately eight hours at a product temperature of 20°C.

How long does it take to dry?
It is hard dry after approximately 2½ hours at 10°C, 1¼ hours at 20°C or 30 minutes at 30°C. At 20°C, it is ready to sand after about two hours.

When can Silic One Tiecoat be applied?
Apply it within 4–8 hours at 10°C, 2–4 hours at 20°C or 60 minutes to two hours at 30°C.

When can Hempaspeed TF be applied?
The stated interval is 30–65 minutes at 10°C, 20°C or 30°C. Follow the Hempel specification supplied for the complete coating system.

What happens if the maximum overcoating interval is exceeded?
Hempel states that the surface must be roughened to support intercoat adhesion and must be clean before overcoating. A project-specific Hempel specification takes precedence.

Which pack sizes are available?
Current UK listings identify 750ml and 2.5L variants, with part numbers H45441-50711-750ML and H45441-50711-2.5L.

How should the product be stored?
Store the components at no less than 5°C in original, tightly closed containers in a dry, shaded, cool and well-ventilated place. The curing agent is moisture-sensitive. Base and curing agent have a stated shelf life of 36 months at 25°C.