A coating system is only as reliable as the bond between the substrate and the protective layer.
Multithane Primer 21 is a single-component polyurethane primer developed to seal porous substrates, improve adhesion, waterproof concrete, and repair minor surface defects before the application of polyurethane, polyurea, epoxy, or waterproofing systems.
Unlike conventional primers that simply improve adhesion, Multithane Primer 21 has a VERSATILITY to functions as a waterproof primer, concrete sealer, and pore-filling repair primer, making it an ideal solution for industrial flooring, roofs, terraces, parking decks, water tanks, balconies, metal structures, and commercial buildings.
Concrete naturally contains thousands of microscopic capillaries and pores.
These pores absorb: Water, Moisture, Oil, Chemicals, Air, etc.
If these pores remain untreated, coating systems may experience: Poor adhesion, Pinholes, Blistering, Delamination, Moisture-related coating failure and Reduced service life.
A high-performance primer seals these pores before the protective coating is applied.
Multithane Primer 21 is a One-Component Polyurethane Primer specially formulated for porous substrates including: Concrete, Cement Screeds, Wood, Steel or Metal Surfaces
The primer penetrates deeply into porous surfaces, strengthening the substrate while creating a moisture-resistant bonding layer for subsequent coatings.
Unlike surface-level acrylic primers, polyurethane primers penetrate into the substrate.
The primer:
✔ Penetrates concrete capillaries
✔ Seals porous surfaces
✔ Reduces water absorption
✔ Creates strong chemical bonding
✔ Improves adhesion of waterproof coatings
✔ Protects against moisture and chemical ingress
The result is a dense, well-prepared substrate capable of supporting high-performance coating systems.
One of the biggest advantages of Multithane Primer 21 is its ability to waterproof concrete before applying the final coating.
It reduces moisture penetration by sealing: Capillary pores, Surface voids and Micro porosity
This minimizes future coating failures caused by moisture migration.
Concrete is naturally porous. Even structurally sound concrete absorbs water.
Multithane Primer 21 creates a water-resistant barrier that:
Unlike ordinary primers, Multithane Primer 21 can fill:
up to approximately 5 mm, creating a smoother and stronger base before applying the topcoat.
This reduces material consumption of subsequent coating systems while improving the final finish.
The polyurethane chemistry creates outstanding adhesion between the substrate and protective coatings.
It serves as the ideal primer for:
| Property | Value |
|---|---|
| Product Type | Single Component Polyurethane Primer |
| Finish | Smooth Matt |
| Colour | Clear Brownish |
| Coverage | 6–10 m²/kg |
| Recommended Coats | 1–2 |
| Dry Film Thickness | 25–50 Microns |
| Hard Dry | 3–10 Hours |
| Recoat Time | 4–5 Hours |
| Complete Cure | 3 Days |
Multithane Primer 21 can be applied on:
Step 1- Remove dust, laitance, grease, loose particles, and contaminants.
Step 2- Allow the substrate to dry completely. Do not apply on damp concrete.
Step 3- Repair honeycomb or cracks up to 5mm with MultiThane primer 21. Larger cracks to be repaired using suitable crack repair compounds after priming the substrate with MultiThane Primer 21 to ensure proper adhesion
Step 4 Apply Multithane Primer 21 using Brush or Roller
Step 5- Allow the primer to become touch dry.
Apply the topcoat within the recommended recoat window for optimum intercoat adhesion
| Conventional Primer | Multithane Primer 21 |
|---|---|
| Surface adhesion only | Deep penetration |
| Minimal waterproofing | Waterproof primer |
| Limited pore sealing | Excellent pore sealing |
| No repair capability | Repairs surface defects up to 5 mm |
| Basic bonding | High-strength polyurethane bonding |
| Lower durability | Long-lasting protection |
Whether you are preparing a concrete floor, waterproofing a terrace, protecting a steel structure, or installing a polyurethane flooring system, proper substrate preparation determines the life of the entire coating.
Multithane Primer 21 combines the functions of a waterproof primer, concrete sealer, adhesion promoter, and minor repair primer in a single, ready-to-use polyurethane formulation. By sealing porous substrates, reducing moisture ingress, improving adhesion, and repairing surface imperfections, it provides a durable foundation for long-lasting waterproofing and protective coating systems.
A waterproof primer seals concrete pores, minimizes moisture absorption, and creates a stronger bond between the substrate and the waterproofing system, improving its long-term durability.
Yes. By sealing porous concrete and improving adhesion, it helps reduce common coating failures such as blistering, peeling, pinholes, and delamination.
It performs multiple functions by acting as a primer, waterproof sealer, and filling minor surface imperfections and pores up to 5 mm before the final coating is applied.
For the best intercoat adhesion, apply the topcoat once the primer becomes touch dry and preferably within the recommended recoating window.
Multithane Primer 21: The Waterproof Primer That Seals, Protects & Repairs Concrete Before Coating A coating system is only as reliable as the bond between the substrate and the protective layer. Multithane Primer 21 is a single-component polyurethane primer developed to seal porous substrates, improve adhesion, waterproof concrete, and repair
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