Fosroc Dekguard Primer WB
Low-VOC, water-based acrylic stabilising primer that prepares alkaline concrete and masonry for Fosroc Dekguard WB300 elastomeric anti-carbonation coatings.
What is it?
A single-component, water-based acrylic-emulsion primer supplied as a white liquid that dries transparent, used to stabilise and consolidate porous concrete and masonry before a Dekguard water-based protective topcoat.
Where is it used?
On atmospherically exposed RC structures, bridges, facades, water-tank exteriors and coastal buildings as the first coat of the Fosroc Dekguard WB300 anti-carbonation protective coating system.
Why use it?
It seals and binds a dusty or porous alkaline substrate, creates a thin hydrophobic barrier against water-borne contaminants, and gives the elastomeric topcoat a uniform, well-keyed surface so the full anti-carbonation protection is achieved.
How is it applied?
Applied by brush, roller or knapsack spray in a single coat at roughly 8-10 m²/litre onto a clean, dry, prepared surface; left to dry about one hour at 30 degrees C before the Dekguard WB300 topcoat is applied.
About Fosroc Dekguard Primer WB
Fosroc Dekguard Primer WB (also catalogued as Dekguard WB Primer) is the water-based priming component of Fosroc’s Dekguard protective-coating family. It is a single-component formulation built on a special water-based acrylic polymer emulsion, supplied as a white liquid that dries to a transparent film. Its defining quality is alkali resistance: ordinary primers can saponify or fail on the high-pH surfaces of fresh and aged concrete, cement plaster and masonry, whereas Dekguard Primer WB is designed specifically to bond reliably to those alkaline substrates. Functionally, the primer penetrates the surface, consolidates loose and chalky material, and lays down a thin film that acts as a hydrophobic barrier, inhibiting the passage of water and water-borne contaminants while giving the subsequent topcoat a sound, uniform key. In Indian practice it is most often specified as the first coat of the Dekguard WB300 system, where a single-component acrylic primer is paired with a single-component elastomeric pigmented coating, both ready for immediate site use. Because it is water-based it is low-VOC, non-flammable and cleaned with plain water, which suits occupied buildings, enclosed areas and projects with environmental or green-building requirements. For contractors, consultants and architects across Delhi NCR and Pan-India, it is the standard, distributor-stocked primer that ensures a Dekguard anti-carbonation coating actually delivers its rated protection rather than peeling, blistering or chalking off a poorly prepared substrate.
The technical insight
The reason a dedicated primer matters on a Dekguard job is that the performance figures of the topcoat are only achievable when the coating is continuous, well-bonded and at full dry film thickness. The Dekguard WB300 system is designed for a total DFT of not less than 300 microns built in two topcoat passes (theoretical 4.2-4.5 m²/litre per coat, roughly 230 microns wet per coat), and at that build it delivers carbonation resistance greater than 50 m equivalent air-layer thickness (DIN EN 1062), low chloride permeability (RCPT, ASTM C1202), a salt-spray result around 0.26 g/m²/1000 hr (ASTM B117) and pull-off adhesion above 1.0 N/mm² (ASTM D4541). None of that holds if the topcoat is laid on a dusty, friable or variably absorbent surface. Dekguard Primer WB equalises substrate suction and binds the surface so the elastomeric topcoat cures into a uniform, pinhole-free membrane and develops full adhesion. Its coverage is deliberately substrate-driven rather than fixed: theoretical coverage is around 10 m²/litre (commonly quoted as 8-10 m²/litre per coat), but on a low-permeability, microsilica-modified concrete penetration is shallow and the area per litre is high, whereas on an open, porous render the primer is drawn in and coverage drops. A short re-coat window (about one hour at 30 degrees C) means the primer should be overcoated promptly once dry, never left exposed for days to collect dust before the topcoat goes on.
Where it is used
- First (priming) coat of the Fosroc Dekguard WB300 elastomeric anti-carbonation coating system on RC structures
- Stabilising and binding chalky, porous or freshly cured concrete and cement plaster before a protective topcoat
- Priming external surfaces of concrete water and storage tanks (above splash zones) prior to Dekguard WB300
- Priming bridge piers, soffits, parapets and crash barriers in carbonation and chloride-exposure environments
- Priming building facades, columns and external plaster in coastal and high-humidity Indian climates
- Sealing alkaline masonry and blockwork ahead of acrylic protective or decorative anti-carbonation finishes
- Equalising substrate absorption across repaired and patched areas (e.g. after Renderoc repairs) for a uniform topcoat finish
Key advantages
- Single component and ready to use straight from the drum with no mixing or induction time
- Water-based and low-VOC, making it suitable for occupied buildings, enclosed spaces and green-building specifications
- Alkali-resistant, so it bonds reliably to high-pH concrete, cement plaster and masonry where ordinary primers fail
- Penetrates and consolidates dusty or friable surfaces, giving the elastomeric topcoat a sound, well-keyed substrate
- Forms a thin hydrophobic film that inhibits ingress of water and water-borne contaminants
- Dries transparent and overcoats quickly (around one hour at 30 degrees C), keeping site programmes moving
- Non-flammable with easy water clean-up of tools and equipment, reducing solvent handling and fire risk on site
- Distributor-stocked in India in 4 and 20 litre drums for both small repairs and large structural contracts
Limitations & considerations
- It is a primer only, not a standalone protective coating, and must be overcoated with a Dekguard topcoat such as Dekguard WB300 to deliver anti-carbonation performance
- Coverage is highly substrate-dependent (around 8-10 m²/litre); dense concretes give high coverage while porous renders consume far more
- Should be overcoated within its short re-coat window once dry rather than left exposed to collect dust or weathering
- As the water-based primer it is matched to the water-based Dekguard line; solvent-based Dekguard coatings (e.g. Dekguard S) use the silane-siloxane Dekguard Primer instead, so the correct primer must be paired with the correct topcoat
- Application should not start if substrate temperature is below the system’s stated minimum or above its maximum, in relative humidity above about 90 percent, or where rain is imminent
- Requires a properly prepared, dry, contamination-free surface; it will not compensate for grease, laitance, curing-compound residue or unsound concrete
- Not intended for permanently submerged or continuously wet exposure as part of the WB300 system
Selection & best practice
Prepare the substrate first: it must be dry, sound and free of oil, grease, laitance, curing compounds, loose particles, moss and algae, ideally by light grit blasting, with blow-holes and irregularities filled (for example with Renderoc) and allowed to cure. Treat any biological growth with a biocide after blasting. Apply Dekguard Primer WB in a single coat by brush, roller or knapsack spray, working it into the surface to consolidate porous areas, and adjust the rate to the substrate so absorbent areas are not left under-primed (expect roughly 8-10 m²/litre, less on open render). Mask glass and protect plants, joint sealants, asphalt and bitumen-painted areas. Do not start in unsuitable weather (substrate too cold or too hot, RH above about 90 percent, or rain likely within a couple of hours) and keep the substrate at least a few degrees above dew point. Let the primer dry (about one hour at 30 degrees C) and overcoat promptly within its window with two coats of Dekguard WB300 to a total DFT of not less than 300 microns, keeping a coating log of rates and times. Clean tools with water immediately after use. Always confirm current figures against the latest Fosroc TDS for the specific topcoat and run a trial area when coating over existing paint or coatings.
Specifications
| Product type | Single-component, water-based acrylic primer (alkali-resistant stabilising primer) |
| Chemistry / binder | Water-based acrylic polymer / acrylic emulsion |
| Appearance | White liquid that dries to a transparent film |
| Primary use | Priming/stabilising coat for the Dekguard WB300 anti-carbonation coating system |
| Number of coats | 1 (priming coat) |
| Coverage (theoretical) | ~10 m²/litre (commonly 8-10 m²/litre per coat, substrate-dependent) |
| Application method | Brush, roller or knapsack spray |
| Overcoating / drying time | Approx. 1 hour at 30 degrees C before Dekguard WB300 topcoat |
| Suitable substrates | Concrete, cement plaster/render and masonry (alkaline surfaces) |
| Compatible topcoat | Fosroc Dekguard WB300 (water-based elastomeric anti-carbonation coating) |
| System DFT (with WB300) | Not less than 300 microns total in 2 topcoat coats |
| System carbonation resistance | >50 m equivalent air-layer thickness (DIN EN 1062) |
| System chloride / salt resistance | Low permeability RCPT (ASTM C1202); salt spray ~0.26 g/m²/1000 hr (ASTM B117) |
| VOC / flammability | Low-VOC; non-flammable |
| Cleaning | Water (clean tools immediately after use) |
| Pack sizes | 4 litre and 20 litre drums |
| Shelf life / storage | 12 months in cool, dry conditions in original unopened packs, away from heat and frost |
Industry use cases
Infrastructure and bridges
Priming RC bridge piers, soffits, parapets and crash barriers before Dekguard WB300 to resist carbonation and chloride attack in pollution- and de-icing-exposed environments.
Coastal and marine buildings
Stabilising chloride-exposed concrete facades and columns in coastal Indian cities so the anti-carbonation topcoat bonds and protects against airborne salt.
Water and effluent infrastructure
Priming the external surfaces of concrete storage and water tanks (above splash zones) ahead of the Dekguard WB300 protective coat.
Commercial and residential facades
Sealing porous cement plaster and masonry on high-rise and institutional facades to give a uniform, durable elastomeric anti-carbonation finish.
Repair and rehabilitation
Equalising suction across patched and Renderoc-repaired areas so the recoat looks and performs uniformly across old and new concrete.
Industrial and process plants
Priming external concrete structures in chemically aggressive, humid plant environments where a low-VOC, non-flammable, water-clean-up primer is preferred.
Frequently asked questions
What is Fosroc Dekguard Primer WB and what is it used for?
What coverage and how many coats should I expect?
Which topcoat goes over Dekguard Primer WB?
How long before I can overcoat the primer?
Is it low-VOC and safe for enclosed or occupied sites?
What pack sizes and shelf life are available in India?
How we position Fosroc Dekguard Primer WB
Dekguard Primer WB is best understood as one piece of the wider Fosroc Dekguard protective-coating system rather than a product bought on its own. On a water-based job it primes for Fosroc Dekguard WB300, the elastomeric anti-carbonation topcoat; where a solvent-based finish such as Fosroc Dekguard S or the high-performance Dekguard E2000 is specified, the matching primer is the silane-siloxane Dekguard Primer, so specifiers should confirm the primer-topcoat pairing against the relevant TDS. It also commonly sits alongside Fosroc repair products like the Renderoc range, which are used to make good the concrete before priming. Against competitor systems, the water-based Dekguard route is comparable to anti-carbonation and acrylic protective coatings from Sika (for example the Sikagard range), MBS, Dr. Fixit and STP (Shalimar/Pidilite group brands), all of which offer their own primer-plus-topcoat protective systems for concrete. Each manufacturer’s primer is formulated for its own topcoat, so primers and topcoats should not be mixed across brands. For specifiers in Delhi NCR and across India, the practical advantage of staying within the Dekguard system is a documented, tested primer-topcoat combination backed by Fosroc technical support, supplied locally by Space Arc Engineering as an authorised Fosroc distributor and applicator. Final material selection should always be made on verified figures from the current Fosroc technical data sheet for the specific Dekguard topcoat being used.
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