About Fosroc Dekguard WB300

Fosroc Dekguard WB300 is a high-performance, water-based elastomeric protective coating built on an acrylic polymer, engineered to protect atmospherically exposed reinforced concrete and masonry from the slow, destructive process of carbonation. In Indian conditions — high humidity, aggressive coastal salts, industrial pollution and wide day-night temperature swings — atmospheric carbon dioxide steadily penetrates uncoated concrete, lowers its pH and strips the passive protection that keeps embedded steel from rusting. Once that happens, corrosion expands the rebar, cracks the cover and triggers spalling. Dekguard WB300 is the preventive answer: it lays down a continuous, low-permeability film that behaves as a comprehensive barrier against carbon dioxide, water and sulphates, so the concrete keeps its alkalinity and the reinforcement stays protected over a much longer service life.\n\nThe product is supplied as a complete two-part system. First, Dekguard WB Primer — a white, single-component acrylic emulsion — penetrates and stabilises the substrate, laying down a thin hydrophobic film that anchors the topcoat and inhibits water-borne contaminants. Over it, Dekguard WB300 itself is applied: a single-component, pigmented, elastomeric aliphatic-acrylic coating available in a wide range of colours. Because it is water-based, it carries low odour and low VOC compared with solvented anti-carbonation systems, which makes it well suited to occupied buildings, enclosed plant areas and projects with tightening environmental specifications.\n\nWhat sets WB300 apart from a plain decorative paint is the combination of three properties that rarely coexist. It is genuinely elastomeric, with around 60% elongation, so it stretches over and bridges the fine shrinkage and thermal cracks that inevitably form in concrete rather than fracturing with them. It is extremely durable, retaining its elastomeric recovery even after long-term UV weathering — important on south- and west-facing facades and exposed bridge soffits. And it is breathable, allowing water vapour already inside the structure to escape rather than building up behind the film and causing blistering. For Space Arc Engineering’s clients across Delhi NCR and Pan-India, that translates into a coating that both protects and decorates, extending the maintenance cycle of structures that are expensive and disruptive to repair.

The technical insight

The headline number is carbonation resistance of greater than 50 metres equivalent air-layer thickness (Sd-CO2), measured to DIN EN 1062. In practical terms, a roughly 300-micron film of WB300 resists CO2 diffusion as if the concrete were shielded by more than 50 metres of still air — comfortably above the 50 m threshold that European anti-carbonation standards treat as the benchmark for an effective protective coating. That barrier is what arrests the carbonation front and keeps the rebar passivated.\n\nThe rest of the data sheet explains how that performance is achieved and held. The cured film is built from 65% volume solids (70% +/-3% by weight) at a density of 1.40 +/-0.05 g/cm3, giving enough body to reach the specified thickness in two coats without sagging. Adhesion to a sound, prepared substrate exceeds 1.0 N/mm2 (ASTM D4541), tensile strength exceeds 3 N/mm2 (ASTM D638) and elongation reaches 60% (ASTM D638) — the elasticity that delivers crack-bridging. Chloride resistance is independently corroborated: a salt-spray figure of just 0.26 g/m2 per 1000 hours (ASTM B117) and a Low permeability rating in the Rapid Chloride Penetration Test (ASTM C1202), which is why the system is specified for coastal and marine-adjacent structures. The critical specification point for any applicator or consultant is film thickness — the protective properties depend on achieving a minimum 300-micron dry film, applied as two topcoat passes over the primer, at the correct coverage. Under-application is the single most common reason an anti-carbonation coating fails to deliver its rated Sd-CO2 value.

Where it is used

• Anti-carbonation protection of bridges, flyovers, elevated road corridors and metro viaducts
• External surfaces of concrete water-retaining and storage tanks (above the splash zone)
• Protective and decorative coating for RCC building facades, columns, beams and soffits
• Coastal and marine-adjacent structures exposed to chloride-laden air
• Industrial plant structures subject to sulphate and atmospheric pollution
• Refurbishment of carbonation-affected concrete after patch repair, as the final protective overcoat
• Car parks, stadiums and other large exposed concrete structures needing crack-accommodating protection

Key advantages

• Comprehensive barrier against carbon dioxide, water and sulphates — arrests carbonation-induced rebar corrosion
• Carbonation resistance greater than 50 m equivalent air-layer thickness (DIN EN 1062)
• Elastomeric with approximately 60% elongation, bridging fine shrinkage and thermal cracks
• Retains elastomeric recovery even after long-term UV weathering
• Breathable — allows internal water vapour to escape, reducing blistering risk
• Water-based with low odour and low VOC; suited to occupied and enclosed environments
• Two-component system (penetrating acrylic primer plus pigmented topcoat) for strong adhesion
• Low chloride permeability — verified by ASTM B117 salt-spray and ASTM C1202 RCPT (Low)
• Available in a wide range of colours, combining protection with a decorative finish
• Single-component, ready-to-use; brush, roller or spray applied

Limitations & considerations

• Designed for atmospherically exposed concrete above splash zones — not a coating for permanently immersed surfaces or internal tank linings holding liquid
• Protective performance depends on achieving the minimum 300-micron DFT; under-application reduces the rated CO2 resistance
• Do not apply if substrate temperature is below 10 C or above 60 C, or where relative humidity exceeds 90%
• Substrate must be at least 3 C above dew point; in high humidity (85-90%) good ventilation is essential
• Not to be applied in windy conditions (early dust pickup) or where rain is likely within 2 hours
• Requires thorough surface preparation — drying, removal of laitance/contaminants, ideally light grit-blasting; biocide treatment where moss or algae are present
• As a water-based film it must be protected from frost in storage and during early cure
• Shelf life is limited to 12 months when stored cool and dry

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Dekguard WB300

Dekguard WB300 sits in the breathable, water-based, elastomeric tier of Fosroc’s anti-carbonation range. Within the Fosroc family it is most naturally compared with Dekguard S and Dekguard AC (acrylic anti-carbonation coatings) and the higher-build elastomeric Dekguard E2000 — WB300’s edge is its combination of >50 m CO2 resistance, ~60% elongation and a low-VOC water-based formulation. On a concrete-repair project it pairs with the Renderoc patch-repair mortars, Nitozinc/Galvashield corrosion-inhibitor systems and Nitoprime primers, acting as the final protective overcoat that seals the whole repair stack. Against the wider Indian market, credible alternatives a consultant may evaluate include Sika’s Sikagard anti-carbonation coatings (e.g. Sikagard-550 W Elastic), MBS / MYK Schomburg protective coatings, Dr. Fixit’s Newcoat / anti-carbonation acrylic systems, and STP’s protective-coating range. The deciding factors are usually the certified Sd-CO2 value, crack-bridging requirement, breathability, UV durability and VOC limits; on those metrics WB300 is a strong, specification-grade choice, and Space Arc Engineering can supply it with the technical and application backing of an authorised Fosroc partner.

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