Fosroc Nitocote SN502
Clear, penetrating silane-siloxane hydrophobic impregnation that waterproofs and protects reinforced concrete and masonry against chloride attack — without forming a film or changing appearance.
What is it?
A single-component, clear, penetrating silane-siloxane water repellent (hydrophobic impregnation) for concrete and masonry — it soaks into the pores and reacts to line them, rather than forming a surface film.
Where is it used?
Atmospherically exposed reinforced concrete and cementitious or masonry substrates: bridge decks and piers, flyovers, coastal and marine RCC structures, building facades, parapets, chajjas, water-retaining and external concrete elements across India.
Why use it?
It reduces water absorption by up to 94% and chloride-ion penetration by up to 92-98%, slowing reinforcement corrosion, while still letting the structure breathe (water vapour escapes) and leaving the surface looking unchanged.
How is it applied?
Applied to a clean, dry substrate in two flood coats by low-pressure knapsack spray, neat (no thinning), at 0.2 litres/m² per coat (5 m²/litre/coat), with a 2-hour interval at 20°C between coats.
About Fosroc Nitocote SN502
Fosroc Nitocote SN502 is a penetrating, hydrophobic concrete water repellent built on silane-siloxane chemistry. Unlike a paint or membrane that sits on the surface, SN502 is an impregnation: the low-viscosity liquid is absorbed into the capillary pore network of concrete, render or masonry, where it reacts and chemically bonds to the pore walls. The result is a hydrophobic lining deep within the substrate that repels liquid water and dissolved salts while leaving the pores open enough for water vapour to pass out. Because nothing builds up on the surface, the treated concrete keeps its natural appearance and texture — there is no gloss, no film to peel or blister, and no change in slip resistance on trafficked areas.
The product is engineered for one of the most common and costly failure mechanisms in Indian reinforced concrete: chloride-induced reinforcement corrosion. Chlorides arriving from sea spray in coastal cities, from de-icing salts, or from contaminated aggregates and water diffuse through the concrete cover and depassivate the steel, triggering rust, cracking and spalling. By drastically cutting the water and chloride that the concrete can absorb, Nitocote SN502 extends the time before chlorides reach the rebar, effectively buying additional service life for the structure. It is equally relevant to new construction — as a specified durability measure on bridges and marine works — and to remedial protection of existing, exposed structures.
For specifiers and contractors in India, SN502 sits in Fosroc’s protective-coatings and concrete-durability family alongside anti-carbonation and elastomeric coatings such as the Dekguard range and crack-bridging systems like Nitocote CM210. Where Dekguard products form a pigmented, anti-carbonation film, SN502 is the invisible, penetrating option chosen when the client wants protection without altering the look of fair-faced concrete, stone or brick. Space Arc Engineering supplies and applies Nitocote SN502 as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India.
The technical insight
The performance of any silane-siloxane impregnation comes down to depth of penetration and active-content reaction, not film thickness — so application discipline matters more than with a conventional coating. Nitocote SN502 is designed to be applied neat as two saturating flood coats totalling 0.4 litres/m² (0.2 litres/m²/coat, i.e. roughly 5 m² per litre per coat). The substrate must be genuinely dry and free of laitance, curing compounds and mould-release agents, because any surface film or moisture barrier prevents the liquid from wicking into the capillaries where it needs to react. Fosroc’s data reports a reduction in water absorption of up to 85% (NCHRP 244) / 94% (CTI method) and a reduction in chloride-ion penetration of up to 92% (NCHRP 244) / 98% (CTI method); independent marketing references to ASTM C642 cite water-absorption reductions of the order of 85%. The treatment remains vapour-permeable, which is what distinguishes a breathable hydrophobic impregnation from a sealing film — trapped moisture behind an impermeable layer in Indian climates is a frequent cause of coating failure, and SN502 avoids that by design. VOC content is 697 g/litre, so it is a solvent-borne system requiring ventilation and the usual solvent-handling precautions on site. Substrate temperature must be above 2°C at application, and a windy or hot environment is actually tolerated well — an advantage in exposed Indian field conditions where slower-curing systems can struggle.
Where it is used
- Protecting atmospherically exposed reinforced concrete against chloride and water ingress
- Durability treatment for new bridges, flyovers, viaducts and elevated road structures
- Protection of coastal and marine RCC — jetties, sea walls, piers and waterfront buildings
- Water repellent for concrete facades, parapets, chajjas and exposed external elements
- Treatment of fair-faced concrete, stone and brick masonry where appearance must be preserved
- Reducing efflorescence and freeze-thaw damage on external masonry and concrete
- Remedial hydrophobic impregnation of existing exposed structures as part of repair systems
Key advantages
- Penetrates and bonds within the pore structure — no surface film to peel, blister or wear off
- Cuts water absorption by up to 94% and chloride-ion penetration by up to 92-98%
- Vapour-permeable — lets the structure breathe so trapped moisture does not build up
- Clear and effectively non-staining; preserves the natural appearance of concrete, stone and brick
- Single-component and applied neat — no mixing, simple knapsack-spray application
- Performs in windy or high-temperature site conditions common across India
- Increases freeze-thaw resistance and minimises efflorescence
- Chemically resistant to de-icing salts, fuels, oils and atmospheric contaminants
- Long 36-month shelf life in sealed containers eases procurement and site stocking
Limitations & considerations
- A penetrating water repellent, not a waterproof membrane — it will not bridge cracks or hold standing/hydrostatic water
- Effectiveness depends on a dry, clean, contamination-free substrate; films, laitance and curing compounds block penetration
- Solvent-borne with high VOC (697 g/litre) — needs ventilation and solvent-handling precautions on site
- May darken some polymer-modified substrates and white cement; a trial area is recommended before full application
- Must not be contaminated with water, and should not be applied below 2°C substrate temperature
- Does not pigment or hide the substrate — for anti-carbonation colour coatings a Dekguard-type system is more appropriate
- Correct two-coat flood rate (0.4 litres/m² total) must be achieved; under-application compromises protection
Selection & best practice
Always start with a trial patch on the actual substrate to confirm penetration, appearance and that no darkening occurs, especially on polymer-modified or white-cement surfaces. Ensure the concrete is fully cured, dry and grit-blasted free of laitance, curing compounds, oils and biological growth; treat moss or algae with a proprietary biocide after blasting. Apply by low-pressure knapsack spray, neat and never thinned, as two flood coats at 0.2 litres/m² each, allowing a minimum of 2 hours at 20°C between coats and confirming the full 0.4 litres/m² total rate is achieved. Avoid application before rain or onto damp surfaces, protect adjacent glass and aluminium from overspray, and clean tools immediately with Fosroc Solvent 10. Co-ordinate any crack repair, structural concrete repair (e.g. Renderoc) or anti-carbonation coating before deciding whether SN502 alone is sufficient or should be part of a wider protection system.
Specifications
| Product type | Single-component penetrating silane-siloxane hydrophobic impregnation (clear water repellent) |
| Appearance | Clear liquid; effectively non-staining (may darken some polymer-modified / white-cement substrates) |
| Number of coats | 2 flood coats |
| Application rate | 0.2 litres/m² per coat (approx. 5 m²/litre/coat); 0.4 litres/m² total |
| Recoat / overcoating interval | Minimum 2 hours at 20°C between coats |
| Reduction in water absorption | Up to 85% (NCHRP 244) / 94% (CTI method) |
| Reduction in chloride-ion penetration | Up to 92% (NCHRP 244) / 98% (CTI method) |
| Vapour permeability | Permeable — allows water vapour to escape from the substrate |
| VOC content | 697 g/litre (solvent-borne) |
| Minimum application temperature | Substrate above 2°C; not to be contaminated with water |
| Application method | Low-pressure knapsack / portable spray, applied neat (no thinning) |
| Cleaning solvent | Fosroc Solvent 10 (immediately after use) |
| Pack size | 20 litre container (ref. FC855145-20L) |
| Shelf life / storage | 36 months in original sealed containers, in a dry store away from heat and naked flame |
Industry use cases
Bridges & infrastructure
Specified on new and existing RCC bridges, flyovers and viaducts to slow chloride ingress into the cover concrete and extend the corrosion-initiation life of the reinforcement.
Coastal & marine construction
Applied to piers, sea walls, jetties and waterfront buildings in coastal cities (Mumbai, Chennai, Kochi, Goa) where sea-spray chlorides are the dominant durability threat.
Commercial & residential facades
Used as an invisible water repellent on fair-faced concrete, exposed brick and stone facades, parapets and chajjas to reduce rain penetration, dampness and efflorescence while keeping the original look.
Water-retaining & industrial structures
Treatment of external concrete on tanks, treatment plants and industrial buildings to resist water, atmospheric contaminants, fuels and oils on exposed surfaces.
Repair & rehabilitation
Specified by consultants as the final hydrophobic impregnation step in concrete-repair programmes after patch repair and crack treatment, to protect the whole element going forward.
Frequently asked questions
Is Nitocote SN502 a waterproofing membrane?
How much Nitocote SN502 do I need per square metre?
Will it change the colour or appearance of my concrete?
How long does it take to dry, and can it be over-coated?
What surface preparation does it need?
Does Space Arc Engineering supply and apply Nitocote SN502 in India?
How we position Fosroc Nitocote SN502
Nitocote SN502 is Fosroc’s invisible, penetrating durability option — the right choice when the goal is to cut chloride and water ingress into reinforced concrete without changing how the structure looks. Within the Fosroc range it complements rather than competes with the Dekguard family (pigmented, anti-carbonation and elastomeric facade coatings) and with film-forming or crack-bridging coatings such as Nitocote CM210; on a typical repair job SN502 is often the final hydrophobic impregnation applied over Renderoc repairs and after crack treatment. Against the wider Indian market, it sits in the same category as silane-siloxane impregnations from Sika (Sikagard-706 Thixo / Sikagard hydrophobic impregnations), MBCC/Master Builders Solutions (MasterProtect H series), Pidilite Dr. Fixit (penetrating water-repellent and crystalline ranges) and STP Limited. SN502’s particular strengths are its single-component neat application, high reported reductions in water and chloride absorption, breathability and tolerance of hot, windy site conditions. Where a client instead needs a coloured anti-carbonation barrier, crack-bridging elasticity or positive-side membrane waterproofing, those requirements point to Dekguard, an elastomeric coating, or a dedicated membrane rather than to SN502.
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