Fosroc Nitocote SN511
A near-100% active isobutyl-silane impregnation that drives deep into concrete to block chloride and water ingress while letting the structure breathe — engineered for marine, coastal and de-icing-salt exposure.
What is it?
A solvent-free, low-viscosity penetrating water repellent based on ~95% active monomeric isobutyl (alkyl) trialkoxy silane that soaks into porous concrete and chemically bonds to form a hydrophobic lining inside the pores.
Where is it used?
Reinforced concrete exposed to chlorides and moisture — sea-facing structures, jetties, bridge decks and piers, flyovers, parking decks, water-retaining structures and facades across coastal and de-icing environments.
Why use it?
It markedly cuts water and chloride-ion absorption (the main drivers of rebar corrosion) without forming a film, so the surface stays breathable, UV-stable and unchanged in appearance — extending the service life of the structure.
How is it applied?
Applied neat (ready to use) by saturation flooding with low-pressure airless spray or roller, working bottom-up on vertical faces, typically as one to two flood coats at roughly 0.25–0.44 litres per square metre per coat depending on substrate porosity.
About Fosroc Nitocote SN511
Fosroc Nitocote SN511 is a penetrating, impregnating water repellent designed to protect reinforced concrete from the twin agents of deterioration: water and chloride ions. Unlike a conventional surface coating that lays a film on top of the concrete, SN511 is a low-viscosity, colourless liquid that is absorbed deep into the capillary pore structure of the substrate. Once inside, the monomeric isobutyl (alkyl) trialkoxy silane reacts with moisture and the alkaline pore environment to chemically bond and line the pore walls with a hydrophobic (water-hating) layer. The pores are not blocked — they are made repellent — so liquid water and dissolved salts are kept out while water vapour can still escape from within the structure. This breathable, non-film-forming behaviour is what distinguishes a silane impregnant from a sealer or membrane. Because the active content is very high (around 95% silane, essentially solvent-free), the small silane molecule penetrates further than diluted or higher-molecular-weight siloxane systems, which is exactly what is needed on dense, well-cured structural concrete. For Indian projects, SN511 is the natural choice wherever chloride-driven rebar corrosion is the governing durability risk — coastal RCC, splash-zone marine works, and decks subject to salt. It is part of Fosroc’s wider Nitocote and concrete-protection range and is frequently specified alongside repair mortars and anti-carbonation coatings as one layer of a complete durability strategy. Space Arc Engineering, as an authorised Fosroc distributor and applicator serving Delhi NCR and Pan-India, supplies SN511 with the technical back-up — substrate assessment, application method statements and trained applicator support — needed to get the specified penetration and performance on site.
The technical insight
The performance of any silane water repellent is governed by depth of penetration and active-ingredient concentration, and SN511 is engineered to maximise both. Isobutyl trialkoxy silane is a small monomer; at ~95% actives with no dilution, it penetrates dense concrete more effectively than emulsion or oligomeric siloxane products, then hydrolyses and condenses in situ to graft a durable, non-soluble hydrophobic resin onto the silica and cement substrate. The protection is therefore physically inside the concrete rather than on it, making it largely immune to UV degradation, surface abrasion and weathering that would erode a film coating. In independent NCHRP 244-type screening test conditions, treated concrete has shown a reduction of around 95% in chloride-ion penetration and around 80% in water absorption versus untreated control — the figures that justify its use as primary corrosion protection. Critically, because it is breathable, it does not trap moisture behind a membrane, avoiding the blistering and osmotic problems that plague impermeable coatings on damp substrates. The trade-off is that SN511 provides no decorative finish, no crack-bridging and no carbonation barrier on its own; where CO2-driven carbonation or aesthetics are also a concern, it is over-coated with an anti-carbonation/elastomeric coating from the Dekguard or Nitocote acrylic range.
Where it is used
- Protection of sea-facing and splash-zone reinforced concrete in marine and coastal structures
- Bridge decks, piers, abutments, crash barriers and substructures exposed to de-icing salts or marine chlorides
- Flyovers, viaducts and elevated road/metro structures in chloride-laden urban environments
- Multi-storey and parking decks where salt-water carry-in accelerates rebar corrosion
- Water-retaining and water-excluding RCC structures requiring breathable protection
- External concrete facades, columns and soffits needing invisible, non-darkening water repellency
- As the impregnation layer beneath an anti-carbonation or elastomeric over-coat in a multi-layer durability system
- Protection of new concrete to extend design service life as part of a durability specification
Key advantages
- Very high active silane content (~95%), essentially solvent-free, giving deep penetration into dense concrete
- Markedly reduces chloride-ion ingress (around 95% in NCHRP 244-type screening) — directly targets rebar corrosion
- Cuts water absorption by around 80% while remaining fully breathable to water vapour
- Penetrating, non-film-forming action: not removed by abrasion, weathering or UV exposure
- Colourless and invisible — does not darken, gloss or discolour the substrate, preserving appearance
- Improves freeze-thaw resistance and minimises efflorescence and salt staining
- Chemically resistant to de-icing compounds and atmospheric pollutants
- Ready to use, no on-site mixing; applied by simple flood spray or roller
Limitations & considerations
- Provides no decorative or coloured finish — purely a functional impregnation
- Does not bridge cracks; structural and dynamic cracks must be repaired separately before treatment
- On its own it is not a dedicated anti-carbonation barrier — over-coat where carbonation governs
- Requires a sound, clean, reasonably dry and absorbent substrate; will not penetrate sealed, very dense, painted or laitance-covered surfaces effectively
- Performance depends on achieving specified penetration depth — under-application or poor surface prep compromises results
- Not a vapour or liquid membrane and not suitable for permanently immersed waterproofing duty on its own
- Solvent-character liquid requiring appropriate ventilation, PPE and protection of adjacent glass, aluminium and finished surfaces during application
- Best applied to concrete that has cured for the recommended period — not for green/freshly placed concrete
Selection & best practice
Achieving the specified penetration is everything. Start with a sound, clean substrate — remove laitance, curing-compound residues, dust, oil and any existing coating by grit blasting or equivalent, and repair cracks and spalls with a Fosroc Renderoc repair mortar first. The concrete should be surface-dry and absorbent at the time of application; avoid treating during or immediately after rain. Apply SN511 neat by saturation flooding using low-pressure airless spray or roller, working from the bottom up on vertical faces so the running excess is re-absorbed into already-wet concrete, and maintain a visible run-down of around 150–300 mm. Apply the second flood coat wet-on-wet or as soon as the first has soaked in, at the full specified rate (typically of the order of 0.25–0.44 l/m² per coat, confirmed by a site trial on the actual substrate). Always run a trial patch to calibrate true coverage and penetration on the specific concrete, mask and protect glass, aluminium, polished stone and vegetation, and allow the treated surface to cure before any over-coating. Store sealed in the original containers away from heat and ignition sources, and follow the current TDS and SDS for ventilation and PPE.
Specifications
| Product type | Penetrating / impregnating silane water repellent for concrete |
| Chemical basis | Monomeric isobutyl (alkyl) trialkoxy silane |
| Active content | ~95% active (essentially solvent-free) |
| Appearance | Low-viscosity, colourless / clear neutral liquid |
| Action | Penetrates pores and reacts to form a bonded hydrophobic pore lining; breathable (water-vapour permeable) |
| Chloride-ion penetration reduction | ~95% (NCHRP 244-type screening) |
| Water absorption reduction | ~80% (NCHRP 244-type screening) |
| Application rate | Approx. 0.25–0.44 l/m² per coat (substrate-dependent; ~0.3 l/m² per coat minimum typical) |
| Number of coats | 1–2 flood coats |
| Application method | Saturation flooding by low-pressure airless spray or roller, bottom-up; not by brush |
| UV / weathering | Not affected by UV; no substrate discolouration |
| Additional benefits | Improves freeze-thaw resistance; minimises efflorescence; resists de-icing salts and pollutants |
| Pack sizes | 20 litre and 200 litre containers (regional availability may vary) |
| Substrate | Sound, clean, dry, absorbent reinforced/precast concrete |
Industry use cases
Marine & Ports
Impregnation of jetties, breakwaters, sea walls and splash-zone RCC where chloride attack is the primary corrosion driver, cutting salt ingress while keeping the concrete breathable.
Bridges & Highways
Protection of bridge decks, piers, crash barriers and substructures against marine chlorides and de-icing salts to extend service life and defer costly repair cycles.
Metro & Elevated Infrastructure
Treatment of flyover, viaduct and elevated metro RCC in chloride-laden coastal cities to slow rebar corrosion on exposed structural surfaces.
Parking & Commercial Decks
Invisible water-repellent protection of parking decks and ramps where vehicle-borne salt water accelerates deterioration, with no change to surface appearance.
Water-Retaining Structures
Breathable protection of tanks, reservoirs and treatment-plant concrete that must repel water without trapping internal vapour behind a film.
Coastal Buildings & Facades
Clear impregnation of external columns, soffits and facades on sea-front buildings to reduce moisture and salt uptake while preserving the natural concrete look.
Frequently asked questions
Is Fosroc Nitocote SN511 a coating or a sealer?
Will SN511 change how my concrete looks?
Does it stop carbonation as well as chlorides?
How much SN511 do I need per square metre?
Can it be applied to cracked or damaged concrete?
Is SN511 available for projects in Delhi NCR and across India?
How we position Fosroc Nitocote SN511
Within Fosroc’s durability portfolio, Nitocote SN511 is the deep-penetration, high-actives silane for primary chloride and water-ingress protection of structural concrete — the layer you specify when corrosion of reinforcement is the governing risk. It is commonly paired with Fosroc Renderoc repair mortars (to reinstate damaged concrete before treatment) and with anti-carbonation/elastomeric over-coats such as Fosroc Dekguard or the Nitocote acrylic range where carbonation resistance or a decorative finish is also required; for crack injection and structural repair, Fosroc Conbextra and Nitomortar systems complete the package. Compared with cream and gel silanes or diluted siloxane water repellents, SN511’s near-neat monomeric isobutyl-silane chemistry is positioned for maximum penetration on dense concrete. Credible alternatives an Indian specifier may evaluate include Sika’s silane impregnations (e.g. Sikagard / Sika FerroGard hydrophobic impregnation range), MBS (MYK Arment) and STP Limited concrete-protection products, and, for general waterproofing-led briefs, Dr. Fixit (Pidilite) repellents — though for high-actives penetrating silane specifically targeting chloride-driven corrosion, SN511 remains a benchmark specification. Space Arc Engineering supplies SN511 and these complementary Fosroc systems with applicator support across Delhi NCR and Pan-India, helping consultants and contractors choose and combine the right layers for the exposure.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.