Fosroc Nitocote NT550
A flexible, environment-friendly graft-polymerised epoxy coating that protects buried concrete and steel without coal tar, pitch or aromatic hydrocarbons.
What is it?
A two-pack, primerless epoxy protective coating based on graft polymerisation of epoxy resins, supplied in pre-weighed packs and applied at 200 micron wet film per coat.
Where is it used?
Buried and underground concrete and steel: foundations, basement retaining walls, manholes, sumps, effluent and water-retaining structures, pipe linings and secondary containment.
Why use it?
It delivers an impermeable, flexible (0.2 mm crack-bridging) barrier against aggressive ground water, salts, acids and alkalis, and is completely free of carcinogenic coal tar and pitch used in older bituminous coatings.
How is it applied?
Site-mix the two pre-weighed components, then apply two coats by brush, roller or spray at 200 micron WFT per coat (approx. 400 micron total) directly onto a clean, sound substrate without a separate primer.
About Fosroc Nitocote NT550
Fosroc Nitocote NT550 is a two-component protective and waterproofing coating developed for concrete and steel surfaces that face an aggressive, water-laden environment, particularly below ground. Its chemistry is based on the graft polymerisation of epoxy resins, which gives the cured film a useful degree of flexibility while retaining the chemical resistance associated with epoxies. The product is supplied as a two-pack material in pre-weighed quantities so that the base and hardener can be combined on site in the correct proportion and used straight away, removing the guesswork and waste that comes with field batching.
For Indian projects, the most important thing NT550 represents is a clean replacement for older coal-tar epoxy and bituminous tanking systems. Fosroc states the product is totally free of carcinogenic materials such as coal tar, pitch and aromatic hydrocarbons, which matters for worker safety, for structures in contact with potable or treated water, and for clients with environmental or ESG obligations. It is also a primerless system, so a single specified material does both the priming and the build, which simplifies procurement and reduces the number of SKUs on a site store.
In service, the cured coating behaves as an impermeable, flexible membrane bonded directly to the substrate. Fosroc rates it to bridge cracks up to 0.2 mm wide, which helps it accommodate the minor hairline movement and shrinkage cracking common in buried concrete without losing watertightness. It is applied as a two-coat system at 200 micron wet film per coat, building a continuous barrier that resists the ingress of ground water and the dissolved salts, sulphates and mild acids typically present in soil and effluent. Space Arc Engineering supplies and applies Nitocote NT550 across Delhi NCR and Pan-India as an authorised Fosroc distributor and applicator, and this page is written to help engineers, consultants and procurement teams specify it correctly.
The technical insight
The defining feature of NT550 is its graft-polymerised epoxy backbone. Conventional rigid epoxies bond and resist chemicals well but are brittle and crack when the substrate moves; flexible bituminous and coal-tar coatings move well but are weak, age poorly and carry the health and environmental baggage of coal tar. Graft polymerisation chemically links flexible segments onto the epoxy chain, so NT550 keeps epoxy-grade adhesion (around 1.5 N/mm to concrete) and chemical resistance while gaining elongation in the order of 30-35% and the ability to bridge 0.2 mm cracks. With roughly 92% solids and a low water absorption of about 0.2%, the cured film is dense and largely non-porous, which is what lets a 400 micron two-coat system function as a true waterproof barrier rather than just a decorative seal. Practically, the engineer should treat NT550 as a flexible barrier coating, not a structural repair: substrate preparation, sound concrete and correct film build per coat (measured with a wet-film comb) are what determine performance, not the product chemistry alone.
Where it is used
- Waterproofing and protection of buried concrete: foundations, footings, pile caps and basement retaining walls
- Internal and external lining of manholes, inspection chambers, wet wells and sumps
- Protective lining for water-retaining and effluent-handling structures such as tanks and treatment works
- Pipe linings and the inside faces of culverts and underground service structures
- Secondary containment bunds where resistance to mild chemical spillage is required
- Tanking of below-ground RCC against ground water, salts and sulphate-bearing soils
- Protection of concrete and steel surfaces in damp, corrosive underground environments as a coal-tar-epoxy replacement
Key advantages
- Completely free of carcinogenic coal tar, pitch and aromatic hydrocarbons, unlike older bituminous tanking systems
- Flexible film that bridges cracks up to 0.2 mm, accommodating minor substrate movement and hairline cracking
- Primerless, single-material system that reduces SKUs, procurement complexity and applied cost
- Supplied in pre-weighed two-pack quantities, eliminating site batching errors
- Forms an impermeable, low-absorption (around 0.2%) waterproof barrier suited to buried structures
- Good chemical resistance to ground water, alkalis, salt solutions and dilute acids
- Versatile application by brush, roller or spray to suit site conditions and geometry
- High solids content (around 92%) gives a dense, efficient film build per coat
Limitations & considerations
- Two-pack epoxy: once mixed it has a limited working/pot life and must be used promptly, so batch sizes should match the area being coated
- Not a structural crack-repair product; cracks wider than 0.2 mm need a dedicated repair or movement-joint solution first
- Performance depends heavily on substrate preparation, surface dryness and soundness; poorly prepared or contaminated concrete will compromise adhesion
- Epoxy systems are sensitive to low temperature and high humidity during cure; application outside the recommended window slows or impairs curing
- As an underground/barrier coating, it is not formulated as a UV-stable decorative topcoat for permanently exposed external faces
- Standard supply colour is grey only; other colours require minimum order quantities
- Confirm exact coverage, pot life, recoat and full-cure times against the current India TDS for the specific site temperature before ordering
Selection & best practice
Specify NT550 as a two-coat system and confirm the project-specific coverage, pot life and overcoat window from the current Fosroc India technical data sheet for your site temperature before ordering, because epoxy cure behaviour shifts with ambient conditions. Prepare the substrate properly: concrete must be sound, clean, free of laitance, oil and curing-compound residue, and surface-dry; mechanical preparation (grit blasting or grinding) and making good of blowholes give the best adhesion. Mix only the quantity that can be applied within the working life, stir the full pack thoroughly to a uniform colour, and apply each coat at the specified 200 micron wet film, checking with a wet-film comb so the full 400 micron build is achieved. Allow the first coat to reach the recommended overcoat condition before the second, protect freshly coated surfaces from water and backfill until cured, and avoid application during rain or onto damp surfaces. For potable-water or effluent contact, verify suitability and curing/ventilation requirements with Fosroc or with Space Arc Engineering’s technical team before starting.
Specifications
| Product type | Two-pack protective & waterproofing coating |
| Chemistry | Graft polymerisation of epoxy resins |
| Coal tar / pitch / aromatic hydrocarbons | None (free of carcinogenic materials) |
| Number of coats | Two coats |
| Wet film thickness | 200 micron per coat (approx. 400 micron total) |
| Crack bridging | Up to 0.2 mm |
| Application methods | Brush, roller or spray |
| Primer | Not required (primerless system) |
| Standard colour | Grey (other colours on minimum order quantity) |
| Adhesion to concrete | approx. 1.5 N/mm |
| Elongation | approx. 30-35% |
| Tensile strength | approx. 5 N/mm |
| Solids content | approx. 92% |
| Water absorption | approx. 0.2% |
| Specific gravity | approx. 1.35 g/cm at 23 C |
| Supply | Pre-weighed two-pack material |
| Manufacturer in India | Fosroc Chemicals (India) Pvt Ltd |
Industry use cases
Water & wastewater infrastructure
Lining of manholes, wet wells, sumps and effluent-handling RCC structures where the coal-tar-free, chemically resistant film protects concrete from sewage gases, salts and mild acids.
Buildings & basements
Tanking of below-ground retaining walls, raft foundations and pile caps in high-water-table Delhi NCR sites, where 0.2 mm crack bridging guards against ground-water ingress.
Industrial & containment
Protective lining of secondary containment bunds and tanks exposed to mild chemical spillage, alkalis and salt solutions.
Pipelines & culverts
Internal protective coating of pipe linings, culverts and underground service ducts subject to continuous damp, corrosive conditions.
Marine & coastal civil works
Protection of buried and splash-zone-adjacent concrete against chloride-laden ground water and salt attack in coastal projects.
Frequently asked questions
What exactly is Fosroc Nitocote NT550 and what is it made of?
Where should NT550 be used on a project?
Does NT550 need a separate primer, and how is it applied?
How is NT550 different from a coal-tar epoxy coating?
Can NT550 bridge cracks in the concrete?
Is NT550 available in India and who can supply it?
How we position Fosroc Nitocote NT550
Within the Fosroc range, Nitocote NT550 sits alongside the company’s other epoxy protective coatings, most notably Nitocote ET550, a high-build solvent-free epoxy widely used in India for tanks and similar duties; NT550 differentiates itself as the flexible, crack-bridging, coal-tar-free option for buried and underground work. It pairs naturally with Fosroc’s repair and substrate systems, such as the Renderoc concrete repair mortars for making good defects and Nitobond bonding aids for surface preparation, and with Conbextra grouts where structural reinstatement is needed before coating. Against competitor systems, credible alternatives an Indian specifier may evaluate include Sika’s epoxy protective and waterproofing coatings (for example the Sikagard and Sikalastic ranges), STP Limited’s bituminous and epoxy tanking products, MBS (MYK Schomburg) protective coatings, and, for lighter-duty or smaller-scale below-ground waterproofing, Dr. Fixit systems from Pidilite. NT550’s strongest positioning is where a client needs an underground epoxy barrier with genuine flexibility and an explicit no-coal-tar formulation; where the duty is simply rigid chemical protection of an internal tank, ET550 or a Sika rigid epoxy may be more economical, and Space Arc Engineering can help match the right product to the exposure, substrate and budget.
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