Fosroc Nitocote EP403
A two-pack, solvent-free, high-build epoxy that bonds to damp concrete and steel — delivering 400 microns of chemical, corrosion and ground-gas protection for basements, tunnels, STPs and marine structures.
What is it?
A two-component, 100% solids (solvent-free) epoxy resin coating from Fosroc that can be applied to damp or wet concrete and mild steel, curing to a smooth, tough, chemically resistant film.
Where is it used?
Basement tanking, water and sewage treatment plants, tunnels, marine and coastal structures, plant rooms, bunds and process areas across India where moisture-tolerant protection is required.
Why use it?
It tolerates damp substrates where conventional solvent-based epoxies fail, gives high build (400 microns in two coats), resists a broad range of chemicals, and blocks water vapour and ground gases such as radon, CO2 and methane.
How is it applied?
Applied by brush, roller or airless spray in two 200-micron coats to a prepared, laitance-free substrate; mix Part A and Part B fully, work within the 30–40 minute pot life, and overcoat after the stated window.
About Fosroc Nitocote EP403
Fosroc Nitocote EP403 is a high-build, two-pack, solvent-free epoxy protective coating engineered for one situation that defeats most coatings in Indian conditions: a damp or wet substrate. On construction sites across Delhi NCR and the rest of the country, concrete rarely reaches the bone-dry state that conventional solvent-based epoxies demand. Water treatment tanks, basement rafts, tunnel inverts and coastal foundations carry residual moisture, rising damp or condensation almost permanently. Nitocote EP403 is formulated to bond and cure on exactly these surfaces, provided there is no standing or running water at the point of application.
Supplied in pre-weighed two-component packs (a base resin and a hardener) ready for on-site mixing, the product cures to a smooth, glossy, easy-to-clean film that is corrosion, chemical and abrasion resistant. Because it is 100% solids and contains no solvent, the film does not shrink as it cures, there is minimal odour, and it can be used safely in confined or poorly ventilated spaces such as underground tanks and tunnels where solvent-borne products are restricted. The standard shade is light grey.
Beyond simple barrier protection, Nitocote EP403 functions as a gas and vapour barrier. The cured coating restricts the passage of water vapour and resists ground gases including radon, carbon dioxide and methane — a meaningful benefit for basements and habitable spaces built over reclaimed or contaminated ground. As a Space Arc Engineering supplied and applied system, EP403 is specified where a single product must combine moisture tolerance, chemical durability and gas resistance in one application.
The technical insight
Nitocote EP403 is a 100% volume-solids, two-pack epoxy applied at a wet film thickness of 200 microns per coat in two coats, giving a nominal 400-micron dry film. Because it is solvent-free, wet and dry film thickness are effectively the same — there is no solvent loss and therefore no film shrinkage, which is what allows reliable high-build deposition in a single pass and a continuous, pinhole-resistant barrier. The moisture tolerance comes from a resin/hardener chemistry that cures in the presence of surface dampness rather than being displaced by it; this is the key differentiator from standard epoxies, which blush or fail to adhere on damp concrete. Theoretical coverage is approximately 3 m² per kg per coat (about 0.2 litres per m² per coat), before allowance for surface profile, porosity and wastage. Pot life after mixing is 30–40 minutes at 20°C — in Indian summer temperatures the working window shortens considerably, so material must be mixed in batches that can be used quickly. The first coat must be overcoated within a defined window (not less than 6 hours and not more than 18 hours at 20°C) to ensure intercoat adhesion; full chemical cure develops over roughly 7 days at 20°C. The film is CE marked to EN 1504-2 as a surface protection product (principles/methods 1.3, 2.2, 5.1, 6.1 and 8.2), achieves Class 1 water vapour permeability, CO2 diffusion resistance equivalent to >50 m, and low capillary water absorption — the quantified backbone for specifying it as a certified concrete protection system rather than a generic paint.
Where it is used
- Internal and external tanking of basement rafts and retaining walls subject to rising damp or water-table pressure
- Lining of water and sewage treatment plant (STP/WTP) tanks, channels and clarifiers
- Protective coating to tunnel linings, inverts and underground structures
- Marine and coastal concrete and steel exposed to splash zones and chloride-laden environments
- Corrosion protection of mild steel pipework, tanks and structural steel in damp plant rooms
- Gas barrier coating to basements and ground-floor slabs over radon, CO2 or methane-bearing ground
- Chemical containment bunds, trenches and process floors in industrial and effluent facilities
- Refurbishment coating to damp concrete in old basements, lift pits and service ducts
Key advantages
- Bonds and cures on damp or wet substrates where conventional epoxies fail (no standing water permitted)
- Solvent-free and 100% solids — minimal odour, no film shrinkage, safe for confined and poorly ventilated spaces
- High build: full 400-micron protection achieved in just two coats
- Applies directly to both mild steel and concrete without a separate primer on properly prepared surfaces
- Broad chemical resistance — water, petrol, xylene, dilute acids, alkalis and salt solutions
- Acts as a vapour and ground-gas barrier (radon, carbon dioxide, methane)
- CE marked and independently certified to EN 1504-2 for surface protection
- Smooth, glossy, easy-to-clean finish that is corrosion and abrasion resistant
- Pre-weighed two-pack units remove site batching errors
Limitations & considerations
- Cannot be applied over standing or running water — damp is acceptable, free water is not
- Short pot life of 30–40 minutes at 20°C, shortening further in hot Indian site conditions
- Must not be applied below 5°C, or at 5°C and falling, or when relative humidity exceeds 90%
- Overcoat window is time-critical (typically within 18 hours at 20°C); missing it compromises intercoat adhesion
- Surface preparation is demanding — steel needs grit blasting (BS 7079 Sa2½) and concrete must be sound, cured and laitance-free
- Standard colour is light grey only, limiting decorative/colour-coding use without a separate topcoat
- Epoxy films can chalk and lose gloss under prolonged UV/sunlight exposure in fully external applications
- Full chemical cure takes about 7 days — areas must be protected from contact and loading during this period
Selection & best practice
Start with substrate preparation: concrete must be fully cured, sound and free of laitance, oil and curing compound (grit blasting, scabbling or acid etching followed by neutralisation), and mild steel must be blast-cleaned to BS 7079 Sa2½ with a clean, dry anchor profile. Ensure the surface is damp but never wet — remove any standing or running water before coating. Check that ambient and surface temperatures are above 5°C and rising and that relative humidity is below 90%. Mix the full contents of Part B into Part A and stir mechanically until uniform — never split packs by eye. Apply the first coat by brush, roller or airless spray at 200 microns wet, work within the 30–40 minute pot life (mix smaller batches in summer heat), and apply the second coat within the stated overcoat window to guarantee intercoat bond. Protect the freshly coated surface from rain, dust and traffic, and allow the full cure period before exposing it to chemicals or immersion. For potable water applications, confirm the appropriate Fosroc grade and any local approvals before specifying.
Specifications
| Chemical type | Two-pack, solvent-free, 100% solids epoxy resin |
| Number of components | Two (base resin + hardener), pre-weighed |
| Colour | Light grey |
| Volume solids | 100% (solvent-free) |
| Wet/dry film thickness per coat | 200 microns |
| Number of coats / total DFT | 2 coats / nominal 400 microns |
| Theoretical coverage | Approx. 3 m² per kg per coat (~0.2 L/m² per coat) |
| Pot life | 30–40 minutes at 20°C |
| Overcoating window | Not less than 6 h, not more than 18 h at 20°C |
| Full cure | Approx. 7 days at 20°C |
| Minimum application temperature | 5°C (not at 5°C and falling) |
| Maximum relative humidity | 90% |
| Substrates | Damp concrete and mild steel |
| Chemical resistance | Water, petrol, xylene, 25% sulphuric acid, 50% sodium hydroxide, saturated NaCl |
| Standard / certification | CE marked to EN 1504-2 (methods 1.3, 2.2, 5.1, 6.1, 8.2) |
| Water vapour permeability | Class 1 (EN 1504-2) |
| CO2 diffusion resistance | >50 m |
| Application method | Brush, roller or airless spray |
| Cleaning solvent | Fosroc Solvent 102 |
| Pack size | 2.5 kg unit (verify current Indian pack with Space Arc) |
| Shelf life | Approx. 18 months from manufacture, unopened |
Industry use cases
Water & Sewage Treatment
Lining of STP and WTP tanks, channels and clarifiers exposed to effluent, dilute acids and alkalis, where the concrete is permanently damp and conventional epoxies cannot be guaranteed to adhere.
Basements & Underground Structures
Internal tanking of basement rafts and walls in Delhi NCR high-rises subject to rising damp and a high water table, doubling as a barrier against radon and methane from made-up ground.
Tunnels & Metro
Protective and gas-barrier coating to tunnel linings and inverts in metro and infrastructure projects where damp surfaces and confined, low-ventilation conditions rule out solvent-borne products.
Marine & Coastal
Corrosion and chloride protection of concrete and mild steel in splash zones and coastal plants where salt solutions and constant moisture demand a moisture-tolerant, salt-resistant film.
Industrial Process & Containment
Chemical-resistant lining to bunds, trenches and process floors handling fuels, solvents and aggressive solutions in effluent and manufacturing facilities.
Steel Asset Protection
Direct-to-steel high-build coating for tanks, pipework and structural members in damp plant rooms and pump houses, eliminating the need for a separate primer on blast-cleaned steel.
Frequently asked questions
Can Nitocote EP403 really be applied to wet concrete?
How many coats and what thickness do I need?
What is the coverage and how much should I order?
Does it need a primer?
What chemicals and gases does it resist?
How long before it is fully cured and can be put into service?
How we position Fosroc Nitocote EP403
Within the Fosroc range, Nitocote EP403 is the damp-tolerant, high-build member of the Nitocote protective-coating family, complementing Fosroc’s repair and waterproofing systems — Renderoc mortars for prior concrete repair, Nitoprime primers for difficult substrates, and Brushbond/Proofex membranes where flexible crack-bridging waterproofing is needed rather than a rigid chemical barrier. Where flexibility or potable-water certification is the priority, those systems may suit better than a rigid epoxy. Among competing brands in India, credible alternatives include Sika’s Sikagard and Sikafloor epoxy coatings, MBS Coatings’ epoxy systems, Dr. Fixit’s epoxy coating range, and STP Limited’s epoxy protective coatings — several offering damp-tolerant or solvent-free grades. EP403’s distinct positioning is the combination of genuine damp-surface application, a fully solvent-free 100% solids formulation safe in confined spaces, high build in two coats, and EN 1504-2 certification with quantified gas and vapour resistance. For Indian basements, STPs, tunnels and coastal structures where the substrate is never truly dry, that mix of moisture tolerance and certified performance is the reason to specify it. Space Arc Engineering supplies and applies EP403 as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India.
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