Fosroc Nitocote ET550
High-build, pitch-extended two-pack epoxy coating engineered for long-term corrosion protection of concrete and steel in immersed, chemically aggressive and effluent environments.
What is it?
A thixotropic, pitch (coal tar) extended epoxy amine-adduct coating supplied as a two-component system: a blend of epoxy resins plus a separate low-viscosity amine hardener, filled with reinforcing inert fillers and a solvent blend.
Where is it used?
Sewage treatment and effluent plants, dock and harbour structures, water and wastewater tanks (above-ground or fully submerged), pipe linings, and steel/concrete exposed to corrosive, chemically aggressive surroundings.
Why use it?
It delivers a tough, impermeable, chemically and abrasion-resistant film with high film build in a single airless-spray coat, needs no primer in most cases, and resists water, sea water, sewage, dilute acids/alkalis and marine growth.
How is it applied?
Two components are mixed thoroughly (viscosity adjustable with up to 5% Nitoflor Sol), then applied by brush or airless spray to a properly prepared substrate to reach a minimum total dry film thickness of 350 microns.
About Fosroc Nitocote ET550
Fosroc Nitocote ET550 is a high-performance, pitch-extended epoxy resin coating designed to protect concrete and metal against corrosion in some of the harshest service conditions encountered in Indian infrastructure and industrial work. Chemically, it is a thixotropic epoxy amine-adduct formulation that is “tar extended” (pitch/coal-tar extended), reinforced with inert fillers and a special blend of solvents. It ships as a two-pack system: a base of blended epoxy resins and a separate low-viscosity amine hardener, supplied in pre-measured 18-litre packs ready for site mixing. The result is a thick, impermeable barrier film that combines the chemical durability of epoxy with the water and moisture resistance characteristic of coal-tar chemistry. For contractors, consultants, architects, structural engineers and procurement teams, ET550 is one of the workhorse barrier coatings in the corrosion-protection segment: it is specified where a coating must survive permanent or intermittent immersion, sewage and effluent exposure, and physical wear, while remaining economical to apply over large areas. Its standout practical feature is film build. Because it is thixotropic and high-solids (volume solids approximately 66% when mixed), the recommended 350-micron dry film thickness can be achieved in a single coat by airless spray, where thinner conventional coatings would need multiple passes. In Delhi NCR and across India, Space Arc Engineering supplies and applies Nitocote ET550 for water-retaining structures, STP/ETP tankage, marine and dock works, buried steel and pipe internals, and concrete subject to aggressive ground or process water.
The technical insight
The defining characteristic of Nitocote ET550 is its pitch-extended (coal-tar) epoxy chemistry. The coal-tar pitch fraction lowers water permeability and improves immersion performance and economy, while the amine-cured epoxy backbone supplies chemical resistance, adhesion and a hard, abrasion-resistant surface. Two engineering numbers drive specification and estimating. First, dry film thickness: ET550 is designed for a minimum total DFT of 350 microns (the corresponding wet film is roughly 530 microns), achievable in a single airless-spray coat or built up over 1 to 3 coats by brush or conventional methods depending on conditions. Second, coverage: theoretical coverage is 1.80–1.90 m² per litre at 350 microns DFT, so an 18-litre pack covers in the order of 32–34 m² theoretically before allowing for wastage, surface profile and overspray. The product is temperature-sensitive on both cure and application. Application temperature should sit within 20°C–40°C; outside this band Fosroc must be consulted. Pot life after mixing is about 4 hours at 20°C but drops sharply to roughly 1 hour 30 minutes at 35°C, so in Indian summer site planning, mixing in small batches matters. Cure is similarly temperature-dependent: touch-dry in about 4 hours (20°C) or 2 hours (35°C), recoatable within 24 hours (20°C) or 18 hours (35°C), and fully cured in about 7 days at 20°C or 4 days at 35°C. Both the base (flash point 36°C) and hardener (26°C), and the Nitoflor Sol thinner (33°C), are flammable, demanding ventilation and no naked flame. Surface preparation is non-negotiable for performance: steel must be abrasive blast-cleaned to Sa 2½, and concrete must be clean, dry and free of laitance, with blowholes filled using a putty such as Nitomortar FC.
Where it is used
- Internal and external protection of sewage and effluent treatment tanks at STPs and ETPs
- Lining of water-retaining structures, clarifiers and process tanks, above-ground or fully submerged
- Corrosion protection of structural steel and concrete in dock, jetty and harbour installations
- Internal pipe linings and buried steel exposed to aggressive ground and process water
- Barrier coating for concrete and steel in chemically aggressive industrial atmospheres
- Protection against exhaust and sewage gases, marine barnacles and organic growth
Key advantages
- High film build (350 microns DFT) achievable in a single airless-spray coat
- No priming necessary in most cases, reducing labour, materials and programme time
- Broad chemical resistance: water, sea water, sewage and effluent, ground/distilled water, dilute mineral acids and alkalis, and many organic solvents
- Tough, impermeable, abrasion-resistant cured film suited to immersion and physical wear
- Resists barnacles and organic growth, useful in marine and harbour service
- Economical and versatile two-pack system supplied pre-measured for straightforward site mixing
- Applies by brush or airless spray, allowing fast coverage of large tank and structural areas
Limitations & considerations
- Coal-tar/pitch chemistry is dark (black/dark brown) and is being phased down globally on health and aesthetic grounds; not suitable where light or decorative finishes or potable-water contact are required
- Both components and the Nitoflor Sol thinner are flammable (flash points as low as 26°C for the hardener); naked flames and smoking must be avoided and ventilation ensured
- Short pot life in hot weather (about 1 hour 30 minutes at 35°C) demands small-batch mixing and disciplined site logistics in Indian summers
- Application is restricted to 20°C–40°C; outside this range Fosroc must be consulted
- Demanding surface preparation, steel to Sa 2½ blast standard, adds cost and access requirements
- Epoxy resins can sensitise skin; gloves, barrier cream and eye protection are mandatory
- Six-month shelf life when stored at 30°C in unopened tins limits long stockholding
Selection & best practice
Prepare the substrate rigorously before anything else: blast-clean steel to Sa 2½ and ensure concrete is clean, dry and laitance-free, filling blowholes with a putty such as Nitomortar FC. In Indian summer conditions, mix only what can be used within the reduced pot life (roughly 1.5 hours at 35°C), stirring both components until fully homogeneous with no unmixed streaks; adjust viscosity with up to 5% Nitoflor Sol if needed. Favour airless spray (minimum nozzle pressure around 140 bar, orifice 0.65–0.79 mm) to achieve the full 350-micron DFT in one pass, and reduce coat thickness in very hot or very cold conditions to avoid solvent entrapment. Verify wet film thickness during application and dry film thickness after cure, respect recoat windows, and allow the full cure period (about 4–7 days depending on temperature) before placing the structure into immersion or chemical service. Maintain ventilation, keep ignition sources away, and clean tools immediately with Nitoflor Sol.
Specifications
| Product type | Thixotropic pitch (coal-tar) extended epoxy amine-adduct, two-pack |
| Components | Base (blended epoxy resins) + low-viscosity amine hardener |
| Specific gravity | 1.38 – 1.40 |
| Volume solids (mixed) | 66% approx |
| Dry film thickness (DFT) | 350 microns (minimum total) |
| Wet film thickness (WFT) | ~530 microns |
| Number of coats | 1 – 3 depending on method (full DFT in one coat by airless spray) |
| Theoretical coverage | 1.80 – 1.90 m²/litre at 350 microns DFT |
| Pot life | 4 hours at 20°C; 1 hr 30 min at 35°C |
| Touch dry | 4 hours at 20°C; 2 hours at 35°C |
| Recoatable | 24 hours at 20°C; 18 hours at 35°C |
| Fully dry / cured | 7 days at 20°C; 4 days at 35°C |
| Application temperature | 20°C – 40°C |
| Application method | Brush or airless spray (≥140 bar, orifice 0.65–0.79 mm) |
| Thinner / cleaner | Nitoflor Sol (up to 5% by volume) |
| Steel surface prep | Abrasive blast clean to Sa 2½ |
| Flash points | Base 36°C; Hardener 26°C; Nitoflor Sol 33°C |
| Pack size | 18 litre packs (Nitoflor Sol in 5 & 20 L jerry cans) |
| Shelf life | 6 months at 30°C in unopened tins, cool dry store |
Industry use cases
Water & Wastewater
Lining the internal faces of STP and ETP tanks, clarifiers and effluent channels where concrete and steel face continuous immersion in sewage and process water, sewage gases and dilute chemicals.
Ports, Marine & Harbour
Protecting steel piles, gates and concrete in dock, jetty and harbour installations against sea water, splash-zone wetting and barnacle/organic growth.
Pipelines & Buried Steel
Internal pipe linings and external protection of buried steel exposed to aggressive ground water, providing a high-build impermeable barrier against electrochemical corrosion.
Industrial & Process Plants
Barrier coating for concrete bunds, sumps and steelwork in chemical, fertiliser and process facilities subject to dilute acids/alkalis, abrasion and aggressive atmospheres.
Water Storage & Infrastructure
Protecting non-potable water tanks, reservoirs and underground structures where a tough, abrasion-resistant immersion-grade coating is required over large areas economically.
Frequently asked questions
What type of coating is Fosroc Nitocote ET550?
What dry film thickness and coverage should I specify?
Does Nitocote ET550 need a primer?
Can it be used for submerged and sewage conditions?
What is the pot life and how does heat affect it?
Is Nitocote ET550 safe for potable (drinking) water tanks?
How we position Fosroc Nitocote ET550
Within the Fosroc range, Nitocote ET550 sits in the heavy-duty, immersion-grade corner of the protective-coatings family. It is the coal-tar epoxy option used where economy and immersion durability matter more than appearance, distinct from the lighter-duty acrylic anti-carbonation coatings such as Dekguard S (formerly Nitocote Dekguard S), and complementary to Fosroc repair and lining products including Nitomortar FC putty for blowhole filling, the Nitoflor Sol thinner, and solvent-free or potable-grade epoxy linings such as Nitocote SN522 where light colour or drinking-water contact is required. For specifiers comparing brands, the closest credible alternatives in India are Sika’s Sikagard and Sika Poxitar coal-tar-free/coal-tar epoxy systems, MBS (MYK / MBCC-lineage) protective coatings, Dr. Fixit’s industrial epoxy coatings, and STP’s epoxy and bituminous protective ranges. Coal-tar epoxies are increasingly being substituted by coal-tar-free (CTF) high-build epoxies on health and environmental grounds, so on new or sensitive projects it is worth weighing ET550 against a coal-tar-free equivalent. As an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, Space Arc Engineering can advise on the right system selection, supply genuine ET550 in 18-litre packs, and provide application support for tank, marine and structural corrosion-protection work.
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