Frequently Asked Questions

What is the difference between Nitoprime 30 and Nitoprime 25 and in what situations should each be used?

Nitoprime 30 and Nitoprime 25 are both two-component epoxy primers from Fosroc for concrete surface preparation before floor coating or repair mortar application, but they differ primarily in viscosity and the corresponding application mechanism. Nitoprime 25 is the standard-viscosity epoxy primer — it is a thicker, more coat-like material that forms a primer film on the concrete surface by providing a uniform adhesive layer and sealing the surface pores. Nitoprime 25 is suitable for most standard concrete floor surfaces with normal porosity and provides a good adhesive interface for epoxy and PU coatings. Nitoprime 30 is the low-viscosity (thin) epoxy primer — it is significantly more fluid than Nitoprime 25 and penetrates into the concrete pores and micro-cracks by capillary action rather than forming primarily a surface film. The penetrating action of Nitoprime 30 provides deeper sealing of high-porosity concrete and more effectively eliminates outgassing (pinhole formation) in subsequent coatings than Nitoprime 25. Nitoprime 30 is the preferred choice for: very porous concrete (low grade concrete, concrete with high water-cement ratio, older concrete floors that have been surface-ground or shot-blasted exposing the aggregate and significantly opening the surface pores); aged concrete floors with dusty or weak surface that has not been fully removed by preparation; and floor coating systems (particularly thin-film coatings of 100 to 250 microns DFT) where any pinhole defect in the primer or coating film is visually unacceptable. In short: Nitoprime 25 is the standard choice for well-compacted, moderate-porosity, recently placed concrete; Nitoprime 30 is the preferred choice for highly porous, old, or dusty concrete where penetrating action and outgassing prevention are required.

How much Nitoprime 30 is needed per square metre of floor area and is the application rate the same as for standard Nitoprime 25?

The application rate of Nitoprime 30 differs from Nitoprime 25 because of the fundamental difference in how the two primers work. Nitoprime 25, as a surface-coating primer, is applied at a controlled coverage rate (typically 5 to 8 square metres per litre, or approximately 125 to 200 grams per square metre) in a relatively thin, controlled film. Nitoprime 30, as a penetrating primer, is applied by flooding the concrete surface and allowing the low-viscosity material to penetrate into the pores — the application method is to pour a generous amount of Nitoprime 30 onto the floor and spread it with a squeegee or roller, allowing it to flood into the surface; after the initial penetration and absorption (typically 5 to 10 minutes), any excess material remaining on the surface is squeegeed off and removed (not left as a standing pool). The coverage rate of Nitoprime 30 therefore depends strongly on the porosity of the concrete — a very porous concrete may absorb 0.25 to 0.40 litres per square metre (absorbing most of the applied material into the pores), while a denser, less porous concrete may absorb only 0.10 to 0.15 litres per square metre with more material remaining as surface excess. Failure to remove excess Nitoprime 30 that has not been absorbed by the concrete is a common application error — if allowed to cure as a thick surface pool, the excess Nitoprime 30 forms a smooth, glossy epoxy layer with much lower adhesion to the concrete than the penetrating primer film, and the subsequently applied floor coating may debond from this thick primer pool. For an accurate material estimate for a specific floor, a small field absorption test (measure the area covered by a known volume) on the specific concrete is the best approach.

Can Nitoprime 30 be used to strengthen a weak or dusting concrete floor surface and how does this work?

Yes — one of the important secondary benefits of Nitoprime 30 (beyond its primary function as a floor coating primer) is the ability to dust-proof and surface-harden weak or dusting concrete floor surfaces. When freshly placed concrete is inadequately cured in hot, dry conditions (very common in India where the combination of high ambient temperature, low humidity, and wind causes rapid surface drying before the concrete has hydrated sufficiently), the surface zone of the concrete slab forms a weak, soft, dusty layer — the cement at the surface did not have enough water to hydrate properly, so it remains as a weak, porous, easily abraded layer. This surface dusting is problematic for industrial floors (fine concrete dust contaminates products, machinery, and food) and also prevents floor coating systems from bonding adequately — a floor coating applied over a dusty, weak concrete surface bonds only to the weak surface layer, which peels away from the sound concrete beneath, causing the floor coating to fail. Applying Nitoprime 30 to a dusting concrete surface floods the low-viscosity epoxy resin into the porous, weak surface layer and throughout the void network in the weak surface zone — when the Nitoprime 30 cures, it creates an epoxy-impregnated surface zone that binds the loose cement particles together, seals the surface porosity, and provides a hardened, non-dusting surface. The resulting surface has significantly higher hardness, abrasion resistance, and bond strength than the original dusty concrete. In light-duty warehouses or storage areas where a full floor coating is not required, this Nitoprime 30 treatment can serve as the final floor treatment — a dust-proofed, sealed concrete floor without the additional cost of a full epoxy coating system.