About Fosroc Nitoprime 25(M)

Fosroc Nitoprime 25(M) is the dedicated concrete primer that sits beneath Fosroc’s epoxy flooring and repair systems. It is supplied as a two-pack epoxy resin: a base and a hardener that are combined on site immediately before use. The product is engineered to do one job extremely well, which is to penetrate the open pore structure of a concrete slab, lock down residual dust and laitance at a microscopic level, and present a tacky, chemically matched surface that the subsequent resin layer can grip. Without a correctly applied primer, even the best epoxy topping or mortar can blister, peel or debond, so on most industrial flooring contracts the primer is not optional but a specified line item. The “(M)” suffix denotes the formulation manufactured and marketed by Fosroc Chemicals (India) Pvt. Ltd., Bangalore, which is the variant Space Arc Engineering supplies to projects in Delhi NCR and across India. Nitoprime 25(M) is intended for use with the Nitoflor SL and TF resin floor toppings, the Nitocote range of protective coatings, and Nitomortar epoxy repair mortars, making it a true companion product rather than a standalone finish. Because it carries solvent to aid penetration, it is classified as flammable and must be handled with the usual ventilation, ignition-source and PPE controls. For Indian sites, where ambient temperatures swing widely between a Delhi winter morning and a peak summer afternoon, the data sheet helpfully tabulates pot life and cure at both 20 degrees C and 35 degrees C so applicators can plan batch sizes and overcoating windows around the day’s heat.

The technical insight

The performance of Nitoprime 25(M) is dominated by two variables: substrate moisture and temperature. Fosroc specifies that new concrete should be at least 28 days old or below 5 percent moisture content before priming, because epoxy chemistry is intolerant of free water and trapped vapour, which is the root cause of blistering and osmotic failure in epoxy floors. Mechanical preparation (scarifying, grit or sand blasting, scrabbling, grinding) is strongly preferred over acid etching alone, since it removes laitance and opens the pore structure for the primer to penetrate. Temperature then governs the working chemistry: pot life is roughly 4 hours at 20 degrees C but collapses to about 1.5 hours at 35 degrees C, so on a hot Indian afternoon batches must be mixed small and used fast. The same logic applies to overcoating, where the gap between coats shortens from 4-6 hours at 20 degrees C to 3-5 hours at 35 degrees C. A subtle but important detail is overcoating behaviour per system: for Nitoflor SL the primer is left to dry overnight, whereas for Nitoflor TF, Nitomortar and Nitocote the topping is applied once the solvent has flashed off and the film is tacky. The characteristic coloured dry patches that appear on porous slabs signal that the primer has been fully absorbed, and Fosroc explicitly calls for a second priming coat there, both to guarantee adhesion and to stop air escaping from the substrate and forming bubbles in the finished topping.

Where it is used

• Priming concrete before Fosroc Nitoflor SL self-levelling epoxy floor toppings
• Priming before Nitoflor TF trowel-applied epoxy floor finishes
• Sealing and keying substrates ahead of Nitomortar epoxy repair mortars
• Priming concrete prior to Nitocote protective and chemical-resistant coatings
• Sealing vacuum-dewatered, power-trowelled floors before resin systems
• Bonding-coat preparation for industrial and warehouse floor refurbishment

Key advantages

• Improves adhesion of epoxy floor toppings and epoxy mortars to the concrete substrate
• Good penetrating properties that seal and stabilise porous concrete
• Suppresses air release from the slab, reducing pinholes and bubbles in the finished topping
• Simple two-component on-site mixing with a slow-speed drill
• Generous coverage of 6-8 m2 per litre, keeping primer cost per square metre low
• India-specific data for both 20 degrees C and 35 degrees C, aiding hot-climate planning
• Chemically matched to the full Nitoflor, Nitomortar and Nitocote system for warranty-friendly build-ups
• 12-month shelf life in unopened containers under normal warehouse storage

Limitations & considerations

• Solvent-based and flammable (flash point 25 degrees C) – no naked flames, no smoking, ventilation and CO2 or foam extinguishers required
• Strict moisture limit: new concrete must be 28 days old or below 5 percent moisture, and rising damp must be eliminated first
• Short pot life in heat (about 1.5 hours at 35 degrees C) demands small batches and rapid application
• Application restricted to a 10 degrees C – 40 degrees C window; outside 5 degrees C to 40 degrees C consult Fosroc
• Demands thorough mechanical surface preparation – it cannot compensate for laitance, oil or weak concrete
• Porous slabs absorb the first coat and need a second priming coat on dry patches
• Is a primer only, not a wearing or protective finish – it must be overcoated with a Nitoflor/Nitomortar/Nitocote system
• Can sensitise skin; epoxy resins, hardeners and solvents require gloves, goggles and barrier creams

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Nitoprime 25(M)

Nitoprime 25(M) is purpose-built to work inside Fosroc’s own flooring and repair family, so the most natural pairings are Nitoflor SL and TF toppings, Nitomortar epoxy repair mortars and Nitocote coatings – specifying the matched primer keeps the whole build-up within one warranted system. Where a project instead calls for a solvent-free or water-based primer (for instance in occupied or poorly ventilated interiors), Fosroc’s broader Nitoprime range and competitor equivalents are worth comparing: Sika offers Sikafloor primers such as Sikafloor-156/161, MBS (MYK/BASF MasterTop and MasterEmaco lineage) supplies comparable epoxy floor primers, Dr. Fixit/Pidilite offers Roffe and Newcoat primers for flooring and repair, and STP (Shalimar) markets its own epoxy primer systems. Space Arc Engineering, as an authorised Fosroc distributor, recommends Nitoprime 25(M) when the topping or mortar is itself a Fosroc product for guaranteed compatibility, and will advise on a solvent-free or low-odour alternative when site ventilation, occupancy or VOC limits make the standard solvent-based primer unsuitable.

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