About MC-Bauchemie Nafufill KMH

MC-Bauchemie Nafufill KMH is the corrosion-protection and bonding-coat component of the Nafufill concrete repair system — the step that most patch-repair jobs on Indian sites either skip or rush, and the one that decides whether a repair lasts five years or fifty. It’s a grey, mineral-based powder (formerly sold as Zentrifix KMH before the MC-Bauchemie rebrand) that you mix with water on site into a brushable slurry. There’s no resin, no hardener ratio, no solvent smell — just cement chemistry doing two jobs at once: re-passivating cleaned reinforcement steel so it stops corroding, and giving the coarse repair mortar that follows a rough, chemically compatible surface to key into.

On a typical spalled-column or beam-soffit repair, the contractor chips out delaminated concrete, exposes rusted rebar, and now has a small window before that bare steel starts rusting again from ambient moisture and oxygen. Nafufill KMH is brushed onto the cleaned steel in two coats to rebuild an alkaline protective layer, and then a second coat goes onto the surrounding concrete as the bond coat before the Nafufill repair mortar is trowelled on fresh-into-fresh. It’s a workmanlike, unglamorous product — no flashy claims, just a mineral bridge between old corroded steel and new repair mortar — which is exactly the role it’s meant to play in RCC rehabilitation across Indian coastal, industrial and infrastructure projects where reinforcement corrosion is the single biggest reason repairs fail early.

The technical insight

What makes Nafufill KMH different from the epoxy or zinc-rich primers often used for rebar protection is that it stays inside the same chemical family as the concrete around it. Epoxy coatings protect steel by forming an impermeable barrier, which works well on paper but creates a rigid, low-permeability film sandwiched between corroded steel and a cementitious repair mortar that wants to move and breathe differently — a classic delamination trap if the interface isn’t handled carefully. Nafufill KMH instead relies on mineral/cementitious chemistry: brushed on as a lump-free slurry (density 2.1 g/cm³, mixed 100:20-25 with water), it forms an alkaline layer around the reinforcement that helps re-establish the passive oxide film steel relies on for corrosion resistance in sound concrete — the same mechanism that protects rebar in un-corroded concrete in the first place, just reapplied locally at the repair zone. Because it’s cementitious, its stiffness and thermal movement track the coarse repair mortar applied over it far more closely than a plastic or resin coating would, which is also why it doubles so naturally as a bonding coat — the same slurry that protects the steel also gives the mortar a compatible, textured surface to key into. The tight 20-minute pot life and the two-coat requirement for the anti-corrosion application aren’t arbitrary: they reflect how thin, controlled mineral coatings need fresh material and adequate build to actually achieve full coverage over an irregular rebar surface, including the fiddly bits like binding wire and the steel-to-concrete interface that a single careless coat tends to miss.

Where it is used

• Active corrosion protection coat brushed onto cleaned, exposed reinforcement steel before patch repair
• Bonding coat under hand-applied coarse repair mortars in the Nafufill concrete repair system
• Spalling and delamination repair on RCC columns, beams and slab soffits in residential and commercial buildings
• Bridge pier, pier cap, parapet and soffit repair on flyovers and highway structures
• Rehabilitation of water-retaining structures — overhead tanks, STP/ETP tanks, sumps — where rebar corrosion is common
• Basement and podium parking structure rebar repair, especially where seepage has accelerated corrosion
• Industrial shed and factory column repair where carbonation or chemical exposure has corroded the cover concrete
• Balcony, chajja and slab-edge repairs where reinforcement is close to the surface and prone to rusting

Key advantages

• Mineral/cementitious chemistry bonds to concrete and steel without a separate primer step — no epoxy-to-cementitious interface mismatch to worry about later
• One-component: mix with water on site, no two-pack epoxy hardener ratio for site labour to get wrong
• Solvent-free formulation, safe to brush on in enclosed basements and confined RCC sections without ventilation concerns
• Does double duty as corrosion inhibitor and bonding coat, cutting the number of separate materials a repair crew has to stock and sequence
• Thermal expansion and stiffness stay close to the cementitious repair mortars applied over it, avoiding the delamination risk you get with rigid coatings under flexible mortars
• Simple brush application — no plural-component pumps, spray rigs or specialist tools needed on site
• Sits inside MC-Bauchemie’s established Nafufill repair system, so specifiers get a documented, system-compatible build-up rather than mixing unrelated brands
• Practical 20-minute pot life keeps batches fresh and forces good site discipline instead of large stagnant mixes

Limitations & considerations

• Only a 20-minute pot life at 20°C — crews used to slower-setting products will waste material if they mix large batches
• Not a standalone long-term corrosion barrier for severe chloride/marine splash-zone exposure; it needs the full Nafufill system (adequate cover, repair mortar, sometimes additional protective coatings) around it to deliver durability
• Minimum application temperature of +8°C, which matters on winter mornings in northern hill stations even if it’s a non-issue across most of the Indian plains
• Performance depends entirely on substrate prep — the spec calls for ≥1.5 N/mm² pull-off strength and SA 2½ blast-cleaned steel, and shortcuts here undermine the whole repair regardless of how well the coat itself is applied
• Two coats are specified for the anti-corrosion application; a single thin coat to save material will under-deliver on protection
• Sold only in 30 kg sacks — there’s no small touch-up pack, so very minor repairs still need a full bag

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie Nafufill KMH

Within MC-Bauchemie’s own range, Nafufill KMH is the prep step, not the finish — it always sits upstream of the Nafufill KM series of hand-applied coarse repair mortars, and on larger jobs alongside other Nafufill system components like fine-finish and structural repair mortars; Space Arc typically quotes it as part of a complete Nafufill repair build-up rather than as a standalone line item. For specifiers already committed to a Fosroc-based repair spec, or preferring a liquid SBR bonding agent over a mineral powder coat, Fosroc’s Nitobond SBR covers similar dual bonding-and-anti-corrosion ground, though the two aren’t a drop-in swap chemically — the choice usually comes down to which brand’s repair mortar system the rest of the job is built around. As an authorised MC-Bauchemie distributor and applicator, Space Arc supplies Nafufill KMH pre-matched to the correct Nafufill mortar grade for the job rather than leaving that pairing to guesswork on site.

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