About Sika FerroGard-901 (IN)

Sika FerroGard-901 (IN) is a corrosion-inhibiting admixture engineered for reinforced concrete that will spend its life fighting chlorides. Unlike a surface treatment brushed onto hardened concrete, this is a liquid that goes into the mix at the batching plant, so the inhibitor is distributed evenly through the matrix and is in contact with the reinforcement from day one. The chemistry is built on Sika’s amino-alcohol FerroGard platform and is chloride-free, so it adds protection without introducing the very ions it is meant to defend against. For engineers specifying new construction in aggressive coastal, marine or de-icing-salt environments, it is a durability decision made at design stage rather than a repair made after damage appears.

What makes the product a “bipolar” inhibitor is that it acts on both halves of the electrochemical corrosion cell. It forms a protective molecular film on the steel surface that interferes with the anodic (metal-dissolution) reaction while also moderating the cathodic reaction, so the whole corrosion process is slowed rather than just one side of it. Crucially, it does this without harming the fresh or hardened concrete and is considered neutral with respect to hydrogen embrittlement, which matters for prestressed and post-tensioned work. For a specifier, that combination means longer time-to-corrosion-initiation and a lower corrosion rate once initiation does begin, both of which translate directly into extended maintenance-free service life.

The technical insight

Chloride-induced corrosion of rebar is an electrochemical process: an anode forms where steel dissolves into ions, a cathode consumes oxygen and moisture, and the concrete pore solution completes the circuit. FerroGard-901 attacks this on two fronts. Its amino-alcohol actives adsorb onto the steel to build a thin passivating film that raises the effective chloride threshold the reinforcement can tolerate before it starts to corrode, while simultaneously damping the cathodic reaction that would otherwise sustain the cell. Because the admixture is homogeneously mixed through the concrete rather than relying on slow inward migration from the surface, protection is in place before chlorides arrive, which is why it is best deployed as a preventive measure in new pours rather than a rescue for already-corroding structures. The result is not that corrosion becomes impossible, but that both its onset and its rate are pushed out in time, buying the asset years of additional low-maintenance life.

Where it is used

• New reinforced concrete in marine and coastal splash or tidal zones
• Bridge decks, piers and substructures exposed to de-icing salts
• Road and highway concrete subject to chloride run-off
• Tunnels, box culverts and underground structures in saline ground
• Retaining walls and foundations in chloride-bearing soils and groundwater
• Multi-storey and basement car parks exposed to carried-in salts
• Industrial and chemical plant concrete in aggressive service
• Water-retaining and effluent structures where long design life is specified

Key advantages

• Dual-action (bipolar) inhibition addresses both anodic and cathodic corrosion reactions
• Chloride-free formulation adds protection without introducing aggressive ions
• Homogeneously distributed through the mix, so protection is present from casting
• Raises the chloride threshold and delays the onset of reinforcement corrosion
• Reduces the corrosion rate once initiation begins, extending service life
• Does not adversely affect the fresh or hardened properties of the concrete
• Considered neutral toward hydrogen embrittlement, suiting prestressed work
• Simple to incorporate at the batching plant with no special site equipment

Limitations & considerations

• It is a preventive, mix-added admixture, not a cure for concrete where corrosion is already advanced
• Best value comes from designing it in at the new-construction stage rather than retrofitting
• As an admixture it cannot be applied to existing hardened concrete; a surface-applied migrating inhibitor is required there
• Dosage must be adjusted to cement type and water-cement ratio, so trial mixes and batching control are essential
• It complements, but does not replace, sound cover depth, low permeability and good crack control
• Performance is a durability enhancement over time, not an instantly measurable strength property

Selection & best practice

Specifications

Industry use cases

How we position Sika FerroGard-901 (IN)

FerroGard-901 (IN) is the preventive, mix-added anchor of Sika’s corrosion-protection line. Where the structure already exists and cannot be re-cast, pair or substitute with a surface-applied migrating inhibitor from the same FerroGard family that is brushed or sprayed onto hardened concrete. It also sits naturally alongside Sika’s repair and protection system, notably the SikaTop and Sika MonoTop repair mortars and Sikagard protective coatings, so an engineer can specify a complete cast-in plus surface-protection package. Among our other brands, the closest genuine equivalent is Fosroc Conplast CN, a calcium-nitrite corrosion-inhibiting admixture; a specifier who prefers nitrite chemistry, or who is matching an existing Fosroc-based specification, may choose that route instead.

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