Sika FerroGard-901
Bipolar amino-alcohol corrosion-inhibiting admixture that shields embedded reinforcement from chloride attack, dosed straight into the concrete mix at batching.
What is it?
A liquid, bipolar corrosion-inhibiting admixture for reinforced concrete, built on Sika FerroGard Technology and based on a modified amino alcohol. It is added to the mix, not painted on the surface.
Where is it used?
New RCC where reinforcement is at risk of chloride-induced corrosion: coastal and marine works, bridges, flyovers, tunnels, retaining walls, multi-storey car parks and industrial structures.
Why use it?
It curbs both the anodic and cathodic halves of the corrosion cell, delaying the onset of rebar corrosion and slowing its rate, so the structure lasts materially longer in aggressive exposure.
How is it applied?
Batched into the gauging water or dosed into the mixer at typically 12 kg per m3 of concrete; there is no separate application step on site once the mix is placed.
About Sika FerroGard-901
Sika FerroGard-901 is Sika’s admixture-grade corrosion inhibitor for reinforced concrete, and it is important not to confuse it with the surface-applied FerroGard-903 range. This is a blueish liquid you add during batching, based on a modified amino-alcohol chemistry that Sika markets under its FerroGard Technology banner. Once in the mix, it becomes part of the concrete’s pore solution and travels with it to the steel, where it goes to work well before any chloride front reaches the reinforcement. For Indian projects sitting in coastal humidity, de-icing regimes or chloride-laden soils, that head start is exactly the point: you are building corrosion resistance into the concrete at the plant rather than trying to retrofit protection later.
What makes the product genuinely useful to a designer is that it is bipolar. Many inhibitors act on only one side of the electrochemical reaction; FerroGard-901 reduces both the anodic and the cathodic processes and forms a protective film across the steel surface. The result is a two-part benefit, a delayed initiation of corrosion and a reduced corrosion rate once it does begin, which together push out the maintenance clock. Just as valuable for a structural engineer, Sika confirms the admixture is neutral to hydrogen embrittlement, so it neither aggravates nor mitigates that risk in prestressing steel, and it has no adverse effect on the properties of either the fresh or the hardened concrete.
The technical insight
Chloride-induced corrosion is an electrochemical process with two coupled sites on the rebar: an anode, where iron dissolves and pits form, and a cathode, where oxygen is reduced. Single-action inhibitors slow one site and let the other keep driving the cell. FerroGard-901’s modified amino-alcohol molecules are bipolar, meaning they adsorb at and suppress activity at both the anodic and cathodic zones, and they build a thin protective film over the steel that raises the chloride threshold needed to trigger corrosion. Because the inhibitor is dispersed uniformly through the mix water rather than diffusing inward from a coated face, it is already present at the steel from day one and does not depend on penetrating a cover that may be dense or already carbonated. That distribution advantage is why an admixture inhibitor is specified for new construction, while penetrating grades are reserved for existing structures where in-situ dosing is no longer possible.
Where it is used
- New RCC in marine and coastal zones exposed to airborne or splash-zone chlorides
- Bridge decks, piers and flyover substructures subject to chloride and moisture cycling
- Tunnels and underground works in aggressive or chloride-bearing ground
- Retaining walls and basement rafts in saline or contaminated soils
- Multi-storey and basement car parks where de-icing salts or wash-down are a factor
- Industrial plants, effluent structures and process areas with a corrosive service environment
- Water-retaining and coastal infrastructure where a long maintenance-free life is specified
- Precast and site-batched concrete where corrosion protection is designed in at the plant
Key advantages
- Bipolar action reduces both the anodic and cathodic reactions of the corrosion cell, not just one
- Delays the onset of reinforcement corrosion and lowers the corrosion rate once initiated
- Specifically targets chloride-induced attack, the dominant threat in coastal and de-icing exposure
- Neutral to hydrogen embrittlement, so it is safe alongside prestressing steel
- No negative effect on the properties of the fresh or the hardened concrete
- Dosed into the mix water, so protection is built in with no extra site application step
- Compatible with all common cements and cementitious materials, and with the wider Sika range
- Reusable after slow thawing and thorough stirring if the drum has frozen in transit or store
Limitations & considerations
- An admixture only, it protects new concrete, it cannot be brushed onto an existing structure
- Corrosion protection depends on it being dosed at batching, it cannot be added after placing
- The manufacturer specifies a water-cement ratio below 0.4, which the mix design must accommodate
- It is not a water reducer or plasticiser and does not replace those workability admixtures
- Product volume must be counted in the water calculation for the target W/C ratio
- Trials are required before combining it with other admixtures in a specific mix
Selection & best practice
Treat FerroGard-901 as part of the concrete mix design, not a site consumable. It is added to the gauging water or dosed into the mixer at the recommended 12 kg per cubic metre; when added into a transit mixer at the point of discharge, run an extra mixing minute per cubic metre and check the load visually for uniform consistency before it is placed. Never introduce it onto dry cement. Because the liquid contributes to the batch water, subtract its quantity when working to a specified water-cement ratio, and hold that ratio below 0.4 as Sika directs. Store the drums dry between +10 and +40 degrees C, out of direct sun and frost; if a drum has frozen, thaw it slowly at room temperature and stir intensively before use rather than discarding it. As with any inhibitor, run a trial batch when it shares a mix with other admixtures, and remember that corrosion protection is a durability strategy that works best paired with good cover and low-permeability concrete, not a substitute for them.
Specifications
| Product type | Bipolar corrosion-inhibiting liquid concrete admixture (Sika FerroGard Technology) |
| Chemical base | Modified amino alcohol |
| Appearance / colour | Blueish liquid |
| Density | 1.04 kg/l at 25 degrees C |
| Recommended dosage | 12 kg per m3 of concrete (any concrete type); 1-3% by weight of cementitious per IIT Madras test report |
| Water-cement ratio | Keep below 0.4 |
| Packaging | 230 kg |
| Shelf life | 12 months from production in sealed, undamaged original containers |
| Storage | Dry, between +10 and +40 degrees C, protected from direct sunlight and frost |
Industry use cases
Marine & Coastal
Jetties, sea walls and coastal RCC in Mumbai, Chennai and Gujarat face constant airborne and splash-zone chloride; dosing the mix at 12 kg/m3 builds rebar protection in from the first pour.
Transport Infrastructure
Bridge substructures, flyover piers and metro tunnels exposed to chloride and moisture cycling gain a longer maintenance-free window when the inhibitor is batched into structural concrete.
Basements & Car Parks
Multi-storey and basement parking decks that see de-icing salt carry-in or frequent wash-down benefit from bipolar protection designed into the slab and column concrete.
Industrial & Effluent
Plants, tank farms and effluent structures in corrosive process environments use the admixture to extend the service life of reinforced elements without an added site coating step.
Retaining & Below-Grade
Retaining walls and rafts cast against saline or contaminated soils get corrosion resistance embedded in the concrete, where a surface treatment would be impractical to maintain.
Frequently asked questions
Is Sika FerroGard-901 a surface coating or an admixture?
What is the recommended dosage?
Does it affect the workability or strength of the concrete?
Can it be used with prestressed or post-tensioned concrete?
How does it protect the reinforcement?
How is it supplied and stored?
How we position Sika FerroGard-901
FerroGard-901 sits at the design-in end of Sika’s corrosion range; if your job is an existing structure that must be treated after the fact, the surface-applied FerroGard-903 line is the correct sibling product, since 901 can only be dosed into fresh concrete. Pair 901 with Sika’s water-reducing and superplasticising admixtures such as the Sika ViscoCrete range to hit the required workability at the low water-cement ratio it calls for, and with a low-permeability mix and adequate cover for a complete durability strategy. From our other brand lines, the closest equivalents worth quoting are Fosroc’s admixture inhibitors, the nitrite-free organic bipolar Auramix BCI and the calcium-nitrite Conplast CN, both of which serve the same design intent and often come up in Fosroc-specified tenders.
Fosroc Auramix BCI — A specifier standardising on Fosroc, or one who wants a nitrite-free and chloride-free organic bipolar inhibitor with a lower dose rate, may prefer Auramix BCI as the direct admixture counterpart to FerroGard-901.
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