Sika Rustop
Two-component, cement-bound anti-corrosive coating that shields exposed reinforcement from water, chlorides and CO2 before patch repair or recasting.
What is it?
A two-component coating (white acrylic-copolymer liquid plus green cementitious powder) brushed onto cleaned steel to stop rebar corrosion during concrete repair.
Where is it used?
On exposed or de-rusted reinforcement in repair patches, low-cover sections, and structures exposed to chlorides or de-icing salts.
Why use it?
It forms an impervious film that blocks water, chloride and carbon-dioxide ingress and carries corrosion inhibitors, so freshly exposed steel does not re-rust before it is re-covered.
How is it applied?
Stir Part B into Part A to a brushable paste, apply the first coat within 20-30 minutes, follow with a second coat after 2-3 hours, then re-concrete after 24 hours.
About Sika Rustop
Sika Rustop is the coat of protection that goes on reinforcement the moment it is exposed and cleaned during a repair. It is a two-component product: Part A is a white acrylic-copolymer liquid and Part B is a green cement-based powder. Mixed at a fixed 1:4 ratio by weight, they combine into a brushable slurry that bonds tightly to steel, concrete and mortar. Because it is cement-bound rather than a pure resin, it stays compatible with the alkaline repair mortar or concrete that follows, which is exactly what you want at the steel-to-patch interface in a rehabilitation job.
For engineers and applicators working on chloride-affected slabs, corroded beams, spalled columns or low-cover elements, the value is straightforward. Once you chip out distressed concrete and wire-brush the rebar back to a sound surface, that steel is bare and vulnerable. Left uncoated for even a day, it starts to flash-rust and the repair is compromised before it begins. Rustop seals the bar with an impervious, inhibitor-loaded film so moisture, chlorides and CO2 cannot reach it, buying the crew a controlled window to complete the repair. Space Arc Engineering supplies it as an authorised Sika distributor across Delhi NCR and Pan-India, typically alongside the repair mortars and bonding aids that make up a complete rehabilitation system.
The technical insight
Corrosion of embedded steel is an electrochemical process: it needs moisture, oxygen and an aggressive agent such as chloride or carbonation to depassivate the bar. Rustop attacks that on two fronts. First, the cured cement-bound film is physically impervious, so it starves the reaction by blocking the ingress of water, chloride ions and carbon dioxide at the steel surface. Second, the formulation carries corrosion inhibitors that keep the immediate environment around the bar passivating rather than aggressive. Because the binder is cement modified with acrylic copolymer, the coating develops a genuine chemical and mechanical grip on steel while remaining alkaline-compatible with the overlying repair mortar, so you do not create a weak, resin-only debond plane at the very interface a repair depends on. The two-coat build ensures full, pinhole-free coverage of the ribbed bar profile, which is where thin single passes usually miss.
Where it is used
- Priming freshly exposed reinforcement in concrete patch repairs before mortar is applied
- Protecting de-rusted steel in structural rehabilitation of beams, columns and slabs
- Coating bars in low-cover sections where the concrete offers limited natural protection
- Shielding reinforcement in structures exposed to chlorides or de-icing salts
- Corrosion protection of embedded steel during refurbishment of ageing RCC
- Priming reinforcement ahead of recasting or micro-concrete jacketing
- Interface protection between old cleaned steel and new repair mortar
- Anti-corrosive treatment of exposed rebar in marine and coastal-influenced structures
Key advantages
- Two-in-one action: impervious barrier film plus built-in corrosion inhibitors
- Cement-bound, so it stays alkaline-compatible with the repair mortar or concrete that follows
- Excellent adhesion to steel, concrete and mortar
- Blocks the ingress of water, chlorides and carbon dioxide at the bar surface
- Simple pre-batched 1:4 sets remove site guesswork on mixing ratio
- Brush-applied by hand, no specialist spray equipment needed
- Fast two-coat cycle lets a repair proceed within the same working day
- Colour-tinted powder makes missed spots on the bar easy to see
Limitations & considerations
- Working life is short once mixed; the paste must be used within 20-30 minutes
- Effectiveness depends on proper surface prep, the steel must be cleaned back to a sound, rust-free surface
- Not a structural mortar or a substitute for adequate concrete cover, it protects, it does not rebuild section
- Both coats must be complete before re-concreting, and concreting waits until 24 hours after application
- Two-component mixing and coat timing demand a trained applicator for consistent film build
- Requires controlled storage between +5 C and +35 C to protect the liquid component
Selection & best practice
Start with the steel, not the coating. Wire-brush or grit-blast the exposed reinforcement back to a bright, sound surface and remove all loose rust, scale, oil and laitance, because the film only performs on clean metal. Mix the whole pre-batched set at once, adding Part B powder gradually into Part A liquid while stirring for about three minutes to a lump-free, brushable consistency, then apply the first coat within 20-30 minutes while the mix is still live. Work it fully into the ribbed bar profile and around the back of the bar so there are no shadowed, uncoated zones. Allow 2-3 hours, then apply the second coat to build a continuous, pinhole-free film. Let it cure and re-concrete after 24 hours, ideally with a compatible Sika repair mortar. Keep unused material stored at +5 C to +35 C, and plan batch sizes to what the crew can lay down inside the pot life rather than mixing more than can be used.
Specifications
| Product type | Two-component, cement-bound anti-corrosive coating for reinforcement |
| Composition | Part A acrylic-copolymer liquid; Part B cement-based powder |
| Component appearance | Part A white liquid; Part B green powder |
| Mixing ratio | Part A : Part B = 1:4 by weight |
| Coverage | Approx. 3.6-4 kg/sqm for two coats, depending on application |
| Recoat interval | Second coat 2-3 hours after the first |
| Overcoating / concreting | Re-concrete after 24 hours |
| Pot life | Apply within 20-30 minutes of mixing |
| Storage | +5 C to +35 C |
Industry use cases
Building repair & rehabilitation
Protects de-rusted rebar in spalled slabs, beams and columns during patch repairs so the steel does not re-corrode before recasting.
Infrastructure & bridges
Shields reinforcement in decks and substructures against chloride and de-icing-salt attack during structural rehabilitation.
Marine & coastal RCC
Barrier-plus-inhibitor film guards exposed steel in chloride-laden coastal structures where corrosion risk is high.
Industrial & water-retaining structures
Primes cleaned reinforcement in ageing tanks, treatment plants and process structures ahead of micro-concrete or mortar repair.
Frequently asked questions
What exactly is Sika Rustop used for?
How much Rustop do I need per square metre?
How is it mixed and how long do I have to use it?
When can I apply the second coat and start concreting?
Does Rustop replace proper concrete cover or a repair mortar?
How should it be stored and what pack does it come in?
How we position Sika Rustop
Sika Rustop sits at the start of a concrete-repair sequence, so it pairs naturally with the rest of the Sika repair family: use it to prime the steel, then rebuild the section with a Sika MonoTop or SikaRep repair mortar and finish with a Sika protective or anti-carbonation coating for durable, system-warranted results. For teams already standardised on Fosroc, the equivalent step is Fosroc Nitozinc Primer, followed by a Renderoc repair mortar. Space Arc supplies all of these as an authorised distributor, so we can match Rustop into whichever repair system your specification is built around.
Fosroc Nitozinc Primer — Specify the Fosroc option when the repair system is built on Renderoc mortars or the client wants an active zinc-rich galvanic primer rather than a cement-bound barrier coating.
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Source Sika Rustop for your project
Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.