STP ShaliKote AC
Water-based, non-yellowing acrylate coating that seals reinforced concrete against carbonation, chloride ingress and UV while keeping the surface breathable.
What is it?
A single-component, water-based acrylate anti-carbonation coating (formerly Architectural Seal) that protects and decorates concrete and masonry.
Where is it used?
Building facades, bridges and flyovers, precast panels, parking structures and other atmospherically exposed RCC surfaces.
Why use it?
It forms a CO2-resistant film equivalent to a thick air layer, slowing carbonation and chloride attack that corrode reinforcement, while staying vapour-permeable and colour-stable.
How is it applied?
Prime and repair the substrate, then apply two coats by brush, roller or airless spray between 3 C and 30 C at roughly 6-7 m2/L per coat.
About STP ShaliKote AC
STP ShaliKote AC is a high-performance anti-carbonation coating built on a pure acrylate binder and carried in water rather than solvent. Marketed earlier as Architectural Seal, it is one of the more established acrylic protective coatings in the Indian market and is specified where concrete needs a durable barrier that also looks good on the finished facade. Because it is water-thinned, non-toxic and low-odour, it suits occupied buildings, hospitals and enclosed structures where solvent coatings are hard to justify. The film is micro-porous and slightly elastomeric, so it clings to the concrete profile and bridges hairline surface imperfections without trapping moisture inside the slab.
The reason engineers reach for a coating like this is corrosion. Atmospheric CO2 slowly neutralises the alkalinity that protects embedded steel, and once the carbonation front reaches the rebar, rusting and spalling follow. ShaliKote AC sits on the surface as a breathable membrane that dramatically increases the diffusion path CO2 must travel, effectively adding decades to the time before carbonation reaches the steel. At the same time it blocks air-borne and water-borne chlorides and resists UV so the colour holds. For Space Arc, it is a practical, cost-sensible choice on projects that need genuine EN 1504-2-style protection without the price and handling constraints of solvent or elastomeric systems.
The technical insight
Protection here is governed by CO2 diffusion resistance, usually expressed as the equivalent air-layer thickness (SD value). ShaliKote AC gives an SD well above 50 m, meaning the applied film behaves like more than 50 metres of still air standing between the atmosphere and the concrete. That is what stalls the carbonation front. Crucially, the same film stays open to water vapour, with vapour permeability around 0.02 mg over 24 hours, so moisture already in the slab can escape and the coating does not blister or trap a wet layer against the concrete, the failure mode that plagues impermeable paints. Water absorption stays under 0.2 kg/m2 per hour, keeping liquid water and dissolved chlorides out. This combination, high resistance to gaseous CO2 but low resistance to water vapour, is precisely the balance EN 1504-2 asks of a surface protection product, and it is why an acrylate coating outperforms ordinary exterior emulsion paint on structural concrete.
Where it is used
- Anti-carbonation protection of RCC building facades and elevations
- External concrete on bridges, flyovers and elevated corridors
- Precast concrete panels and architectural elements
- Multi-level car parks and parking structure soffits and walls
- Industrial and commercial building exteriors in polluted urban air
- Coastal and near-marine concrete exposed to chloride-laden air
- Repaired and patched concrete surfaces needing a uniform protective finish
- Decorative recoating of ageing concrete where appearance and durability both matter
Key advantages
- Water-based, low-odour and non-toxic, so it can be used on occupied and enclosed sites
- High CO2 diffusion resistance (SD greater than 50 m) that slows carbonation of the concrete cover
- Breathable, micro-porous film that lets trapped vapour escape and resists blistering
- Blocks air-borne and water-borne chlorides that drive reinforcement corrosion
- Non-yellowing acrylate base with good UV and weather resistance for lasting colour
- Slightly elastomeric film that follows the concrete profile and hides minor surface defects
- Combined protective and decorative function in one product, reducing coats and cost
- Simple application by brush, roller or airless spray with water clean-up
Limitations & considerations
- Not crack-bridging in the structural sense; active or moving cracks need an elastomeric coat such as Dekguard Elastic over a repair
- Water-based chemistry needs surface and ambient temperatures within roughly 3 C to 30 C and dry conditions to cure
- Full carbonation protection depends on achieving the specified two-coat build; thin single coats under-perform
- A decorative surface coating, not a deep impregnant, so heavily cracked or contaminated concrete must be repaired first
- Colour and gloss retention, while good, are still exposure-dependent on very harsh south and west elevations
- Not intended for permanently immersed, buried or negative-side waterproofing duties
Selection & best practice
Success is mostly about the substrate. Clean the concrete back to a sound, dust-free surface, remove laitance, oil and old flaking paint, and make good all spalls, blowholes and cracks with a suitable repair mortar before coating. Damp-cure fresh repairs and let them dry. Prime absorbent, dark or heavily textured surfaces so the topcoat builds evenly. Apply ShaliKote AC in two coats, allowing the first to dry before the second, and always specify the two-coat system where full carbonation protection is required. Keep application within the 3-30 C window, avoid rain and dew for the drying period, and maintain a wet film thick enough to reach the theoretical 6-7 m2/L per coat rather than over-spreading. On large facades, work to natural breaks to avoid visible lap marks and keep a consistent applicator technique across the elevation.
Specifications
| Type | Water-based acrylate anti-carbonation protective / decorative coating |
| Binder | Pure acrylate; water as thinner |
| pH | 9 to 11 |
| Density | Approx. 1.35 g/cm3 |
| CO2 resistance (SD value) | Greater than 50 m equivalent air layer |
| Water vapour permeability | Approx. 0.02 mg over 24 hours |
| Water absorption (DIN 52617) | Less than 0.2 kg/m2 per hour |
| Theoretical coverage | 6 to 7 m2 per litre per coat |
| Application temperature | 3 C to 30 C |
Industry use cases
Commercial & High-Rise Facades
Protects exposed RCC elevations and fins in polluted city air, keeping carbonation away from the reinforcement while holding a clean decorative finish.
Bridges & Infrastructure
Coats piers, girders and deck edges on flyovers and bridges where CO2 and traffic-borne pollutants accelerate carbonation of the cover concrete.
Precast & Prefab
Gives factory-cast panels and architectural elements a uniform, non-yellowing protective coat before or after erection.
Car Parks & Podiums
Shields parking structure walls and soffits from carbonation and chloride splash while brightening dim internal spaces.
Coastal Buildings
Provides a breathable barrier against air-borne chlorides on near-marine structures where reinforcement corrosion is the primary durability risk.
Frequently asked questions
What exactly does anti-carbonation mean for my structure?
Is it waterproofing?
How many coats do I need and what coverage should I plan?
Can it bridge cracks in the concrete?
Will the colour fade or yellow over time?
Can it be used inside occupied buildings?
How we position STP ShaliKote AC
STP ShaliKote AC is the value-engineered, water-based choice within our anti-carbonation range. Where a project has active or moving cracks, step up to STP’s own elastomeric options, or on Fosroc jobs specify Fosroc Dekguard Elastic for genuine crack-bridging. If the requirement is a penetrating, invisible hydrophobic treatment rather than a film coat, Fosroc Dekguard S (silane-siloxane impregnation) is the better fit. On specifications that call the coating out against BS EN 1504-2, the closest like-for-like upgrade is Fosroc Dekguard A Plus. Pair any of these with an STP or Fosroc repair mortar for spall reinstatement and a suitable primer for absorbent substrates, and talk to Space Arc for the right combination on your structure.
Fosroc Dekguard A Plus — Choose Dekguard A Plus when the specification explicitly calls for a water-based acrylic anti-carbonation coating certified to BS EN 1504-2 with documented CO2 and chloride barrier data.
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