What is anti-carbonation paint?
Anti carbonation paint is formulated to reduce the passage of carbon dioxide into concrete. A suitable anti carbonation coating creates a carbon dioxide barrier while still allowing an appropriate level of water vapour movement. Carbonation paint matters on reinforced concrete because embedded steel reinforcement relies on the alkalinity of the surrounding concrete. Once carbonation reaches the reinforcement, reinforcement corrosion becomes more likely.
What is the carbonation process in concrete?
The carbonation process begins when carbon dioxide in the atmosphere reacts with moisture in the pore structure of concrete. Carbon dioxide penetrates porous concrete and reacts with calcium hydroxide, forming calcium carbonate. As the process progresses, the concrete can fall below pH 9, removing alkaline protection.
When the pH drops far enough, the protective condition around reinforcing steel is reduced. The steel reinforcement can then corrode when sufficient moisture and oxygen are present. Expansion of corrosion products can create cracks, delamination and spalling, subsequently damaging the surrounding concrete and reducing structural integrity. If corrosion continues unchecked, structural integrity can be affected further.
Anti carbonation paint does not reverse existing carbonation damage. It is a surface treatment intended to slow further carbon dioxide ingress after the concrete has been assessed and any necessary repair treatment has been completed.
Why does reinforced concrete need anti carbonation protection?
Reinforced concrete combines concrete in compression with steel reinforcement for tensile strength. The alkaline concrete normally protects the reinforcing steel, but carbonation gradually lowers that alkalinity. In weather-facing reinforced concrete structures, pollution, rain, high humidity, salt and repeated wetting can increase the need for planned concrete protection.
Anti carbonation paint can protect concrete by adding a protective coating over prepared concrete surfaces. The aim is to slow carbonation, limit moisture ingress and support service life.
How does an anti carbonation coating protect concrete?
A correctly specified anti carbonation coating has high resistance to carbon dioxide. Under EN 1504-2 type performance criteria, a resistance to carbon dioxide expressed as an equivalent air layer thickness of more than 50 m is a well accepted method of demonstrating carbonation resistance for protective surface coatings.
Many anti carbonation systems are designed to remain water vapour permeable while resisting liquid water. This balance protects concrete surfaces while reducing the risk of moisture becoming trapped behind the coating.
Where is anti carbonation paint used?
Anti carbonation paint is used on concrete assets subject to traffic pollution, weather and an aggressive atmosphere. Typical projects include car parks, bridges, retaining walls, parapets, balconies, precast concrete elements, facades, industrial structures and RC structures.
Coastal environments introduce additional exposure to salt and chloride ions. In coastal locations, an anti carbonation coating may be selected as part of a broader concrete protection specification where resistance to carbonation, water and chlorides is required.
Buildings beside busy roads can benefit from carbonation paint. Commercial buildings and public buildings with external walls or fair-faced concrete close to vehicle emissions may receive more carbon dioxide and other deleterious substances than concrete in a sheltered environment.
Anti carbonation paint is not a general-purpose coating for wood, metal or plastic surfaces. Use products approved for the substrate.
Can anti carbonation paint be used on cracked concrete?
Cracks must be assessed before painting. Fine non-structural cracks may suit a crack-bridging anti carbonation coating, but moving or structural cracks need diagnosis and repair first.
Sika Sikagard 550W Elastic is designed for outdoor concrete surfaces with a risk of cracking and offers crack-bridging performance, including at low temperatures. Fosroc Dekguard E2000 is another crack-accommodating anti carbonation paint for reinforced concrete and masonry structures, including coastal environments.
A failure pattern following existing cracks can indicate unresolved movement or insufficient crack-bridging capability. Product data should guide the choice.
Preparing concrete before applying carbonation paint
Surface preparation is critical. Anti carbonation paint should be applied to sound, clean and suitably cured concrete. Remove loose particles, dust, dirt, laitance, weak material and contamination that could reduce adhesion. Oil, grease, biological growth and unsound existing coatings also need suitable treatment.
Repair damaged concrete, visible reinforcement and defective areas before coating. Where reinforcement corrosion is present, the repair process may include removing unsound concrete, cleaning or treating the reinforcing steel, selecting compatible repair materials, reinstating the concrete cover and allowing repairs to cure before the anti carbonation coating is applied.
The substrate moisture condition matters. Do not assume every anti carbonation paint can go onto damp concrete. Check the technical data sheet for the selected coating, primer, curing requirements and permitted humidity or temperature range.
Do anti carbonation systems need a primer?
Primer requirements vary. Some systems need a dedicated primer to stabilise the substrate, control absorbency or support adhesion. Other products may use a diluted first coat as part of the specified system. The correct primer and total dry film thickness should come from the manufacturer’s data.
For a porous or repaired substrate, a primer can help create a consistent surface. On existing coatings, adhesion testing and compatibility checks may be required before a new carbonation paint system is applied.
How many coats of anti carbonation paint are needed?
Two coats are common for anti carbonation paint, but the number of coats is only part of the specification. The requirement is achieving the recommended film thickness and continuous coverage.
Apply the initial coat evenly by the approved method and allow it to dry for the stated period. Apply the second coat only when the first coat is ready to overcoat. Some products require two coats while others may require two or three depending on the system and substrate.
Brush, roller or airless spray may be permitted. A brush can help work coating into textured masonry and detailed areas, while roller or spray can improve productivity on broad concrete surfaces. Follow the manufacturer’s application guidance rather than assuming one method provides ultimate protection in every situation.
Film thickness and anti carbonation performance
Anti carbonation performance depends on the complete dry film rather than colour alone. If a coating is applied too thinly, the carbon dioxide barrier may not achieve the tested resistance. Excessive thickness can also cause curing problems with some products.
Check the recommended film thickness, spreading rate and total dry film thickness for the selected anti carbonation coating. This matters on rough concrete, textured masonry and repaired surfaces where consumption varies.
Anti carbonation paint for bridges and car parks
Bridges and parking garages are common anti carbonation applications because concrete structures can face carbon dioxide, road spray, moisture, chloride ions and temperature cycling. The protection strategy may need to address several mechanisms at once.
For bridges, inspect cracks, joints, drainage and visible reinforcement before coating. For parking garages, columns, walls, ramps and soffits may need different surface treatments depending on exposure and whether abrasion, impact or vehicle contact is expected.
In such an extreme environment, the coating should be selected from tested systems with suitable resistance, adhesion and durability rather than from general masonry paint alone.
Anti carbonation paint for coastal structures
Coastal structures and coastal environments expose concrete to wind-driven rain and airborne salts. Fosroc Dekguard E2000 is formulated for weather-facing reinforced concrete structures and is suitable for use in coastal environments where acid gases, chloride ions, oxygen and water may all be relevant.
Glixtone AC1 is a water-borne high-performance masonry and anti carbonation paint promoted for coastal properties and other severe locations. Promain’s supporting technical literature states long-term protection and strong weathering and UV resistance for this system.
What are the main types of anti carbonation coating?
Common systems include rigid acrylic coatings, elastomeric acrylic coatings, polyurethane coatings and mineral or silicate systems. The best type depends on tested carbonation resistance, movement, moisture behaviour and substrate compatibility.
Choosing between rigid and elastomeric anti carbonation coatings
Not every structure needs the same anti carbonation coating. Rigid protective paint can suit stable concrete surfaces where crack movement is limited. Elastomeric carbonation paint is more suitable where fine cracks or movement need accommodation within the tested capability of the system.
Mapei Elastocolor Pittura Zero is a crack-bridging anti carbonation paint for concrete structures and rendered facades with micro-cracks. It is intended for internal and external use within its stated application conditions and requires prepared, cured surfaces rather than damp or contaminated substrates.
Fosroc Dekguard S is a solvent-based acrylic protective and decorative coating for concrete and masonry. It is formulated for weather-facing reinforced concrete structures and can be applied at lower temperatures than many water-based coatings, subject to its own data sheet.
Breathability, moisture and water resistance
A good anti carbonation paint is not simply a waterproof layer. Many concrete assets need resistance to rain while still allowing water vapour to escape. This helps reduce moisture pressure behind the coating and supports longer-term adhesion.
Sika Sikagard 550W Elastic combines high CO2 diffusion resistance with water vapour permeability. Tikkurila Finngard Opaque is listed by Promain as a breathable anti carbonation coating for internal and external use.
UV resistance, weathering and service life
Exterior anti carbonation paint is subject to sunlight, rain, freeze-thaw cycles, pollution and temperature change. UV resistance and weathering performance therefore matter alongside carbonation resistance.
Service life depends on the product, film thickness, preparation, exposure and maintenance work. Some anti carbonation systems are promoted for 7–10 years, while specific products such as Glixtone AC1 carry substantially longer stated protection periods. Do not apply a generic life expectancy to every coating.
Local damage, cracks, impact or failed joints can create a route for water and carbon dioxide even when the wider protective coating remains sound.
What products are available from Promain?
Promain’s anti carbonation paint category includes several specialist systems for different concrete and masonry projects. Sika Sikagard 550W Elastic is a crack-bridging carbonation paint with outstanding anti carbonation properties, high CO2 diffusion resistance and strong weathering performance for exposed concrete.
Sika Sikagard 675W ElastoColor is a one-part water-dispersed coating for the protection and decoration of fair-faced concrete. Mapei Elastocolor Pittura Zero combines anti carbonation protection with crack bridging for appropriate facades and concrete structures.
Fosroc Dekguard S provides a protective coating and decorative surface finish for concrete and masonry, while Fosroc Dekguard E2000 is a water-based elastomeric anti carbonation coating for reinforced concrete and masonry structures where subsequent cracking is a concern.
KEIM Concretal C is listed by Promain as a sol-silicate paint that protects against carbonation and chloride exposure. Tikkurila Finngard Opaque provides a breathable anti carbonation coating for appropriate facades. Rust-Oleum Murfill is an elastic waterproofing and anti carbonation paint for exterior walls.
Can anti carbonation paint repair damaged concrete?
No. Anti carbonation paint is a protective coating, not a substitute for structural repair. If carbonation has already reached the embedded steel reinforcement and caused corrosion, coating over the damage will not restore lost concrete or steel section.
Repairs should address loose concrete, corrosion, cracks and defective substrate before the protective coating is installed. The anti carbonation coating can then help slow renewed ingress and protect the repaired concrete structure.
Testing concrete for carbonation
Carbonation depth is commonly assessed on a freshly broken concrete surface using an indicator solution such as phenolphthalein. The uncarbonated alkaline concrete typically changes colour while carbonated concrete remains different, allowing the carbonation front to be estimated. Testing should be carried out by competent personnel where the result affects a repair or protection specification.
The test does not describe every cause of deterioration. Chloride contamination, reinforcement depth, concrete quality, cracks and moisture also affect corrosion risk and should be considered on reinforced concrete structures. That wider corrosion assessment matters before a coating specification is finalised.
What should a specification check?
A robust anti carbonation specification should consider substrate condition, carbonation depth, repair needs, crack movement, exposure, water vapour permeability, chloride exposure, required decorative coating finish and resistance to carbon dioxide.
For protective systems covered by international standards such as EN 1504-2, check declared performance and relevant test data. Strong CO2 resistance is important, but adhesion, crack bridging, capillary water absorption and vapour permeability may be equally important for a particular structure. Coating materials should match the repair system and exposure.
Cost efficiency comes from selecting and preparing the right system, not simply the lowest price paint. Correct surface preparation, the correct number of coats and the required film thickness reduce the risk of early maintenance.
Order anti carbonation paint from Promain Paints
Choose anti carbonation paint by the concrete condition and exposure rather than by colour alone. For reinforced concrete, determine whether the job needs a rigid or elastomeric anti carbonation coating, whether cracks require repair and whether coastal, industrial or high-humidity exposure changes the specification.
Promain stocks anti carbonation paint for concrete surfaces, masonry, facades, bridges, parking structures and exposed buildings. Browse the products above or contact Promain for technical help with coating selection, primers, surface preparation and the complete concrete protection system.