STP ShaliProtek 2AC PU TC (T)
Two-component aliphatic acrylic polyurethane clear topcoat that shields concrete, stone and steel from UV, weather and mild chemicals without yellowing or clouding the surface beneath it.
What is it?
A 2K, isocyanate-cured aliphatic acrylic polyurethane clear topcoat (the transparent variant of the ShaliProtek 2AC PU TC range) that dries to a tough, flexible, non-yellowing film.
Where is it used?
As the final protective layer over epoxy floors, waterproofing systems, decorative concrete, natural stone and blasted steel — heavily specified in coastal, industrial and chemical environments.
Why use it?
Aliphatic PU resists UV, weathering, impact and abrasion far better than aromatic coatings, so the finish stays clear and colour-stable for years instead of chalking or turning yellow.
How is it applied?
Blend Component A and B at 9:1 by volume, wait five minutes to release air, prime the substrate, then apply by brush, roller or spray in one or more coats to build the required DFT.
About STP ShaliProtek 2AC PU TC (T)
STP ShaliProtek 2AC PU TC (T) is the transparent grade of STP’s 2K aliphatic acrylic polyurethane topcoat family. Because it is isocyanate-cured and built on aliphatic resins rather than the cheaper aromatic type, the cured film holds its clarity and gloss under prolonged sunlight — it does not chalk, crack or discolour the way ordinary polyurethanes do. That makes the clear version particularly useful where the appearance of the base surface matters: exposed-aggregate concrete, dressed natural stone, or a coloured epoxy floor that the client wants sealed but not hidden. The same chemistry is offered by STP in a full range of opaque colours for asset-protection duty.
For the engineer specifying it, the appeal is durability packaged as a thin sacrificial layer. The topcoat carries the weathering, UV and chemical load so the expensive system underneath — the waterproofing membrane, the epoxy screed, the anti-corrosive primer on steel — is not the surface taking the abuse. It reflects the reality of Indian project sites, where intense sun, coastal salt and industrial fumes shorten the life of unprotected finishes. Applied as a maintenance-friendly wear coat, it can be recoated at the end of its service life without disturbing the substrate, extending the whole assembly’s working life at a modest cost.
The technical insight
The performance comes down to the resin backbone. Aromatic polyurethanes are cheaper but their molecular structure absorbs UV and breaks down, which is why they yellow and chalk outdoors. ShaliProtek 2AC PU TC uses an aliphatic acrylic polyurethane, whose saturated structure is transparent to UV and resists photodegradation — so after 1,000+ hours of accelerated weathering the colour change stays under 2 ΔE and gloss loss under 25%. Curing is a two-part reaction: the Component B isocyanate hardener cross-links with the Component A acrylic polyol to form a dense, tightly bonded film. That cross-linked network is what delivers the measured hardness (Shore A 80–90), high impact and abrasion resistance, and roughly 1.5–2 MPa pull-off adhesion that fails in the concrete rather than at the coating interface. The 57% volume solids and 9–11 m²/L theoretical coverage per coat mean a genuine dry film is being laid down, not just a thin cosmetic wash — and because it is flexible as well as hard, it accommodates minor substrate movement without micro-cracking.
Where it is used
- Clear UV-protective seal over decorative and exposed-aggregate concrete where the natural finish must show through
- Non-yellowing topcoat on dressed natural stone facades and cladding
- Final wear-and-weather coat over epoxy floor systems and coloured screeds
- Protective overcoat on waterproofing and anti-corrosive coating systems
- Aliphatic PU finish over blasted steel and metal artistic structures
- Exterior protection for petrochemical, pharmaceutical, chemical and fertiliser plant surfaces
- Coastal and marine structures exposed to salt-laden air and spray
- Rail coach, chemical wagon and offshore-structure exteriors requiring colour stability
Key advantages
- Aliphatic chemistry gives genuine UV and weather resistance — no yellowing, chalking or cracking over prolonged exposure
- Transparent grade protects without masking the concrete, stone or coloured base beneath it
- High impact and abrasion resistance (Shore A 80–90) suits trafficked and industrial surfaces
- Strong adhesion — pull-off failure occurs in the concrete, not at the coating bond
- Tough yet flexible film tolerates minor substrate movement
- Good resistance to alkalis, mild acids and solvents in corrosive environments
- Can be applied direct to blasted metal, simplifying the coating build-up on steel
- Factory pre-weighed A and B components at 9:1 reduce on-site mixing error
Limitations & considerations
- Contains isocyanate and is flammable — needs trained applicators, ventilation, PPE and control of ignition sources
- Only mildly chemical-resistant; not a substitute for a dedicated immersion or aggressive-chemical lining
- A single coat rarely reaches high DFT — multiple coats are usually required, adding time and cost
- Curing is sensitive to conditions: low temperature, high humidity, rain or water ponding during or after application can cause incomplete cure or blistering
- As a topcoat it protects but does not itself waterproof or repair — the substrate system must be sound first
- Short pot life once mixed means material must be used promptly and cannot be stored back
Selection & best practice
Success is decided before the topcoat is even opened. Concrete must be cured at least 28 days, mechanically ground or blasted clean of laitance, dust, oil and old paint, and have a moisture content below 2%; steel should be abrasive-blasted to Sa 2–2.5. Prime first — ShaliPrime PUM on concrete, or ShaliPrime 2E on metal — and let it reach touch-dry (about 6–8 hours) before topcoating. Mix Component A on a slow-speed drill (300–400 rpm) until homogeneous, add all of Component B at the 9:1 ratio, then stand for five minutes so entrapped air escapes. Apply only when substrate and ambient temperatures are between 10°C and 40°C, and never with rain, dew or ponding expected during cure. Build the specified DFT in more than one coat rather than flooding a single heavy pass, and clean all tools immediately with STP Thinner before the material hardens.
Specifications
| Chemistry | 2K isocyanate-cured aliphatic acrylic polyurethane |
| Mixing ratio (A:B) | 9 : 1 by volume |
| Theoretical coverage | 9–11 m² per litre (per coat, DFT-dependent) |
| Volume solids | 57 ± 2 % |
| Gloss @ 60° | >80 (1 day) |
| Weathering (min 1000 hrs) | Gloss loss < 25%, colour change < 2 ΔE |
| Shore A hardness (7 days) | 80–90 |
| Pack sizes | 4 L & 20 L unit packs |
| Shelf life | 12 months, sealed, stored at 5–38°C |
Industry use cases
Decorative & Architectural Concrete
Sealing exposed-aggregate slabs, stamped concrete and stone cladding so the natural texture stays visible while gaining a UV-stable, dust-free protective skin.
Industrial & Chemical Plants
Overcoating epoxy floors and steel structures in petrochemical, pharma and fertiliser facilities to resist mild chemical attack, abrasion and corrosive atmospheres.
Coastal & Marine
Protecting facades, jetties and offshore-adjacent steel from salt-laden air and intense sun where aromatic coatings would rapidly chalk and fail.
Infrastructure & Transport
Colour-stable exterior finish for rail coaches, chemical wagons and bridge components that must hold appearance through years of weathering.
Waterproofing Protection
Applied as a sacrificial wear-and-UV coat over membranes and roof/deck systems, taking the weathering load so the waterproofing layer lasts longer.
Frequently asked questions
Is the transparent version really clear, or does it add a tint?
Will it yellow in Indian sunlight like ordinary polyurethane?
How many coats and what coverage should I plan for?
Can it go directly onto steel?
What is the pot life and how is it mixed?
Is it safe to apply and does it need special precautions?
How we position STP ShaliProtek 2AC PU TC (T)
Within the STP family, pair this clear topcoat with its intended primers — ShaliPrime PUM on concrete and ShaliPrime 2E on metal — and specify the pigmented ShaliProtek 2AC PU TC (coloured grade) where an opaque, asset-protection finish is wanted instead of a see-through seal. For floor build-ups, STP’s ShaliFloor 2AC PU TC and ShaliFloor TC 2PU cover the same aliphatic-PU topcoat role over epoxy screeds. Across our other brands, when a project needs a full anti-carbonation protective system on concrete rather than a bare clear coat, Fosroc’s Dekguard range is the natural cross-sell; for high-performance PU floor toppings and coloured industrial finishes, look at Sika’s Sikafloor PU line. Space Arc supplies and applies all of these across Delhi NCR and Pan-India.
Fosroc Dekguard S300 — Choose the Fosroc Dekguard S300 system when a specifier needs a complete anti-carbonation protective build for exposed reinforced concrete — silane/siloxane primer, undercoat and UV-stable aliphatic acrylic topcoat — rather than only a transparent clear seal.
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