STP ShaliUrethane PU TC 2K
A two-component aliphatic polyurethane finish coat that holds its colour and gloss against sun, rain and industrial exposure on steel and concrete.
What is it?
A two-component, liquid aliphatic polyurethane topcoat from STP that cures to a hard, flexible, UV-resistant film. It is the finish layer over a primed steel or concrete surface, not a standalone waterproofing membrane.
Where is it used?
Exposed exterior steelwork and concrete on plants, bridges, refineries and infrastructure across Delhi NCR and pan-India, plus heritage structures and statues where colour stability matters.
Why use it?
Aliphatic PU chemistry resists yellowing and gloss loss under UV, so painted structures keep their appearance for years instead of chalking and fading like standard coatings.
How is it applied?
Mix Component A and B, then brush, roller or spray in coats of 70-80 microns DFT over a compatible dried primer such as ShaliPrime ERO or Zn Ph 60.
About STP ShaliUrethane PU TC 2K
ShaliUrethane PU TC 2K is STP Limited’s two-component, solvent-based aliphatic polyurethane topcoat, supplied as a resin base (Component A) and a hardener (Component B) that are blended on site immediately before use. It is built for the last, visible layer of a protective coating system on exposed steel and concrete. Where an epoxy primer or intermediate coat delivers the corrosion barrier, this topcoat delivers the weathering defence and the finished appearance. The cured film is hard and tough yet retains enough flexibility to move with the substrate, and it brings useful solvent and gasoline resistance to surfaces that see splashes and wipe-downs.
The reason engineers specify an aliphatic PU rather than a cheaper aromatic PU or an epoxy finish comes down to sunlight. Epoxies and aromatic polyurethanes chalk, yellow and lose gloss under prolonged UV, which is unacceptable on a bridge, a refinery pipe rack or a monument that has to look maintained for a decade. ShaliUrethane PU TC 2K is formulated to hold colour and gloss under those conditions, which is why STP positions it for on-shore and off-shore industry, petrochemical and pharmaceutical complexes, cement, steel, chemical and power plants, transportation assets and heritage restoration. For a distributor-applicator working across Delhi NCR and the rest of India, it is the coat that keeps a completed job looking new long after handover.
The technical insight
The performance hinges on the aliphatic backbone of the polyurethane. In any PU, an isocyanate reacts with a polyol to build the film; the difference is what carries the isocyanate. Aromatic isocyanates are cheaper but their benzene-ring structure absorbs UV and breaks down, which shows up as yellowing, chalking and gloss loss within months of sun exposure. Aliphatic isocyanates have no such UV-sensitive ring, so the film stays colour-stable and glossy far longer. That is the entire case for paying more for a 2K aliphatic topcoat over an aromatic one on any exterior asset. Being two-component, the film also cures by chemical crosslinking rather than simple solvent evaporation, which is what gives it the density behind its hardness (Shore D 60-70 after 7 days), its abrasion and impact resistance, and its solvent and gasoline resistance. The trade-off is that curing chemistry is unforgiving of mistakes: once Component B is added, the pot life at 30 degrees C is about 5 hours, and any material left past that will gel in the pot whether or not it has been applied.
Where it is used
- UV-resistant finish coat on exposed structural steelwork at refineries, power plants and cement plants
- Colour-stable topcoat on bridge steel and transportation infrastructure
- Weather-protective finish over primed concrete building exteriors
- Topcoat for on-shore and off-shore oil, gas and petrochemical structures
- Finish coat in pharmaceutical and chemical process complexes where wipe-downs and mild chemical splash occur
- Protective, non-yellowing coating for heritage structures, monuments and statues
- Finish over fully cured epoxy or PU intermediate coats needing UV protection
- Topcoat on pipe racks, tank exteriors and steel gantries in aggressive coastal environments
Key advantages
- Aliphatic chemistry resists UV yellowing and gloss loss, keeping structures looking maintained for years
- High-gloss finish above 80 percent at 60 degrees that resists chalking on exposure
- Hard yet flexible film that moves with the substrate without cracking
- Good solvent and gasoline resistance for surfaces exposed to splashes
- Excellent adhesion to both steel and concrete when correctly primed
- Proven weathering: colour change under 2 delta-E after 1000 hours of exposure testing
- Available in a wide range of colours for asset coding and aesthetics
- Applies by brush, roller or spray, suiting both site touch-ups and large-area work
Limitations & considerations
- Not a primer and not a standalone waterproofing membrane; it must be applied over a compatible dried primer or intermediate coat
- Two-component product with roughly a 5-hour pot life at 30 degrees C, so mixed material must be used promptly or it is wasted
- Concrete must be cured at least 28 days with moisture below 5 percent before priming, which can delay programmes on fresh pours
- Solvent-based with flash points above 23 degrees C, requiring good ventilation, no ignition sources and proper PPE
- Offers only mild chemical resistance, so it is not a substitute for a dedicated chemical-resistant lining on immersion or strong-acid duty
- Correct film build and recoat windows (minimum 6 hours, maximum 48 hours) must be respected or intercoat adhesion suffers
Selection & best practice
Success with this topcoat is decided at the substrate. On steel, blast to Sa 2 to Sa 2.5 depending on condition, remove all mill scale, oil and grease, and prime with ShaliPrime ERO or ShaliPrime Zn Ph 60, letting the primer dry free of solvent for 6-8 hours until touch-dry. On concrete, mechanically grind to a slightly textured profile, confirm the slab is at least 28 days cured with moisture below 5 percent, and prime before topcoating. Mix Component A on its own with a spiral-blade speed drill at 350-400 rpm until homogeneous, then add Component B slowly under slow stirring for full dispersion, and let the blend stand briefly so entrapped air escapes. Apply within the pot life at 70-80 microns DFT per coat, thinning 5-15 percent for conventional spray or up to 5 percent for airless. Observe the recoat window of minimum 6 and maximum 48 hours between coats. Clean all tools immediately with xylene before the material hardens, and allow the full 7-day cure before the surface is placed into demanding service.
Specifications
| Type / chemistry | Two-component (2K) aliphatic polyurethane UV-resistant topcoat |
| Finish / gloss | Glossy; gloss at 60 degrees greater than 80 percent |
| Volume solids | 60 +/- 2 percent |
| Theoretical coverage | 6 – 8 m2 per litre (depending on surface condition) |
| DFT per coat | 70 – 80 microns |
| Pot life at 30 degrees C | 5 hours |
| Drying time at 30 degrees C | Surface dry 30 minutes; hard dry 6 hours; full cure 7 days |
| Recoating time | Minimum 6 hours, maximum 48 hours |
| Hardness / temperature / weathering | Shore D 60-70 after 7 days; temperature resistance up to 120 degrees C; colour change under 2 delta-E after 1000 hrs exposure |
| Packing / shelf life | 5 L and 20 L units (Component A + B); 12 months in sealed original packing |
Industry use cases
Oil, Gas & Petrochemical
Colour-stable finish coat on exposed steel pipe racks, tanks and structures at on-shore and off-shore refineries and petrochemical complexes, where UV and salt-laden air would quickly degrade a lesser topcoat.
Bridges & Transportation
UV-resistant finish over primed structural steel on bridges and transport infrastructure, holding gloss and colour so assets look maintained through long inspection cycles.
Power, Cement & Chemical Plants
Weather-protective topcoat on plant steelwork and concrete exteriors exposed to sun, dust and mild chemical splash, with solvent and gasoline resistance for routine wipe-downs.
Heritage & Public Structures
Non-yellowing protective coating for monuments, statues and heritage steel and concrete where long-term colour and gloss stability are essential to the finished appearance.
Pharmaceutical & Process Facilities
Hard, cleanable aliphatic PU finish on exposed structural and equipment surfaces in pharma and chemical complexes needing a durable, UV-stable exterior coat.
Frequently asked questions
Can ShaliUrethane PU TC 2K be applied directly onto bare concrete or steel?
What coverage should I plan for?
How is it different from an aromatic PU or an epoxy topcoat?
What is the pot life once the two components are mixed?
Does it provide chemical resistance for immersion or strong acids?
What pack sizes and shelf life should I order for?
How we position STP ShaliUrethane PU TC 2K
Position ShaliUrethane PU TC 2K as the UV-stable finish layer of an STP protective coating system, not a one-coat solution. It is normally specified over an STP primer such as ShaliPrime ERO or ShaliPrime Zn Ph 60 on steel, and pairs with STP epoxy intermediates where extra corrosion barrier is needed before the topcoat. Where a project wants a single-component aliphatic PU that can go over cured epoxy without a fresh priming step, the Fosroc equivalent is the natural cross-sell. Across our other brands, teams standardised on Sika or MC-Bauchemie protective-coating systems may prefer to keep the whole stack within one manufacturer, and we can specify matching primer-plus-topcoat build-ups from those ranges too. For interior or immersion duty where UV stability is irrelevant but chemical resistance is critical, steer the client toward a dedicated chemical-resistant epoxy lining instead of this topcoat.
Fosroc Nitocote PU Aliphatic — A specifier who wants a single-component aliphatic PU topcoat that can be applied directly over fully cured epoxy or PU without a separate priming step may prefer the Fosroc option for its simpler on-site handling, where STP’s two-component build gives a denser crosslinked film.
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