STP ShaliProtek PC N
A two-component, high-build flexible polyurethane topcoat that armours steel and concrete against corrosion, abrasion and chemical splashes in demanding atmospheric service.
What is it?
A 2K solvent-borne polyurethane protective coating (mix ratio A:B = 3:1 by volume) that builds a thick, flexible anti-corrosive film over primed steel and concrete.
Where is it used?
Storage tanks, penstocks, pipelines, marine piles, sewer and STP tanks, cooling-tower sumps and other exposed steel or concrete structures.
Why use it?
It seals hairline cracks, resists impact and abrasion, and shrugs off salt water, oils, mild acids and alkalis while staying flexible instead of turning brittle.
How is it applied?
Blast or prime the substrate, mix both components for 5-7 minutes, then apply 250-350 microns wet per coat by brush, roller or airless spray.
About STP ShaliProtek PC N
ShaliProtek PC N is STP Limited’s two-component, high-build polyurethane protective coating built for structures that live in hostile atmospheric conditions. Once Component A is mixed with the isocyanate hardener (Component B) at a 3:1 volume ratio, it cures into a tough yet flexible film that clings to steel and concrete alike, sealing hairline cracks and standing up to moisture condensation, impact, abrasion and splashes of mild chemicals. Unlike a rigid anti-corrosive paint, it flexes with the substrate, which is exactly why STP places it on assets that expand, contract and vibrate through daily service.
For a distributor-applicator like Space Arc Engineering, the appeal is practical. The product is engineered for brush, roller or airless-spray application, so crews can coat congested structural steelwork, tank internals and pipe exteriors without depending solely on spray rigs. It carries a genuine track record on demanding infrastructure: crude-oil storage tanks, onshore and offshore structures, hydro-electric penstocks, dam gates, sewer lines and water-containment channels. Delivered in a 20-litre unit pack (15 L base plus 5 L hardener), it slots neatly into project logistics across Delhi NCR and the wider Pan-India footprint we service.
The technical insight
The performance comes from polyurethane chemistry. Component A carries the polyol resin and pigments; Component B is an isocyanate hardener. When the two react, they form a densely cross-linked urethane network that is simultaneously hard (Shore A 80-90) and elastic enough to pass a 12 mm mandrel bend. That combination is the reason a single film can resist a 3 kg scratch load at 200 microns DFT yet still bridge the fine cracking that opens up as steel and concrete move. At 79 percent volume solids it builds fast, laying down 250-350 microns wet per coat so the target dry film is reached in fewer passes with less solvent flash-off. The trade-off, common to all aromatic polyurethanes, is that prolonged sunlight will shift the colour over time. STP is explicit that this is cosmetic only and does not compromise the corrosion barrier, which is why PC N is positioned as a protective topcoat rather than a colour-critical architectural finish.
Where it is used
- Corrosion protection for crude-oil storage tanks and underground structures
- Onshore and offshore steel structures, pipes and marine piles
- Sewer lines and STP (sewage treatment plant) tanks
- Hydro-electric penstocks and dam gates
- Internal and external coating of water and waste-water pipelines
- Cooling-tower sumps, water containments and waterway channels
- Protective topcoat over primed structural steelwork in industrial plants
- Concrete storage tanks and containment linings in atmospheric service
Key advantages
- Application-friendly formulation goes on cleanly by brush, roller or airless spray
- High-build film delivers 250-350 microns wet per coat at 79% volume solids
- Flexible cured film bridges hairline cracks and passes a 12 mm mandrel bend
- Excellent resistance to sea and salt water, oils, crude, acids, alkalis and minerals
- Withstands 2000 hours of salt-spray at 300 microns DFT and 1000 abrasion cycles
- Strong adhesion of 4-6 MPa on steel, with concrete failure recorded on concrete
- Bonds to both steel and concrete over a suitable epoxy or PU primer
- Practical 50-60 minute pot life gives crews a workable window on site
Limitations & considerations
- Aromatic polyurethane will change colour under prolonged UV; cosmetic only, not a performance loss
- Contains isocyanate and is flammable, so it demands ventilation, PPE and ignition control
- Requires proper priming and near-white-metal blasting on steel to achieve rated adhesion
- Curing suffers under low temperature, high humidity, rain or water ponding during application
- Multiple coats are needed where very high dry film thickness is specified
- Substrate and ambient temperature must stay within +10 to +40 degrees C with substrate moisture below 5 percent
Selection & best practice
Preparation decides the outcome. On steel, abrasive blast to near-white metal (SSPC-SP 10 / NACE No.2 / ISO 8501 Sa 2.5) and keep the surface at least 3 degrees C above dew point, coating straight after blasting to prevent flash rusting. Apply PC N directly to freshly blasted metal or over a compatible primer such as ShaliPrime Zn Ph 60, ShaliPrime Zn R, ShaliPrime 2E SF or ShaliPrime 2PU at 50-100 microns DFT. New concrete must be at least 28 days old and dust-free. Mix both components with a slow-speed paddle for 5-7 minutes to a uniform colour, keeping the blade submerged to avoid trapping air, and never mix by hand. Do not thin: adding thinner cuts sag resistance, solids and DFT. Recoat once the first coat has dried (5-8 hours at 30 degrees C); if you exceed 16 hours, wipe the surface with a suitable solvent before the next coat. Respect the 50-60 minute pot life, and clean all tools with STP Thinner before the material hardens.
Specifications
| Chemistry | Two-component solvent-borne polyurethane, high-build flexible coating |
| Mixing ratio | Component A : Component B = 3:1 (v/v) |
| Recommended wet film thickness | 250-350 microns per coat (ASTM D 4414) |
| Theoretical consumption | 3-4 m2/L (IS 101) |
| Volume solids | 79 +/- 3% (ASTM D 2697) |
| Pot life (100 g) | 50-60 minutes at 27 deg C, 60% RH (ASTM D 2471) |
| Drying (touch / surface) | Touch dry 1-2 h; surface dry 4-6 h (IS 101) |
| Adhesion (pull-off, 7 days) | 4-6 MPa on steel; 2-3 MPa concrete (concrete failure) (ASTM D 4541) |
| Packaging & shelf life | 20 L unit (15 L Comp A + 5 L Comp B); 12 months at 5-38 deg C |
Industry use cases
Oil & Gas / Petrochemical
Lining and external protection of crude-oil storage tanks, onshore and offshore structures and pipelines against corrosion and hydrocarbon attack.
Water & Waste-Water
Internal and external coating for water and sewage pipelines, STP tanks, sewer lines and water-containment channels.
Power & Hydro Infrastructure
Abrasion- and cavitation-exposed hydro-electric penstocks, dam gates and cooling-tower sumps that need a flexible, tough film.
Marine & Coastal
Marine piles and coastal steelwork where salt-water resistance and 2000-hour salt-spray performance are decisive.
General Industrial Plants
Structural steel and concrete assets requiring a brush- or spray-applied anti-corrosive topcoat that seals fine cracks.
Frequently asked questions
Is ShaliProtek PC N a primer or a topcoat?
What coverage should I plan for?
How long is the pot life once mixed?
Will it stay the same colour outdoors?
Can it be applied by brush, or is spray mandatory?
What surface preparation does the steel need?
How we position STP ShaliProtek PC N
ShaliProtek PC N is the workhorse anti-corrosive topcoat within STP’s protective-coatings range, and it is normally specified alongside STP primers. For steel we pair it with ShaliPrime Zn Ph 60, ShaliPrime Zn R, ShaliPrime 2E SF or ShaliPrime 2PU to complete a certified system. Where the priority shifts from steel corrosion to elastomeric roof or deck waterproofing, STP’s ShaliProtek PuR L (a polyurethane/polyurea hybrid) is the sister product to consider. Across our other brands, teams needing a zero-VOC solvent-free tank lining often look at Fosroc Nitocote EN901 for aggressive chemical exposure, or Fosroc Dekguard Elastic for anti-carbonation facade protection on concrete. Space Arc Engineering supplies and applies all of these, so the choice can be matched to the substrate and the exposure rather than to whatever is on the shelf.
Fosroc Dekguard Elastic — Choose Dekguard Elastic when the job is anti-carbonation and anti-chloride protection of exposed concrete facades with crack-bridging up to 6 mm, rather than PC N’s core strength in steel corrosion protection and chemical-splash resistance.
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