STP ShaliPrime Zn PE
A two-component phenolic-epoxy primer loaded with metallic zinc that guards steel and reinforcement bars through sacrificial cathodic action, conforming to IS 14589:1999.
What is it?
A two-pack, cold-cure phenolic-epoxy primer blended with metallic zinc dust and a polyamide hardener. The cured film behaves like a coat of zinc bonded to the steel, offering barrier and galvanic protection in one product.
Where is it used?
Structural steelwork, fabricated sections, tanks, containers and exposed reinforcement bars where long-term corrosion resistance is needed before a decorative or heavy-duty topcoat goes on.
Why use it?
Because the zinc corrodes in place of the steel, minor scratches or damage do not spread rust underneath the film. It gives dependable protection in industrial and moisture-prone settings and accepts most topcoat systems.
How is it applied?
Blast-clean or mechanically prepare the steel, mix Component A into Component B, then brush, roller or airless-spray at 6 to 7 m2 per litre, keeping each coat under 50 microns DFT.
About STP ShaliPrime Zn PE
STP ShaliPrime Zn PE is the primer many fabricators and repair contractors reach for when a steel surface has to survive years of exposure rather than months. It is built on a phenolic-epoxy resin carrying a heavy load of metallic zinc, cured with a polyamide hardener supplied as a separate pack. Once the two parts are combined and applied, the film sets cold on site and leaves behind what is effectively a layer of zinc firmly anchored to the steel. That zinc is the working part of the coating. The product is manufactured to IS 14589:1999, the Indian standard covering zinc-rich epoxy primers, so specifiers can reference it with confidence on tender documents.
What makes this primer worth specifying is the way it handles damage. Ordinary barrier paints protect only as long as the film stays intact; the moment a scratch or a welding spark breaks through, rust creeps sideways under the coating. A zinc-rich primer works differently. Even where the film is broken, the surrounding zinc keeps sacrificing itself to hold the steel passive, so corrosion does not undercut the repair. At Space Arc we supply this grade to fabrication yards, infrastructure contractors and rehabilitation crews across Delhi NCR and Pan-India, and we back it with application guidance so the coating performs the way the data sheet promises.
The technical insight
The protection comes from electrochemistry, not just from a physical seal. Zinc sits below iron in the galvanic series, so when the primed steel is exposed to moisture and oxygen the zinc particles become the anode and corrode preferentially, feeding electrons to the steel and keeping it cathodic and therefore passive. For that circuit to work the zinc loading must be high enough that the particles touch each other and the steel, which is why surface preparation matters so much: mill scale, loose rust and burnished spots all break the electrical contact. The phenolic-epoxy binder does two jobs at once. It locks the zinc in place and forms a tough, chemically resistant barrier film with low water-vapour transmission (0.12 mg per cm2 per mm over 24 hours by ASTM D 1653), while the polyamide cure develops adhesion above 3 MPa on steel by ASTM D 4541. The result is a coating that protects both actively, through the sacrificial zinc, and passively, through the resin barrier, which is why zinc-rich epoxy primers are the accepted first coat under demanding industrial and marine-influenced paint systems.
Where it is used
- Shop and site priming of structural steelwork, columns, beams and fabricated sections before topcoating
- Anti-corrosive base coat for storage tanks, vessels and steel containers
- Priming of exposed reinforcement steel during concrete repair and rehabilitation
- Online coating of containers and fabricated items on the production line
- First coat under two-pack epoxy or polyurethane heavy-duty protective systems
- Touch-up and repair of damaged galvanized steel surfaces
- Protection of steel in humid, industrial and coastal-influenced atmospheres
- Priming of pipework and structural members ahead of insulation or cladding
Key advantages
- Sacrificial zinc keeps steel passive even where the film is scratched or locally damaged
- Manufactured to IS 14589:1999, so it references cleanly on specifications and tenders
- Cold-cure two-pack system that sets on site without ovens or external heat
- Long two-hour pot life at 30 C gives a comfortable working window per batch
- Compatible with acrylic, epoxy and polyurethane topcoats for a full protective build
- Applies by brush, roller or airless spray to suit both shop and field conditions
- Strong pull-off adhesion above 3 MPa and low water-vapour transmission for durable protection
- Also serves to repair and touch up galvanized steel, reducing the number of products on site
Limitations & considerations
- Performance depends heavily on surface preparation; mill scale and loose rust must be removed or the cathodic protection is compromised
- Each coat must stay under 50 microns DFT, so heavy single-pass builds are not possible
- Being a two-pack product, mixed material has a limited pot life and cannot be part-mixed carelessly
- Application is restricted to a substrate temperature band of above 10 C and below 50 C
- Zinc particles settle in the can, so both components need thorough power stirring before use
- Requires epoxy thinner for cleaning and adequate ventilation, so it is not a low-hazard water-based option
Selection & best practice
Start with the steel, not the primer. For new work, abrasive-blast to a clean profile not exceeding 65 microns; for older structures where blasting is impractical, use mechanical tools with chipping and wire brushing to strip loose rust, then dust the surface down thoroughly and avoid over-burnishing. Stir Component A and Component B separately to redisperse settled zinc, then add all of Component B into Component A and mix for about three minutes with a slow 400 to 500 rpm paddle until fully homogeneous. Apply at 6 to 7 m2 per litre by brush, roller or airless spray (nozzle 327, filter mesh 30) and keep each coat below 50 microns DFT. Allow one hour before the second coat. Plan the topcoat window carefully: overcoating is possible after 6 to 8 hours, but leaving 12 to 24 hours gives noticeably better adhesion and performance. Clean all tools with epoxy thinner immediately after use, and work in well-ventilated conditions with gloves and eye protection.
Specifications
| Composition | Two-component cold-cure phenolic-epoxy resin with zinc dust and polyamide hardener |
| Standard Conformance | IS 14589:1999 |
| Appearance of Cured Film | Flat, Grey |
| Theoretical Coverage | 6 – 7 m2 / L |
| Dry Film Thickness | 70 ± 5 micron (max 50 micron per coat) |
| Pot Life at 30 C (100 gm) | 2 hrs |
| Touch Dry Time | 1 hr |
| Full Cure | 48 ± 2 hrs |
| Pull-Off Adhesion on Steel (ASTM D 4541) | > 3 MPa |
| Specific Gravity | 1.5 ± 0.02 |
| Packing | 15 L set (Component A 12 L + Component B 3 L) |
| Shelf Life | 12 months in original sealed condition |
Industry use cases
Steel Fabrication
Shop priming of columns, beams and built-up sections so members leave the yard already protected and ready for topcoat on site.
Concrete Repair & Rehabilitation
Brushed onto cleaned reinforcement bars in patch and spall repairs to keep exposed rebar passive before the repair mortar goes on.
Industrial Plants & Tanks
Anti-corrosive base coat for storage tanks, vessels and structural steel exposed to humid or chemically aggressive plant atmospheres.
Infrastructure & Bridges
First coat in heavy-duty epoxy or polyurethane systems on steelwork that must resist long-term weathering and moisture.
Galvanized Steel Maintenance
Touch-up and repair of damaged galvanizing, restoring sacrificial protection without replacing the component.
Frequently asked questions
Is ShaliPrime Zn PE a single-pack or two-pack primer?
How does it protect steel if the coating gets scratched?
What coverage and film thickness should I plan for?
Which topcoats can I use over it?
Does it meet an Indian standard?
What surface preparation does it need?
How we position STP ShaliPrime Zn PE
STP ShaliPrime Zn PE is our go-to zinc-rich epoxy primer for structural steel and exposed reinforcement, and it slots neatly into a full STP protective system. Pair it with an STP epoxy or polyurethane finish coat where a decorative or chemically resistant topcoat is required, and consider STP’s ShaliPrime range for other substrates on the same project. For concrete-repair crews who want a specialist rebar primer as part of a matched repair-mortar system, we also stock Fosroc’s Nitozinc Primer alongside Fosroc’s Renderoc repair mortars. Where budget or availability favours another supply chain, comparable zinc-rich primers are available from Sika and MC-Bauchemie; our team can help match the right primer to the exposure class and topcoat you are specifying.
Fosroc Nitozinc Primer — A specifier working within a Fosroc concrete-repair system may prefer Nitozinc Primer on exposed rebar so the primer, repair mortar and coatings all come from one matched Renderoc range.
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