STP ShaliPoxy CTE 306
100% solids, solvent-free coal tar epoxy that builds 250 microns in a single coat — heavy-duty immersion protection for steel and concrete, safe to apply in confined spaces.
What is it?
A two-component, 100% solids coal tar epoxy protective coating cured with a polyamine hardener. Solvent-free, fast setting and moisture compatible, it dries to a black semi-gloss film and is built for direct-to-metal work where high film thickness is specified.
Where is it used?
Internal and external lining of MS and concrete pipes, crude oil storage tanks, penstocks and barrage gates, sheet and pipe piling, cooling towers, sumps, and steel or concrete structures in sewage treatment plants and chemical works.
Why use it?
It delivers 250 micron DFT in one coat, carries zero VOC for confined-space work, pulls 8 MPa adhesion off steel, works alongside cathodic protection, and conforms to AWWA C210-2015 and SSPC Paint 16.
How is it applied?
Brush, roller or airless spray onto blast-cleaned steel or prepared concrete — direct to metal or over ShaliPrime Zn Ph 60. Mix 3:1 by volume; use within the 1 to 1.5 hour pot life at 27 degrees C.
About STP ShaliPoxy CTE 306
ShaliPoxy CTE 306 from STP Ltd is the heavy-build member of the ShaliPoxy coal tar epoxy range: a two-pack, 100% solids coating in which a polyamine hardener cures the tar-extended epoxy into a hard, flexible, black semi-gloss barrier. Because there is no solvent in the formulation, everything you apply stays on the substrate — a single pass lays down 250 microns of dry film, and the coating can be worked in tanks, sumps and other confined spaces without forced ventilation. It conforms to AWWA C210-2015, SSPC Paint 16 and Corps of Engineers C-200/C-200a, the specifications most Indian consultants reference for buried and immersed pipeline coatings.
The film it produces is what buried and submerged assets need: nil water absorption to ASTM D570, excellent 1000-hour salt spray performance at 250 microns, dielectric strength above 250 V/mil, and cathodic disbondment under 10 mm — so it sits comfortably on pipelines running impressed-current protection. Space Arc Engineering supplies and applies CTE 306 across Delhi NCR and pan-India for water, oil and sewage infrastructure.
The technical insight
Coal tar epoxies work because the two ingredients cover each other’s weaknesses. The epoxy-polyamine network provides adhesion and mechanical strength — 8 MPa pull-off on blasted steel — while the coal tar fraction fills the cured matrix with a hydrophobic pitch that water simply cannot migrate through, which is why the absorption result is nil rather than merely low. Being 100% solids matters twice over: there is no solvent to flash off, so wet film equals dry film and 250 microns arrives in one coat without pinholing from solvent escape; and there is nothing to ventilate, so applicators can work inside vessels safely. The polyamine cure is tolerant of substrate moisture and sets fast — touch dry in 3 hours at 30 degrees C — while the finished film keeps over 22% elongation, letting it flex with thermal movement instead of cracking.
Where it is used
- Internal and external lining of MS and RCC water pipelines and pipe networks
- Crude oil storage tanks, underground structures and buried steel pipework
- Penstocks, dams and barrage gates in hydro and irrigation projects
- Sheet and pipe piling exposed to sea water and aggressive ground
- Cooling tower basins and other water-retaining structures
- Steel and concrete surfaces in sewage treatment plants
- Foundation walls and sumps in continuous ground contact
- Process floors and structures in paper mills and chemical plants handling mild chemical and oil spillage
Key advantages
- 250 micron DFT in a single coat — fewer coats, shorter programme, lower labour cost
- Zero VOC, solvent-free formulation safe for confined-space application without forced ventilation
- Moisture compatible — tolerates slightly damp substrates that would blister conventional epoxies
- High adhesion: 8 MPa pull-off on metal, 2.5 MPa on concrete (ASTM D4541)
- Compatible with controlled cathodic protection; cathodic disbondment under 10 mm at 30 days
- Nil water absorption with proven resistance to sea water, acids, alkalis, crude oil and minerals
- Fast setting — touch dry in 3 hours at 30 degrees C, buried lines can be backfilled after 72 hours
- Flexible film with over 22% elongation resists impact, abrasion and thermal shock
Limitations & considerations
- Supplied in black semi-gloss only — this is a protective barrier, not a decorative or light-coloured finish
- Pot life is 1 to 1.5 hours at 27 degrees C and shrinks further in Indian summer temperatures, so mix only what the crew can place
- Application window is 10 to 50 degrees C ambient; at 10 degrees C full cure stretches to 15 days
- Recoat window is finite (8 to 24 hours at 30 degrees C) — miss it and the first coat needs abrading before overcoating
- Immersion duty demands Sa 2.5 blast-cleaned steel, which adds surface preparation cost and access requirements
- Confirm current potable-water contact certification with STP before specifying for drinking-water linings
Selection & best practice
Surface preparation decides the outcome. Blast steel to Sa 2.5 for immersion duty; on concrete, grind and remove all dust, laitance, oil and loose particles. Apply direct to metal, or prime with ShaliPrime Zn Ph 60 and give it a minimum 4 hours to touch dry. Stir each component separately with a slow-speed mixer at roughly 400 rpm, then combine the pre-weighed Part A and Part B (3:1 by volume) and mix for 5 minutes, keeping the blade submerged to avoid dragging air in. Allow 5 to 10 minutes induction time, restir gently, then apply by brush, roller or airless spray using a 0.48 to 0.88 mm tip at 110 to 160 kg/cm2. Apply the second coat within the recoat window from the curing schedule. On buried pipework, hold backfilling for 72 hours. Clean tools immediately with STP Thinner — the cured material will not come off.
Specifications
| Mixing ratio (by volume) | 3 : 1 (Component A : Component B) |
| Volume solids | 100% |
| Theoretical coverage | 3.5 – 3.8 m2/L at 250 micron DFT |
| DFT per coat | 250 microns |
| Pot life (27 deg C, 100 g) | 1 – 1.5 hours (ASTM D2471) |
| Adhesion, pull-off (ASTM D4541) | 8 +/- 0.5 MPa on metal; 2.5 +/- 0.5 MPa on concrete |
| Touch dry / full cure at 30 deg C | 3 hours / 7 days |
| Pack size | 20 L unit (15 L Component A + 5 L Component B) |
| Standards | AWWA C210-2015, SSPC Paint 16, CoE C-200/C-200a |
Industry use cases
Water Infrastructure
AWWA C210-compliant lining for MS and concrete water pipelines, penstocks and barrage gates, with cathodic-protection compatibility for buried transmission mains.
Oil & Gas
External protection of crude oil storage tanks and buried steel pipework, where crude, lubricant and mild chemical spillage resistance is required.
Marine & Ports
Sheet and pipe piling in tidal and buried zones — nil water absorption and proven sea-water resistance keep steel sound below the waterline.
Sewage & Effluent Treatment
Steel and concrete in STPs and pumping stations, applied without forced ventilation in wet wells and other confined structures thanks to zero VOC.
Industrial Plants
Cooling tower basins, sumps and process structures in paper mills and chemical plants that see continuous water contact and abrasion.
Frequently asked questions
How much area does one 20 L pack cover?
Can it be applied on damp surfaces?
Is a primer required?
Does it work with cathodic protection?
How soon can a coated buried pipeline be backfilled?
What is the recoat window?
How we position STP ShaliPoxy CTE 306
ShaliPoxy CTE 306 is the grade to specify when the job needs high build fast — 250 microns per coat, solvent-free, and workable inside tanks and wet wells. For conventional lower-build coal tar epoxy specifications, STP’s wider ShaliPoxy CTE range, including CTE 103 and CTE 303, covers that ground at standard film thicknesses. Pair it with ShaliPrime Zn Ph 60 where a primed system is specified, and keep STP Thinner on site for tool cleaning. Projects standardised on Fosroc can look at Nitocote ET550, the tar-extended epoxy in our Fosroc range. Space Arc supplies all of these ex-stock and can deploy approved applicator crews for immersion-grade work across Delhi NCR and pan-India.
Fosroc Nitocote ET550 — Specifiers standardised on Fosroc systems get comparable tar-extended epoxy protection from Nitocote ET550, while CTE 306 remains the pick where a 100% solids, 250-micron single-coat build is the priority.
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