About STP ShaliPoxy CTE 403

ShaliPoxy CTE 403 sits at the top of STP Limited’s coal tar epoxy range. Where the CTE 103 and CTE 303 grades build 135–165 and 300 microns respectively, this grade lays down a full 400 microns of dry film from a single wet-on-wet application — a build that most solvent-borne coal tar epoxies only manage over multiple visits to site. The film cures cold into a black, semi-gloss barrier with strong resistance to sea water, crude oil, dilute acids and alkalis, and it holds an 8 ± 0.5 MPa pull-off adhesion on properly prepared substrates. It conforms to AWWA C-210, SSPC Paint 16 and US Corps of Engineers C200/C200a, the specifications most Indian consultants reference for buried and immersed service coatings.

For contractors, the practical appeal is speed: direct-to-metal application removes the primer stage, and the single-coat build compresses painting programmes on pipelines, tank farms and hydraulic structures where access is expensive — inside cofferdams, on live jetties, or along trenched alignments that must be backfilled quickly. Space Arc Engineering supplies genuine STP material with current TDS documentation across Delhi NCR and pan-India, and can support applicator selection for larger protective coating packages.

The technical insight

Coal tar epoxy works because two chemistries cover each other’s weaknesses. The epoxy resin contributes adhesion, toughness and chemical resistance; the coal tar pitch fills the cured matrix with hydrophobic material that water molecules struggle to migrate through, giving the film very low permeability in permanent immersion. CTE 403 pushes this further with 90 ± 2% volume solids — there is very little solvent to flash off, so a heavy wet film of 480 microns collapses to about 410 microns dry without sagging or solvent entrapment. The cured film stays flexible (22% elongation to ASTM D 638), so it tolerates thermal movement and handling shock on pipe strings. Critically for pipeline engineers, its dielectric strength above 250 V/mil and cathodic disbondment under 10 mm (30 days, AWWA C-210) mean it works alongside impressed-current or sacrificial CP systems instead of disbonding around holidays.

Where it is used

• External protection of buried MS and concrete pipelines, including CP-protected lines
• Crude oil storage tank externals, underground steel structures and plant pipework
• Sheet piling and pipe piling in marine, tidal and splash-zone exposure
• Dams, barrage gates and penstocks in continuous water contact
• Foundation walls, sumps and below-grade concrete needing a heavy-duty barrier
• Steel and concrete surfaces in sewage and effluent treatment plants
• Structural steel in paper mills, chemical plants and similar aggressive environments

Key advantages

• 400 micron DFT in one wet-on-wet coat — fewer site visits and faster handover than 2–3 coat systems
• Direct-to-metal application; no separate primer required on prepared steel
• 90 ± 2% volume solids gives high build with low solvent release and 2.1 ± 0.1 m²/L theoretical coverage
• Proven in immersion: 30 days in demineralised water, 1% H2SO4 and 1% NaOH with no blistering, peeling or disbondment
• Compatible with cathodic protection — dielectric strength >250 V/mil, cathodic disbondment <10 mm
• Withstood 1,000 hours salt spray (ASTM B 117) at 300 micron DFT
• Flexible film with 22% elongation and only 108 mg abrasion loss (1,000 cycles, CS-10, ASTM D 4060)
• Cures cold from 10°C ambient — usable across most Indian site conditions year-round

Limitations & considerations

• Available only in black semi-gloss; not a decorative or colour-stable finish, and like all coal tar epoxies it will chalk under prolonged UV exposure
• Coal tar chemistry demands strict PPE and ventilation, and most current specifications exclude it from potable water contact surfaces
• Pot life is 2.5 hours at 30°C — mix only what the crew can place, and expect shorter working time in peak summer
• Application window is 10–50°C ambient with the substrate between 10°C and 49°C; new concrete must be at least 28 days old
• Recoat window at 30°C is 8–30 hours; a second coat applied after the window closes needs the first coat abraded
• Solvent-borne formulation — confined-space application (tank interiors, sumps) requires forced ventilation and flameproof precautions

Selection & best practice

Specifications

Industry use cases

How we position STP ShaliPoxy CTE 403

Within the STP family, pick the CTE grade by required build: ShaliPoxy CTE 103 (135–165 micron) and CTE 303 (300 micron) suit lighter-duty specifications, CTE 403 owns the single-coat 400 micron class, and CTE 503 is the polyamide-cured option where abrasion governs. For damp or green concrete, the moisture-insensitive CTE 103 MI and CTE 303 MI variants remove the drying wait. Pair with ShaliPrime Zn Ph 60 where a zinc phosphate primer is specified. Projects standardised on Fosroc can specify Nitocote ET140, the equivalent solvented coal tar epoxy we also stock, while asset owners moving away from coal tar altogether should discuss solvent-free epoxy alternatives with our technical team.

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