STP ShaliDCT 102A
A solvent-free, processed dehydrated coal tar coating that shields buried and embedded steel and concrete against moisture, corrosion and chemical attack — with a cleaner surface finish than ordinary tar.
What is it?
A ready-to-use, solvent-free protective coating based on processed dehydrated coal tar (Grade 102A) from STP Limited, formerly sold as ShaliKote CT 102A.
Where is it used?
On steel and concrete surfaces that need long-term corrosion protection — buried pipwork, embedded structural steel, tank exteriors, foundations, sumps and below-ground concrete.
Why use it?
It forms a dense, water-repellent film that keeps oxygen, moisture and aggressive salts away from the substrate, slowing the electrochemical corrosion that destroys unprotected steel and concrete.
How is it applied?
Applied by brush or spray onto a clean, dry, prepared surface in two or more coats, each allowed to set before the next, building a continuous protective membrane.
About STP ShaliDCT 102A
ShaliDCT 102A is STP Limited’s Grade 102A processed dehydrated coal tar — the “DCT” standing for dehydrated coal tar. Raw coal tar carries moisture and light fractions that make it slow-drying, smelly and inconsistent on site. STP processes and dehydrates the base material so that what reaches the contractor is a stable, solvent-free protective medium that lays down a harder, cleaner film. The 102A grade sits in a family of variants (101 through 105) tuned to different viscosities and end uses; 102A is positioned where a better surface finish is wanted alongside strong anti-corrosive performance, which makes it a common pick for surfaces that will be inspected or handled after coating.
For Indian site conditions, the appeal is simple economics and reliability. Coal tar has protected buried steel and concrete for over a century because it is genuinely hydrophobic, chemically inert to most soil salts, and inexpensive per square metre compared with epoxy or polyurethane systems. ShaliDCT 102A packages that heritage chemistry in a modern, processed form so that Delhi NCR and pan-India contractors get repeatable results on pipelines, tank bottoms, plinth beams and embedded steelwork where a heavy-duty, low-cost corrosion barrier — not a decorative topcoat — is the actual requirement.
The technical insight
Corrosion of steel and reinforcement is an electrochemical reaction that needs three ingredients at the surface: water, oxygen and an electrolyte (typically dissolved chlorides or sulphates from soil and groundwater). Remove any one of them and the reaction stalls. ShaliDCT 102A works as a barrier coating — it does not chemically passivate the metal, it physically excludes the moisture and ions that drive the cell. Because processed coal tar is strongly hydrophobic and has very low water permeability, the cured film holds back liquid water and slows vapour and ion diffusion to the substrate. Dehydration of the base tar matters here: by driving off water and volatile fractions before packing, STP produces a film that cures denser and with fewer pinholes than raw tar, so there are fewer weak points for an electrolyte to reach the steel. Being solvent-free, the film also builds thickness per coat without the shrinkage and solvent-entrapment defects that thin-solvent coatings can suffer, which is why a well-applied two-coat system behaves as a continuous membrane rather than a porous skin.
Where it is used
- Anti-corrosive coating on buried and below-ground mild steel pipelines
- Protection of embedded and structural steelwork in foundations and plinths
- External coating of steel storage tank shells and tank bottoms
- Damp-proof and corrosion-resistant treatment of below-grade concrete
- Protection of sumps, pits, culverts and drainage structures against soil moisture
- Coating of steel fabrications before backfilling or encasement
- Refractory and industrial plant steelwork where a chemical-resistant tar film is specified
- General maintenance re-coating of previously tar-protected assets
Key advantages
- Solvent-free formulation, so higher film build per coat and no solvent-entrapment defects
- Strong hydrophobic barrier that keeps water and dissolved salts off steel and concrete
- Better surface finish than ordinary coal tar, easier to inspect and handle after curing
- Very economical per square metre compared with epoxy or PU protective systems
- Good resistance to common soil-borne chemicals, moisture and mild chemical exposure
- Ready to use and simple to apply by brush or spray with unskilled-friendly technique
- Processed and dehydrated for consistent, repeatable film quality batch to batch
- Proven, long-service coal tar chemistry backed by STP Limited
Limitations & considerations
- Coal tar coatings are dark and utilitarian — this is a protective barrier, not a decorative or colour-matched finish
- Not UV-stable; prolonged direct sunlight can degrade the film, so it is best on buried, embedded or concealed surfaces
- Performance depends heavily on surface preparation — oil, rust, loose scale or damp substrate will undermine adhesion
- Coal tar products carry handling, odour and PPE requirements; follow the MSDS and local environmental rules
- Not intended for potable-water contact or as a food-grade lining
- Overcoating or later bonding of other systems onto a tar film can be problematic and needs checking case by case
Selection & best practice
Start with the substrate. Steel should be cleaned back to a sound, rust- and scale-free surface (mechanical or abrasive cleaning) and be dry and grease-free; concrete should be cured, clean and dry with no laitance or standing moisture. Stir the material thoroughly to a uniform consistency before use. Apply the first coat evenly by brush or spray, working it well into the surface, and allow it to set before applying the second coat so the film builds without sagging or trapping. Two or more coats give a more continuous, pinhole-free barrier than a single heavy pass. Protect freshly coated work from rain, dust and mechanical damage until set, and where the surface will be exposed to sunlight, plan to backfill, encase or otherwise conceal it. Maintain ventilation and correct PPE throughout, and always confirm current coverage, coats and drying times against STP’s latest ShaliDCT 102A technical data sheet for your specific batch and site conditions.
Specifications
| Product | ShaliDCT 102A (formerly ShaliKote CT 102A) |
| Manufacturer | STP Limited, India |
| Type | Processed dehydrated coal tar, Grade 102A |
| Solvent content | Solvent-free |
| Primary function | Anti-corrosive protective coating for steel and concrete |
| Finish | Better surface finish than ordinary coal tar |
| Application method | Brush or spray, two or more coats |
| Documentation | TDS and MSDS available from STP Limited |
Industry use cases
Water & wastewater infrastructure
Protecting buried steel pipelines, sump steel and below-ground concrete in STP/WTP and pumping installations where soil moisture drives corrosion.
Oil, gas & industrial plant
Coating tank exteriors, tank bottoms and embedded steelwork that need a durable, chemical-resistant barrier before backfilling or encasement.
Building foundations & substructure
Damp-proofing and corrosion protection of foundation steel, plinth beams and below-grade concrete against ground water and salts.
Roads, culverts & drainage
Treating culverts, drains, pits and buried structures that are permanently exposed to soil moisture and mild chemical attack.
Refractory & heavy industry
Protecting structural and plant steelwork where a low-cost, chemically inert tar film is specified over more expensive coatings.
Frequently asked questions
What exactly is ShaliDCT 102A?
How is it different from ordinary coal tar or bitumen?
Where should ShaliDCT 102A not be used?
How many coats are needed and how is it applied?
Does the surface need special preparation?
Which grade should I choose from the ShaliDCT range?
How we position STP ShaliDCT 102A
ShaliDCT 102A sits within STP’s coal tar range, so the natural companions are the adjacent ShaliDCT grades — ShaliDCT 101, 102, 103 and 104 for different viscosity and finish requirements, and ShaliDCT 105, a PU-compatible saturated processed tar with waterproofing properties, where the surface will later receive a polyurethane system. For hot-applied joint and surface protection on steel and concrete, STP’s ShaliModulate LS low-smell hot-pour coal tar mastic is the related choice, while ShaliPitch serves aluminium, graphite and refractory applications. Where a specifier prefers a modern polymer barrier over classic coal tar for below-grade concrete, Space Arc also supplies Fosroc’s pitch-modified and cementitious protective coatings as an alternative route. Space Arc Engineering stocks and applies the STP construction-chemicals range across Delhi NCR and pan-India and can help match the right grade to your corrosion-protection specification.
Fosroc Nitoproof 600 — Choose this pitch-modified polyurethane when a below-grade concrete surface needs a black, bitumen-like protective membrane but the specifier wants modern single-component PU chemistry and elasticity rather than classic coal tar.
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