When can I backfill or bury a surface coated with Bitumastic 50?

Backfilling or burial may begin 7 days after the final coat is applied, provided the surface temperature has remained above 60°F (16°C). Final cure for immersion service is 14 days at 75°F. Cooler temperatures, high humidity, or higher film builds extend these times.

What surface preparation is required for Bitumastic 50?

For steel in immersion service, abrasive blast to SSPC-SP10. For non-immersion, SSPC-SP6 gives maximum protection (SSPC-SP2 or SP3 minimum), with a 2.0–3.0 mil angular profile. Galvanized steel should be sweep blasted to a 1.0–2.0 mil profile. Concrete must be cured 28 days and prepared per ASTM D4258 and D4259. All surfaces must be clean and dry.

Carboline Bitumastic 50 Coal Tar Coating

Q: What is the coverage rate for Bitumastic 50?

Bitumastic 50 has a theoretical coverage of 1,091 ft²/gal at 1 mil and 61 ft²/gal at the typical 18-mil DFT. At 12 mils it is about 91 ft²/gal; at 30 mils about 36 ft²/gal. Recommended total DFT is 18 mils, with 12–30 mils acceptable. Allow for loss in mixing and application — concrete absorption reduces practical yield.

Q: Is Bitumastic 50 a one-part or two-part product?

Bitumastic 50 is a single-component coal tar mastic. There is no Part A and Part B, no mixing ratio, and no induction time. Simply power mix the contents of the container until uniform in consistency before applying. It is also self-priming, so no separate primer is required.

Q: Can Bitumastic 50 be used above grade or in sunlight?

No. Bitumastic 50 is a coal tar coating designed for below-grade, buried, and submerged service only. Coal tar degrades under UV exposure, so it must not be used on above-grade or sun-exposed surfaces. For immersion service the temperature should not exceed 120°F (49°C).

Q: Is Bitumastic 50 self-healing?

Yes. Bitumastic 50 is a self-healing coating designed to remain soft. This allows the film to flow back together and reseal minor mechanical damage during backfilling and burial, which is a key advantage for below-grade and buried-steel protection.

Q: Is Bitumastic 50 approved for potable water contact?

No. Bitumastic 50 coal tar is not approved for potable water requirements. Do not use it in drinking water tanks, reservoirs, or any infrastructure with direct potable water contact. Contact us for NSF/ANSI 61-listed alternatives.

Thinner	Use With	Notes
Thinner #10	All application methods	Approved coal tar thinner — consult TDS for rates

Product Specs — Bitumastic 50

Bitumastic 50 — Single-Component Coal Tar Mastic by Carboline.
An ultra-high-build coal tar coating for below-grade dampproofing and corrosion protection of steel and concrete in aggressive buried and submerged service. Self-priming and single-component — no mixing, no separate primer. Builds up to 30 mils in a single coat. A self-healing film that stays soft, resealing minor damage during backfill. Complies with MIL-C-18480-B and Bureau of Reclamation CA50. For below-grade use only — not for UV-exposed surfaces.

✓ Single-Component — No Mixing • ✓ Self-Priming • ✓ Up to 30 mils Single Coat • ✓ Self-Healing Film • ✓ MIL-C-18480-B & Bureau of Reclamation CA50 • ✓ Below-Grade Only

✏️ Need a project quote? Request Online

📞 Questions? Call (800) 567-5358 — Mon–Fri 8AM–5PM EST

Bitumastic 50 by Carboline

Bitumastic 50 single-component coal tar mastic below-grade dampproofing coating by Carboline — black coating for buried and submerged concrete and steel — Bitumastic 50 — Single-Component Coal Tar Mastic, Black, Below-Grade Use Only (1-Gal & 5-Gal)

Shipping Map — Carboline Delivery Timing

US regional warehouse map showing estimated shipping transit times for Carboline product orders from Material Warehouse — Typical transit times vary by destination zone. Click map to enlarge.

Shipping Time

Call (800) 567-5358 for pricing and logistics questions.

Carboline orders ship from regional warehouses nearest to your location, with full product stock maintained at each facility.

Most orders ship within 2–3 business days of order placement. Transit times shown on the map are typical but not guaranteed.

Available sizes: 1-gallon (13 lbs) • 5-gallon (65 lbs)

Note: Coal tar contains flammable solvents (flash point 80°F). Hazmat freight rules may apply — call ahead to confirm shipping for your destination.

Coverage Rates

Recommended total DFT: 18 mils (457 microns). Total dry film below 12 mils or above 30 mils is not recommended. Builds up to 30 mils in one or two coats. Allow for loss in application — concrete absorbs material and reduces practical yield.

DFT	Theoretical Coverage
1 mil (25 µm) — basis	1,091 ft²/gal (26.8 m²/l)
12 mils (300 µm) — min	~91 ft²/gal
18 mils (457 µm) — typical	61 ft²/gal (1.5 m²/l)
30 mils (750 µm) — max	~36 ft²/gal

Solids by volume: 68% ±2%. Allow for loss in application. Source: Carboline Bitumastic 50 PDS (March 2021, doc 0025).

Thinning & Cleanup

Power mix until uniform before applying — no induction time. May be thinned up to 12 oz/gal (10%) with Thinner #10; thinning the first coat is required for proper soak-in on concrete. Clean up with Thinner #2 or Xylene.

Curing & Backfill Schedule

Times based on 18-mil DFT. Backfill or bury 7 days after the final coat, provided surface temperature stays above 60°F (16°C).

Surface Temp.	Dry to Touch	Final Cure (Immersion)	Min. Recoat
50°F (10°C)	24 Hours	30 Days	36 Hours
75°F (24°C)	12 Hours	14 Days	24 Hours
90°F (32°C)	8 Hours	7 Days	16 Hours

Higher film build, cooler temps, or high humidity extend cure times. Source: Carboline Bitumastic 50 PDS (March 2021, doc 0025).

Surface Preparation

All surfaces must be clean and dry. Remove dirt, dust, oil, and contaminants that interfere with adhesion.

Substrate / Service	Requirement
Steel — Immersion	SSPC-SP10 (Near-White) · 2.0–3.0 mil profile
Steel — Non-Immersion	SSPC-SP6 for max protection (SP2/SP3 minimum) · 2.0–3.0 mil profile
Galvanized Steel	Sweep blast to a 1.0–2.0 mil profile (non-immersion)
Concrete / CMU	Cure 28 days; prep per ASTM D4258 & D4259; surface voids as needed

Substrate must be above the dew point. Condensation causes flash rusting and poor adhesion. Source: Carboline Bitumastic 50 PDS (March 2021, doc 0025).

Key Specifications & Storage

Property	Value
Generic Type	Coal Tar (single component)
Color	Black (0900)
Primer	Self-priming
Solids by Volume	68% ±2%
Recommended DFT	18 mils · 12–30 mils acceptable
VOC (As Supplied)	2.3 lbs/gal (276 g/l)
Dry Temp. Resistance	350°F (177°C) continuous · 400°F (204°C) non-continuous
Immersion Temp. Limit	120°F (49°C) max
Application Temp	Min 50°F all · Max: material 90°F, surface 125°F, ambient 110°F
Humidity Range	0–90% RH
Application Methods	Conventional Spray, Airless Spray, Brush, Roller
Thinning	Thinner #10 · up to 12 oz/gal (10%)
Cleanup	Thinner #2 or Xylene
Compliance	MIL-C-18480-B · Bureau of Reclamation CA50
Flash Point	80°F (26°C)
Shelf Life	Min. 24 months at 75°F (24°C)
Storage	Indoors · 40–110°F (4–43°C) · 0–100% RH
Kit Sizes	1-Gal (13 lbs / 6 kg) · 5-Gal (65 lbs / 30 kg)

Source: Carboline Bitumastic 50 PDS (March 2021, doc 0025).

Good to Know Before You Buy

⚠️ Key Points for Buyers

Single-component and self-priming — no mixing, no primer. Unlike two-part epoxies, Bitumastic 50 comes ready to use: power mix the container until uniform and apply directly to prepared steel or concrete. There is no Part A/Part B, no mix ratio, and no separate primer step — which speeds up below-grade dampproofing work.
Below-grade, buried, and immersion service only — never in sunlight. Coal tar degrades under UV, so this is strictly for foundations, buried steel, piling, and submerged surfaces (immersion temperature up to 120°F). It is also not approved for potable water. For above-grade or splash-zone service, ask about Bitumastic 300M.
Self-healing film that stays soft. The coating is designed to remain pliable and flow back together, resealing minor scrapes and punctures that happen during backfilling and burial — a durability advantage barrier coatings can't match on buried steel.
Up to 30 mils in a single coat, spec-compliant. Its ultra-high-build chemistry hits full protective thickness fast (typical system 18 mils), and it complies with MIL-C-18480-B and Bureau of Reclamation CA50 — the specs that matter for government and water-infrastructure projects. Backfill 7 days after the final coat (surface above 60°F).

Frequently Asked Questions — Bitumastic 50

What is the coverage rate for Bitumastic 50?

Bitumastic 50 has a theoretical coverage of 1,091 ft²/gal at 1 mil and 61 ft²/gal at the typical 18-mil DFT. At 12 mils it is about 91 ft²/gal; at 30 mils about 36 ft²/gal. Recommended total DFT is 18 mils, with 12–30 mils acceptable. Allow for loss in application — concrete absorbs material and lowers practical yield.

Is Bitumastic 50 a one-part or two-part product?

Single-component. There is no Part A and Part B, no mix ratio, and no induction time. Power mix the contents of the container until uniform, then apply. It is also self-priming, so no separate primer coat is needed.

Can Bitumastic 50 be used above grade or in sunlight?

No. Coal tar degrades under UV exposure, so Bitumastic 50 is for below-grade, buried, and submerged service only. For immersion, the temperature should not exceed 120°F (49°C). For above-grade or splash-zone use, ask about Bitumastic 300M instead.

When can I backfill or bury a coated surface?

Backfilling or burial may begin 7 days after the final coat, provided the surface temperature has stayed above 60°F (16°C). Final cure for immersion is 14 days at 75°F. Cooler temperatures, high humidity, or heavier film builds extend these times.

Is Bitumastic 50 self-healing?

Yes. Bitumastic 50 is designed to remain soft and self-heal, allowing the film to flow back together and reseal minor mechanical damage during backfilling and burial. This is a key durability advantage for buried steel and below-grade concrete.

Is Bitumastic 50 approved for potable water?

No. Coal tar is not approved for potable water requirements. Do not use Bitumastic 50 in drinking water tanks, reservoirs, or any infrastructure with direct potable water contact. Contact us for NSF/ANSI 61-listed alternatives.

What surface preparation is required?

For steel in immersion service, abrasive blast to SSPC-SP10. For non-immersion, SSPC-SP6 gives maximum protection (SP2/SP3 minimum), with a 2.0–3.0 mil angular profile. Galvanized steel: sweep blast to a 1.0–2.0 mil profile. Concrete must be cured 28 days and prepared per ASTM D4258 and D4259. All surfaces must be clean and dry.