If you're responsible for maintaining asphalt — whether it's a commercial parking lot, a municipal road, or an HOA community — the sealer you choose matters more than most people realize. The two dominant products in the market, coal tar emulsion and asphalt emulsion, have fundamentally different chemistries, performance characteristics, and cost profiles.
This isn't a debate with a simple answer. Each product has genuine advantages depending on your specific situation. This guide provides the facts so you can make an informed decision — or have an informed conversation with your contractor.
Understanding the Chemistry
Coal Tar Emulsion Sealer
Coal tar sealer is derived from the distillation of coal. The resulting tar is mixed with water, clay, and additives to create an emulsion that can be spray-applied or squeegee-applied to asphalt surfaces.
Key chemical properties: - Highly resistant to petroleum-based chemicals (gas, oil, hydraulic fluid) - UV-stable compound that maintains its protective properties longer - Does not chemically bond with asphalt — creates a separate protective layer on top - Darker, richer black finish that lasts longer between applications
Asphalt Emulsion Sealer
Asphalt emulsion sealer is derived from the same petroleum crude oil as the asphalt pavement it protects. It's mixed with water, clay, and polymers to create a sprayable or brushable coating.
Key chemical properties: - Chemically compatible with the underlying asphalt — bonds at the molecular level - More flexible in extreme temperature swings - Less resistant to petroleum solvents (gas and oil can soften it) - Lighter appearance that fades faster, sometimes with a brownish tint
Head-to-Head Performance Comparison
| Factor | Coal Tar Emulsion | Asphalt Emulsion |
|---|---|---|
| Fuel/Oil Resistance | Excellent — #1 advantage | Poor to Moderate — gas/oil softens it |
| UV Protection | Excellent — 3-5 year cycle | Good — 2-3 year cycle |
| Durability | 3-5 years typical | 2-4 years typical |
| Color Retention | Deep black, lasts 2+ years | Fades to gray/brown within 12-18 months |
| Flexibility | Moderate | Excellent — better in freeze-thaw |
| Application Temp | 50°F+ ambient, rising | 50°F+ ambient, rising |
| Cure Time | 24-48 hours | 24-48 hours |
| Cost per Gallon | $0.20-0.35/SF applied | $0.15-0.30/SF applied |
| Odor During Application | Strong (dissipates in 24-48 hrs) | Mild |
| Environmental Regulations | Banned in some states/cities | No restrictions |
When Coal Tar Is the Better Choice
High-traffic commercial parking lots: Gas stations, [auto dealerships](/industries/auto-dealers), truck stops, and any property where vehicles drip fuel and oil regularly. Coal tar's petroleum resistance is unmatched — a gas spill on coal tar-sealed pavement wipes clean. The same spill on asphalt emulsion can dissolve the sealer.
Properties where appearance matters: [Retail](/industries/retail) centers, office complexes, and high-end residential communities where the rich black appearance is a selling point. Coal tar maintains its deep black color significantly longer than asphalt emulsion.
Budget-conscious maintenance programs: While coal tar costs slightly more per application, its longer lifespan means fewer applications over the pavement's life. Over a 15-year period, coal tar typically costs 15-25% less in total maintenance spend.
Montana, Idaho, and Washington (where legal): Coal tar is legal and commonly used throughout our entire service territory. No municipal bans exist in our region.
When Asphalt Emulsion Is the Better Choice
Properties in jurisdictions with coal tar bans: Several states and municipalities (primarily in the Pacific Northwest and Upper Midwest) have restricted or banned coal tar sealers. While our service territory is unaffected, it's worth checking local regulations.
Environmentally sensitive areas: Properties adjacent to streams, lakes, or wetlands where runoff is a concern may prefer asphalt emulsion as a precautionary measure.
Residential driveways with low traffic: For a typical residential driveway that sees 2-4 vehicle trips per day and minimal fuel exposure, asphalt emulsion provides adequate protection at a lower cost per application.
Extreme cold climate applications: In areas with severe temperature swings (common in Montana), asphalt emulsion's greater flexibility can be an advantage on pavement already showing minor cracking. The sealer moves with the pavement rather than becoming brittle.
The Environmental Debate
Coal tar sealers have faced scrutiny for their polycyclic aromatic hydrocarbon (PAH) content. PAHs are present in coal tar and can enter waterways through runoff from sealed surfaces. This has led to bans in Washington, D.C., Austin, TX, and several other jurisdictions.
What the research shows: - Studies by the USGS found elevated PAH levels in waterways adjacent to coal tar-sealed parking lots - However, PAHs are also present in automobile exhaust, tire wear, and the asphalt pavement itself - The sealant industry has responded with refined formulations that reduce PAH content - No bans exist in Montana, Idaho, or Eastern Washington
Our position: We offer both products and recommend based on the specific property, traffic patterns, and owner preferences. We believe in providing options and information, not making the environmental decision for our clients.
The Pitch Black® Advantage
Summit Surface Partners manufactures and applies Pitch Black® sealer — a premium coal-tar-free asphalt emulsion formulated specifically for Northern Rocky Mountain conditions. Here's what makes it different from generic coal tar products:
• Polymer-modified formula — Added polymers improve flexibility without sacrificing fuel resistance
• Engineered for altitude — Formulated to cure properly at elevations from 2,000 to 6,000 feet
• Freeze-thaw optimized — Additional plasticizers prevent the brittleness that causes standard coal tar to crack in severe cold
• Higher solids content — More sealer per gallon means better coverage and longer protection
• Consistent quality — We manufacture it ourselves, so every batch meets our standards
Cost Analysis: 15-Year Comparison
For a 30,000 SF commercial parking lot maintained over 15 years:
| Coal Tar (Pitch Black®) | Asphalt Emulsion | |
|---|---|---|
| Application cycle | Every 4 years | Every 3 years |
| Applications over 15 years | 4 | 5 |
| Cost per application | $7,500 | $6,000 |
| Total 15-year sealer cost | $30,000 | $30,000 |
| Crack sealing needed | Less (better protection) | More (fuel damage compounds) |
| Est. crack seal costs | $8,000 | $14,000 |
| Total 15-year maintenance | $38,000 | $44,000 |
The total cost of ownership often favors coal tar despite the higher per-application price — primarily because its superior fuel resistance reduces supplemental repair needs.
FAQ: Common Questions
Q: Can I switch from one sealer type to the other?
A: Yes. If your pavement was previously sealed with asphalt emulsion, you can switch to coal tar (or vice versa) on the next application. The new sealer adheres to the existing surface regardless of what was used before.
Q: Does sealer type affect my pavement warranty?
A: Not typically. Most paving contractors' warranties are based on the asphalt installation itself, not the sealer used. However, regular sealcoating (of either type) is usually a condition of maintaining the warranty.
Q: Is one sealer better for ADA-compliant striping?
A: No difference. Traffic paint adheres equally well to both sealer types once properly cured. We always allow full cure time before striping.
Q: How do I know which one is currently on my pavement?
A: Coal tar-sealed surfaces tend to maintain a darker, more uniform appearance. Asphalt emulsion surfaces show a lighter, sometimes brownish color as they age. If you're unsure, we can identify it during a free assessment.
Our Recommendation
For the majority of commercial properties in Montana, Idaho, and Eastern Washington, we recommend a polymer-modified asphalt emulsion (specifically Pitch Black®) based on:
• Superior fuel and chemical resistance for high-traffic areas
• Longer application cycles reducing total cost of ownership
• Better color retention for professional appearance
• No regulatory restrictions in our service territory
For residential driveways and environmentally sensitive properties, asphalt emulsion is a perfectly acceptable alternative that provides good protection at a lower upfront cost.
Contact Summit Surface Partners for a free consultation. We'll evaluate your property, discuss your priorities, and recommend the sealer that makes the most sense for your specific situation.
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