Sealcoat is a liquid that is applied to asphalt to protect it from oxidation and the damage caused by winter cracking, as well as UV rays and traffic. In areas of the world that experience freezing and thawing, the reapplication timeline will likely be sped up.
Sealcoating is needed in cold climates, but is useful in warmer climates as well. Since asphalt is a petroleum product, other petroleum products will react with the surface. This includes vehicle oil and gasoline. The sealcoat will act as a barrier against those materials. A sealcoat is not a crack filling agent; this must be done prior to applying the sealcoat. Properly applied, sealcoat can save an owner huge costs over the life of a hot mix asphalt pavement.
Periodic asphalt maintenance such as sealcoating will extend the life of the asphalt up to 30 years. New asphalt surfaces that are sealcoated within their first year will experience less degradation from UV damage, water and traffic. When applied appropriately and at the right time, sealcoating prevents oxidation caused by harsh weather like rain and snow. By sealcoating annually, asphalt can be preserved for an extended period of time. Sealcoating also saves property owners and local government from spending money on costly asphalt repairs. 
There are primarily three types of asphalt sealers. They are commonly known as coal-tar, asphalt emulsions, and acrylics. All three have their advantages but are typically chosen by the contractors’ preference unless otherwise specified. Some States in North America have banned the use of coal tar based sealants primarily based on a United States Geological Survey Department study. f
Acrylic sealers are typically produced in multiple colors and are a niche product for sealing and beautifying properties such as driveways, golf cart paths or as identifiers to specific parking areas or entrances.
Pavement sealers are applied with either pressurized spray equipment, or self-propelled squeegee machines or by hand with a squeegee. Equipment must have continuous agitation to maintain consistency of the sealer mix. The process is typically a two coat application which requires 24 to 48 hours of curing before vehicles can be allowed back on the surface. Prior to application the surface must be completely clean using sweeping methods and/or blowers. If the surface is not clean, then poor adhesion could result. Once the surface is properly prepared, then properly mixed sealer will be applied at about 60 square feet per gallon per coat. 
Polycyclic aromatic hydrocarbons
There are some studies that suggest that refined tar sealants are a significant contributor to polycyclic aromatic hydrocarbon levels in streams and creek beds. As a result, a few municipalities in the United States have banned this material. The same studies also suggest that it can be harmful if ingested before curing and ingesting soil or dust contaminated by eroded coal tar sealant. It is also known to have effects on fish and other animals that live in water. Other water based seal coating materials often perform poorly, especially in climates where temperatures drop below freezing point.
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- "Actions to Restrict or Discontinue the Use of Coal Tar-Based Sealants in the United States". Pca.state.mn.us. Retrieved 5 October 2014.
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