Coal tar epoxy is a protective coating consisting of tar, fillers, a gelling agent, and a curing agent. The substance wards off corrosion on equipment used in or near fresh or salt water. It is also resistant to some mild chemicals, acids, and alkali solutions in extreme environments.
Epoxy resins allow for expansion and contraction in coal tar epoxy applications. The mixture also adheres to oily surfaces, making it suitable for painting onto garage floors or applying on underground petroleum tanks and pipelines. Other storage tanks buried underground, such as septic tank systems, can also be treated with this type of epoxy to extend their lives.
One common use of this epoxy involves coating the hulls of ships. The protective coating repels water and protects against tide action that can lead to corrosion. Docks are often coated with the material to guard against deterioration from salt or fresh water.
Industrial uses of coal tar epoxy include protecting metal equipment used in sewage treatment plants and in food industries where pickling brine is used. Chemical waste pipes can also be coated with the material to increase the life of the equipment. Manufacturers who use weak acids to produce goods typically use coal tar epoxy to protect against chemical immersion.
Coal tar comes from crude coke that is distilled using extremely high temperatures. The pitch created from this process is mixed with epoxy polymer resins and other ingredients, and is purchased in two parts. Before use, the coal tar and epoxy mixtures are combined, causing a chemical reaction between the base product and the hardening substance.
The mixture can be sprayed or brushed onto cement, metal, or asbestos. The first coat should be allowed to dry for about 10 hours before a second coat is applied. The curing process typically takes about a week.
Protective goggles and skin protection are advised while applying the substance. Proper ventilation is also suggested to avoid breathing vapors that smell like asphalt. Coal tar epoxy can also stain the skin.
Tar has been used as a sealant for hundreds of years. In the 1700s, the Chumash Indians of coastal California used natural tar that washed ashore to seal canoes and waterproof baskets. The canoes were called tomals, and were used to travel up and down the coast and to nearby islands. Although the Chumash tribe no longer seals canoes with the tar, it continues to appear on beaches in the region.