Pipeline environmental cracking

Asphalt mastic is a heavy duty system that is shop-applied in thicknesses up to 1 in. (25.4 mm). Although asphalt mastics perform well, they are very costly. Their use is usually limited to river crossing and swamp areas. Coal-tar enamel has more than 50 y of successful performance underground, but it is subject to cracking when the temperature is below 20° F (-7°C), and there are environmental constraints. The EPA has shut down applicators in the middle of production because of air pollution. These problems rule out asphalt mastic and coal-tar enamel as feasible materials for most pipelines. In addition, coal-tar enamels are often ruled out because of long-term deterioration. Asphalt enamel is generally considered inferior to coal-tar enamel therefore, its use is limited. Polyvinyl chloride tape is becoming obsolete because of the superior performance of polyethylene tape. 

The total cost of material fracture is about 4% of gross domestic product in the United States and Europe (88,89). Fracture modes included in the cost estimates were stress-induced failures (tension, compression, flexure, and shear), overload, deformation, and time-dependent modes, such as fatigue, creep, SCC, and embrittlement. The environmentally assisted corrosion problem is very much involved in the maintenance of the safety and reliability of potentially dangerous engineering systems, such as nuclear power plants, fossil fuel power plants, oil and gas pipelines, oil production platforms, aircraft and aerospace technologies, chemical plants, and so on. Losses because of environmentally assisted cracking (EAC) of materials amount to many billions of dollars annually and is on the increase globally (87). 

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