الفهرس 
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Abstract
Thermal insulation and corrosion protection of heated pipelines used in moving oil/gas and preheated products are accomplished industry-wide by using protective and insulating coatings supplemented by cathodic protection to protect any defected coating areas. Currently, a coat consisting of three successive layers is applied on heated pipelines. The first coal tar epoxy layer is applied on the pipe surface as an electrical insulation. The second layer of polyurethane (PUR) is applied on the top of the first layer as heat insulation, and the third (outer) layer of polyethylene (PE) is applied as a mechanical protection. In the presence of defected areas (e.g., scratches) in the outer layer the electrolyte, which could be present in the surrounding soil, will diffuse through the insulating (porous) layer and impair the applied cathodic protection. Thus, a series of tests were carried out to study how the resistivity of the applied insulating layer (PUR) can be affected by the salt (NaCl) concentration in the surrounding electrolyte (water). The current density required for cathodic protection of insulating steel pipe at worst condition (i.e., lower resistivity of the insulating material) at ambient and elevated temperature was also determined.