عنوان مقاله [English]
The mechanism and control of premature disbondment of three-layer polyethylene (3LPE) coatings have been the subjects of many research activities which are still going on. Also, the substitution of 3LPE with better coatings has been the aims of different research works and this paper is going to discuss it. Based on what is mentioned above, the quality and performance of two polyurethane and one polyurea coating samples were closely examined by running important standard tests including adhesion, cathodic disbondment, impact, bendability (flexibility), water absorption, surfaces hardness, and dielectric strength. The results of cathodic disbondment tests of these three samples were compared with that of 3LPE coating. In this research, it was shown that polyurethane had better cathodic disbondment results than 3LPE coating. With reference to the fact that there is no report in the literature on the early disbondment of polyurethane from pipe surface, and that the coating is applicable on-site with one third thickness of 3LPE, polyurethane is recommended as a suitable substitution for 3LPE. Moreover, it was found the cathodic disbondment result of the polyurea was comparable with that of 3LPE. With reference to the same reasons argued for polyurethane, polyurea can be a good substitute for 3LPE as well.