Characterization of the permeability of a high performance composite coating to cathodic protection and its implications on pipeline integrity

In this work, the permeability of a high performance composite coating (HPCC) and its component layers, fusion bonded epoxy (FBE) and medium-density polyethylene (MDPE), to cathodic protection (CP) was investigated by various electrochemical measurements. Results demonstrate that the permeability of the coatings to water is ranked as FBE > MDPE > HPCC. Compared to FBE, MDPE, as a highly non-polar coating, plays a key role in protecting the HPCC from the water permeation. HPCC is impermeable to CP, and shows a pure capacitive behavior, with ultra-high low-frequency impedance at the order of 1010 Ω cm2 during the test period. Both FBE and MDPE coatings are permeable to CP, which will make up the degradation of the coatings due to the water-uptaking. Therefore, under an appropriate CP application, the two coatings are capable of maintaining the pipeline integrity. HPCC provides an excellent alternative to maintain the pipeline integrity in the soil environment.

► To characterize the permeability of a high-performance composite coating to water and cathodic protection. ► To determine the critical role of FBE and MDPE layers in the coating permeability. ► To demonstrate the excellence of the coating in maintenance of pipeline integrity.