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Modified Cathodic Disbondment Test Methods for Comparing the Performance of HPPC and FBE Coatings

Product Number: 51321-16219-SG
Author: Min Xu/Edouard Asselin/Catherine Lam/Dennis Wong
Publication Date: 2021
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Modified CD test methods, based on NACE TM0115-2015, were developed to evaluate the performance of pipeline coatings in specific field conditions, such as those that exist in the Rockies in British Columbia, Canada, where pipelines will encounter rough terrain with potentially corrosive and abrasive rocks. One modified CD test uses an overhead agitator to suspend acid generating pyrite particlesin the electrolyte to introduce both abrasion and acidification effects. It was found that increasing the mixing rate causesa decrease in coating impedance for fusion bonded epoxy (FBE) coatings. High performance powder coating (HPPC) haveabout 60% less disbondment compared with FBE, especially in acidic solutionsat room temperature. A pH-controlled CD test was alsodeveloped to evaluate HPPC and FBE coating performance in electrolytes with pH ranging from 0 to 12. As revealed byscanning electron microscopy and dry film thicknessstudies, HPPC slows the migration of water and ionic species through the coating, contributing to less disbondment than FBE over the entire pH range. Both coating systems exhibit the poorest resistance to CD at near neutral pH conditions. DifferentCD mechanismswere proposed and discussed in terms of the solution pH.

 

Modified CD test methods, based on NACE TM0115-2015, were developed to evaluate the performance of pipeline coatings in specific field conditions, such as those that exist in the Rockies in British Columbia, Canada, where pipelines will encounter rough terrain with potentially corrosive and abrasive rocks. One modified CD test uses an overhead agitator to suspend acid generating pyrite particlesin the electrolyte to introduce both abrasion and acidification effects. It was found that increasing the mixing rate causesa decrease in coating impedance for fusion bonded epoxy (FBE) coatings. High performance powder coating (HPPC) haveabout 60% less disbondment compared with FBE, especially in acidic solutionsat room temperature. A pH-controlled CD test was alsodeveloped to evaluate HPPC and FBE coating performance in electrolytes with pH ranging from 0 to 12. As revealed byscanning electron microscopy and dry film thicknessstudies, HPPC slows the migration of water and ionic species through the coating, contributing to less disbondment than FBE over the entire pH range. Both coating systems exhibit the poorest resistance to CD at near neutral pH conditions. DifferentCD mechanismswere proposed and discussed in terms of the solution pH.