Filled reactive ethylene terpolymer primers for cathodic disbondment mitigation

A reactive ethylene terpolymer (RET) with inorganic fillers of clay, talc, and zinc was examined for its cathodic disbondment (CD) performance and as a potential coating primer material for pipeline applications. The filler type and volume fraction influenced the mechanical, thermal, adhesion, and CD resistance of the coatings. The tensile modulus and strength of the RETs increased at higher loadings of selected fillers. The dry adhesive strength of the clay-filled RET maintained the same level of adhesion up to approximately 23 vol %, whereas the talc- and zinc-filled RETs showed decreases in adhesive performance. CD resistance was significantly improved with 18-23 vol % clay, whereas the overall disbondment area was reduced approximately 82% from pure RET. However, the post-cathodic-disbondment adhesive strength for the clay-filled RET decreased as a result of the degradation of the primer/topcoat interface caused by moisture absorption.