A unique polymer-based composite coating with superior corrosion resistance under high-pressure CO2 environment

Abstract

Corrosion in CO₂-enhanced oil recovery (CO₂-EOR) projects has aroused wide attention for its typical environment of high-pressure CO₂ and high-concentration Cl⁻ solution where the application of conventional corrosion protective coatings was severely limited. The structure integrity and corrosion protective performance are greatly weakened by acid, high-pressure water and gas in the environment. Here, we prepared a novel reinforcement composite filler by bridging glass flakes (GF) and carbon nanotubes (CNT) with 3-aminopropyltriethoxysilane (APTES), and then introduced them into EP resin to obtain the superior coating named MGF@CNT/EP. The novel composite coating shows superior barrier capability due to the combination of "maze effect" of GF and the "capture effect" of CNT. Moreover, the addition of hybridized fillers greatly enhanced the structure strength and adhesion value between coating/steel interface. Consequently, the composite coating exhibits improved interfacial stability, superior gas barrier property and long-time anti-corrosion performance even in harsh high-pressure CO₂ environments. The |Z|_0.01 Hz after high-pressure CO₂ anti-corrosion test was 1.58 × 10¹¹ Ω cm², representing a high level of corrosion resistance. Additionally, MGF@CNT/EP coating achieved excellent acid durability (|Z|_0.01 Hz maintaining 2.58 × 10¹¹ Ω cm² in 21 days), low water absorption (1.87 wt% in 15 days) and CO₂ permeability (approximately 81.47 % decrease in comparison with pure EP coating). This study shows that the performances of coatings in the above three experiments mutually affect its application in high-pressure CO₂ anti-corrosion environment, which is expected to guide the design evaluation of composite coatings in CO₂-EOR projects.