Preparation and Performance Study of Self-Repairing External Anticorrosion Coating for Submarine Crude Oil Pipeline Based on Organic Corrosion Inhibitor

This study systematically investigates the corrosion inhibition mechanism of imidazoline (IM) and gallic acid (GA) within boron nitride-reinforced epoxy-phenolic composite coatings (GIBE) for subsea crude oil pipelines. Microstructural characterization via field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) confirms the formation of a molecularly dispersed system in acetone, wherein IM promotes interfacial passivation through amino-metal coordination bonding with the substrate. Electrochemical impedance spectroscopy (EIS) demonstrates a strong positive correlation between IM content and corrosion resistance. GA facilitates self-healing capacity by forming Fe3+-chelated barriers at localized defects (as verified by X-Ray photoelectron spectroscopy (XPS) analysis of Fe3+–GA complexes); however, its inherent hydrophilicity introduces microchannels, as evidenced by a 28.6% reduction in the water contact angle, which ultimately compromises the barrier performance at elevated concentrations. The optimized formulation (5 wt.% IM with 2 wt.% GA) exhibits protective performance in simulated seawater at 60 °C: after 7 days of immersion, the low-frequency impedance modulus (|Z|0.01Hz) reaches 6.28 × 1010 Ω·cm2 with no visible corrosion at scribed regions; after 28 days, |Z|0.01Hz remains above 1010 Ω·cm2, surpassing the service durability threshold of conventional epoxy coatings under high-temperature saline conditions. This work proposes a novel engineering approach for designing anti-corrosion coatings tailored to marine extreme environments.