چكيده لاتين
In this study, for the first time, a pH-responsive sandwich-like nanostructure with excellent anticorrosion potential was developed and incorporated into an epoxy coating. Initially, multi-walled carbon nanotubes (MCs) were oxidized, and chemical polymerization of aniline was carried out in the presence of 8-hydroxyquinoline-5-sulfonic acid (HQSA) as a dopant, forming the first polymeric layer on the oxidized MCs (OMC). Subsequently, dopamine was polymerized in the presence of OMC/PANI-HQS-, resulting in the formation of a sandwich structure (OMC/PANI-HQS-/PDA), composed of an MC core, a middle PANI-HQS- layer, and an outer polydopamine shell. The synthesized nanostructure and its intermediates were incorporated into epoxy resin and thoroughly investigated. The chemical structure and surface morphology of OMC, OMC/PANI-HQS-, and OMC/PANI-HQS-/PDA were characterized using FT-IR, XRD, TEM, and FESEM analyses. Mechanical properties of the coatings were evaluated through tensile testing, while the controlled release behavior of the HQSA inhibitor from OMC/PANI-HQS-/PDA nanocarriers was monitored by UV-Vis spectroscopy. The corrosion protection performance of the coatings containing different nanostructures was examined via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) measurements. The results demonstrated that incorporation of only 0.5 wt% of the sandwich-like OMC/PANI-HQS-/PDA nanostructure into epoxy resin led to a significant enhancement—by more than three orders of magnitude—in corrosion resistance (as evidenced by the reduction of corrosion rate from 2.07×10−2 to 8.44×10−6 mm/year). Furthermore, the addition of this nanocarrier resulted in an approximate 100% reduction in coating porosity. EIS analysis revealed that the coating containing 0.5 wt% of the nanocarrier exhibited a much higher impedance value (1.38×109Ω•cm²) after 10 days of immersion, compared to the neat epoxy coating (4.05×106 Ω•cm²).This superior performance was attributed to enhanced ionic barrier resistance, improved charge-transfer inhibition, strong interfacial bonding between the modified nanotubes and the polymer matrix, uniform dispersion, and effective corrosion inhibition. Additionally, EDX analysis and release studies confirmed the release of HQSA from the nanocarrier, along with the formation of a compact passive Fe₂O₃/Fe₃O₄ layer on the steel surface,
