pH-responsive β-cyclodextrin-grafted chitosan microspheres: Dual-action smart carriers for enhanced corrosion...

Micro/nanocontainers, as smart carriers of corrosion inhibitors, capable of intelligently detecting corroded areas and dispensing inhibitors precisely for targeted corrosion control. Here, pH-responsive chitosan-grafted-β-cyclodextrin (CS-g-β-CD) microspheres (CgCM) loaded with various corrosion inhibitors are prepared via an emulsification cross-linking method. By FT-IR and ¹H NMR characterizations, the successful loading of corrosion inhibitor BTA into β-CD is achieved, with the obtained BTA@β-CD being further grafted on the CS chain by degree 28.8 %. The prepared CgCM possess a size range from 15 to 20 μm, and a surface zeta potential range from positive in acidic solution (33.7 mV at pH = 3) to negative in alkaline solution (-20.4 mV at pH = 10). In addition to loading BTA into β-CD, three compound agents (AIM, AMIM-Cl, and 3-SAMA) are selected to be loaded into the crosslinking gaps of the CgCM, with the loading ratios of BTA, AIM, AMIM-Cl, and 3-SAMA determined to be 31.59 %, 13.85 %, 16.93 %, and 19.30 %, respectively. When subjected to acidic stimulation, the CgCM undergo swelling and dissociation, leading to the responsive release of the four loaded inhibitors into the solution, for which the accumulative release ratios (48 h, pH = 3) are determined to be 93 %, 86 %, 84 %, and 81 %, respectively. Weight loss and electrochemical evaluations firmly establish that these CgCM, laden with inhibitors, are adept at forming dense protective barriers on steel surfaces, achieving a corrosion inhibition efficiency exceeding 90 %. Corrosion morphology, surface elemental distribution, and binding status reveal a compact compounding protective layer formation on the steel/solution interface, by a physicochemical synergistic adsorption pattern. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations reinforce the findings, revealing that all three CgCM systems exhibit targeted, stimulus-responsive release capabilities, coupled with robust adsorption strengths and remarkable corrosion resistance characteristics.