Preparation and corrosion inhibition performance of controlled-release ethyl cellulose@D-sodium gluconate microcapsules in simulated concrete pore solution

The application of corrosion inhibitors is a widely adopted strategy for protecting reinforcing steel against electrochemical degradation. However, conventional direct-addition approaches often lead to premature inhibitor depletion and lack controlled-release functionality. In this study, a novel sustained-release capsule-type inhibitor was developed to combat chloride-induced steel corrosion. Ethyl cellulose with high alkali resistance, controllable release and good mechanical properties was used as the shell material and D -sodium gluconate as the core, using a phase separation method and the preparation of the capsule was verified by TG, FT-IR and SEM. The experiment showed that the resulting capsules displayed a "pea-pod" shape (about 0.5–1.0 μm in length and 0.2 μm in diameter) with a compact core/shell structure and when the core/shell ratio was 1:5, the maximum encapsulation efficiency of the capsules was 73.3 %. When dispersed in simulated concrete pore solution, the capsules enabled sustained release of D -sodium gluconate over multiple days. EIS and LPR were used for electrochemical test. And the electrochemical analysis confirmed that the capsule-based inhibitor effectively suppressed corrosion and improved corrosion resistance. Specifically, a dosage of 0.05 % resulted in an inhibition efficiency of 90.7 ± 1.2 % after 7 days. The core-to-shell ratio was identified as a critical factor governing both the release kinetics and the overall protective performance, with the 1:5 formulation demonstrating optimal corrosion inhibition. This study offers a promising strategy for the design and application of intelligent corrosion inhibitors in reinforced concrete structures. • Novel microcapsules for sustained D -sodium gluconate release were successfully prepared using a phase separation method. • The release kinetics were effectively controlled by precisely tuning the core/shell ratio of the microcapsules. • An outstanding inhibition efficiency of 90.69 % was achieved with a low microcapsule dosage of 0.05 %. • The critical influence of the sustained release characteristics on the corrosion inhibition efficiency was thoroughly investigated and discussed.