Bidirectional Electromigration Behavior in Conductive Mortar with Restorative Properties Based on Rust Inhibitors

Reinforced concrete structures in marine environments face rapid deterioration due to chloride-induced corrosion. This paper explores a bi-directional electromigration (BIEM) repair method using a cement composite conductive mortar containing an imidazoline rust inhibitor (IMZ), which achieves rapid extraction of chloride ions (Cl−) and sustained enrichment of IMZ in the vicinity of the steel. The findings reveal that the applied current density must be strategically selected based on the repair objective. A high current density of 5 A/m2 was highly effective for the rapid electromigration and extraction of chloride ions (Cl−), capitalizing on the strong electrochemical driving force. In contrast, for the sustained migration and enrichment of the larger IMZ molecules at the steel surface, a prolonged application of a lower current density (3 A/m2 for 28 days) proved far more effective, achieving a critical concentration of 0.18 wt%. This is mainly due to a positive shift of the corrosion potential by +600 mV and a 16-fold increase in polarization resistance after 28 days of continuous energization at 3 A/m2. The IMZ/ Cl− concentration ratio (R/C) evaluation index was established to assess the repair effect of corroded concrete and the degree of corrosion relief of steel reinforcement, when R/C > 1 indicates that the passivation. This approach provides a practical and effective framework for restoring durability in chloride-damaged marine concrete structures.