Unveiling the corrosion inhibition mechanism of titanium nitride composite carbon dots in saline-alkali environments: An experimental and theoretical study.

The salt-alkali environment induces corrosion due to incomplete passivation film formation on metal surfaces, enabling corrosive ion penetration. Despite its widespread use as a high-performance coating for metal anti-corrosion, titanium nitride (TiN) has seen minimal adoption in corrosion inhibitor applications. Carbon dots (CDs), an eco-friendly category of nanomaterials, exhibit significant inhibitive potential. Based on this, this work pioneers the exploration of titanium nitride composite carbon dots corrosion inhibition (TiN@Ma-CDs) hybrid composites as corrosion inhibitors for carbon steel in alkaline-chloride media, elucidating their anti-corrosion mechanisms through experimental and theoretical approaches. TiN@Ma-CDs demonstrates excellent corrosion inhibition efficiency in simulated high-alkali concrete pore solution (HACPS: 0.6 M KOH + 0.2 M NaOH +3.5 wt% NaCl + sat. Ca(OH)₂). At 298 K, carbon steel in HACPS containing 100 mg/L TiN@Ma-CDs exhibits a corrosion current density reading of 0.649 μA/cm2, significantly lower than that in the blank solution (2.378 μA/cm2). Atomic force microscopy reveals a tightly-packed anti-corrosion layer was established by TiN@Ma-CDs on the carbon steel surface. Molecular orbital theory identifies multiple strong adsorption sites, and molecular dynamics simulations confirm the inhibition performance, showing the diffusion coefficient of Cl- ions decreasing from 1.71 × 10-9 m2/s to 3.17 × 10-12 m2/s. These experimental results collectively demonstrate the superior anti-corrosion performance of TiN@Ma-CDs. This research provides theoretical and experimental support for the deployment of modified CDs in corrosion inhibition.