Ligand Coordination Equilibria–Drived Homogeneous Electrodeposition Enables Coatings with Superior Corrosion Resistance and Mechanical Strength

Electroplating technology is crucial for interfacial engineering due to its flexible controllability and excellent protective performance. However, electroplated coatings often exhibit uneven deposition morphology due to the uncontrollable nucleation and growth of metal grains, which results in degraded coating performance. Here, we propose ligand coordination equilibria (LCE) that creates a dense coating by simultaneously modulating the solvation structure and optimizing the reduction process, exemplified by Al/Zr alloy electroplating. Multiscale calculations revealed that Cl^- coordination with AlCl₃ and ZrCl₄ forms a dynamic equilibrium between active ionic species Al₂Cl₇ ^- and ZrCl₅ ^-, which is predominantly governed by AlCl₃ due to its stronger Lewis acidity. This coordination mechanism was directly validated by Raman spectroscopy. The dynamic equilibrium between Al₂Cl₇ ^-, which dominates nucleation density and growth rate, and ZrCl₅ ^-, which increases the interfacial diffusion barrier, synergistically promotes the small-sized alloy grain. The resulting compact microstructure significantly enhanced the hardness (268 HV) and corrosion resistance (-0.78 V versus SCE) of the coating, far surpassing that of conventional aluminum alloys coatings. This work highlights the innovative use of LCE for interfacial engineering by tailoring the dynamic equilibrium of active ionic species, providing new insights for the industrial electroplating of high-performance alloys.