Anodic coordination polymerization for bilayer passivation of copper against oxidation

Copper corrosion under elevated temperature, humidity, and salinity environments has always been an important challenge in the engineering application. To enhance the corrosion protection of copper, an anodic oxidation induced coordination polymerization strategy was proposed, in which copper ions are released and in situ coordinated with 1,4-benzenedithiol (BDT) molecules to construct a bilayer passivation film, which consists of an outer Cu-BDT coordination polymer layer (~5.2 nm) and an intermediate cuprous sulfide layer (~ 1.8 nm) intrinsically grown on the underlying copper substrate. This passivation film markedly improves corrosion resistance, reducing the corrosion current density over three orders of magnitude in salinity environments. It also demonstrates chemical and thermal stability under acidic, alkaline, and high-temperature conditions. DFT calculations demonstrate that the passivation film increases the adsorption energy barriers of corrosive species, including O₂ (from - 2.07 eV to - 0.18 eV) and Cl^- (from - 1.12 eV to 0.13 eV) on the copper surface. Furthermore, the strategy has been integrated into a roll-to-roll system, highlighting its potential for large-scale application. This work presents an effective and innovative strategy for enhancing the corrosion protection of copper through the construction of a nano-scale (~7 nm) bilayer passivation film.