Rational construction of a protective layer for corroded bronze based on composite corrosion inhibitors

Bronzes, as crucial cultural relics, face preservation challenges from chloride-induced corrosion. This study develops a composite inhibitor system using 2-acetylamino-5-mercapto-1,3,4-thiadiazole (AMT) and disodium ethylenediaminetetraacetate (EDTA) to protect corroded bronzes through surface passivation and structural optimization. The artificially corroded bronze (R0) has a loose and porous layer with main compositions of Cu2O and Cu2(OH)3Cl. The corroded bronzes after treated by single AMT inhibitor (R1) and AMT-EDTA composite inhibitors (R2) possess the flatter corrosion layers than R0. Furthermore, the chelation effect of EDTA removes unstable corrosion products on R2, creating a denser structure with lower roughness and weaker water-droplet wettability than R1. The denser layer reduces reactive areas for corrosive reactions on bronzes, and the weaker wettability can suppress the diffusion of corrosive mediums, endowing R2 with the optimal corrosion resistance. These findings advance understanding of bronze corrosion inhibition and provide a scientific basis for developing new protective agents.