Background/Objectives: Biocorrosion, driven by microbial colonization and biofilm formation, poses a significant threat to the integrity of metal artifacts, particularly those composed of copper and its alloys. Pseudomonas aeruginosa, a bacterial species that reduces nitrates, plays a key role in this process. This study explores the potential of two metabolite-rich plant extracts, Aloe vera and Opuntia ficus-indica, as sustainable biobased inhibitors of microbial-induced corrosion (MICOR). Methods: The antibacterial and antibiofilm activities of the extracts were evaluated using minimal inhibitory concentration (MIC) assays, time-kill kinetics, and biofilm prevention and removal tests on copper, bronze, and brass samples. Spectrophotometric and microbiological methods were used to quantify bacterial growth and biofilm density. Results: Both extracts exhibited significant antibacterial activity, with MIC values of 8.3% (v/v). A. vera demonstrated superior bactericidal effects, achieving reductions of ≥3 log₁₀ in bacterial counts at lower concentrations. In antibiofilm assays, both extracts effectively prevented biofilm formation and reduced established biofilms, with A. vera exhibiting greater efficacy against them. The active metabolites—anthraquinones, phenolics, flavonoids, and tannins—likely contribute to these effects. Conclusions: These findings highlight the dual role of A. vera and O. ficus-indica extracts as both corrosion and biocorrosion inhibitors. The secondary metabolite profiles of these plants support their application as eco-friendly alternatives in the conservation of metal cultural heritage objects.

Metal conservators face challenges in restoring archaeologically significant metal items, particularly copper and its alloys, due to biocorrosion from bacteria. Research focuses on effective, eco-friendly methods for removing microbiological corrosion and preserving cultural heritage. We assessed the antibacterial and antibiofilm properties of Aloe vera and Opuntia ficus-indica extracts, which have unique secondary metabolites. These plants have already been investigated as corrosion inhibitors, but not as biocorrosion inhibitors for metals against a specific type of corrosive bacteria, Pseudomonas aeruginosa. Time-kill assays were conducted to evaluate antimicrobial activity. Both plant extracts exhibited strong antimicrobial activity, eliminating nearly all bacterial strains in every test. We evaluated the anti-biofilm efficiency on copper, brass, and bronze using the spread-plate method and microscopic staining. The extracts left removable traces on the metal surfaces, essential for future conservation and restoration use.