Opposite corrosion behaviour of aluminum bronze induced by Pseudomonas fluorescens and its metabolites

The corrosion behaviour of CuAl10Fe3 was investigated for 120 h in 0.1 M NaCl solution in three different conditions i) presence of active Pseudomonas fluorescens; ii) filtered metabolites; iii) sterilized solution. Elec-trochemical and physical-chemical characterizations were performed. Bacteria growth and metabolism were verified by UFC count and RNA transcriptomics. Results indicate that the aerobic P. fluorescens, despite expressing aggressive pyocyanin, induces a complex corrosion inhibition mechanism promoting the growth of protective Al, Cu, and Fe corrosion oxides-hydroxides. On the contrary, filtered metabolites do not consume oxygen and allow an intermetallic re-precipitation of less protective hydroxychlorides, increasing the corrosion rate.