Corrosion of aluminum alloy 2024 caused by Aspergillus niger

• Corrosion of aluminum alloy 2024 exposed to the fungus Aspergillus niger was studied.
• The presence of A. niger accelerated the corrosion of AA 2024.
• The corrosion was mainly caused by the oxalic acid produced by A. niger.
• A. niger caused aluminum depletion accompanied with copper enrichment.
• Micro pits and pit clusters resulted in AA 2024 when it was exposed to A. niger.

Corrosion of aluminum alloy 2024 (AA 2024-T3) exposed to fungus Aspergillus niger cultured on glucose containing potato dextrose agar was studied in a high humidity and sterile atmospheric environment. The biofilm evaluation, weight loss measurement, quantitative pit analysis and corrosion product characterization were carried out. Results showed that, under this condition, the presence of A. niger accelerated corrosion process. The corrosion rate of AA 2024-T3 by A. niger was more than 4 times of that exposed to NaCl. Also, severe pitting corrosion, comparable to AA 2024-T3 exposed to NaCl, and aluminum depletion accompanied with copper enrichment were observed. Furthermore, the corrosion morphology was found to be related to the biofilm thickness. The dominant metabolite of A. niger under our experimental condition was identified to be oxalic acid, an aggressive corrodent that causes similar corrosion rate and corroded pit morphology as those observed in this study. Therefore, oxalic acid produced by A. niger under our specific experimental condition is believe to be the main cause for the corrosion of AA 2024-T3.

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