Corrosion of AISI 1030 mild steel is influenced by bacteria type, oxygen availability, and biofilm formation under controlled laboratory conditions.

Abstract

Aim: Bacteria are reported to have both stimulatory and inhibitory effects on the corrosion of metal. To investigate this, we measured corrosion of AISI 1030 mild steel by four species of bacteria: Pseudomonas aeruginosa, Lelliottia WAP21, Bacillus subtilis, and Enterobacter cloacae in cultures with normal and restricted access to O2.

Methods and results: Scanning electron microscopy, three-dimensional profilometry and inductively coupled plasma-mass spectrometry were used to measure corrosion. Under aerobic conditions, all four bacterial strains protected the metal surface from pit formation compared with abiotic cultures, most likely through the formation of a biofilm that restricting oxygen access. In contrast, in low-oxygen environments, bacteria caused greater surface corrosion and biofilm formation. Specifically, Lelliottia WAP21 caused corrosion pits more than 10 times deeper than those in abiotic cultures and 18-fold more Fe release relative to abiotic controls. Biofilm structures varied with oxygen availability, with each bacterial strain producing distinct biofilms with different elemental composition compared with the abiotic corrosion products. The O2 utilization in the presence of metal may be related to bacterial metabolic activities including biofilm formation. The presence of Fe was metabolically favourable for bacteria and stimulated growth particularly in low O2 conditions.

Conclusion: Our findings show species-specific effects of bacteria on corrosion, where bacterial activity can either enhance or inhibit corrosion depending on oxygen availability.