Corrosion inhibition of mild steel by bacteria

Abstract

Mild steel coupons were incubated in cultures of three different aerobic bacteria, viz. Rhodococcus sp. C125, Pseudomonas pulida mt2 and Streptomyces pilosus DSM 40714 and then exposed to a corrosive aqueous medium. A significant reduction in the corrosion rate was observed in a corrosive medium when the steel had been incubated in mineral media containing more than 2 mM phosphate with growing, biofilm‐forming bacteria which had direct access to the steel surface, but not with the non biofilm‐forming S. pilosus DSM 40714. Rhodococcus sp. C125 and P. putida mt2 induced a surface reaction, resulting in the formation of vivianite. This barely insoluble iron(II)‐phosphate was found to be the cause of the corrosion inhibition. The surface reaction was always accompanied by an increase in the iron concentration in the medium. In contrast to biocorrosion processes known so far, iron release stopped after some days. The results suggest that bacterial activity may induce the inhibition of corrosion of mild steel.

Key words:

• biofilm
• biocorrosion
• corrosion
• inhibition
• mild steel
• protection

Notes

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