title: Corrosion protection by anaerobiosis.
abstract: Biofilm-forming bacteria can protect mild (unalloyed) steel from corrosion. Mild steel coupons incubated with Rhodoccocus sp. strain C125 and Pseudomonas putida mt2 in an aerobic phosphate-buffered medium containing benzoate as carbon and energy source, underwent a surface reaction leading to the formation of a corrosion-inhibiting vivianite layer [Fe3(PO4)2]. Electrochemical potential (E) measurements allowed us to follow the buildup of the vivianite cover. The presence of sufficient metabolically active bacteria at the steel surface resulted in an E decrease to -510 mV, the potential of free iron, and a continuous release of ferrous iron. Part of the dissolved iron precipitated as vivianite in a compact layer of two to three microns in thickness. This layer prevented corrosion of mild steel for over two weeks, even in a highly corrosive medium. A concentration of 20 mM phosphate in the medium was found to be a prerequisite for the formation of the vivianite layer.
authors.affiliation: Swiss Federal Institute for Environmental Science and Technology, EAWAG, Duebendorf.
authors.forename: H P
authors.initials: HP
authors.lastname: Volkland
authors.forename: H
authors.initials: H
authors.lastname: Harms
authors.lastname: Wanner
authors.forename: A J
authors.initials: AJ
authors.lastname: Zehnder
mesh_terms: D018441:Biofilms; D019149:Bioreactors; D011232:Chemical Precipitation; D003343:Corrosion; D004563:Electrochemistry; D007501:Iron / Q000737:chemistry; D010710:Phosphates; D016958:Pseudomonas putida / Q000502:physiology*; D012240:Rhodococcus / Q000502:physiology*; D013232:Steel
chemical_list: D010710:Phosphates; D013232:Steel; D007501:Iron