Corrosion and protection of iron and zinc in an organotrophic bacterium environment

• A.A. Kalinina, V.I. Naumov and T.N. Sokolova

Nizhny Novgorod State Technical University, 24, ul. K. Minina, 603950 Nizhny Novgorod, Russian Federation

Abstract: The reasons for the formation of corrosive metabolites of organotrophic bacteria, in particular hydrogen peroxide that stimulate the development of corrosion processes on the surface of zinc and steel have been determined. The amount of hydrogen peroxide accumulating in the exudate has been shown to depend on the type of bacteria, the nature of the nutrient medium, and the nature of the metal. It has been found that the respiratory activity of organotrophs and their viability in general play an important role in the formation of corrosive metabolites, such as oxygen and hydrogen peroxide, and in the increase in the exudate pH. All these manifestations result from natural cellular processes involving molecular oxygen. A relationship between the respiratory ability of organotrophic bacteria and the amount of corrosive metabolites has been established. It has been shown by electrochemical methods that the processes of O2 reduction and joint reduction of O₂ and H₂O₂ are limited by diffusion, which is confirmed by the dependences of current on electrolyte stirring. Approaches to the selection of metal corrosion inhibitors in the environment of organotrophic bacteria are outlined. In addition to the developed tetrazolium inhibitors, the efficiency of the protective ability of various variants of zinc-aluminum lamellar coatings based on titanium-oxide and epoxy binders in the environment of the most corrosive bacteria, i.e., Pseudomonas aeruginosa (Gram-negative bacteria) and Bacillus subtilis (Gram-positive bacteria), has been estimated. It has been shown that incorporation of aluminum into the composition of zinc coatings in amounts >3% increases the time of protective effect of coatings manyfold.

Keywords: electrochemical corrosion, bacterial corrosion, low-carbon steel, zinc, tetrazolium salts, lamellar coatings, hydrogen peroxide, ammonia

Int. J. Corros. Scale Inhib., 2023, 12, no. 4, 2239-2255
doi: 10.17675/2305-6894-2023-12-4-42

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