Corrosion Enhanced By Hydrogenotrophic Methanogens Differently Enriched on Copper Alloys

Copper and its alloys, such as brass and bronze, are widely used in heat exchangers valves, fitting, and other components of industrial facilities due to their corrosion resistance, high conductivity, and biocide properties. However, they can suffer of microbial corrosion like or more than other non-toxic materials, as several bacteria and archaea can settle and form thick biofilm on them. Nowadays, there is a growing interest in studying the metabolisms of methanogens and their effects for materials [1], due to the pivotal role that these microorganisms play in the biotechnological processes. The production of methane by CO2 and H2, for instance, is one of the most promising bioprocesses addressing the energy transition [2].

In this context, the aim of this work is to evaluate, and underline, the corrosiveness of biofilm growth on different copper alloys, starting from a common microbial pool enriched of bacteria and hydrogenotrophic archaea, treated at different temperatures and autoclaved. The study was evaluated based on 16 days test on the surface of two different copper materials, a pure Cu and a CuZn brass (40 wt. % Zn). Electrochemical investigations were performed using a three-electrode cell consisting of a working electrode (test alloy), a reference electrode (saturated Ag/AgCl electrode) and a counter electrode (titanium mesh). Investigations included open circuit potential (OCP) monitoring and electrochemical impedance spectroscopy (EIS). Chemical characterizations of the corrosion products and post-experiment observations were performed by SEM and micro-Raman spectroscopy (μRS). Molecular analysis by next generation sequencing (NGS) of 16S RNA was performed by swabbing the surface of the material and identifying the microorganisms constituting the microbial communities for each case. Results evidenced a different corrosion behavior of materials, which corresponded to different enrichment of microorganisms and different corrosion products, depending on the material and the treatment of the inoculum.

[1] Lahme S, Mand J, Longwell J, Smith R, Enning D. Severe Corrosion of Carbon Steel in Oil Field Produced Water Can Be Linked to Methanogenic Archaea Containing a Special Type of [NiFe] Hydrogenase. Appl Environ Microbiol. 2021 Jan 15;87(3)

[2] Hirano SI, Ihara S, Wakai S, Dotsuta Y, Otani K, Kitagaki T, Ueno F, Okamoto A. Novel Methanobacterium Strain Induces Severe Corrosion by Retrieving Electrons from Fe0 under a Freshwater Environment. Microorganisms. 2022 Jan 25;10(2):270.