In Situ Investigation of Under-Deposit Microbial Corrosion and its Inhibition Using a Multi-Electrode Array System

Toward simulating offshore oilfield conditions: insights into microbiologically influenced corrosion from a dual anaerobic biofilm reactor

Oilfield systems are a multifaceted ecological niche, which consistently experiences microbiologically influenced corrosion. However, simulating the environmental conditions of an offshore system within the laboratory is notoriously difficult. A novel dual anaerobic biofilm reactor protocol allowed a complex mixed-species marine biofilm to be studied. Interestingly, electroactive corrosive bacteria and fermentative electroactive bacteria growth was supported within the biofilm microenvironment. Critically, the biotic condition exhibited pits with a greater average area, which is characteristic of microbiologically influenced corrosion. This research seeks to bridge the gap between experimental and real-world scenarios, ultimately enhancing the reliability of biofilm management strategies in the industry.

IMPORTANCE

It is becoming more widely understood that any investigation of microbiologically influenced corrosion requires a multidisciplinary focus on multiple lines of evidence. Although there are numerous standards available to guide specific types of testing, there are none that focus on integrating biofilm testing. By developing a novel dual anaerobic reactor model to study biofilms, insights into the different abiotic and biotic corrosion mechanisms under relevant environmental conditions can be gained. Using multiple lines of evidence to gain a holistic understanding, more sustainable prevention and mitigation strategies can be designed. To our knowledge, this is the first time all these metrics have been combined in one unified approach. The overall aim of this paper was to explore recent advances in biofilm testing and corrosion research and provide recommendations for future standards being drafted. However, it is important to note that this article itself is not intending to serve as a standard.

Synergistic corrosion effects of magnetite and microorganisms: microbial community dependency

The synergistic corrosion effect of acid-producing bacteria (APB) and magnetite on carbon steel corrosion was assessed using two different microbial consortia. A synergistic corrosion effect was observed exclusively with Consortium 2, which was composed of Enterobacter sp., Pseudomonas sp., and Tepidibacillus sp. When Consortium 2 was accompanied by magnetite, uniform corrosion and pitting rates were one-time higher (0.094 mm/year and 0.777 mm/year, respectively) than the sum of the individual corrosion rates promoted by the consortium and deposit separately (0.084 and 0.648 mm/year, respectively). The synergistic corrosion effect observed exclusively with Consortium 2 is attributed to its microbial community structure. Consortium 2 exhibited higher microbial diversity that benefited the metabolic status of the community. Although both consortia induced acidification of the test solution and metal surface through glucose fermentation, heightened activity levels of Consortium 2, along with increased surface roughness caused by magnetite, contributed to the distinct synergistic corrosion effect observed with Consortium 2 and magnetite. KEY POINTS: • APB and magnetite have a synergistic corrosion effect on carbon steel. • The microbial composition of APB consortia drives the synergistic corrosion effect. • Magnetite increases carbon steel surface roughness.

Electrochemical Study on the Macro-Cell Corrosion of Pipeline Steel Partially Covered by Different Kinds of Mineral Deposits

This study presents the impact of mineral deposits (SiO2, Al2O3, and CaCO3) on the corrosion behavior of X65 pipeline steel in CO2-containing brine solution with low pH. The study investigates the initiation and propagation of under deposit corrosion (UDC) using a wire beam electrode (WBE) partially covered by different mineral deposit layers, in conjunction with electrochemical measurements and surface characterization. The results indicate that the corrosion behavior varies, depending on the characteristics of the deposit. During the test period, the Al2O3-covered steel acted as the main anode with more negative potential, while the bare steel acted as the cathode. The SiO2-covered steel acted as the cathode with more positive potential and a localized FeCO3 layer formed beneath the silica mineral. The CaCO3-covered steel initially acted as an anode with a more negative potential but transformed into the cathode at the end of the test. Additionally, shallow and small pits were observed beneath the deposits with the depth in the sequence Al2O3 > SiO2 > CaCO3.