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It is estimated that MIC (microbiologically influenced corrosion) accounts for 20% of all corrosion damages. It is a problem in many industries such as oil and gas, water utilities and biomedical implants. MIC not only cause pinhole leaks, but also catastrophic failures such as gas pipeline ruptures that can lead to explosions. The OHIO MIC group has 20 years of experience in MIC research. Current and past sponsors of our MIC research include BP, ExxonMobil, Petrobras, Petronas, PHMSA, Pioneer Natural Resources, PTTEP, SABIC, Saudi Aramco, Total, etc.

Dr. Tingyue Gu, professor of chemical and biomolecular engineering (also graduate faculty in Biological Sciences), is the first MIC investigator to apply bioenergetics systematically to investigate how biofilms attack metals. His work has achieved a brand-new understanding of basic MIC mechanisms and synergy in biofilm consortia. This has resulted in several discoveries that have immediate practical applications in biofilm and MIC detections. It has also led to our first truly mechanistic MIC model based on electrochemical kinetics and mass transfer for the prediction of MIC pit growth in 2009. Both SRB (sulfate reducing bacteria) MIC and APB (acid producing bacteria) MIC are modeled in MICORP Version 1. In 2022, MICORP was upgraded to Version 2 to include many new features including both pitting corrosion rate and uniform corrosion rate predictions, biocide treatment impact on MIC, H2 impact, Fe2+ impact, and electron mediator impact. The model comes with a database for various input parameters.

Over the years, there was a 10X gap in lab-created MIC rates vs. fast field MIC rates. In 2022, the gap was closed by OHIO. We achieved very severe SRB pitting corrosion in enriched artificial seawater with 7-day pits 10X deeper and clearly visible to the naked eye, accompanied by weight loss 10X higher than before. The extrapolated pitting corrosion rate reached a record high of 1.5 cm/year. The OHIO MIC group pioneered several key methods in MIC mechanism investigations. They include the carbon source starvation theory to prove extracellular electron transfer MIC (EET-MIC), electron mediator acceleration of EET-MIC, electron mediators to distinguish EET-MIC from metabolite-MIC (M-MIC), and headspace change to prove that H2S is not behind SRB corrosion when broth pH is near neutral.

The current belief that the most abundant microbe in a mixed-culture field biofilm is automatically responsible for MIC is fundamentally inconsistent with MIC science. Electroactive microbes are bottom dwellers. They can be the minority in a mixed culture. A metagenomic bug list from next-generation sequencing offers very limited value unless the researcher knows what to look for. Many microbes are electroactive only when needed and there are no other more efficient ones present. Many microbes are labelled as APB but they do not actually secrete organic acids in the operating environment (as evidenced by local non-acidic pH). Our MIC science research is aimed at discovering and elucidating MIC mechanisms to help MIC forensics, detection and treatment.

In 2022, OHIO made key advances in electrochemical biofilm/MIC sensors for pipelines and storage tanks. We are developing biofilm/MIC sensors that are inexpensive (when used with a portable potentiostat), capable of distinguishing MIC from abiotic corrosion (e.g., CO2/H2S corrosion), capable of distinguishing MIC caused by electroactive microbes (e.g., SRB) from MIC caused by corrosive metabolites such as organic acids from APB. The new biofilm/MIC sensors can be deployed widely due to their low cost and usefulness. The sensors can provide key input data for MICORP.

MIC mitigation relies on biocide and scrubbing (pigging). When the same biocide system is used over and over again, the elimination of vulnerable microbes leaves behind a growth environment for resistant microbes from the surrounding environment to move in. Over time, biocide dosage escalation occurs. Environmental concerns desire more effective biocide applications. It鈥檚 unlikely that there will be another blockbuster biocide like THPS or glutaraldehyde on the market any time soon. It鈥檚 a rational approach to enhance existing biocides for more effective biofilm treatment. The best way to do it is to "convince" sessile (biofilm) cells to become planktonic cells. We have worked on several non-biocidal green biocide enhancers that are very effective in the presence of a biocide stress. They can cut biocide dosage by half. A nature-mimicking non-biocidal peptide is highly effective at ppb levels while exhibiting excellent enhancement of biocide treatment of recalcitrant biofilms in lab tests. We are ready for field testing if a partner is found.

We are constantly soliciting sponsors for various MIC projects. Our MIC-JIP (joint industry project) started on Jan. 1, 2012. If you鈥檙e interested in joining the MIC-JIP, please feel free to contact gu@ohio.edu. Sponsors can join and quit anytime. Sponsorship comes with a free license of our MIC software and free MIC technical consulting. Sponsors meet twice a year to discuss project reports and to decide new projects.

Some of the projects we have worked on or are working on include the following:

(A) MIC mechanisms and modeling

We continuously work on MIC mechanisms and provide reliable data to calibrate MICORP Version 2. We investigate biofilm electron transfer mechanisms and identification of corrosive microbes. We investigate energy sharing between microbes that can lead to more aggressive MIC in both EET-MIC and M-MIC. We investigate flow condition impact and underdeposit impact on MIC. We study MIC impact on mechanical property (e.g., loss of ultimate strength and loss of ultimate strain) damages and biotic SCC (stress corrosion cracking).

(B) Biofilm/MIC sensor/probe

We have resolved theoretical roadblocks and entered development stage in sensor design and testing. We test the sensor to distinguish MIC from abiotic corrosion. We test the sensor鈥檚 response to biocide injection and biocide decay. We aim at developing both permanently mounted sensor with remote control via data link, as well as portable sensor. We are seeking partners for field trials. The sensor can provide data for MIC modeling.

(C) Enhanced biocide treatment

We continue to investigate better ways to use biocides. We investigate biocide efficacy and the biocide compatibility with oilfield chemicals. Our biocide efficacy studies include not only biocide kill effect, but also impact on MIC reduction and electrochemical responses. We investigate biocides and biocide enhancers in hydrotest and downhole conditions in addition to pipeline flow condition.