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Graphene Tops Polymer for MIC

Monday, October 19, 2015

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In its ongoing investigations into graphene coatings and corrosion prevention, a global science team has determined that the graphene coatings minimize corrosion better than commercial polymer coatings in extreme microbial conditions.

The research group, composed of scientists from Rensselaer Polytechnic Institute, South Dakota School of Mines and Technology, Oklahoma State University, and Shenyang National Lab for Materials Science, found that the protection offered by graphene surface coatings can be up to a “100-fold improvement” over the polymer coatings on the market today.

The team recently had its research published in September in a Scientific Reports paper “Superiority of Graphene over Polymer Coatings for Prevention of Microbially Induced Corrosion.”

INchendio
© iStock.com / INchendio

A global science team has determined that the graphene coatings minimize corrosion better than commercial polymer coatings in extreme microbial conditions, Nanowerk reported.

"This finding is remarkable considering that graphene is nearly 4,000 times thinner than several commercial coatings but offers more than an order of magnitude higher resistance to microbial attack," Dr. Ajay Krishnamurthy, the paper’s lead author and current guest researcher at the Engineering lab (EL) at National Institute of Standards and Technology (NIST), told Nanowerk, a site that reports on nanotechnologies and nanosciences.

Graphene vs. Polymer Coatings

Building off of earlier research with Chemical Vapor Deposition-grown graphene coatings and nickel (published as "Passivation of microbial corrosion using a graphene coating" in Carbon in 2013), in this round the scientists looked into how the colonization of microbial communities affects corrosion rates.

The team used a CVD-grown graphene coating as its benchmark and compared it to two popular polymer coatings, Parylene and Polyurethane, according to Krishnamurthy.

"Though initially promising, these [polymer] coatings failed due to various reasons including microbial attack—fermentation, acid production, etc.—and the non-conformity of hand-applied coatings," he said.

While the surface showed complete colonization by microbes, only the electrochemically inert graphene-coated nickel surface maintained its integrity without noticeable surface corrosion, Nanowerk reported.

The parylene- and polyurethane-coated nickel surfaces both displayed rapid corrosion with visible surface byproducts, according to the team.

Wet-Transfer Performance

Once the group saw that the few layers of CVD-grown graphene provided “superior resistance” to MIC, the researchers set out to test the grown graphene coating against graphene films, transferring the films (wet-transfer) onto surfaces that don’t support CVD growth, Krishnamurthy said.

© iStock.com / coffeeyu

The scientists plans to test coatings for other technologically relevant metals, including mild steel, in their next phase of research.

In this case, the team placed between one and three layers of graphene onto silicon dioxide surfaces and studied whether the transfer process caused any defects on the graphene layers. Defect peak intensity (ID/IG) ratios were mapped using confocal raman spectroscopy, according to Krishnamurthy.

"We concluded that the wet etch chemical methods introduce significant amount of defects, while the CVD growth process in itself is less deterrent,” he said.

Outcomes and Next Steps

The research demonstrates that microbial conditions provide a unique dimension to corrosion research. Microbes can form insulating polysaccharide films on the graphene surface to further mitigate metal corrosion.

Based on these findings, the researchers believe that the graphene/microbe interaction is providing a unique benefit to corrosion applications.

The team plans to test coatings for other technologically relevant metals, including mild steel.

"Our past research work evaluated graphene coatings for porous metallic electrodes under immersed conditions," Dr. Venkata Gadhamshetty, fellow author and associate professor at South Dakota School of Mines and Technology, told Nanowerk.

He will continue to investigate MIC in collaboration with Professor Nikhil Koratkar at Rensselaer Polytechnic Institute. Together they will analyze graphene coatings for flat metal sheets used in the construction industry, as well as aggressive atmospheric conditions, including C5-I category as defined by ISO, he said.

   

Tagged categories: Asia Pacific; Coating Materials; Colleges and Universities; EMEA (Europe, Middle East and Africa); Graphene; Laboratory testing; Latin America; Microbiologically Induced Corrosion (MIC); NIST; North America; Polymers; Research; Research and development

Comment from Jerry Trevino, (10/19/2015, 1:14 PM)

Two layers (coats) of graphene will be approximately 0.44 nm or 4.4 x 10e-8 cm thick. I don't think my wet film gage can measure that. Putting on my painting estimator's hat on, WITHOUT doing the math, just guestimating, I guesstimate that two, five gallon buckets of this coating will be sufficient to apply two coats to an average American city. Using a crop duster or a large military helicopter, and of course using a diluent to help with the spread rate and for proper dispersion, We could coat the entire city and eliminate future painting. Overspray will not be a problem since no one will detect the multiple coats of graphene on everything, including coating the microbial inducers of corrosion themselves. . I would also think this will reduce global warming. I NEED another cup of coffee and come back to this estimate later. I only used a flat surface area to guesstimate this, I did not account for the third dimension. I also stated an average American city so that I have a way out on un-average cities. I hear sirens coming to get me.


Comment from Jerry Trevino, (10/19/2015, 2:09 PM)

While reading this article my small brain gears were turning to see if it was something we could use to coat over epoxies used in infrastructure where MIC is a major contributor to the demise of under ground concrete structures. I have attempted to use tertiary amines or quaternary amines in a compounds to combat MIC. Primarily thiobacillus and their offsprings which in create H2S gas and ultimately low ph acids which in turn corrodes concrete. The CVD growth process in this article and the microscopic film build thickness got me in a loopy mental tangent. I do apologize to researchers and those who did not get my sarcasm.


Comment from Tom Schwerdt, (10/22/2015, 4:32 PM)

Graphene would be nice over epoxies since it has an absorption peak right in the UV region around 270nm. Unfortunately to keep that epoxy from chalking due to UV degradation you will need considerably more than 2 layers.


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