Exposed metal surfaces are highly vulnerable to corrosion, but paint or other protective coatings can interfere with some uses, as well as add significant costs. Now, a comprehensive series of experiments suggests a new form of protection: bacteria.
Brass, mild steel (MS) and copper (Cu) samples compared after incubation with (+MR1) and without the presence of the bacteria. Credit: Corrosion and Environmental Effects laboratory, Mork Family Department of Materials Science and Chemical Engineering, Viterbi School of Engineering
Viterbi School post-doctoral researcher Ersa Kus, is the lead author on a forthcoming report on experiments by a team of materials scientists analyzing the ability of an organism called Shewanella oneidensis MR-1 (hereinafter MR-1) to protect a number of metals. The team made a preliminary presentation at a Denver conference last month, and will make a more detailed one in Mexico in October.
Scientists have long known that some bacteria can accelerate corrosion on metal surfaces, says Kus, who works in the Corrosion and Environmental Effects laboratory of Professor Florian Mansfeld of the Viterbi School's Mork Family Department of Materials Science and Chemical Engineering. A bacterium of the same genus as MR-1, S. algae, has earlier been shown to prevent pitting of aluminum and some steel.
MR-1 is a remarkable organism that can incorporate metal into its metabolism, "inhaling certain metal oxides and compounds in one form, exhaling them in another," according to Kus's presentation. MR-1 has previously been used to precipitate uranium out of contaminated water. And "it can grow almost anywhere and does not cause disease in humans or animals," Kus notes.
And it can protect metal.
The experiment was simple. Matched pairs of samples of four metals -- aluminum 2024, zinc, mild steel, copper, and brass -- were prepared. One sample set of each pair was incubated in a growth medium containing MR-1; the other in a sterile bath of the same growth medium, containing neither MR-1 nor any other organism.
After a week, corrosion was monitored, both visually and by measuring electrochemical impedance (resistance to conducting alternating current.) Because electrical effects play a role in many forms of corrosion, higher AC impedance is associated with increased corrosion resistance.
The results were clearcut. For all the materials, impedance increased with exposure to bacteria, and the longer the metals were exposed, the more resistant they became. The increase was particularly marked in the aluminum samples. By the end of the week the control samples showed obvious visual pitting, while the ones with MR-1 colonies were unscathed.
The pattern of impedance varied from metal to metal. Aluminum showed drastic reduction in resistance to electrical currents in all frequencies. Brass and, particularly copper showed nearly as dramatic an effect -- readings indicated active corrosion in the control samples, but a large reduction in the MR-1 samples. The copper MR1 samples, in fact, showed a profile similar to that demonstrated by copper covered with a protective polymer plastic film.
The patterns for steel and zinc were much less marked, but still significant, as was the difference in the metals' appearance.
The next step, according to Kus, is to figure out exactly what is going on and determine where and how the presence of bacteria is altering the corrosion equation. To do this, the group will be making molecular scale analysis of bacteria/metal interfaces, and looking to determine what the properties of MR1 biofilm are, as well as why the pattern of interaction differs from metal to metal.
While MR1 itself may not be the metal protector of the future, it may well suggest an agent that can be, Kus says. The research will be presented at the 210th Meeting of The Electrochemical Society in Cancun, Mexico, October 29-November 3, 2006
Eric Mankin | EurekAlert!
3-D-printed structures shrink when heated
26.10.2016 | Massachusetts Institute of Technology
From ancient fossils to future cars
21.10.2016 | University of California - Riverside
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
27.10.2016 | Life Sciences
27.10.2016 | Life Sciences
27.10.2016 | Power and Electrical Engineering