Pulses, rather than paint, may prove to be the next big thing in protecting structural steel from corrosion.
Researchers at the UK’s University of Hertfordshire have found that applying high-intensity electromagnetic fields (EMF) to steel dramatically increases the material’s resistance to corrosion.
International Molybdenum Association
|Researchers say the technique has dramatically increased corrosion resistance in high-strength, low-alloy (HSLA) steels.|
Exactly how and why that happens remain the subjects of continuing research—specifically, a new, two-year FP7 Marie Curie International Incoming Fellowship (IIF) project to investigate the effect of EMF on the properties of structural metals. The fellowship carries a €278,680 (about $382,000 US) grant.
“Our previous work has shown that using electromagnetic treatment as a post-processing routine increases corrosion resistance in steel by about 50 percent,” said Dr. Andreas Chrysanthou, founder and leader of the university’s Materials Research Group.
“Now, we need to understand the microstructural effects that take place when the field acts on the steel.”
The results have been replicated in seven previous studies conducted with the school’s Dr. Anatoli Babutskyi, Chrysanthou said. But the researchers still don’t fully understand how the currents affect the electrochemical corrosion mechanism.
One possible factor, they say: Pulsed electric current (PEC) treatment relaxes the mechanical stresses that lead to metal defects and causes “homogenization” of the stress structures, the scientists wrote in research published in 2009 in the journal Strength of Materials.
By manipulating the composition of the material at the microstructure level, the scientists hope to produce a “more uniform structure” that will then reduce corrosion levels, Chrysanthou recently told The Engineer, a UK publication.
2 Techniques, 1 Outcome
The researchers have tested two techniques. One involves passing an electric current through a material; the other, applying an electromagnetic field to a material for two to three minutes. Most of the testing has focused on the first technique, but both have produced the same effect, Chrysanthou says.
Most of the tests have used sheet material ranging 0.8mm to 1.5mm in thickness; one was done on a 10mm-diameter cylindrical bar, The Engineer reported.
Although research shows that the electrical current treatment “substantially affects corrosion of metals,” Chrysanthou has written, the results haven’t always been positive.
The treatment increased corrosion resistance in high-strength, low-alloy (HSLA) steel and in 5182 aluminum alloy (the metal used primarily for the bottoms of soda cans in North America).
However, the same treatment dramatically reduced corrosion resistance in 5754 aluminum alloy, commonly used in Europe in pressure vessels, tanks and boat hulls, the scientists found.
Corrosion is a high-stakes issue worldwide, and Europe is no exception, with most EU countries spending 3 to 4 percent of their GDP on corrosion control and remediation, according to Chrysanthou.
Globally, 10 to 30 percent of the annual production of iron is irreversibly lost to corrosion every year, and corrosion accounts for 90% of failures in oil-field pipes, he has written.
“When we have established how exactly this technique works,” he says, “it will be a useful cost-saving tool for the automotive, construction, defense and aerospace industries.”