Hydrogen causes metal to break

Aug 11, 2010

Hydrogen is considered the fuel of the future. Yet this lightest of the chemical elements can embrittle the metals used in vehicle engineering. The result: components suddenly malfunction and break. A new special laboratory is aiding researchers’ search for hydrogen-compatible metals..

Most likely, there is hardly a soul that cannot recall K.I.T.T. - the legendary talking supercar from the US television series "Knight Rider". A turbo motor fuels the fantasy vehicle and propels it on the chase for the bad guys at over 300 miles an hour. In the future, cars may be equipped with hydrogen propulsion not just in the movies, but in real life as well. In the transportation and energy sectors, hydrogen is viewed as an eventual alternative to the raw materials of fossil-fuel power, such as coal, petroleum and natural gas. However, for metals like steel, aluminum and magnesium - which are commonly used in automotive and - hydrogen is not quite ideal. It can make these metals brittle; the ductility of the metal becomes reduced. Its durability deteriorates. This can lead to sudden failure of parts and components. Beside the itself, or parts of the fuel cell, but ordinary components like ball bearings could also be affected. These are found not only in the car, but also in almost all industrial machinery.

This lightest of the chemical elements permeates the raw materials of which the vehicle is made not only when fi lling the tank, but also through various manufacturing processes. Hydrogen can infi ltrate the metal lattice through corrosion, or during chromium-plating of car parts. Infi ltration may likewise occur during welding, milling or pressing. The result is always the same: the material may tear or break without warning. Costly repairs are the consequence. To prevent cracks and breakage in the future, the researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg are studying hydrogen-induced embrittlement. Their objective: to fi nd materials and manufacturing processes that are compatible with hydrogen. "With our new special laboratory, we are investigating how and at which speed hydrogen migrates through a metal. We are able to detect the points at which the element accumulates in the material, and where it doesn’t," says Nicholas Winzer, researcher at IWM.

Since the risk potential mostly emanates from the diffusible, and therefore mobile, portion of the hydrogen, it is necessary to separate this from the entire hydrogen content. Researchers can release and simultaneously measure the movable part of the hydrogen by heat treatment, where samples are continuously heated up. In addition, the experts can measure the rate that hydrogen is transported through the metal while simultaneously applying stress to the material samples mechanically. They can determine how the hydrogen in the metal behaves when tension is increased. For this purpose, the scientists use special tensile test equipment that permit simultaneous mechanical loading and infi ltration with hydrogen. Next, they determine how resis- tant the material is. "In industry, components have to withstand the combined forces of temperature, mechanical stress and hydrogen. With the new special laboratory, we can provide the necessary analytical procedures," as Winzer explains the special feature of the simultaneous tests.

The researchers use the results from the laboratory tests for computer simulation, with which they calculate the hydrogen embrittlement in the metals. In doing so, they enlist atomic and FEM simulation to investigate the interaction between hydrogen and metal both on an atomic and a macroscopic scale. "Through the combination of special laboratory and simulation tools, we have found out which materials are suitable for hydrogen, and how manufacturing processes can be improved. With this knowledge, we can support companies from the industry," says Dr. Wulf Pfeiffer, head of the process and materials analysis business unit at IWM.

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User comments : 7

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gunslingor1
3 / 5 (2) Aug 11, 2010
This is a truely deceptive article.

Antifreeze is far more corrosive than hydrogen, and it's used in cars just fine.

Most of the brittleness comes from the low temperatures, not from any chemical processes... and this is really only a concern in the fuel tank.

"Hydrogen can infiltrate the metal lattice through corrosion, or during chromium-plating of car parts. Infiltration may likewise occur during welding, milling or pressing"
-Who the heck would mill car parts with fuel in them?
maxcypher
not rated yet Aug 11, 2010
I believe they are referring to the hydrogen found in atmosphere during manufacturing, but I too find this article hazy, e.g., why didn't they list which metals are found to be compatible with hydrogen? Proprietary reasons? They should state whenever business considerations prevent relevant reporting.
hudres
5 / 5 (2) Aug 11, 2010
Hydrogen embrittlement is a very real phenomenon. It is well know in the nuclear industry and is one of the primary reasons that nuclear reactors have a finite life cycle. The article clearly states that steel, aluminum and magnesium are subject to embrittlement. I do not think that the Fraunhofer Institute has a commercial motivation. While this is not a particularly well written article, the underlying facts are unfortunately quite real and true.
gunslingor1
1 / 5 (1) Aug 12, 2010
Sure, but it's not a chemical process. H2 brittlizes metal because of extremely low temperatures. Once expanded into a gas from the liquid state, it's not really a concern.
complexChemicals
not rated yet Aug 12, 2010
I would like to see a study determining if/how Aluminum with Fullerenes brittlizes, or if this harder material resists the H2 better.

as per http://www.physor...048.html

Javinator
not rated yet Aug 12, 2010
Sure, but it's not a chemical process. H2 brittlizes metal because of extremely low temperatures. Once expanded into a gas from the liquid state, it's not really a concern.


That's pretty incorrect.

Hydrogen gas (H2) molecules will sometimes split on the surface of a metal into two separate hydrogen atoms.

These hydrogen atoms will diffuse into the lattice of the metal. When the separate hydrogen atoms "find" each other, they will bond and form H2 again. This reaction produces pressure within the metal (since H2 is a gas). This pressure causes deformations within the metal which weakens and sometimes cracks the metal.

This phenomenon is actually more prevalent at high temperatures.
gunslingor1
not rated yet Aug 12, 2010
Javinator,

hmm... well, I could very well be wrong. It's not my field. Anyway, if you are right, I'm sure there is a way to account for this affect with good engineering.