Temperature and humidity—two factors that influence corrosion— are routinely monitored in museums to protect the artifacts from the ravages of time. However, corrosion is dramatically accelerated by air containing pollutants such as nitric or sulphur oxides. If unchecked, corrosion can literally pulverize metals over time.
Now, scientists have developed a new type of sensor to monitor corrosion in metals, under the EU-funded consortium MUSECORR. The device is up to 2,000 times more sensitive than the current technology, and works in real-time.
The sensor is about the size of printer cartridge and contains a tiny sheet of metal. If the metal corrodes, the electrical resistance increases. Thus corrosion can be monitored in real-time. Part of the metal track is protected by an insulating coating and is used as a reference to account for changes in temperature. "If there is a danger of corrosion, you are alerted immediately and take countermeasures. You cannot do it with the current systems," says Tomas Prosek from the French Corrosion Institute (ICO) in Brest who coordinates the project.
By contrast, the current method for monitoring corrosion relies on so-called metal coupons. These are exposed next to the artworks and are brought to a laboratory every few months to check for rust. The analysis itself may take up to one month. "During this period, valuable objects might further deteriorate if there is air contamination," says Prosek. The metal track in the new sensor is up to 10,000 times thinner (50nm) than current coupons and is therefore more sensitive.
Besides museums, the sensor may be useful in many industrial applications where it is essential to check for corrosion. Prosek says that a US- based paper company is currently testing the prototype developed for museums to monitor its sensitive equipment, such as computers. These may be affected by the highly corrosive environment associated with pulp and paper production.
There are also plans to use the new sensor in some parts of car bodies and in ships, where corrosion is a major issue. Project researchers are currently testing the device by collaborating with both car manufacturers and with the French Navy.
Techniques like to monitor corrosion are needed by industry, says Robert H. Heidersbach, Jr., a corrosion expert based in Cape Canaveral, Florida, USA, affiliated with the Intota Expert Network. "The increased sensitivity will prove useful in many mildly-corrosive environments, like atmospheric corrosion both indoors and outdoors,” he says. However, “it may not be as useful in monitoring aqueous corrosion rates, where localized corrosion (e.g. pitting corrosion) is the most likely mode of corrosion attack."
By Sergio Pistoi