Optical Sensors for Corrosion Monitoring

The new regulations imposed by the environmental protection agency (EPA) in the USA and REACH in Europe has forced manufacturers to use chromate-free corrosion protection. These new treatments and paints may perform differently to the traditional protection coatings based on chromates. Therefore, quantitative information about corrosion is a key parameter in these structures treated with the new protection. This chapter covers the different techniques and devices for the detection of corrosion by means of optical methods. Most of these methods pursue a nondestructive evaluation of the structure to be monitored that can be from a civil construction to an aircraft. In the former case the detection of corrosion has to be performed in reinforced concrete. In the latter, the whole structure is metallic. Usually, these sensors measure the by-products generated by corrosion, and therefore, are in fact chemical sensors that monitor specific substances that can give information about corrosion. Other approaches involve the coating of an optical fiber with a metallic film that can suffer a similar corrosion to the structure that the device is monitoring. This chapter reviews all of these techniques.