Laser-based multichannel fiber optic sensor for multipoint detection of corrosion

Abstract

We report on a multichannel sensor for multipoint corrosion monitoring of an aluminum film, which was corroded by nitric acid as a corrosive solution. The sensor head was a commercial 1×4 optical fiber coupler combined with the optical time domain reflectometry technique. The effects of the concentration and pH of acid on the corrosion rate of the aluminum film are initially studied and characterized. Then, about 100 nm of pure aluminum is coated on the end facets of each fiber channel and reduction of the back reflected signals is simultaneously monitored as a measure of corrosion rate. It is found that the fabricated sensor is very sensitive to the variation of pH as by increasing of the pH up to ~13, the corrosion rate of aluminum is raised to ~75 millimeter per year. Our experimental results have been verified by the standard immersion test, indicating very good consistency and reliability. Eventually, the sensor is used to trace the corrosion of sea water provided from the Persian Gulf, confirming the validity of laboratory results.