Corrosion monitoring of stainless steel 304L in lithium bromide aqueous solution using transmittance optical detection technique

We report a method based on the power ratio of transmittance for monitoring the corrosion rate in stainless steel 304L immersed in an aqueous solution of lithium bromide at 50 wt%, at 70 °C. The optical transmittance measured in the solution contaminated with corrosion oxides at different times of exposure is related to the physical degradation of the stainless steel samples. Lasers at 532 and 632 nm were utilized for monitoring the accumulation of corrosion oxides dissolved in the lithium bromide solution of the metallic samples for 480 h. The change in the optical power of transmittance was 13 μW/480 h measured at 532 nm and 3.6 μW/480 h at 632 nm. The variation of the power ratio for 532 nm was from 0.01 to 0.24, and for 632 nm, from 0.01×10−3 to 15.61×10−3; this is proportional to an accumulated corrosion rate of [0.0142×10−3–0.552×10−3 g/cm2] for an exposure time of 432 h.