Fe Thin Film-Coated Optics for Corrosion Monitoring: Optical and Electrochemical Studies

Corrosion proxy materials integrated with an optical sensing platform enable a real-time optical corrosion sensor for natural gas pipelines to prevent methane leaks and catastrophic events. Effects of CO2, pH, and film thickness on corrosion of Fe thin films (25 nm, 50 nm, 100 nm) were studied using optical and electrochemical methods in 3.5 wt.% NaCl solutions at 30°C. An increase in light transmission (T%) corresponded to corrosion of Fe thin films. CO2 accelerated corrosion of Fe thin films because of the lower pH and the promoted corrosion reactions, resulting in a faster increase of T% than without CO2 or at higher pH. While the corrosion rate increased with increasing film thickness, electrochemical corrosion of Fe thin films was in good agreement with that of bulk carbon steel, verifying that Fe thin films can serve as a representative corrosion proxy when integrated with the optical sensing platform.