Raman Spectroscopy of Thin Corrosion Films on Iron at 100 to 150 C in Air

Laser Raman spectroscopy (LRS) has been applied for the detection and characterization of thin corrosion films formed on iron in air at a temperature range from 100 to 150 C. In situ ellipsometric measurements have also been conducted for quantitative estimations of the film growth kinetics. It is found that (1) the oxidation of iron in dry air leads to the formation of a surface oxide film composed primarily of magnetite and (2) the water vapor in air accelerates the formation of hematite. The ratio of magnetite to hematite in the surface oxide film appears to increase with (1) increasing water vapor pressure, (2) ascending temperature, and (3) extending oxidation time.