In-situ Studies of the Initial Atmospheric Corrosion of Iron

A unique experimental setup has been developed with the intent to provide molecular information during initial atmospheric corrosion of the iron surface. Infrared reflection absorption spectroscopy (IRAS) and quartz crystal microbalance (QCM) have been integrated into one surface analytical system. The results show that an aqueous adlayer of constant mass was physisorbed on the surface at a given relative humidity. The aqueous adlayer was found to be thicker when compared to previous studies performed on copper. A linear relationship between mass change and the intensity of the water absorption band at 3400 cm^-1 (IRAS) was found when altering the relative humidity. At high relative humidity a thick aqueous adlayer was formed, whereby an absorbance band at 1100 cm^-1 was observed that disappeared when dry air was introduced. When introducing SO₂ and O₃ in the sub-ppm range, the formation of sulfate surface species could be monitored quantitatively with monolayer sensitivity and a significant increase in reaction kinetics could be discerned.