The surface nanostructure of pure iron after combined electrochemical passivation and thermal annealing treatments

The properties of the surface oxide film on pure iron after electrochemical passivation and thermal annealing treatments were investigated using a variety of techniques. Passivation was carried out with an applied potential of 800 mV (vs Ag/AgCl) for 15 min in a pH 8.4 borate buffer solution at 30 °C, whilst annealing was carried out in air in an electric furnace at temperatures up to 300 °C. Analysis of the surface properties was then carried out using X-ray diffraction to determine oxide composition, a spectroscopic ellipsometer to measure the optical properties and oxide thickness, and a scanning probe microscope to measure the surface roughness using tapping mode AFM and to observe the nanoscale structure using constant height mode STM.