Surface cleaning and passivation of an iron foil by a nitrogen post-discharge surface treatment

Interactions occurring between an argon–nitrogen post-discharge and oxidised iron surfaces are studied by measurements based on optical emission spectroscopy. Transient effects observed for the first 10 min shed light on the partial cleaning which permanently modifies the topmost surface of oxidised iron substrates, as shown by XPS analysis. A special device was built to analyse the treated substrates without breaking the vacuum. The influence of the temperature on surface cleaning is determined. At room temperature, nitrogen is grafted on the iron topmost surface, very likely by means of NCO groups. This is no longer the case at 323 K and 373 K. In any case, the iron foil is not completely cleaned but covered by a thin film which partially protects the iron foil against corrosion.