X-ray photoelectron spectroscopy study of the corrosion behaviour of galvanised steel implanted with rare earths

The present paper studies the effect of ion implantation of 2 × 10¹⁶ ions/cm² of Ce⁺ and 2 × 10¹⁶ ions/cm² of La⁺ at 150 keV on the corrosion behaviour of hot-dip galvanised steel. After implantation, galvanised steel was characterised by means of XPS previous to and following immersion in the medium. The results revealed incorporation of cerium and lanthanum on the surface as Ce₂O₃ and La₂O₃, respectively. Electrochemical impedance spectroscopy was carried out in order to evaluate its corrosion behaviour in 0.6 M NaCl during 1 month of immersion. The corrosion resistance was improved by an increase in the charge transfer resistance of the implanted specimens in the medium. This effect could be associated with changes in the morphology/microstructure of the corrosion products layer rather than in its composition variations.