Structure and corrosion behaviour of pure iron bombarded with single- and multi-elements

The effect of multi- and single-element implantation on the structure and corrosion of pure iron in sulphuric acid solution has been investigated. The implanted elements, chosen for their beneficial effect on corrosion resistance, were Yb, Ni, Cr, Ti and Mo. Doses were determined by reference to the composition of corrosion resistant alloys. Transmission electron microscopy revealed the formation of an amorphous layer in the surface and a high density of dislocations in the sub-surface layer. A second phase with polyhedral morphology is induced in the sub-surface layer by multi-element implantation. Corrosion resistance is in general significantly increased by implantation of these ions, though Yb has no effect at low doses. Ti is effective even at low doses because of its property of forming a passivation film. Increasing the Mo dose in Cr + Mo implantation does not obviously increase the corrosion resistance. (5 figures, 2 tables, 6 references). (UK) (author)