Mössbauer investigations of some chemical treatments of iron surfaces

Abstract

The nature of corrosion- and abrasion-resistant surface phases formed by the chemical treatment of iron-containing solids has been investigated by conversion electron and conventional transmission mode Mössbauer spectroscopy. Corrosion-resistant films produced by oxidising alkaline solutions contain iron(III) oxyhydroxides and their formation appears to resemble the actual process of corrosion. Nitriding processes which harden the surface by reaction of the metal with cyanide ions give superficial phases which include the iron nitrides Fe₂N and Fe₄N. Sulphiding processes produce abrasion resistant surfaces by reaction of the metal with thiocyanate ions and give a surface phase containing the iron sulphide ‘Greigite.’ No evidence was found for the presence of iron carbides in materials treated by cyanate or thiocyanate.