Analysis of oxalate coating on steels by conversion electron Mössbauer spectrometry

Abstract

Mild and stainless steels were treated in an oxalate bath for surface finishing and the chemical states of the iron species, produced in the oxalate coating, were investigated using conversion electron Mössbauer spectrometry. The quadrupole splitting of the iron (II) oxalate produced on the stainless steel was slightly smaller than that of the iron (II) oxalate on mild steel. The chemical states of the deposited iron (II) oxalate on both steels were not affected by rolling, although a large part of the oxaiate coating on mild steel was easily stripped off by the process. It was found that surface conditioning of stainless steel by oxalate was more effective than that of mild steel, and that the different states of FeC₂O₄ were formed as a thermal decomposition product by the different thermal treatment. The thermal property of oxalate coating was similar to that of FeC₂O₄·2H₂O. The oxalate coating is concluded to work as a good lubricant rather than a corrosion-resistant material, especially at the surface of stainless steel.