Goro Shimaoka and Kichizo Niwa
The procedures of electrolytic polishing of 18-8 and 18 Cr stainless steel in electrolyte containing H2SO4, H3PO4 and glycerine (1:3:1, by vol.) were examined by electron diffraction. (1) In the first process of electrolysis, the surfaces gave sharp α -Fe patterns. In the process of brightening, the surfaces gave diffuse patterns of α -Fe overlapped by Fe3O4. These diffuse patterns changed into 2 diffuse haloes when the surfaces were treated in this process again and again. In the process of active gas evolution weak γ -FeOOH patterns appeared. (2) Though slightly electrolytically polished surfaces had a tendency to increase oxide formation, sufficiently polished surfaces showed rather decrease or stop of oxide formation. (3) Transmission patterns of thin sections in electrolytically polished surfaces showed no reformation of elements in alloys. (4) Results of low temp. air oxidation indicated that the oxide films of electrolytically polished surfaces might be solid soln. of γ -(Fe,Cr)2O3, in which Cr content might be richer than Fe. (5) It was concluded that, in the process of brightening, dissolution and formation of surface oxide proceeded almost continuously under the condition in which amorph. oxide layer covered the surface, and this resulted in a bright surface.
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