A Study on Corrosion-Process of Iron by Means of Electron Diffraction.

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A systematic study was made on corrosion-products of iron by means of electron and X-ray diffraction, with the following results; When metallic iron is immersed in salt solution, amorphous white precipitate, Fe(OH)_2, is formed as the primary corrosion-product. (1) Fe(OH)_2, thus formed changes into lepidocrocite, γ-Fe_2O_3H_2O, when pH of the solution so very low and oxidation takes place rapidly, while under usual conditions it is oxydized partly lepidocrocite, which combines with the remaining Fe(OH)_2 to form green rust, 2FeO.Fe_2O_3.H_2O. (2) The green rust is oxydized, under usual conditions, to lepidocrocite, while in case oxygen in the solution is less, it changes partly to lepidocrocite, which combines with the remaining green rust giving magnetite, Fe_3O_4, On the other hand, when oxidation is accelerated by H_2O_2, it changes to haematite, α-Fe_2O_3. (3) Goethite, α-Fe_2O_3.H_2O, was never observed in corrosin-products of metallic' iron, and it was concluded that it is formed only from ferric salts: for example from the unstable yellow substance, which is precipitated in aqueous FeCl_3 solution under certain conditions. (4) This very substance was assumed as β-Fe_2O_3.H_2O by Weiser and Milligan, but it is more reasonable to identify it with Fe(OH)_3 isomorphous to Al(OH)_3. Its unit cell was determined by X-ray data: -monoclinic, a=8.99, b=5.12, c= 9.92 and β=86°34'.
社団法人日本物理学会の論文
1951-10-25