PURPOSE: To form a magnetite layer having high resistance to corrosion on the surface of metallic powder consisting essentially of iron by forming an oxidized film on the surface of said metallic powder, then oxidizing the same in an aq. soln. contg. ferrous salt and alkali.
CONSTITUTION: Iron powder or the like is subjected to forced oxidation in a gaseous phase in an oxygen atmosphere under the reduced pressure or to an oxidation treatment under controlled content of oxygen in a liquid phase to form oxidized film on the surface thereof. Said iron powder is added and dispersed into an aq. soln. contg. ferrous salt such as ferrous sulfate and alkali such as caustic soda, and an oxidative gas such as air is blown thereto to cause reaction, whereby the dense magnetite layer is formed on the surface of the iron powder and the corrosion resistance thereof is improved remarkably.
HAYASHI AKINARI
SUEYOSHI TOSHINOBU
TASHIMO KATSUNORI
AMAMIYA MASAHIRO
