PURPOSE: To produce a magnetic metal powder having sufficient corrosion resistance without deteriorating the initial characteristic by forming an oxide film on the surface of a magnetic metal powder obtained by reducing the vapor of a metal halide contg. iron, etc., and forming a chromium oxide film thereon.
CONSTITUTION: The vapor of a metal halide (e.g. iron chloride) contg. at least one kind among iron, cobalt and nickel is reduced by a reducing gas (e.g. gaseous hydrogen) to obtain a magnetic metal powder. The powder is cleaned, then brought into contact with an oxygen-contg. gas (oxygen concn. is kept at about 1-3% at the start and at 21% at the end) at 10-100°C to form an oxide film on the surface and stabilized. The powder is dipped and dispersed in an aq. soln. of a chromium compd. (concn. is kept at 0.05-0.20mol/l) in an inert gas atmosphere for about 3-20min, and a chromium oxide film is formed on the surface. A magnetic metal powder excellent in corrosion resistance is inexpensively obtained in this way.
MAEDA TOMOO
SHIBUYA YOSHIKI
OKUYAMA KEIICHI
