Katsuo Mitsuji

52863662, Feb 15, 1994

Nov 5, 1991

7/788181

Katsuo Mitsuji - Alma MI

Hitachi Magnetic Corp. - Erdmore MI

C25D 510
C25D 534

205176

A magnetically anisotropic magnet substrate is coated with a triple layer of nickel plating preferably followed by a chromate layer. The layer of nickel plating includes an inner layer of a non-bright nickel plating, followed by an intermediate nickel-strike layer, followed by an outer layer of a semi-bright nickel plating. The inner layer contains much less sulfur than the other two layers, whereby the resulting difference in electromotive force provides a localized battery that permits the outer layers to be sacrificed without permitting the inner layer to be destroyed. One embodiment adds a copper under-layer below the nickel plating.

53486390, Sep 20, 1994

Aug 6, 1991

7/740999

Katsuo Mitsuji - Alma MI

Hitachi Magnetics Corporation - Edmore MI

C25D 534

205181

A surface treatment for a R-TM-X type of permanent magnet comprising the steps: Etching the magnet with nitric acid having a concentration of 0. 2 to 10 vol %, then etching the magnet with a mixture of oxygenated water having a hydrogen peroxide concentration of 0. 2 to 10 vol % and acetic acid having a concentration of 10-30 vol %, and next plating the magnet with a copper plating initially followed by a nickel plating. R represents an element or a mixture of rare earth elements, TM is mainly composed of iron and transition elements other than iron and X represents one or more of a mixture of elements to enhance the coercivity of the magnet. This improvement of the magnet material itself improves the corrosion resistance of the protective film on the magnet surface.

53324889, Jul 26, 1994

Mar 1, 1993

8/024519

Katsuo Mitsuji - Alma MI

Hitachi Magnetics Corporation - Endmore MI

C25D 500

205181

A magnetically anisotropic magnet substrate is coated with at least one layer of nickel plating followed by a chromate layer. The chromate top layer improves the corrosion resistance of the coated magnet substrate. In a preferred embodiment, the layer of nickel plating includes a first layer of a non-bright nickel plating followed by a second layer of a semi-bright nickel plating. One embodiment adds a copper under-layer below the nickel plating.