Process for producing a corrosion and wear-resistant oxide layer with locally reduced layer thickness on the metal surface of a workpiece
AssigneeITT Manufacturing Enterprises, Inc.
InventorsHorst Rothbauer, Ewald Renner
Life of this patent
Estimating the term…
Abstract
The invention relates to a method to produce an oxide coating that protects against corrosion and wear on the metal surface of a workpiece, more specifically, for the metal surface of a body for accepting a valve, wherein with the use of a cathode, the workpiece, as an anode, is subjected to constant or pulsating direct current in an electrolyte, with an auxiliary anode, which is resistant to the electrolyte, being attached to the workpiece before the workpiece is dipped into the electrolyte, which discharges the anodizing current at locations where no anodized coating is required or only a limited anodized coating is required.
Claims17
A method for producing an oxide coating on a metal surface of a workpiece, which comprises:
- providing a cathode in an anodizing electrolytic bath;
- providing said workpiece, as an anode, in said anodizing electrolytic bath;
- providing at least one auxiliary anode in said anodizing electrolytic bath in a vicinity of a portion of said workpiece where said oxide coating is undesirable,
- attaching said at least one auxiliary anode to a cover that is electrically passive in said electrolytic bath, and placing the cover on said workpiece, whereby said portion of said workpiece is closed by said cover, but said at least one auxiliary anode is not in contact with said workpiece;
- subjecting said workpiece and said cathode to a first direct current source;
- and
- preventing formation of said oxide coating in said portion of said workpiece by subjecting said at least one auxiliary anode to the first direct current source or to a second direct current source.
A device for producing an oxide coating on a metal surface of a workpiece, which comprises:
- a cover which is electrically passive in an electrolytic bath, and is adapted to be placed on a predetermined portion of the workpiece where said oxide coating is undesirable;
- at least one auxiliary anode, attached to said cover in a vicinity of said predetermined portion;
- a first direct-current source in a circuit which is electrically parallel to the workpiece, and connected to said auxiliary anode;
- and
- a connection from said first direct-current source to said workpiece or a second direct-current source connected to said workpiece,
- wherein said cover is configured to electrically separate said workpiece from said auxiliary anode when the cover is placed on the predetermined portion of the workpiece, and said cover facilitates reduction of said oxide coating by said auxiliary anode at said predetermined portion.
Dependencies are inferred from the claim text.