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US 4,305,795 AGranted
Method for the manufacture of stampers
AssigneeRCA Corporation
InventorCharles A. Weaver
Life of this patent
Estimating the term…
Abstract
It has been found that metal stampers, and more particularly nickel stampers, can be simultaneously hardened and passivated by cathodically treating the stampers in an aqueous bath of a passivation agent.
Claims9
The method for hardening and passivating the surface of a metal record stamper which comprises the steps of:
- (a) immersing the stamper in an aqueous electrolytic bath having dissolved therein a passivation agent selected from the group consisting of sodium dichromate, potassium dichromate, sodium permanganate, potassium permanganate, and mixtures thereof wherein the passivation agent is present in an amount of from about 0.15 to 1.0 gm/l;
- (b) connecting said stamper in a cathodic position in said bath;
- (c) applying a current across said bath sufficient to cause the evolution of hydrogen at the cathode position, said electric current being maintained so as to provide a current density at the stamper surface of about 4 to 6.5 amp/dm.sup.2 ;
- and
- (d) maintaining said current until the surface of the metal reacts with the evolved hydrogen;
- whereby the surface of the stamper is simultaneously hardened and passivated.
3 more elements
Dependencies are inferred from the claim text.