The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 06, 2004
Filed:
Jun. 15, 2001
Applicant:
Inventors:
Thomas Kruse, Dortmund, DE;
Peter Meisterjahn, Iserlohn, DE;
Assignee:
Ewald Dorken AG, , DE;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
C25D 1/102 ;
U.S. Cl.
CPC ...
C25D 1/102 ;
Abstract
The invention relates to a method for darkening a superficial layer of a workpiece which contains zinc by anodic oxidation. The workpiece is oxidized in a soaking bath containing an aqueous solution comprised of a hydroxide and of a nitrate. The anodic oxidation may be carried out in an aqueous solution containing NH NO or NaNO , and having a pH value ranging from 8 to 14, at a dipping bath temperature (T) ranging from 15 to 45° C., and with a current density (i) ranging from 3×10 to 0.5 A/cm . The workpiece is placed in the soaking bath at the beginning of the anodic oxidation after the voltage has already been applied.