GB761466A - Improvements in or relating to methods of applying metal layers by electro-deposition - Google Patents

Abstract

761,466. Electrodeposition. NAAMLOOZE VENNOOTSCHAP PHILIPS GLOELAMPENFABRIEKEN. Nov. 18, 1953 [Nov. 21, 1952], No. 31978/53. Class 41. A method of electrodepositing a metal layer on an object comprises applying a voltage across the object and an electrode and interposing an auxiliary electrode between the object and first electrode, relative movement between the object and auxiliary electrode being provided such that for each portion of the object a current of varying magnitude is produced, the auxiliary electrode being at least periodically negative with respect to the object. The object may be a disc supported in a bath above and parallel to a stationary anode, a sector-shaped auxiliary electrode being arranged coaxially between the disc and anode. A constant potential of 2 volts is applied between the anode and the disc and the sector is made 1.5 volts negative with respect to the disc. The disc or the sector is rotated whereby the direction of current flow to each portion of the disc is re-. versed once per revolution as that portion comes opposite the negative sector, which may have convex side edges. The sector may be screened on the anode side. If the object is a cylinder or shaft, the auxiliary electrode is a coaxial curved plate, and the anode a cylinder, and if the object is a rectangular plate the auxiliary electrode is likewise rectangular having one dimension equal to that of the plate and one unequal. In this last example, only the auxiliary electrode moves, between the object and an anode. In all the above embodiments, the direct negative voltage between the object and the auxiliary electrode may be replaced by an alternating voltage or by a pulsatory direct voltage which makes the auxiliary electrode only periodically negative relative to the object.