GB1101093A - Electrodeposition of nickel - Google Patents

Abstract

In a process of electro-depositing (e.g. electroplating or electro-forming) Ni from a plating bath containing 500 to 700 g/1 of nickel sulphamate, the electrolyte is subjected to subsidiary electrolysis using a nonactivated Ni anode at a current density of from 1 to 30 A/sq. ft. on the subsidiary <P\1> anode surface. By non-activated Ni is meant Ni which contains only such very minor proportions of depolarizing elements (e.g. S, P and Si) an impurities that its anodic dissolution potential under any given conditions is substantially the same as that of pure Ni under the same conditions. The subsidiary electrolysis serves to purify the electrolyte. By the process, desired stresses can be obtained in the deposited Ni. The plating anode may be of non-activated or activated Ni. Fig. 2 shows a plating bath 1 containing a workpiece 4, shield 5, main plating anode 2 and subsidiary anode 3. The subsidiary electrolysis, instead of being performed in the plating bath, may be performed in a subsidiary tank and the electrolyte be circulated between this tank and the plating bath. The subsidiary cathode may have a corrugated surface so as to have a varying current density over its surface thus aiding the removal of a wide range of contaminating metals. In an example an electrolyte containing 600 g/1 nickel sulphamate 10 g/1 nickel chloride 40 g/1 boric acid is purified by a two-stage electrolytic process and cathodes are then plated for 30 mins at 50A/sq. ft. on the cathode surfaces.