Hydrogenation and cracking of nickel coatings electrodeposited in the presence of brighteners

During cathodic polarization in an acidic media containing hydrogenation-enhancing additives, nickel absorbs large quantities of hydrogen and a new crystal phase, nickel hydride is formed. The investigation of the phase transformation of electrodeposited nickel into nickel hydride under cathodic charging showed that the organic compounds 1,4-butynediol and saccharine, both being typical representatives of two classes of additives for nickel electrolytes, which are usually added in order to improve the properties of the layers such as their appearance, internal stresses, etc., contribute to a more complete phase transformation of nickel into nickel hydride. This is assisted by the fine structure of the nickel deposits with a higher density of defects as well as the incorporated compounds containing sulphur as a product of electrochemical transformation of the saccharine. The type of the additives influences both the tendency of the nickel layers to form cracks and the shape of the cracks.