Abstract
A study of the effects of chromium (III) ion added as CrK(SO4)2 on average internal tensile stress in nickel deposits electroplated from a Watts bath of pH3.0 enabled us to detect variations in elastic deformation in deposits in situ using a resistance wire strain gauge on the reverse side of a copper electrode.
Chromium (III) ions close to the electrode surface changed to chromium hydroxide due to increased solution pH during nickel electroplating with hydrogen evolution. This is included in deposits as chromium oxide and chromium hydroxide.
With increasing CrK(SO4)2 concentration, total chromium oxide and chromium hydroxide in deposits increased and average internal tensile stress in deposits also rose. Internal tensile stress rose markedly at 1.5mM CrK(SO4)2, causing numerous cracks on the surface of nickel deposits at a concentration of 2.0 to 10.0mM CrK(SO4)2. The dependence of chromium oxide and chromium hydroxide content on CrK(SO4)2 concentration showed that these two compounds greatly enhance internal tensile stress in nickel deposits.
