Internal Stresses In Functional Chromium Electrodeposits

The internal stresses in thin chromium electrodeposits plated in an additive-free and three solutions containing different additives were determined. The stress-measuring device consisted of an electrobalance which applied a force to prevent the bending due to the stress of a copper or steel strip plated on only one side. The graphs of the force applied by the electrobalance vs deposit thickness showed four distinct regions: (1) compression to a thickness of 5 nm, (2) rapidly increasing tension to 50 nm followed by slight decrease in tension to 60 nm, (3) rapid decrease in tension between 250 and 300 nm and (4) decrease in tension to zero or small compression after 400-600 nm. The tensile stresses were probably caused by hydrogen diffusion out of the surface layer and crystallite coalescence. The tensile stresses were relieved when the deposits cracked. It was found that the deposits with the lowest tensile stresses had the highest degree of preferred orientation and vice versa. The additives affected crystallite coalescence and thereby the stress.