Hydrogen Absorption into Electroplated Palladium Films and Formation of the Compressive Stress

The relation between the absorbed hydrogen contents and compressive stress in palladium deposits during cathodic electrolysis at current density of 4.0 mA/cm2 in 0.5 M H2SO4 was investigated. Using an electric balance, the amount of hydrogen absorbed in palladium and its evolution during electrolysis were evaluated quantitatively based on the buoyancy attributable to the hydrogen gas bubble. Variation of the internal strain with the absorption and desorption of hydrogen was also measured in situ using a resistance wire-type strain gauge placed on the reverse side of the copper substrate. Compressive strain with hydrogen absorption occurred immediately after cathodic electrolysis began. Then it relaxed spontaneously with desorption of hydrogen from the palladium deposits when the current was turned off. However, buoyancy attributable to the hydrogen gas bubble started after a considerably long elapsed time from application of cathodic electrolysis, which resulted from hydrogen absorption into palladium deposits. The variation of compressive stress with increasing hydrogen contents was described as δσ/δn(Hab), which was -4.6 kgfmm-2 mol%-1 in palladium deposits of 2.5-5.0 μm thickness.