Diffusivity of Hydrogen in Electrodeposited Cadmium-Titanium Alloy

The likelihood of high strength steel parts showing hydrogen embrittlement after the electrodeposition of a cadmium-titanium alloy plate depends mainly upon the ability of hydrogen to pass out of the steel through the plated coating. This ability, i.e., the hydrogen diffusivity of the plate, was measured using a simple permeation method. Diffusivity values in the range 10⁻⁸ to 10⁻¹¹ cm²/sec were found at room temperature. The surface structure of the deposit was characterized using scanning electron microscopy, X-ray diffraction, and electron microprobe analysis. This characterization was done to relate the surface features and physical structure to the diffusivity. The mode of hydrogen transport through the deposit varies from molecular gas permeation through a porous material to an atom by atom diffusion through a solid material, depending on the structural characteristics of the deposit.