Hydrogen coevolution and permeation in nickel electroplating

Abstract

Nickel coatings were electrodeposited onto a steel membrane in a conventional Devanathan cell in order to measure the diffusion rate of hydrogen into the steel substrate during electrodeposition. In most cases a Watts' solution containing various organic additives was used: butyne-2 diol-1, 4; saccharine or thiourea. The structure of the electrodeposits was studied by X-ray and Transmission electron microscopy (TEM). It was shown that the electrodeposition parameters (pH, composition of the bath, additives) have a strong effect on hydrogen permeation. The use of organic additives during Ni plating increased the penetration of hydrogen into the substrate. In particular, sulfur-containing additives cause a fast initial increase of the permeation rate, which is attributable to a high surface concentration of Hads when steel is not totally covered with nickel. By performing permeation experiments with Ni coatings during hydrogen charging from a H2SO4 solution, it was shown that hydrogen permeation through nickel coatings is influenced by their fibre texture and by their grain sizes. A low permeation rate was observed in coatings plated in the presence of butyne-2 diol-1,4, which exhibit a strong 100 texture with large grains and a low density of defects. Conversely, the hydrogen diffusion rate is very high in coatings plated in the presence of thiourea or saccharine. These coatings exhibit a weak texture with very small grains.