The effect of brightners added to Watt's nickel plating bath on the permeation of hydrogen through steel substrate during plating was investigated by means of an electrochemical permeation technique. The additions of 1,5 naphthalene disulfonic acid, o-benzosulfimide, sodium formate, thiourea, Cu and Fe (III) etc., increase the hydrogen permeation with the amount of their agents, while additions of p-toluenesulfone amide, formalin, Cd, Fe (II), Co, Se and S etc., when present in relatively small concentrations have a marked effect in increasing hydrogen entry during plating. The additions of propagyl alcohol, gelatin and Zn etc., do not affect a remarkable change on the permeation. The nickel deposits from baths contained these additives have relatively a high porosity. The apparent correspondences among the behavior of hydrogen permeation, current efficiency, lattice parameter and half value breadth of x-ray diffraction line of the deposits are not necessarily observed.
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