The insertion of hydrogen in metals promotes severe modifications of physical and mechanical properties. in the case of nickel, hydrogen induces intergranular cracking [1] and decrease of ferromagnetism [2]. Hydrogen occupies the octahedral interstices of the fee structure promoting cell expansion. Large amounts of the fcc (β hydride may be produced by high pressure hydrogenation [3] or electrolytic charging [4]. The H/Ni relation (x) in the P hydride range from 0.6 to 1.0, depending on the method and conditions of hydrogenation. The β hydride is known to be metaestable at room temperature and normal pressure [5].

In this work, a thin foil (0.02mm thick) of high purity nickel was hydrogenated by electrolytic charging in a 1N H2SO4 solution with 20 mA/cm2 by 24 hours. AS2O3 was used as catalyst in a concentration of 5xl0−5mol/l. The hydrogenated samples were analysed by X-ray diffraction and SEM immediately after and 4 hours after the charging (room temperature aging).