To improve the performances of Nickel-Metal-Hydride batteries, an important step is the understanding of the corrosion processes that take place in the electrode material. In particular, the present study focuses for the first time on the model (La, Mg)(2)Ni-7 system. The calendar corrosion in 8.7 M KOH medium was investigated from 6 h to 16 weeks immersion. By a unique combination of structural and elemental characterisations, the corrosion products are evidenced in those systems. In particular, we demonstrate that Ni and Mg combine in a pseudo-binary hydroxide Mg1-xNix(OH)(2) whereas La corrodes into nanoporous La(OH)(3) needles with inner hollow nanochannels. (C) 2014 Elsevier B.V. All rights reserved.