Intermetallic compounds A 2 B 7 (A = rare earth, B = transition metal) are of interest for Ni‐MH batteries. Indeed they are able to absorb hydrogen reversibly and exhibit good specific capacity in electrochemical route. To understand the effect of rare earth on properties of interest such as thermodynamic, cycling stability and corrosion, we synthesized and studied three compounds: Y 2 Ni 7 , Gd 2 Ni 7 and Sm 2 Ni 7. Using Sieverts' method, we plot pc‐isotherms up to 10 MPa and study hydride stability upon solid‐gas cycling. Electrochemical cycling was also performed, as well as calendar and cycling corrosion study. Corrosion products were characterized by means of X‐ray diffraction, electron diffraction, Raman micro‐spectroscopy and scanning and transmission electron microscopies. Magnetic measurements were also performed to calculate corrosion rates. A corrosion mechanism, based on the nature of corrosion products, is proposed. By combining results from solid‐ gas cycling, electrochemical cycling and corrosion study, we attribute the loss in capacity either to corrosion or loss of crystallinity.