The characteristic features of the electrochemical behaviour of the treated hydrogen-storage alloy TiMn1.6Ni0.4 in an etching solution containing hydrogen fluoride and untreated alloy in alkaline media are investigated. Alloy characteristics such as discharge capacity, high-rate dischargebility and cycle-life are examined. The exchange current density, polarisation resistance and diffusion coefficients are also determined as functions of state-of-charge of the electrodes. The diffusion coefficient is found to be of the same order for the treated and the untreated alloy.