In this work the effect of boric acid on the nickel transport properties through an IONICS 67-HMR-412 cation-exchange membrane was evaluated by means of chronopotentiometry. Nickel chloride solutions with and without boric acid were investigated. The obtained results showed that the addition of boric acid to a nickel chloride solution does not affect the limiting current density value nor the nickel transport number through the membrane. The obtained results also revealed that, under very high current densities, the secondary transfer phenomenon associated to water splitting occurs when nickel chloride solutions are employed, and a bipolar membrane structure is formed, resulting from a Ni(OH)(2) precipitation on the The addition of boric acid to the nickel chloride solution can minimize or avoid this membrane surface. phenomenon depending on the boric acid concentration in the solution. (C) 2009 Elsevier B.V. All rights reserved.