The influence of monovalent cations on the stability of electrochemically formed nickel fluoride films

摘要

The stability of electrochemically formed NiF_2 film in 1.0 M perchloric acid containing monovalent fluorides namely, NH_4F, HF, NaF, KF and LiF, is investigated using cyclic voltammetry, chronoamperometry, atomic absorption spectroscopy and scanning electron microscopy. In addition to direct dissolution of nickel and dissolution through the oxide layer, a new mode of dissolution of NiF_2 film as NiF~-_3 and NiF~(2-)_4 through complex formation is proposed. This process is significantly influenced by the alkali metal fluorides. On a comparative basis the stability of NiF_2 decreases in the order NH_4F>HF>KF>LiF.