An Investigation on Polyethyleneimine and Saccharin on Controllable Electro-Healing Cracks in Nickel

To minimize pores or voids that left after electro-healing by plain solution without additives, controllable electro-healing was investigated in pure Ni plates with a through-thickness crack in a Watts bath by adding polyethyleneimine (PEI) and saccharin. Controllable electro-healing means that the growth velocity of healing crystals from crack tips is much faster than that from sidewalls of the crack, which reduces the number of pores owing to depletion of healing solution. Rotating disk electrode (RDE) was introduced to evaluate the electrochemical behavior in crack tips and crack center. Voltammograms and galvanostatic measurements indicated that PEI exhibits a convection-dependent inhibition effect on Ni deposition. The addition of saccharin will much enhance the inhibition behavior of PEI, controllable electro-healing was achieved with the presence of both PEI and saccharin.