Grain size effect in corrosion behavior of electrodeposited nanocrystalline Ni coatings in alkaline solution

Effects of grain size reduction on the electrochemical corrosion behavior of nanocrystalline Ni produced by pulse electrodeposition were characterized using potentiodynamic polarization testing and electrochemical impedance spectroscopy; X-ray photoelectron spectroscopy were used to confirm the electrochemical measurements and the suggested mechanisms. The corrosion resistance of Ni coatings in alkaline solutions considerably increased as the grain size decreased from microcrystalline to nanocrystalline. The higher corrosion resistance of NC Ni may be due to the more rapid formation of continuous Ni(OH)2 passive films compared with coarse-grained Ni coatings. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.