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Journal of Materials
Volume 2013 (2013), Article ID 985763, 7 pages
http://dx.doi.org/10.1155/2013/985763
Research Article

Effect of Deposition Time on the Morphological Features and Corrosion Resistance of Electroless Ni-High P Coatings on Aluminium

Department of Metallurgical and Materials Engineering, NITK Surathkal, Karnataka 575025, India

Received 26 December 2012; Revised 13 April 2013; Accepted 13 April 2013

Academic Editor: Ram Katiyar

Copyright © 2013 N. Sridhar and K. Udaya Bhat. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

High phosphorus Ni-P alloy was deposited on aluminium substrate using electroless deposition route. Using zincating bath, the surface was activated before deposition. Deposition time was varied from 15 minutes to 3 hours. Deposit was characterised using scanning electron microscope with energy dispersive spectroscope, X-ray diffraction, and microhardness tester. The corrosion resistance was measured using Tafel extrapolation route. The medium was aqueous 5% HNO3 solution. The analysis showed that the deposit consisted of nodules of submicron and micron scale. The predominant phase in the deposit was nickel along with phosphides of nickel. Compared to substrate material, deposit showed higher hardness. With increase in deposition time, the deposit showed more nobleness in 5% HNO3 solution and nobleness reached a limiting value in 1 hour deposition time.