An Experimental Study on the Effect of Aqueous Hypophosphite Pre-Treatment Used on an Aluminium Alloy Substrate before Electroless Nickel Plating

Abstract:

A new surface pre-treatment procedure has been developed in one of our laboratories [1] for electroless nickel (EN) plating, which appears to be an effective and environmentally benign treatment for the following deposition of a sound and high quality surface nickel coating with good adhesion. For that purpose, the aluminium substrate was immersed in a mildly acidic solution (lactic acid) of sodium hypophosphite in order to modify the passive surface and make it suitable for the reductive chemical precipitation of the nickel-phosphorus nuclei from the electroless nickel plating bath. During this novel pre-treatment technique, the surface adsorption of the hypophosphite anions play an important role therefore several advanced surface testing and analytical techniques (Scanning Electron Microscopy-SEM, Transmission Electron Microscopy-TEM, Energy Dispersive X-ray Spectrometry-EDX, X-ray Photoelectron Spectroscopy-XPS were applied in order to monitor and characterize the surface reactions and adsorption phenomena taking place during the pre-treatment. The Al excited XPS (studying P 2p, O 1s, C 1s, Al 2p, Ni 2p photoelectron lines) proved to be one of the most powerful technique in the identification of the chemical species formed and present on the surfaces examined in this study.

• Periodical: Materials Science Forum (Volume 659)
• Pages: 103-108
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.659.103
• Online since: September 2010
• Authors: Georgina Szirmai, József Tóth, Tamas I. Török, Norbert Hegman
• Keywords: Electroless Nickel Pre-Treatment, Sodium Hypophosphite, XPS

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