TITLE:
Chromium Electroplating of Aluminium Alloys Using Electroless Nickel as Underlayer
AUTHORS:
Chike F. Oduoza, Enam Khan, Tarsem Sihra
KEYWORDS:
Aluminium Alloys, Electroless Nickel, Chromium Plating, Corrosion Testing, Scratch and Hardness Testing
JOURNAL NAME:
Journal of Materials Science and Chemical Engineering,
Vol.2 No.7,
July
28,
2014
ABSTRACT:
The
growing demand for chromium coated aluminium components especially for the
automotive industry is due to their favourable physical properties (density,
strength to weight ratio etc.). However, their frequent use under harsh
environmental conditions renders them corrosion sensitive and consequently they
need to be protected. An approach that has been applied in industry is to
directly electroplate nickel onto aluminium substrate prior to a top metallic
finish; however, in components with complex geometry, certain areas could
become exposed to corrosion attack due to poor surface coverage during plating.
In this study, a modified electroless nickel undercoat was applied to
pre-treated aluminium alloys prior to duplex nickel and chromium plating with a
view to enhance corrosion resistance, improve coating adherence and durability,
and overall, to achieve substrate protection. Hexavalent and trivalent chromium
were applied to pre-treated Al 1050 and Al 6061 following electroless nickel
deposition, and plating performance was assessed by surface and corrosion
techniques, while durability was measured by scratch, adhesion and hardness
tests. Overall, while chromium plating with an electroless nickel undercoat did
not improve corrosion resistance or hardness of the materials, it provided an
additional protective layer for the substrate with a potential for longer term
durability.