John, S. and Pushpavanam, M. and Shenoi, B.A.
(1985)
Studies on post-treatment of gold plated silver.
Bulletin of Electrochemistry , 01 (02).
pp. 129-130.
ISSN 0256-1654
Abstract
Silver articles like jewellery, silverwares, cosmetic containers, novelties, presentation
items etc. are usually plated with gold in very thin deposits to give good appearance and
to protect silver from tarnishing. A verythin deposit of gold is often porous, and the silver
tarnishes through the pores. This tarnishing will spread laterally over the gold and the
whole component will turn black. This is often thought to indicate that the gold has
tarnished, but this is not true. Thick layers of gold is useful in preventing tarnish films.
However, it is very expensive. Other methods of reducing the tendency of silver to
tarnish are to coat the surface with a special lacquer, grease, oil or wax or to apply special
oxide or chromate films. Electrolytic treatment of goldplated silver in an electrolyte
containing 40 g/l potassium chromate, 40 g/l potassium carbonate at pH 8.8 at a
cathodic current density of 2.5 A/dm2'for 1-3 minutes significantly improves the tarnish
resistance as revealed by the accelerated stain proofing test
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