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"Parts turns blue after silver plating"

February 1, 2010

Q. Greetings,

Copper parts requiring Ni-Ag plating has become a norm for my company.
However, recently these parts turn blue after silver plating.
I wonder what causes it & what's the countermeasures?

Eagerly looking forward to replies

Mel Y
Engineer - Singapore

February 2, 2010

A. You cannot rinse off cyanide, so dip in 5% acetic acid, then apply a weak aluminum chromate, then it will not tarnish.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

February 4, 2010

A. Mel Y,

I agree that removing the residual solution/salts from the surface is critical. Generally an immersion rinse of cleaned water RO or DI works very well. You can make your rinsing system more effective by vigorous agitation and heating the water 50 deg C and hotter. After you get your parts clean, you will need to prevent sulphur from coming in contact with the silver and promoting your oxide layer (blue color). Sulphur is present in high enough quan. in air to start the oxide. You can block the attack with sulphur free packaging. You can also use an additional organic post dip specifically designed to prevent these issues. These are available in aqueous and solvent based formulations. There are at least two that are sold in the US and Europe. I would guess that a quick search would find a supplier in your area. These post dips are currently being spec'd for automotive electronic applications. They do not have the various issues that using Cr brings.


Thomas Horn
- Indianapolis, Indiana, USA

December 23, 2018

Q. Is it safe to use the silver plate with food while it is still blue?

Sharon Wingate
Consumer - Washington, DC USA

December 2018

A. Hi Sharon. What do you mean 'still blue'. What silver plated item do you have that is 'still blue'? Did you buy it blue? Are you sure it's actually silver plated? Did it turn blue? Is it brand new just out of the box or have you had it for years. Please tell us your situation -- people can't attempt to answer your question until we understand it.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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