Metal finishing Q&As since 1989

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What makes plating stick?

2007

I think perhaps I should be able to work this out for myself but.....
Could you briefly explain what makes electroplating stick to the parent material.
Since straightforward immersion of any electronegative alloy/metal (say copper or steel) will be plated with silver in a simple solution of a silver salt, will not adhere, but simply drop off, whatever the surface finish or cleanliness.
So I presume it's the current and/or composition of the electrolyte.
Some guidance on what's going on please.
Best regards

Martin Rich
Metallurgical Technician - Plymouth, UK

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I can't answer precisely, Martin, but in general: slowly applied current can cause the reduction from ions to metal to occur right at the surface and at a slow enough rate that a proper crystal structure can be built upon the surface of the substrate. Electricity applied at too great a rate, whether externally applied or by immersion deposition, can cause the ions to instantly reduce to metal while they are still a loose conglomeration.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

Also, please note that in immersion plating, a dissolution of the substrate is taking place at the same time as the deposition of the more noble metal. So, this surface is not stable during the process, but continuously interchanging ions. In electroplating, the deposited ions always travel in the same direction and the surface is not disrupted.

Guillermo Marrufo
Monterrey, NL, Mexico
2007