Metal finishing Q&As since 1989
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Silver Plating Problem: Roughness
Intro / synopsis: Roughness is generally caused by suspended solids, and addressed by filtration. Adhesion problems are minimized by using a silver strike process before silver plating.
⇦ (tip: readers rarely show interest in abstract questions, but people's actual situations usually prompt responses) 
Q. What causes the roughness if plating in silver plating? And what are the solutions to be made?
Crispin Grace- Taoyuan, taiwan
December 21, 2018
"The Canning Handbook of Surface Finishing Technology"
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A. Hi Crispin. The Canning Handbook has the best charts of defects vs. causes that I'm aware of →
and says that roughness is caused by suspended solids, and should be solved by filtering or at least letting them settle. Can you give us some background? Thanks.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Poor adhesion
Q. Similar to Crispin Grace we are experiencing rough deposits of normal color and appearance. I checked The Canning Handbook as Mr. Mooney suggested; it says that roughness is caused by the presence of suspended solids. We normally allow the bath to settle overnight, decant the clear solution and filter the last few liters.
This normally is a solution. However, when we cyanide silver plate copper parts, the time of activation makes a huge difference. Copper disks are loaded on racks, degreased, submerged in activation bath (water, 15 w% H2SO4, 5 w% H2O2) for a few seconds. If time of activation is too long the deposit is rough on some parts, if it is too short we experience poor adhesion on some parts - depends on the age and condition of activation bath. Why in your opinion does the activation phase have such a significant effect on the surface roughness?
- Klagenfurt, Austria
July 9, 2019
A. Hi Tobias. Your approach is apparently workable, but seems rather unconventional to me in that the peroxide oxidizing agent turns the activating bath into a bright dip / etch bath and apparently an adhesion promoter if the immersion time causes etching rather than brightening.
I am more familiar with using sulfuric acid without peroxide as the activator, followed by a silver strike bath before the silver plating bath to solve the adhesion problem. Have you tried activating in just the sulfuric acid without the peroxide? Have you tried using a silver strike bath before the silver plating?
It is possible, of course, that you are using a different copper alloy with a different heat treatment schedule such that your approach is indeed more reliable than the one I mentioned; still, silver plating baths tend to "immersion deposit" on copper, causing low adhesion, and this is usually addressed by using a low concentration silver strike bath before the plating bath (which is also useful as a 'trash collector' to minimize contamination of the plating bath).
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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