Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing 1989-2024
-----
Remove dried plating salts that leaked into cavities
Q. We sent some electrical components out for silver plating. We spec'd out per ASTM B700 Type II, grade D(99%), Class S (anti tarnish)
The components are small assemblies, with copper conductors. We only desired the copper to be plated. Because we only wanted the copper plated and due to the assembly having small cavities. The assembly was sent out with EPDM synthetic rubber caps/plugs.
We received the parts back. The EPDM was apparently the wrong choice -- looks like we should have chosen silicone. The plating baths dissolved bits of the EPDM caps and allowed the baths into the cavities. The parts we received back have marks left from the rubber and dried plating salts in the cavities.
We have had problems with trapped plating sails before so while I have a specific problem at hand. The solution can be made broader to allow Nickel, Gold and copper plating.
I am looking for some recommendations on removing dried plating salts and bath solution from parts and cavities of parts. I'm thinking this involves dissolving them but without knowing what I need to dissolve I'm not sure what to use.
Thanks
- New York
November 1, 2023
A. Hi E.,
If any actual electroplating occurred, then what you would have to use would depend on which metal you need to remove, and what substrates would remain safe in those stripping agents.
But if the problem is strictly dried plating salts and crud, that should be water soluble. Maybe try putting a few in a small ultrasonic cleaner with a warm mild detergent solution like Simple Green
⇦ this on
eBay or
Amazon [affil links]
?
If it works, but the volume is too high for you, then you would need to find a shop who can do the ultrasonic cleaning for you.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi Ted,
You are correct the problem really is dried plating salts and crud.
I am bit hesitant to use water. The areas of copper that we wanted exposed are still exposed. My thought is the water will oxidize the copper -- furthering my issues. Though the simple green may be acidic enough to remove surface copper and its oxides as they form.
Yesterday the assemblies spent about 6 hours submerged in an acetone ultra sonic bath. The bath gets heated from the ultra sonics, so the acetone was near or at its boiling point of 56 °C (128 °F). The bath was changed multiple times throughout the day and final rinsing and drying was done. The assemblies looked better but still had crud left on them. This morning I inspected them and there was Green/blue re-growth on the copper within the cavities.
From the re-growth, I'm thinking that there are still salts or a reactant (acid, base) left on the surface of the copper. I'm bringing this up because I initially thought that I had to dissolve the dried salts but do I need to be neutralizing a leftover acid or base?
Are plating baths traditionally acidic or basic?
Are there additives that aid the solubility of the plating constituents?
Thanks
- New York
November 2, 2023
A. Hi again, apologies for the delay.
Silver plating is almost always cyanide based (alkaline). Nickel is almost always acid based. Copper & gold can be either.
Plating solutions often have surfactants in them (detergent). I think what is missing in your cleaning effort is detergent, but possibly water as well. I am not confident that crud which is soluble in water and detergent is soluble in pure acetone. Please remember that acetone is highly flammable.
I don't know how valuable these parts are, but maybe you could risk one in the simple green.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q, A, or Comment on THIS thread -or- Start a NEW Thread