Where the
world gathers for metal finishing
Q&As since 1989


-----

Cyanide bombing to clean up gold jewelry

1996

Dear Sir,

We manufacture award jewelry. I'm looking into setting up a cyanide/bombing sink. Is this still the preferred method to clean soldering scale and oxidation from karat gold and silver? Is there a more environmentally friendly alternative?

Thanks,

Dennis Dion

---

I'm not sure what you mean by "bombing" but analytical bombs are pressure vessels that are heated with reagents inside them to decompose hard to react substances or to conduct tests such as for caloric value. Anyway, here's my shot at an answer to your cyanide question.

Yes, we in the plating and surface finishing business still use cyanide for cleaning metals (occasionally), but we have learned to try other things first, mostly because of environmental restrictions. You will find that the cyanide free products are much more acceptable to the regulatory types and they won't scare the average person so much either. Even when you know the dangers involved in improper handling and you use the acceptable ways to properly treat cyanide wastes, it's sometimes less trouble to go with a non-cyanide alternative.

Here are a couple for cleaning metals. Try any proprietary cleaner with a chelating agent such as EDTA, NTA, or ammonia [on eBay or Amazon]. They all tend to dissolve base metal residues (oxides, salts) such as are in soldering scale and the wetters will help lift off any organics too. Proprietary acid cleaners are also a good alternative. Some use citric and other organic acids.

By the way, none of these cleaners or their rinses can legally be dumped directly to sewer if they contain metals, either suspended or dissolved, but at least you don't have to worry about CYANIDE in your wastewater. Check with the cleaning agent supplier for proper treatment and disposal methods.

Bill Vins
microwave & cable assemblies - Mesa (what a place-a), Arizona
1996

---

The "bombing" that Mr. Dion is talking about is covered in topic 82.

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