Proper treatment and storage of copper electroforms and masters?

A. Hi, Hernando. Look into a dip into benzotriazole ⇦this on eBay or Amazon [affil links] followed by favorable storage conditions. This copper preservative is available as a proprietary from plating chemical distributors if you want some technical support and experience rather than experimenting with raw chemicals. Best of luck.

Regards,

A. Hi, Aaron. I think that what you need for copper electroforms is a dip in benzotriazole. Good luck.

Regards,

A. Mirror finished cavities of valuable injection molds (made of either steel or copper) are protected with a mist of a mixture that evaporates leaving behind a thin coating of a wax or rust inhibitor compound before storage. When ready for next use, it can be readily wiped off with clean paper tissues moist with solvent. The product is sold in inexpensive spray cans. Look for mold releases or mold rust preventatives. Another option would be to immerse them in mineral oil.

Hi, Aaron. Yes, Benzotriazole is fairly soluble (20 g/l) -- but immersing things into it for storage is not the way I've seen it used. I've seen it applied by dipping the article and removing it. It is a conversion coating for copper, forming insoluble complex cupric compounds. I've seen the electroforms stored for periods of perhaps a month after treatment in a cabinet in an air conditioned room. If wrapped in VOC paper/plastic I don't think there will be any deterioration in that time period.

Argon sounds like it would work, but probably be more complex than necessary/ Good luck.

Regards,

A. Hi, Dante

I haven't heard that, and hope someone will inform me about it. But I believe that some electroformers treat copper masters with sodium benzotriazole and keep them clean and dry for fairly long periods (weeks or months).

Regards,

A. Hi Dante,

We have had pryo discussions before.

I recall being approached some years ago by someone using acid copper for this application. He wanted to try copper pyro to see if this was as susceptible to the problem you describe as acid copper is. This is not one of tarnishing for which benotriazole, suggested by Ted, would do. It was one of a change of structure which would take place within 24 hours of plating if the electroform was held at room temperature. By refrigerating, the process was slowed down and they would remain usable for a couple of weeks.

There was a simple test which consisted of using a scalpel or similar sharp tool to scratch/gouge copper from the surface. If a continuous spiral was obtained then electroform was usable but if the copper formed small chips, it was not.

Copper pyro electroforms remained OK for several weeks. I don't know if they were susceptible to the structural changes and ever failed. Typically, the company decided stay with the devil they knew. That's metal finishing folks.

Very interesting, Harry. Thanks! I've never been employed by an electroformer, but my recollection from visits to a vinyl record manufacturer and another electroformer were that after the benzotriazole dip, the masters were simply put in a "drafting file" style metal storage cabinet protected with VOCs and kept in a regular air-conditioned room for a period of at least several weeks ... but recollections can be faulty :-)

I suppose it's possible the copper masters were created in copper pyrophosphate, but it was a long time ago and the copper plating process was not what I was looking at, so my guessing won't help :-)

Regards,