Letter 34076

Copper plating from hydrochloric acid  

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Hello,

Could anyone recommend a source for paper / publication on plating metals in Hydrochloric acid? There seems to be precious little available on this topic.

As you can see from the above I am a plating noob.

Edouard Gerard
waste acid recycling - Singapore

If I am looking at your picture correctly, do I see a 2 expanded mesh electrodes (they look like they have DSA coating on them?!?) in a glass beaker?

Well, lets start off with the simple things:

1. You can plate copper out of an HCl solution, but it takes one heck of a lot of current. Since your buisness claims to be in spent acid recycling, do i take it your looking at removing copper from a copper chloride (cupric) etch bath? If so - then good luck.

2. The chloride background of the bath is so strong and stresses the deposit so much that what you will see happen is really just a bunch of dendritic deposits forming. Copper electrodeposited from a chloride bath forms an elongated, columnar metal crystal - ripe for making dendrites (or tree's). These will grow much faster than any deposit that you may get on a flat surface of a cathode.

3. High surface area cathodes will etch off the conductive copper foli surface long before you can actually get anything to plate on them. In most cases, the cathode foam becomes useless. You also cannot get a high enough current density to overcome the etch rate of the solution on a HSA type electrode without it typically catching on fire (it does make pretty blue flames, however, when it does!)

4. The typical current density that you will have to use is actually well over 100 asf. This can be brought down if the concentration is more dilute, but that might not be feasible in your application. Also, if the solution is heated in any fashion (either intentionally or due to the inefficiency of the reaction itself), the current density will need to go even higher.

I'd be happy to discuss my experience with you further - I have done many years of R&D on this very application, and there are ways to get around some of these issues, but if your looking for a quick and dirty plate it out type system, your not going to be very happy with what you have. We do have other types of acid recovery technologies, however, that might be more useful to you to evaluate, but would need more specifics.

Tom Baker       wastewater treatment specialist Warminster, Pennsylvania

Mr Baker,

Thanks for your response.

The picture is of a single DSA mesh anode with a Ti cathode.

The current density was quite high indeed, and quite a lot of chlorine was being evolved.

The aim of the exercise was to see what kind of solution would remain after plating out the copper to the limit of what is expedient, and the kinds of likely treatment solutions that would be required there after.

Edouard Gerard
- Singapore

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