Reusing PCB Etchant?

bpeezer

bpeezer

Joined
Jan 27, 2013
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Just wondering if it's possible to recycle or get multiple uses out of PCB etchant for acid washing blades. I wouldn't want to dump some of the scum back into the container, but it seems like there's a lot of clean acid left unused.
 
bpeezer said:
Just wondering if it's possible to recycle or get multiple uses out of PCB etchant for acid washing blades. I wouldn't want to dump some of the scum back into the container, but it seems like there's a lot of clean acid left unused.
Click to expand...

I've done reused PCB etchant for a few cycles. Very minimal use really though. I'm sure eventually you will need to replace the etchant, but if you're reusing it only a few times it should be fine.
 
Thanks! I'm really just experimenting with it right now, I just didn't want to go through 5 bottles figuring out if I actually like it or not :o
 
There's only so much acid that can react with the metal, so reuse is possible, but it's finite and will give diminishing return (i.e. weaker/slower the next time).

As exaggerated and simplified example: a measure that's being used now contain 10 gr of pure acid. For each blade (assuming same size, surface area & material) it takes 1 gr.
The next time it's used, the acid is only 9 gr of same liquid volume (=diluted), so it might take slightly longer for the next 1gr to react fully, as each volum/surface contact will have 10%less acid.

Hope this helps.
 
Last edited:
Chris "Anagarika";12665473 said:
There's only so much acid that can react with the metal, so reuse is possible, but it's finite and will give diminishing return (i.e. weaker/slower the next time).

As exaggerated and simplified example: a measure that's being used now contain 10 gr of pure acid. For each blade (assuming same size, surface area & material) it takes 1 gr.
The next time it's used, the acid is only 9 gr of same liquid volume (=diluted), so it might take slightly longer for the next 1gr to react fully, as each volum/surface contact will have 10%less acid.

Hope this helps.
Click to expand...

It seems that the "used" acid takes on a slightly different appearance than the acid that didn't come into any contact with the blade. I have been trying to simply separate the acid that was actually involved with the reaction and avoid pouring that back into the bottle. That way it's not a big deal if I pour in more acid than I need, as I only dump out the acid that was really used. I know I could dump it all back in and continually dilute the acid, but I'd like to avoid dilution as much as possible. Thanks for the thought experiment, it did help :)
 
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