Ferric Chloride

Scott Gravenhorst chordman at flash.net
Wed Mar 11 17:00:07 CET 1998

On Wed, 11 Mar 1998 10:02:05 -0500, "List, Chris"
<Chris.List at sc.siemens.com> wrote:

>Speaking of FeCL, does anyone know if it will etch the anodizing off of
>aluminum (or etch aluminum at all)? This would be a radical way of doing
>I know aluminum can be etched with Chromic Acid, and I think lye (NaOH -
>right?) can do it as well - but I don't think I want to mess with that
>stuff... I didn't feel like buying some FeCL just to try this out.

FeCl works by what is called a single replacement reaction.  This
occurs because the copper on the PCB is more chemically reactive than
the Fe ions in the water.  The copper atoms are ripped free and
replace the iron (Fe) and gradually turns the FeCl to CuCl or copper
chloride and a metalic iron sludge.  Since aluminum is also more
reactive than iron, it should work on that metal too, though I don't
know if the rate of replacement is similar or not.

This works well for the etching purpose without the problem of being
dangerously caustic.

However, both FeCl and CuCl are highly toxic and great care should
still be observed when employing this method.  Gloves and protective
eyewear (lab goggles) are mandatory.

-- Scott Gravenhorst

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