If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #29
Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500
It seems that by adding about 200ml 29% HCl to 1 litre of a nearly exhausted FeCl3 etchant bath breathes new life into it! All the cloudy black iron floating around disappears and the solution again etches well (becoming yellow tinged with green, Iprobably from increasing CuCl2 content).
I'm not a chemist, but I presume the iron goes back into solution as FeCl3 where it does it's etching work. Any new iron eveolved from the etching process goes back into solution if there continues to be excess HCl in the solution... I don't see any hydrogen evolution taking place, tho'... Any ideas on the reaction?
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
There's a lot of complex reaction go on in the etch bath but here's a rough guide. If you are etching Cu 2 FeCl3 + Cu --> FeCl2 + CuCl2 and CuCl2 + Cu --> 2 CuCl If you are etching steel then Fe+2FeCl3 --> FeCl2 And (anyway). 2FeCl2 +O2 +2 H2O --> 2Fe(OH)3 + 4HCl ( this is the one that produces the brown sludge)
Adding the HCl gets the Fe(OH)3 back into solution as more FeCl3
Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
Adding HCl corrects a bit the pH and sequestrates some Cu as a complex as you have correctly stated and dissolves iron idroxydes, but it doesn't reverse back Fe (II) to oxidizing Fe (III) ion. For this you need an oxidizer with a reduction potential higher than the reduction potential of the Fe3+ (III) + e- ----> Fe2+ (II) reaction. On the net there are many tutorials how to regenerate the etchant
Registered Member #8
Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214
The only way to actually regenerate FeCl3 in the spent solution is to bubble chlorine gas through it, chlorinating FeCl2 to FeCl3. You would remove the CuCl2 with fractional crystallization I guess. All routes to FeCl3 involve chlorine gas. It is made industrially by first chlorinating scrap iron with HCl giving FeCl2, then chlorinating that to FeCl3 with chlorine gas. In any case just a mixture of one part HCl (32%) with two parts topical H2O2 (3%) etches several times faster than FeCl3 and is many times cheaper and less messy. I have etched boards in about 5 minutes with that solution, it attacks copper like nothing else.
Registered Member #69
Joined: Thu Feb 09 2006, 07:42AM
Location:
Posts: 116
Electrolysis could also be used to plate out copper and reoxidize Fe back to ferric in a 'spent' FeCl3 bath. Never tried it but it seems like it would work.
Registered Member #8
Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214
I suppose that would work as long as the electrode potential for the plating is not too high. It would have to be done in a cell where chlorine is not allowed to escape as a gas, like cells for electrolyzing salt to NaClO3/4. Overall it's much simpler than membrane cells and stuff and could be very easy.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.