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Etching 304 Stainless Steel with Ferric Chloride Problems



 
 
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  #1  
Old April 5th 04, 06:02 PM
Jon Lorber
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

Hello,

We use Ferric Chloride in a spray etching application to etch 304 Stainless
Steel. We are having problems and cannot determine what they are. We do not
have a scientific background and are just looking for a few simple answers.
When the bath is new it seems to work beautifully. Then at some point we
start to get peculiar undesirable results.

We use 45 Baume Ferric Chloride and etch at 45. The Ferric is less than 3%
hyrdro-chloric acid when received.

The following website I put up clearly demonstrates the problems with
photos.

http://www.precisionsigns.com/badetchingindex.htm

1.) What is actually happening in these pictures? Is part of the steel
decomposing faster than other parts?

2.) What measuring equipment should we be using to monitor the Ferric
Chloride? We have been measuring it's Baume with a hydrometer but should we
also be measuring the pH or anything else? If so, what type of instruments
and what are the ranges that they need to be?

3.) I've heard of regeneration. Is regeneration of the Ferric Chloride safe
to do with HCL (Muriatic)? By safe I mean are there any harmful / flammable
fumes generated? Do I need to make sure that the HCL stays at 3%? And how
much tolerance is there with it?

I feel like I'm on the right track here but need some good advice or
confirmation.


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  #2  
Old April 5th 04, 06:31 PM
Jon Elson
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems



Jon Lorber wrote:
Hello,

We use Ferric Chloride in a spray etching application to etch 304 Stainless
Steel. We are having problems and cannot determine what they are. We do not
have a scientific background and are just looking for a few simple answers.
When the bath is new it seems to work beautifully. Then at some point we
start to get peculiar undesirable results.

We use 45 Baume Ferric Chloride and etch at 45. The Ferric is less than 3%
hyrdro-chloric acid when received.

The following website I put up clearly demonstrates the problems with
photos.

http://www.precisionsigns.com/badetchingindex.htm

1.) What is actually happening in these pictures? Is part of the steel
decomposing faster than other parts?

2.) What measuring equipment should we be using to monitor the Ferric
Chloride? We have been measuring it's Baume with a hydrometer but should we
also be measuring the pH or anything else? If so, what type of instruments
and what are the ranges that they need to be?

3.) I've heard of regeneration. Is regeneration of the Ferric Chloride safe
to do with HCL (Muriatic)? By safe I mean are there any harmful / flammable
fumes generated? Do I need to make sure that the HCL stays at 3%? And how
much tolerance is there with it?

I feel like I'm on the right track here but need some good advice or
confirmation.



What are you using for resist? Is there a possibility that some resist
is left in the large areas to be etched, and affecting the surface?

I only use FeCl to etch copper, as on printed circuit boards. But, I have
a good deal of experience doing that.

How old is your FeCl solution? Have you tried starting with new solution?
You should know that stainless steel is NOT pure iron, therefore, you can't
replenish the etchant with HCl (muriatic acid). You have a significant
Nickel concentration building up in any spent solution.

To test, take a piece of totally clean scrap and try etching it. If you
still get the knobby surface, then it is the etchant that must be the problem.
it is probably full of Nickel, and is preferentially etching the material
depending on small local variations in the nickel mixture, grain boundary
orientation, or something like that.

If it comes out smooth, then your problem is the resist masking process
is leaving a trace of something that blocks the etching action of the
FeCl. I've seen a LOT of that, even water spots left after rinsing
after the resist pattern is developed can do stuff like this. And, the
smooth near an edge but rough in the wide open spaces is something I've
seen before, too.

Jon

  #3  
Old April 5th 04, 07:51 PM
Jon Lorber
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

We use Hydro-coat which is a sprayed on resist most of the time but
sometimes we use a dye cut vinyl mask. I've had the bumpy areas on
un-treated test pieces as well. In fact the last piece with the really bad
etch was done with vinyl masking.

Yes I have found that generally speaking new bath has etched alot better but
I don't know why. I have imagined the exact situation that you mention:

"it is probably full of Nickel, and is preferentially etching the material
depending on small local variations in the nickel mixture, grain boundary
orientation"

I think I can almost see it happening looking at it with a 25x Microscope.
It almost looks like shingling on a house where as its flaking off at
different rates in the same areal.

Will the nickel settle out into the bottom? Can it be filtered out? The
Ferric is 4 or 5 months old. I'm fine with buying new Ferric if I have to
but I just wish that I could determine that it was no good through some sort
of measurement. Thanks for your help!





"Jon Elson" wrote in message
...


Jon Lorber wrote:
Hello,

We use Ferric Chloride in a spray etching application to etch 304

Stainless
Steel. We are having problems and cannot determine what they are. We do

not
have a scientific background and are just looking for a few simple

answers.
When the bath is new it seems to work beautifully. Then at some point we
start to get peculiar undesirable results.

We use 45 Baume Ferric Chloride and etch at 45. The Ferric is less than

3%
hyrdro-chloric acid when received.

The following website I put up clearly demonstrates the problems with
photos.

http://www.precisionsigns.com/badetchingindex.htm

1.) What is actually happening in these pictures? Is part of the steel
decomposing faster than other parts?

2.) What measuring equipment should we be using to monitor the Ferric
Chloride? We have been measuring it's Baume with a hydrometer but should

we
also be measuring the pH or anything else? If so, what type of

instruments
and what are the ranges that they need to be?

3.) I've heard of regeneration. Is regeneration of the Ferric Chloride

safe
to do with HCL (Muriatic)? By safe I mean are there any harmful /

flammable
fumes generated? Do I need to make sure that the HCL stays at 3%? And

how
much tolerance is there with it?

I feel like I'm on the right track here but need some good advice or
confirmation.



What are you using for resist? Is there a possibility that some resist
is left in the large areas to be etched, and affecting the surface?

I only use FeCl to etch copper, as on printed circuit boards. But, I have
a good deal of experience doing that.

How old is your FeCl solution? Have you tried starting with new solution?
You should know that stainless steel is NOT pure iron, therefore, you

can't
replenish the etchant with HCl (muriatic acid). You have a significant
Nickel concentration building up in any spent solution.

To test, take a piece of totally clean scrap and try etching it. If you
still get the knobby surface, then it is the etchant that must be the

problem.
it is probably full of Nickel, and is preferentially etching the material
depending on small local variations in the nickel mixture, grain boundary
orientation, or something like that.

If it comes out smooth, then your problem is the resist masking process
is leaving a trace of something that blocks the etching action of the
FeCl. I've seen a LOT of that, even water spots left after rinsing
after the resist pattern is developed can do stuff like this. And, the
smooth near an edge but rough in the wide open spaces is something I've
seen before, too.

Jon



  #4  
Old April 6th 04, 01:45 AM
Unknown
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

On Mon, 05 Apr 2004 17:02:26 GMT, "Jon Lorber"
wrote:

,;Hello,
,;
,;We use Ferric Chloride in a spray etching application to etch 304 Stainless
,;Steel. We are having problems and cannot determine what they are. We do not
,;have a scientific background and are just looking for a few simple answers.
,;When the bath is new it seems to work beautifully. Then at some point we
,;start to get peculiar undesirable results.
,;
,;We use 45 Baume Ferric Chloride and etch at 45. The Ferric is less than 3%
,;hyrdro-chloric acid when received.
,;
,;The following website I put up clearly demonstrates the problems with
,;photos.
,;
,;http://www.precisionsigns.com/badetchingindex.htm


Unfortunately I can't view this because the site requires a download
which I am not about to do.

,;
,;1.) What is actually happening in these pictures? Is part of the steel
,;decomposing faster than other parts?
,;
,;2.) What measuring equipment should we be using to monitor the Ferric
,;Chloride? We have been measuring it's Baume with a hydrometer but should we
,;also be measuring the pH or anything else? If so, what type of instruments
,;and what are the ranges that they need to be?


A density measurement is useless on solutions which have been used as
an etchant because you now have ferrous chloride, nickel chloride and
probably chromium chloride. Note that the ferrous chloride now
includes the iron you removed from the stainless plus the reduced
ferric chloride.

The easiest way (for me) would be an iodometric titration.
,;
,;3.) I've heard of regeneration. Is regeneration of the Ferric Chloride safe
,;to do with HCL (Muriatic)? By safe I mean are there any harmful / flammable
,;fumes generated? Do I need to make sure that the HCL stays at 3%? And how
,;much tolerance is there with it?


Regenerate FeCl3 by bubbling air through the solution. You will build
up nickel and probably chromium as you etch and of course the total
iron in solution increases as you use the solution. The HCl is there
to keep the FeCl3 in solution. You can't regenerate with HCl.
,;
,;I feel like I'm on the right track here but need some good advice or
,;confirmation.


This solution isn't going to last forever as you are continually
adding salts. Try regenerating by bubbling air through the solution
and you probably will need to add some HCl but sooner or later you
will need to start a fresh solution.

  #5  
Old April 6th 04, 02:13 AM
Mike Henry
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

I've no experience with etching or the chemistry thereof, but you might want
to check out Hach, which is a company that sells all manner of wet chemistry
test kits. It looks like they have quite a bit of info on their web site:

www.hach.com

If you can pin down the problem to a particular metal or chemical, Hach
might a a fairly low priced test method and many of them are dead simple to
use.

You might also want to check out www.finishing.com (I think) which is a
web-based forum for metal treating professionals (and not so professional).

"Jon Lorber" wrote in message
et...
We use Hydro-coat which is a sprayed on resist most of the time but
sometimes we use a dye cut vinyl mask. I've had the bumpy areas on
un-treated test pieces as well. In fact the last piece with the really bad
etch was done with vinyl masking.

Yes I have found that generally speaking new bath has etched alot better

but
I don't know why. I have imagined the exact situation that you mention:

"it is probably full of Nickel, and is preferentially etching the material
depending on small local variations in the nickel mixture, grain boundary
orientation"

I think I can almost see it happening looking at it with a 25x Microscope.
It almost looks like shingling on a house where as its flaking off at
different rates in the same areal.

Will the nickel settle out into the bottom? Can it be filtered out? The
Ferric is 4 or 5 months old. I'm fine with buying new Ferric if I have to
but I just wish that I could determine that it was no good through some

sort
of measurement. Thanks for your help!





"Jon Elson" wrote in message
...


Jon Lorber wrote:
Hello,

We use Ferric Chloride in a spray etching application to etch 304

Stainless
Steel. We are having problems and cannot determine what they are. We

do
not
have a scientific background and are just looking for a few simple

answers.
When the bath is new it seems to work beautifully. Then at some point

we
start to get peculiar undesirable results.

We use 45 Baume Ferric Chloride and etch at 45. The Ferric is less

than
3%
hyrdro-chloric acid when received.

The following website I put up clearly demonstrates the problems with
photos.

http://www.precisionsigns.com/badetchingindex.htm

1.) What is actually happening in these pictures? Is part of the steel
decomposing faster than other parts?

2.) What measuring equipment should we be using to monitor the Ferric
Chloride? We have been measuring it's Baume with a hydrometer but

should
we
also be measuring the pH or anything else? If so, what type of

instruments
and what are the ranges that they need to be?

3.) I've heard of regeneration. Is regeneration of the Ferric Chloride

safe
to do with HCL (Muriatic)? By safe I mean are there any harmful /

flammable
fumes generated? Do I need to make sure that the HCL stays at 3%? And

how
much tolerance is there with it?

I feel like I'm on the right track here but need some good advice or
confirmation.



What are you using for resist? Is there a possibility that some resist
is left in the large areas to be etched, and affecting the surface?

I only use FeCl to etch copper, as on printed circuit boards. But, I

have
a good deal of experience doing that.

How old is your FeCl solution? Have you tried starting with new

solution?
You should know that stainless steel is NOT pure iron, therefore, you

can't
replenish the etchant with HCl (muriatic acid). You have a significant
Nickel concentration building up in any spent solution.

To test, take a piece of totally clean scrap and try etching it. If you
still get the knobby surface, then it is the etchant that must be the

problem.
it is probably full of Nickel, and is preferentially etching the

material
depending on small local variations in the nickel mixture, grain

boundary
orientation, or something like that.

If it comes out smooth, then your problem is the resist masking process
is leaving a trace of something that blocks the etching action of the
FeCl. I've seen a LOT of that, even water spots left after rinsing
after the resist pattern is developed can do stuff like this. And, the
smooth near an edge but rough in the wide open spaces is something I've
seen before, too.

Jon





  #6  
Old April 6th 04, 06:22 AM
Jon Elson
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems



Jon Lorber wrote:
We use Hydro-coat which is a sprayed on resist most of the time but
sometimes we use a dye cut vinyl mask. I've had the bumpy areas on
un-treated test pieces as well. In fact the last piece with the really bad
etch was done with vinyl masking.

Yes I have found that generally speaking new bath has etched alot better but
I don't know why. I have imagined the exact situation that you mention:

"it is probably full of Nickel, and is preferentially etching the material
depending on small local variations in the nickel mixture, grain boundary
orientation"

I think I can almost see it happening looking at it with a 25x Microscope.
It almost looks like shingling on a house where as its flaking off at
different rates in the same areal.

Will the nickel settle out into the bottom? Can it be filtered out?

No, to both. The ferric chloride is depleted, creating metal X chloride
and iron dust. That metal x chloride may then etch something else, producing
metal Y chloride and metal x dust. But, eventually, it forms a chloride
that doesn't react with any of the metal present, and the action slows down
and stops.
The
Ferric is 4 or 5 months old. I'm fine with buying new Ferric if I have to
but I just wish that I could determine that it was no good through some sort
of measurement. Thanks for your help!

And, the specific gravity (that's what you are measuring with the Baume
hydrometer) is not going to change much as these reactions progress.
If you are etching one element only, like I do (copper) then you know
that you are converting the etchant to copper chloride and iron dust.
I can put some muriatic acid in there when etching a big batch, and the
iron is quickly converted back to ferric chloride. But, eventually,
the bath is "poisoned" by the saturation of copper, and has to be replaced.

Jon

  #7  
Old April 6th 04, 02:58 PM
Jon Lorber
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

Great thanks all I will check out these leads.

Unfortunately I can't view this because the site requires a download
which I am not about to do.


What downloads does it show are required? They pictures JPGs referenced in
the HTML file.


  #8  
Old April 6th 04, 04:16 PM
Jon Lorber
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

Thanks for the help. I found this on finishing.com:

"A strong possibility is that you sometimes get 304F instead of 304 or 304L.
The F grade has a high sulfur content for improved machineability, and
etching on any plane that is not parallel to the rolling direction from when
the material was originally hot-rolled, will give the sort of finish you
describe. The sulfur forms discrete particles of manganese sulphide in the
steel, which elongate with the steel during rolling. On any plane of the
rolled product that is not parallel to the rolling direction, the sulphide
stringers break the surface as spots (cross-sections of the stringers), and
these spots are particularly susceptible to corrosion." -B. Reynolds

Any comments on this? While I think that the chemistry of the bath is
critical but I have been miffed by the fact that one plate will come out
pitted and another fine in the same bath.

Another point of interest is that there are some many things that can go
wrong that it's sometimes difficult to determine the exact reason. That is
what I need to do however and the stainless grade seems to be the most
plausible so far.


  #9  
Old April 6th 04, 07:01 PM
Xane T.
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

On Mon, 05 Apr 2004 17:02:26 GMT, "Jon Lorber"
wrote:

snip


I should finish up the metal etching FAQ that I'm working on. Since
it's not my main business anymore, I can drop this hint at least. You
can regenerate Ferric Chloride with air bubbling and muriatic acid for
about 3 refresh cycles. After that, it will become way too saturated
with whatever you're etching in it. For copper/brass, the copper
chloride will eventually crystalize into rings of needle crystals at
the bottom of the tank. I would reccomend chilling your spent etchant
to attempt to force more of the contaminant out of the solution. After
that, you can regenerate what's left with 40 volume hydrogen peroxide
from a hair salon [try Sally Beauty Supply]. Clairol hair bleach has
nothing in it but the peroxide [some other brands have
cleaning/foaming agents]. Make sure the etchant is in a heatproof
container, I use a 3.5 gallon bucket inside of a 5 gallon bucket in
case the bottom drops out. This causes a pretty violent reaction
[foaming], so make sure the container is less than half full and add
it slowly, stirring constantly with something like an acrylic stick. I
use about one 16 oz bottle per gallon of etchant. You /could/ use 100
volume peroxide if you can get it, but the reaction may be extremely
violent at that concentration. This /does/ produce hydrogen gas, so
you need to do this outdoors and be careful with it. Then let it air
bubble overnight using an aquarium pump or something. This seems to
force the FeCl2 back into FeCl3. I don't measure baume or ph, but it
changes etchant that took six hours to etch through a sheet with no
agitation into a 2 hr job, which is a little longer than 'fresh'
etchant. This has only been tested with etchant that's used with
brass, but you can try it with stainless [I have yet to find a resist
that will stay on the steel so I can't do steel etching yet]. You can
also buy dry ferric chloride to add in if it doesn't seem strong
enough, but don't add as much as if you were mixing it with water.
It's still a lot cheaper than buying new etchant. You will need to use
peroxide for each future regeneration, while keeping the pH up with
muriatic acid. If you have testing equipment, then you can probably do
a better job at finding out what ratios of each chemical to use than I
do [I'm just a hobbyist].
  #10  
Old April 7th 04, 06:02 AM
Mike Henry
external usenet poster
 
Posts: n/a
Default Etching 304 Stainless Steel with Ferric Chloride Problems

Not to be a safety nag, but concentrated hydrogen peroxide can be seriously
dangerous chemixal and anyone contemplating it's use would be well advised
to spend a least a few minutes looking over safety data on it. I saw a
safety film once that demonstrated the result of pouring 50-70% H2O2 on a
leather boot - the boot burst into flame - and that sure made an impression
on me.

"Xane T." wrote in message
...
On Mon, 05 Apr 2004 17:02:26 GMT, "Jon Lorber"
wrote:

snip


I should finish up the metal etching FAQ that I'm working on. Since
it's not my main business anymore, I can drop this hint at least. You
can regenerate Ferric Chloride with air bubbling and muriatic acid for
about 3 refresh cycles. After that, it will become way too saturated
with whatever you're etching in it. For copper/brass, the copper
chloride will eventually crystalize into rings of needle crystals at
the bottom of the tank. I would reccomend chilling your spent etchant
to attempt to force more of the contaminant out of the solution. After
that, you can regenerate what's left with 40 volume hydrogen peroxide
from a hair salon [try Sally Beauty Supply]. Clairol hair bleach has
nothing in it but the peroxide [some other brands have
cleaning/foaming agents]. Make sure the etchant is in a heatproof
container, I use a 3.5 gallon bucket inside of a 5 gallon bucket in
case the bottom drops out. This causes a pretty violent reaction
[foaming], so make sure the container is less than half full and add
it slowly, stirring constantly with something like an acrylic stick. I
use about one 16 oz bottle per gallon of etchant. You /could/ use 100
volume peroxide if you can get it, but the reaction may be extremely
violent at that concentration. This /does/ produce hydrogen gas, so
you need to do this outdoors and be careful with it. Then let it air
bubble overnight using an aquarium pump or something. This seems to
force the FeCl2 back into FeCl3. I don't measure baume or ph, but it
changes etchant that took six hours to etch through a sheet with no
agitation into a 2 hr job, which is a little longer than 'fresh'
etchant. This has only been tested with etchant that's used with
brass, but you can try it with stainless [I have yet to find a resist
that will stay on the steel so I can't do steel etching yet]. You can
also buy dry ferric chloride to add in if it doesn't seem strong
enough, but don't add as much as if you were mixing it with water.
It's still a lot cheaper than buying new etchant. You will need to use
peroxide for each future regeneration, while keeping the pH up with
muriatic acid. If you have testing equipment, then you can probably do
a better job at finding out what ratios of each chemical to use than I
do [I'm just a hobbyist].



 




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