KevinG wrote:

I am interested in a chemical that will heavily etch, and even dissolve cast
iron. Spent the afternoon searching the archives, and reading about Ferric
Chloride and other options that people have posted about when mild etching
was required.

I have not tried Ferric, but I have tried Nital (4% nitric with ethanol),
also Muriatic with a few oz of Lye and the results were not as aggressive
for what I am looking for. The goal is to remove a few pounds(!) of
material from the inside of a cast iron intake manifold over the period of
around
48 hours. This is all in areas where tooling / blasting cannot reach.
Alternatively, electro-etching is not an option either, as the manifold has
many deep internal passages and twists.


I think this is going to be a disaster. I have experience with Ferric
Chloride, at
least, as a copper etchant. Your problem is that you may initially get
just what you
are looking for, and then, 2 weeks later, you find the manifold in
pieces, with big
hunks missing. The trouble is getting the etchant (whatever you use) to
STOP when
it is done. Cast iron is notoriously porous, and the etchant will hide
in the pores and
do mischief over time. If you do try Ferric Chloride, you will need a
very aggressive
neutralizer to fully inert any remaining etchant hidden in pores of the
metal. Alkalis
are probably going to be good for that.

My other reason to suspect problems is the grain structure of cast Iron.
It has a very
loose grain structure, with lost of inclusions. Most etchants will
follow grain boundaries,
preferentially working BETWEEN the grains. This leads to faster
etching, but very
UNEVEN etching! In other words, the surfaces start off somewhat smooth,
and become
very jagged as the etching progresses. Instead of moving a wall back
while preserving
the general contour, it will turn the wall into swiss cheese, or moon
mountains, or
something like that. Maybe this will still get you what you want.

Jon

I am interested in a chemical that will heavily etch, and even dissolve cast
iron. Spent the afternoon searching the archives, and reading about Ferric
Chloride and other options that people have posted about when mild etching
was required.

I have not tried Ferric, but I have tried Nital (4% nitric with ethanol),
also Muriatic with a few oz of Lye and the results were not as aggressive
for what I am looking for. The goal is to remove a few pounds(!) of
material from the inside of a cast iron intake manifold over the period of
around
48 hours. This is all in areas where tooling / blasting cannot reach.
Alternatively, electro-etching is not an option either, as the manifold has
many deep internal passages and twists.

I have built plates to block off the ports and fill the manifold, and also
have an outdoor, fan ventilated area... along with the necc safety apparel.
Looking for someone with experience in this area for guidance. This has
been called acid porting in the past, and I am not interested in anyone's
opinion on the benifits regarding increased engine output, just looking for
some chemistry help,

TIA,

Kev

Muriatic acid will be more aggressive if you don't mix lye with it.
8^).

Randy


"KevinG" wrote in message
. ..
I am interested in a chemical that will heavily etch, and even dissolve
cast
iron. Spent the afternoon searching the archives, and reading about
Ferric
Chloride and other options that people have posted about when mild etching
was required.

I have not tried Ferric, but I have tried Nital (4% nitric with ethanol),
also Muriatic with a few oz of Lye and the results were not as aggressive
for what I am looking for. The goal is to remove a few pounds(!) of
material from the inside of a cast iron intake manifold over the period of
around
48 hours. This is all in areas where tooling / blasting cannot reach.
Alternatively, electro-etching is not an option either, as the manifold
has
many deep internal passages and twists.

I have built plates to block off the ports and fill the manifold, and also
have an outdoor, fan ventilated area... along with the necc safety
apparel.
Looking for someone with experience in this area for guidance. This has
been called acid porting in the past, and I am not interested in anyone's
opinion on the benifits regarding increased engine output, just looking
for
some chemistry help,

TIA,

Kev

"KevinG" wrote in message ...
I am interested in a chemical that will heavily etch, and even dissolve cast
iron. Spent the afternoon searching the archives, and reading about Ferric
Chloride and other options that people have posted about when mild etching
was required.

I have not tried Ferric, but I have tried Nital (4% nitric with ethanol),
also Muriatic with a few oz of Lye and the results were not as aggressive
for what I am looking for. The goal is to remove a few pounds(!) of
material from the inside of a cast iron intake manifold over the period of
around
48 hours. This is all in areas where tooling / blasting cannot reach.
Alternatively, electro-etching is not an option either, as the manifold has
many deep internal passages and twists.

I have built plates to block off the ports and fill the manifold, and also
have an outdoor, fan ventilated area... along with the necc safety apparel.
Looking for someone with experience in this area for guidance. This has
been called acid porting in the past, and I am not interested in anyone's
opinion on the benifits regarding increased engine output, just looking for
some chemistry help,

TIA,

Kev


If you're going to remove pounds of metal, you're going to need pounds
of acid. The inside surface is going to look like the moon, too,
high-carbon ferrous material will pit terribly. Mixed
perchloric/phosphoric acid was what we used to desolve iron for
chemical analysis, didn't care about surface finish with that.

I guess my question is, why? Edelbrock too high priced, or you think
you've got a better idea?

Stan

Randy - an unscientific (but theoretically accurate) test we did found that
the muriatic alone would just give the cast iron a deep cleaning. We took a
100 gram chuck of cast iron and immersed it in a container with straight
muriatic. Leaving it in 12 hour steps, we would remove it, then put it in a
bath of baking soda, then place it on our .01 increment digital paint scale,
measuring how much lighter the chuck would get over a 48 hr period.

Now I do not remember what the actual numbers were, but when doing the same
test with a similar sized cast iron chunk, the lye mixed with the muriatic
deteriorated the chunk alot quicker, some 30% if memory serves.

Not saying I know anything about chemistry, but this seemed to be a pretty
valid test. Where did I go wrong?

----

Jon - Agreed... on the outside this may look like a disaster, but we did
plan on immersing in with some sort of neutralizer, maybe a 15 gallon
plastic tub filled with a mix of H20 and baking soda? Or it seems you are
hinting that something more powerful will be needed. Your concerns
certainly warrant an investigation into that.

---

Stan & Jon - the surface finish is of little consequence (within reason)...
in fact the peaks and valleys would be somewhat beneficial, as a smooth
surface is not desired.

Stan - Edelbrock is out of the question, as this is to be used in an
application where the original cast iron manifold is mandated.

Would you be so kind as to suggest as mixture or concentration of the
perchloric / phosphoric?

thank you all,

kev


--------------------------------
Muriatic acid will be more aggressive if you don't mix lye with it.
8^).

Randy

-----------------


I think this is going to be a disaster. I have experience with Ferric
Chloride, at
least, as a copper etchant. Your problem is that you may initially get
just what you
are looking for, and then, 2 weeks later, you find the manifold in
pieces, with big
hunks missing. The trouble is getting the etchant (whatever you use) to
STOP when
it is done. Cast iron is notoriously porous, and the etchant will hide
in the pores and
do mischief over time. If you do try Ferric Chloride, you will need a
very aggressive
neutralizer to fully inert any remaining etchant hidden in pores of the
metal. Alkalis
are probably going to be good for that.

My other reason to suspect problems is the grain structure of cast Iron.
It has a very
loose grain structure, with lost of inclusions. Most etchants will
follow grain boundaries,
preferentially working BETWEEN the grains. This leads to faster
etching, but very
UNEVEN etching! In other words, the surfaces start off somewhat smooth,
and become
very jagged as the etching progresses. Instead of moving a wall back
while preserving
the general contour, it will turn the wall into swiss cheese, or moon
mountains, or
something like that. Maybe this will still get you what you want.

Jon

-------------------

If you're going to remove pounds of metal, you're going to need pounds of
acid. The inside surface is going to look like the moon, too, high-carbon
ferrous material will pit terribly. Mixed perchloric/phosphoric acid was
what we used to desolve iron for
chemical analysis, didn't care about surface finish with that. I guess my
question is, why? Edelbrock too high priced, or you think
you've got a better idea?

Stan

You'll do a lot better if you abrade the surfaces while the acid is there.
One problem that often happens with corrosion processes is thatt the end
result isn't soluable in the liquid and thus blocks the continuing action.
In addition, cast iron being a mixture of a number of elements, will not
erode evenly.
I'll also note that the application of an electric current will make things
proceed a lot faster.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!

KevinG wrote:
...
Now I do not remember what the actual numbers were, but when doing the same
test with a similar sized cast iron chunk, the lye mixed with the muriatic
deteriorated the chunk alot quicker, some 30% if memory serves. ...

Lye is sodium hydroxide (NaOH), muriatic acid is hydrochloric acid
(HCl). Mixing them gives salt (NaCl) and water and a lot of heat.
IIRC, also hydrogen gas. But the point is that they neutralize each
other. It's a mystery to me how the mix of the 2 of them could be more
powerful.

Bob

Disclaimer! Use at your own risk! I've never tried these and I don't know
if they'll even work, but maybe it'll give you some ideas for
experimentation. I usually only read this book for amusement. These
etching formulas for iron come from a 1939 book "Fortunes in Formulas"
(Which explains the archaic chemical names);

(all parts by weight)
1/ Pure Nitric Acid with an equal weight of water (for deep etching)
2/ 1 part Tartaric Acid by weight, 15 parts Mercuric Chloride, 420 parts
water, 16 to 20 drops nitric acid if one part equals 28.5 grains.
3/ 120 parts of 80% Spirit, 8 parts pure nitric acid, 1 part Silver Nitrate.
4/ 40 parts of 30% Pure Acetic Acid, 10 parts absolute Alchohol, 10 parts
pure Nitric Acid.
5/ 10 parts fuming Nitric Acid, 50 parts 30% pure Acetic Acid.
6/ A Chromic Acid solution.
7/ 1 part Bromine, 100 parts Water.
8/ 1 part Mercuric Chloride, 30 parts Water.
9/ 1 part Antimonic Chloride, 6 parts Water, 6 parts Hydrochloric Acid.

They seem to have been fond of Nitric Acid...


In article , "KevinG"
wrote:

I am interested in a chemical that will heavily etch, and even dissolve cast
iron. Spent the afternoon searching the archives, and reading about Ferric
Chloride and other options that people have posted about when mild etching
was required.

I have not tried Ferric, but I have tried Nital (4% nitric with ethanol),
also Muriatic with a few oz of Lye and the results were not as aggressive
for what I am looking for. The goal is to remove a few pounds(!) of
material from the inside of a cast iron intake manifold over the period of
around
48 hours. This is all in areas where tooling / blasting cannot reach.
Alternatively, electro-etching is not an option either, as the manifold has
many deep internal passages and twists.

I have built plates to block off the ports and fill the manifold, and also
have an outdoor, fan ventilated area... along with the necc safety apparel.
Looking for someone with experience in this area for guidance. This has
been called acid porting in the past, and I am not interested in anyone's
opinion on the benifits regarding increased engine output, just looking for
some chemistry help,

TIA,

Kev

--
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