Tom Swift <spam@me.com> wrote:

> If you want to make your own rust converter, I believe Jeff Lieberman 
> posted a link to phosphoric acid in 1 gal jugs available at Home Depot
> for $12.97. The link is
> 
> <http://www.homedepot.com/p/Eagle-1-Gal-Etch-and-Clean-for-Concrete-in-
> 4- 1-Concentrated-EEC1/203075984>
> 
> It is not available in Canada.

Sorry, it was  James Arthur. I take the liberty to repost his information 
since it confirms the effectiveness of H3PO4 on rust:

Date: Tue, 30 Sep 2014 18:03:32 -0700 (PDT)

On Monday, September 29, 2014 2:38:03 PM UTC-4, Cydrome Leader wrote:

> jrwalliker...@gmail.com wrote:

>> On Sunday, 28 September 2014 13:25:43 UTC+1, Lasse Langwadt
>> Christensen wrote:

>> Concentrated phosphoric acid is a very useful rust treatment. It
>> does not dissolve the rust away, but converts it into an
>> insoluble phosphate (to which paint adheres very well). The iron
>> surface is passivated against further rusting by this process.

>> Conc. phosphoric acid is also an excellent flux for soldering
>> stainless steel.

> Are there any easy ways to get the strong phosphoric acid? How
> concentrated must it be? I've actually got some stainless I was
> thinking about soldering and wasn't sure about the flux.

Yes. Home Depot sells it, pretty concentrated too. It was for
etching concrete IIRC, or some such. Liquid, not gel. It was a lot
cheaper than the Naval Jelly, which they had too.

Oh, here it is:

http://www.homedepot.com/p/Eagle-1-Gal-Etch-and-Clean-for-Concrete-in-4-
1-Concentrated-EEC1/203075984

Phosphoric-acid containing products are magic as rust-converters. I
used a bit on ye olde car as a stop-gap to temporarily keep an
exposed rusty spot from propagating. It stopped the rust cold, and
it's been years.

I never did get around to "fixing it."

Cheers,
James Arthur

"Tim Williams" <tiwill@seventransistorlabs.com> wrote:

> "Tom Swift" <spam@me.com> wrote in message 
> news:XnsA3E8650B4A9BCidtokenpost@69.16.179.22...
>> But this seems to be a different reaction, where the vinegar is
>> applied to rust on a hot surface. The reaction has to be very quick,
>> since the vinegar will evaporate fast. I know iron makes a lot of
>> different compounds, but I hadn't heard of this one before so I was
>> curious to find the reaction. 

> Yeah, it's not going to be anything remarkable.  If you want a more
> robust corrosion and heat resistant layer, you might try phosphating. 
> Iron(II) phosphate is black, and highly insoluble.

> Standard surface prep applies -- degrease, strip the rust, convert it 
> (something phosphoric acid is already good at, e.g. Naval Jelly), and
> if that doesn't do it already (I haven't used it myself), clean the
> surface in preparation for a process like Parkerizing.

> Of course, for temperatures red hot and up, it's hard to beat good old
> fashioned enamel, the kind made with ceramic and glass particles.

> Tim

Yes, I discovered phosphate a while ago. I live in the rust belt in 
Ontario, and I have never seen such problems with rust. I tried all the 
rust preventers but they only lasted a short while then disappeared.

We have a product at Canadian Tire called Rust Converter. It is 30% 
phosphoric acid, 30% Tannic Acid and 30% isopropyl alcohol. I tried it on 
my car and it is simply amazing. Wherever the rust starts, it quickly 
lifts the paint and continues underneath. Soon there is a huge hole that 
costs a fortune to fix.

Not with this rust converter. It takes only a few seconds to wire brush 
the loose paint, then spray or brush it on. A few seconds later, the rust 
starts turning black. I leave it on overnight. Then you can wash it, 
prime and paint. It only takes a few minutes of work and the results are 
amazing. No More Rust! I also found most of my tools had started to rust, 
so I treated them. They turned black and have stayed that way for years 
without any additional protection. 

I even did the face on my hammer, fully expecting the iron phosphate to 
chip or fall off. After a year, the hammer has been used a great deal but 
the coating is still there, and it has stopped rusting.

I applied various chemicals to the coating, including sodium hypochlorite
(bleach). Nothing had any effect. I use pressure cookers to sterilize 
fabrics each day. An inner liner was starting to rust even though it is 
stainless steel. A quick coat of rust converter, and it turned black in 
all the places that were rusting. The rust stopped and no new rust has 
appeared. This stuff is amazing.

I found the chemical reactions which I list here. There are two 
reactions, a fast one and a slow one.

The fast reaction works on rust and takes 15 minutes to an hour:

  Fe2O3 + 2H3PO4 --> 2FePO4 + 3H2O

The slow reaction works on bare steel and takes overnight to run:

  2Fe + 2H3PO4 --> 2FePO4 + 3H2

Both reactions produce iron phosphate, FePO4. This is a hard coating that 
bonds to the surface and prevents rust from forming.

The Rust Converter from Canadian Tire also contains Tannic Acid. This 
apparently produces ferric tannate, which is another hard coating. There 
have been numerous papers published on the protection from rust, and a 
good example is "Performance of rust converter based in phosphoric and 
tannic acids", by L. M. Ocampo, I. C. P. Margarit, O. R. Mattos, S. I., 
available at

http://libgen.org/scimag/get.php?doi=10.1016/j.corsci.2003.09.021

If you want to make your own rust converter, I believe Jeff Lieberman 
posted a link to phosphoric acid in 1 gal jugs available at Home Depot 
for $12.97. The link is

<http://www.homedepot.com/p/Eagle-1-Gal-Etch-and-Clean-for-Concrete-in-4-
1-Concentrated-EEC1/203075984>

It is not available in Canada.

All you need is then some Tannic acid powder and isopropyl alcohol, and 
you should be able to duplicate the rust converter that sells for $250 
for 5 gallons. But you can try just phosphoric acid, since many of the 
rust converters only contain it and none of the tannic acid or isopropyl 
alcohol.

One caution - if you leave parts immersed in phosphoric acid overnight, 
it will eat them down to nothing. Obvious, but I learned the hard way.

"Tom Swift" <spam@me.com> wrote in message 
news:XnsA3E8650B4A9BCidtokenpost@69.16.179.22...
> But this seems to be a different reaction, where the vinegar is applied
> to rust on a hot surface. The reaction has to be very quick, since the
> vinegar will evaporate fast. I know iron makes a lot of different
> compounds, but I hadn't heard of this one before so I was curious to
> find the reaction.

Yeah, it's not going to be anything remarkable.  If you want a more robust 
corrosion and heat resistant layer, you might try phosphating.  Iron(II) 
phosphate is black, and highly insoluble.

Standard surface prep applies -- degrease, strip the rust, convert it 
(something phosphoric acid is already good at, e.g. Naval Jelly), and if 
that doesn't do it already (I haven't used it myself), clean the surface 
in preparation for a process like Parkerizing.

Of course, for temperatures red hot and up, it's hard to beat good old 
fashioned enamel, the kind made with ceramic and glass particles.

Tim

-- 
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

"Tim Williams" <tiwill@seventransistorlabs.com> wrote:

> "Tom Swift" <spam@me.com> wrote in message 
> news:XnsA3E7BBAC3E026idtokenpost@69.16.179.22...
>> I have heard of this before. Any thoughts on the chemical equations?
>> Red rust (magnetite) is Fe3O4, hematite is Fe2O3, acetic acid is
>> CH3COOH (various spellings). How do you convert rust to iron oxide
>> with vinegar and what do you really end up with? 

> Probably finer mixed oxides and hydroxides, which do well enough to
> look black.  Both ferrous and ferric acetate are real things, and
> their decomposition will lead to both oxides, with products including
> CO2, ethane or acetone, I think.  The reducing effect of these gasses
> may prefer Fe3O4.  Decomposition temperature is over 150C, I guess.

> Tim

Thanks, Tim. 

From the op, this is on a hot stove, so the temperature is already well
over 150C. Now that you have given some keywords for a search, I found
Iron(II) acetate, with the following reaction: 

"Iron powder reacts with hot acetic acid to give the product:"

    Fe + 2CH3CO2H --> Fe(CH3CO2)2 + H2 

http://en.wikipedia.org/wiki/Iron%28II%29_acetate

It decomposes at 190&#4294967295;200C, so your guess was bang on.

I also found the following:

ferrous acetate

Fe(CH3COO)2&#4294967295;4H2O 

"Soluble green crystals, soluble in water and alcohol, that are
combustible and that oxidize to basic ferric acetate in air; used as
textile dyeing mordant, as wood preservative, and in medicine. Also
known as iron acetate." 

http://encyclopedia2.thefreedictionary.com/ferrous+acetate

It doesn't look like this would withstand a hot stove either. 

There are zillions of web pages and Youtube videos on removing rust with
vinegar. The reaction is usually slow and means immersing the piece in
vinegar overnight then brushing vigorously. Many of these mention you
have to protect the surface with oil or it will start rusting again
immediately. 

But this seems to be a different reaction, where the vinegar is applied
to rust on a hot surface. The reaction has to be very quick, since the
vinegar will evaporate fast. I know iron makes a lot of different
compounds, but I hadn't heard of this one before so I was curious to
find the reaction. 

Thanks for your reply.

"Tom Swift" <spam@me.com> wrote in message 
news:XnsA3E7BBAC3E026idtokenpost@69.16.179.22...
> I have heard of this before. Any thoughts on the chemical equations? Red
> rust (magnetite) is Fe3O4, hematite is Fe2O3, acetic acid is CH3COOH
> (various spellings). How do you convert rust to iron oxide with vinegar 
> and
> what do you really end up with?

Probably finer mixed oxides and hydroxides, which do well enough to look 
black.  Both ferrous and ferric acetate are real things, and their 
decomposition will lead to both oxides, with products including CO2, 
ethane or acetone, I think.  The reducing effect of these gasses may 
prefer Fe3O4.  Decomposition temperature is over 150C, I guess.

Tim

-- 
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

whit3rd <whit3rd@gmail.com> wrote:

> On Friday, November 14, 2014 1:39:38 PM UTC-8, Joe Gwinn wrote:

>>   There are high-temperature black paints
>> intended for woodburning iron stoves (graphite and water-glass based?). 
>> I bet these paints wouldn't be bothered by a laser that small. 

> Graphite isn't good at high temperatures, it oxidizes.  Rather, they
> use magnetite/hematite (i.e. black iron oxides).  Heck, for a woodburning
> stove, you can just wipe a rusty spot with vinegar, it'll blacken it
> dandy (do this with the stove hot, of course).

I have heard of this before. Any thoughts on the chemical equations? Red 
rust (magnetite) is Fe3O4, hematite is Fe2O3, acetic acid is CH3COOH 
(various spellings). How do you convert rust to iron oxide with vinegar and 
what do you really end up with?

On Friday, November 14, 2014 1:39:38 PM UTC-8, Joe Gwinn wrote:

>   There are high-temperature black paints
> intended for woodburning iron stoves (graphite and water-glass based?). 
> I bet these paints wouldn't be bothered by a laser that small. 

Graphite isn't good at high temperatures, it oxidizes.  Rather, they
use magnetite/hematite (i.e. black iron oxides).  Heck, for a woodburning
stove, you can just wipe a rusty spot with vinegar, it'll blacken it
dandy (do this with the stove hot, of course).

Actually you want to minimize the sand if possible.  Adding any large amoun=
t of  epoxy causes far less scattering  as it more or less index matches th=
e glass.=20

I first saw the beads during a visit to the left coast as a Service Enginee=
r.

The graduate student who invented the hollow bead technique had up to 5 Jou=
le pulses attenuated by stacked "Tic-Tac" boxes in front of his photodiode =
detector. This was because his professor would not give him further budget =
for ND filters. He would add or remove boxes to change OD as needed. The sa=
me craft store had a wide variety of plastic boxes.

Necessity is often the mother of invention.

While I would not suggest his technique for day to day work, when you need =
a quick improvisation it works.=20


I left him a spare beam sampling wedge from my tool kit. That should have m=
ade his life a bit easier.

Steve

On Fri, 14 Nov 2014 16:39:30 -0500, Joe Gwinn <joegwinn@comcast.net>
Gave us:

>In article <mirc6alooidf2o47bm138urlg6n2mam0gs@4ax.com>,
>DecadentLinuxUserNumeroUno <DLU1@DecadentLinuxUser.org> wrote:
>
>> On Fri, 14 Nov 2014 16:00:58 -0500, Joe Gwinn <joegwinn@comcast.net>
>> Gave us:
>> 
>> >In article <xY-dnfNdu5Jr2fvJnZ2dnUU7-U-dnZ2d@supernews.com>, Phil Hobbs
>> ><pcdhSpamMeSenseless@electrooptical.net> wrote:
>> 
>> >> >
>> >> 
>> >> Yup.  My fave is Krylon #1602, as noted upthread.  Works amazingly well 
>> >> on fused quartz.
>> >
>> >I have always used 1602 too.  One odd use - the top of the shelf below
>> >the windshield and above the dashboard, to cut down on reflections
>> >interfering with vision.
>> >
>> >Joe Gwinn
>> 
>> 
>>  You must be a football player.  :-)
>
>I think the intent is warpaint, not optics.
>
>
>>   What about mil paints actually meant to be baked on and have high temp
>> service applications?
>
>The dashboard would melt.
>
>
>>   Those guys had decades to get to know what they were doing (the chem
>> engineers making mil paints way back when).
>
>But it's a good point.  There are high-temperature black paints
>intended for woodburning iron stoves (graphite and water-glass based?). 
>I bet these paints wouldn't be bothered by a laser that small.  There
>are also shiny black paints intended for gas grills and exhaust
>systems.
>
>
>Joe Gwinn

 We mixed powdered silica into our potting to conduct heat better in HV
applications.

  I'd bet that beads, and silica powder and an absorptive epoxy like
stycast as a binder inside a sealed outer skin, might trap pretty good.
Make the receiving "cup" just that.  A (deep) cup shape with a parabolic
end, of course...  Or I guess a single pinpoint on a narrow stalk of a
super-reflective media, and then those reflections get fed to the
absorbing media.  Instead of just a little added, like we were doing,
one would flood the cup with beads and silica powder and barley have
enough epoxy to bind it all together.  Stycast can almost be peered
though in thin enough cross section.  Of course, I refer to human eye
observations.

 Kind of like a bunch of hunting arrowheads together.  Instead of razor
blades, the points style would reduce any incidental reflection count to
a very low number.  I guess particulars of the beam which will be
entering would weigh in.