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Topic Review (Newest First)
03-22-2015 09:48 AM
MikeMoss Hi

I've used Muriatic Acid to remove rust when restoring cars for many years and there's something that a lot of people don't know about the process, if someone else has already suggested this I apologize I didn't read through all the posts.

After you remove the now rust free parts (only takes a few minutes and is less destructive then wire brushing or grinding) from the solution rinse them in water, and then submerge them in a hot (or boiling if you can) solution of water and Arm and Hammer backing soda (half a box to a gallon of Water).

This both neutralizes the acid, and etches the surface, ready for paint, it also deposits a coating that is very resistant to corrosion.

I one took a pair of pliers that was so rusted that you couldn't open them.
Put them through the process and then laid then on a shelf in the garage no oil or anything on them.

A year later then didn't has a speck of rust on them, I still have them 30 years later and they are still pretty much rust free.

If you've done the muriatic acid thing you know that you need to get the item coated quickly so they won't rust again. That's not true after the soda bath.

10-08-2012 10:23 AM
41 kustom Why not use POR or some other rust stop paint. I used a popular brand on some jack stands years ago and they still look fine. Just a thought.
10-08-2012 12:10 AM
Silver Shadow Acid eats rust.
Acid also eats metal parts.

Any acid will quickly remove rust, so will sand blasting or an angle grinder.
Fast brutal and usually very damaging.

Try putting a piece of iron or steel into ANY acid, and leave it there for a month, there will be nothing left to remove.

Now try something very different.
Make up a VERY strong alkali solution of lye (caustic soda) (NaOH) in water.
Toss in some Zinc chips, and boil it up in a steel container.
It will convert Iron oxide (rust) back to pure iron. The hotter and stronger the solution, the faster it works.
It not only stops rust, it actually reverses the rusting process.
Very strong alkali has no effect whatsoever on iron or steel, you can leave a part in there for a year and it will not have any effect at all. That is the secret.
It will however rapidly dissolve any non ferrous metal parts, so make absolutely sure there are no brass or aluminium parts in what you are de rusting.
Not only will it reverse the rusting process, the part will stay rust resistant for a very long time without painting or any other treatment.

The trick is not to remove rust, but to reverse the rusting process.

The strong alkali solution also quickly strips and dissolves paint and grease, which is an added bonus.

Putting iron or steel parts into any strong acid to remove rust, is like using a shotgun to clean a wound.
10-06-2012 06:46 PM
Found this old thread and have a question

According to all the info in this old tread, muriatic acid is death for iron or steel, but how about cleaning a heater core ? I used it about 30 years ago for cleaning heater cores still installed in the vehicle. Just rinsed good with water afterwards and hooked the hoses back up. Will the corrosion inhibitors in anti-freeze keep the muriatic acid from doing any damage ? I need to clean the heater core on my recently acquired (march 5th of 2012) C-1500 . Thanks, Big Al
06-30-2011 11:23 AM
Thanks for valued information!

Hi, Everyone,

Thanks for the very valuable information on NOT using muriatic acid on metal but using phophoric acid instead. That is worth knowing, and I'll pass it on to my mechanic who told me I could use muriatic acid!

Thanks again!

06-10-2009 08:00 AM
Originally Posted by jimlinhill
. Tea has tannic acid and is the reason why you shouldn't drink tea with meals. It will convert the iron compounds to iron tannate and may result in being anemic.

There is no evidence to suggest that tea drinking should be restricted in healthy individuals who are not at risk of iron deficiency and are consuming a well balanced, mixed diet.
06-09-2009 10:43 PM
Rust Removal

Convert the rust (iron oxide) to iron tannate by wetting the rusted surface down with tannic acid. The the surface will turn black. If it doesn't, then the surface wasn't rusted or the rust was not treated sufficiently. Tea has tannic acid and is the reason why you shouldn't drink tea with meals. It will convert the iron compounds to iron tannate and may result in being anemic.
02-25-2008 02:18 PM
ChevyThunder They hydrogen cracking is an excellent point. Hydrogen atoms are small enough they can penetrate the crystal structure of steel (unless you have a very small grain size even then hydrogen doesn't help) This will cause stress corrosion cracking as the hydrogen which pentrates the steel helps corrode the steel fromt he inside and creates pits.

Similiar to what H2S gas will do to pipelines and pressure vessels if they aren't the right type of steel.
02-22-2008 08:23 PM
1947Chevy1989 Hello,
My dad and I tried the muriatic acid trick on our old tractor rim, it removed the rust, but it damn near killed both of us at one point with the fumes, and we were outside in my driveway. it didn't do much good for the rim either, we found another after than, needed to really patch that one we had....but I wouldn't recommend doing that, sand blasting or other alternatives would do just as nice a job in my opinion...
02-22-2008 07:57 PM
Kruzin Karl And I suppose, it keeps on "Antiquing" them, Real Quickly, right?
02-22-2008 05:34 PM
BUT it has allowed a surface rust to form on all the parts. SO I need to remove this rust and re-paint. This mill is broken down to about 6 LARGE parts i.e. they are large, and being cast iron weight a ton!

So wirebrush it off,+ Slap a coat or 2 of Rustolium on it........
No Muss, No Fuss,.... If it chips, touch it up......

You'll be a Pile of Dust, long before those Cast Iron Parts are.....

I still can not comprehend how anyone would even begin to consider using muriatic acid on any type of metal.
Ayuh,.... I use it on steel sculptures,......

It "Antiques" them,....... Really Quickly............
02-22-2008 03:48 PM
Kruzin Karl Just come on down here to sunny South Florida and look at all of the rotted out pool trucks.

This subject has been beaten to death, and I still can not comprehend how anyone would even begin to consider using muriatic acid on any type of metal.
02-22-2008 03:54 AM
oldred I think when someone is contemplating using Hydrochloric/Muriatic or even battery acid for rust removal, and this has come up a bunch of times here, they tend to look at acids in the wrong way. There seems to be a misconception that "acid" is a substance in itself instead of being just one of the properties of different chemicals that happen to be acidic, thus the mistaken idea that acid is acid just some acids are stronger than others. Phosphoric acid and Muriatic acid are two different chemicals that affect iron in drastically different ways but because Phosphoric acid removes rust then some get the idea that a stronger acid would work even better. Also that book makes a good point in that the way different acids affect iron has been well known for a heck of a long time and if Muriatic acid or Sulfuric acid (sulfuric acid for rust removal has come up a couple of times) were a good choice for rust removal they would be popular for that use, they are not.
02-22-2008 12:48 AM
grouch Found some information that might be relevant here:

MSDS for Picklex [PDF] Less than 10% phosphoric acid

MSDS for Rust Mort (Leads to a PDF) phosphoric acid 25 - 50%

I'm kinda partial to 19th century writing, so I dug up an old book:

A Dictionary of Chemistry, On the Basis of Mr. Nicholson's; The Principles of the Science are Investigated Anew, and Its Applications to the Phenomena of Nature, Medicine, Mineralogy, Agricultures, and Manufactures, Detailed.
By Andrew Ure, M.D., 1821

"Diluted muriatic acid rapidly dissolves iron at the same time that a large quantity of hydrogen is disengaged, and the mixture becomes hot."

"Phosphoric acid unites with iron, but very slowly."

I don't think basic inorganic chemistry has changed all that much since 1821, so you have a choice of acid that dissolves or acid that unites.

BTW, keep in mind that one of the things produced from putting muriatic acid on iron is ferrous chloride -- used for etching -- so it's an accelerating process. Leave it on too long (how long is that?) and you could end up with holes or hydrogen embrittlement. Leave phosphoric acid on too long and you get iron phosphate -- a rust inhibitor.
02-12-2008 05:38 PM
Originally Posted by F&J
Don't use muriatic on cast iron...period. If you soak a cast iron part for a while, it will look like the moon...only the craters will be deeper

That is what I meant earlier when I said "especially cast iron" because it is slightly porous and will retain some of the acid. I guess technically it may not actually be porous but the irregular micro-grainy type surface will be just as bad.
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