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Discussion Starter · #1 ·
After reading EricD's post on oxalic acid for rust removal, I decided to give this a try. I purchased a small container of wood bleach at a local hardware store, for a mere $8.

Took awhile to find it. In this store it was with the wood stains/solvents etc and not the cleaning supplies.

I read on this site to use a 5% solution. This felt like too much.
http://oxalic-acid.info/oxalic-acid-rust-remover

I read on another site to use 1 tablespoon per gallon, which is what I used.

EricD mentioned about keeping the solution warm.

For the first round I mixed the oxalic acid in hot water and left the items overnight. The rust was mostly removed. I did not have a white or black patina. The solution was a slight green colour.

For the next round the solution was now room temperature, about 65 deg F. I had the solution in a zip lock bag since I did not have a suitable container.

I decided to use nature to warm up the solution so put the zip lock bag in a black plastic paint roller tray and laid this on a stool in my sunroom in the morning.

When I removed the items later in the afternoon I saw there was white particles in the solution and on the metal. This was not a patina and just washed off.

Today I tried round three. Again leaving in the same solution with the white powder, but only for a few hours.

The metal had a greenish coating which washed off. Some of the metal had black patina which I had to work on with wet-dry paper to remove.

One mark puzzled me. It was on the edge of a plane blade I had sharpened the day before, so this edge had no rust.

I thought oxalic acid only worked on rust.

So anyone have any comments on what I may have done wrong?

Too much heat, wrong solution, or just my bad luck?
 

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Discussion Starter · #4 ·
I'm interested to find out how this works Dave.
As to a secondary rust removal. I'm happy how electrolysis worked, but would like to see what the two differences are.
From what I have read on the forum and elsewhere, electrolysis is preferred when the finish AND rust need to be removed. Very inexpensive method as you can attest.

The bicycle crowd seem to like oxalic acid because it is inexpensive, so they can dunk entire frames in the solution and it does not harm paint or especially chrome.

Evapo-Rust also does not harm paint or chrome, but it is expensive. I think this is the old stand-by when the finish needs to be kept and the parts are small enough so the cost of the Evapo-Rust is not a factor. I found using ziplock bags helped me to minimize the volume needed.
 

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Discussion Starter · #7 ·
Sounds as if it worked. The cold temperature cause it to fall out of solution, I think 658F is too cold, I use minimum 80* (fish tank heater temp) and start with hot tap water. I try to watch the process closely to pull the object before the white residue coat happens.
How do we know when the solution is spent?

Any comments on the black patina. Harder to remove than the Evapo-Rust grey patina.
 

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Discussion Starter · #19 ·
The oxalic acid is not a dipping method, rather submerging the parts for an extended period of time.

The oxalic acid is not as difficult to handle as muriatic acid but does a good job when the parts are left for long enough perioid.

Rust removal is not the intended use of oxalic acid, but it is effective.
 
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