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Old 02-20-2012, 12:38 AM
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Default Rust removal with molasses.By popular demand

Everyone has heard how molasses dissolves rust, so make a trip to the local pet food and grain store and get your molasses.
The formula is two litres of molasses in 7 litres of water. Put this mixture in a plastic bucket or container and partly cover to help stop evaporation. Leave for about three weeks, down by the back fence (it pongs a bit), until it ferments. It should now have a skin on the top, which should be peeled off. Now you can immerse your rusty parts in this solution. Leave for about two weeks before removing them, by then all the rust should be dissolved (use rubber gloves, long tongs, or tie pieces of wire to the parts before you start, as this mixture contains ACETIC ACID).

After removal, wash off the brown muck straight away with a stiff brush under hot running water. As soon as the parts are dry, treat them with rust converter and paint them as soon as possible, or if not painted, wire brush and oil them. This must be done immediately because surface rust will start to form as soon as the metal is dry, because it is so clean it has no protection.

Apparently the water and molasses mixture when left exposed to air, ferments and produces, amongst other things, Acetic Acid. This reacts with the oxygen in the rust and when the iron oxide (rust) is all reduced the process stops, so the steel or iron is not affected, but the surface of the metal is now virtually in original condition and subject to immediate attack by oxygen in the air and begins to rust, so must be protected.

The benefit of using molasses is that it dissolves that rock-hard rust that even wire brushes can't touch and carborundum cloth can't reach and by using arrangements of odd-shaped containers like old concrete troughs half full of dirt and lined with heavy plastic sheet, it is possible to derust larger objects that would not stand sand blasting.

This mixture will still derust for quite some time, (six months or even more).
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Old 02-20-2012, 01:17 AM
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What would it cost to set up a 5 gallon pail ?
a 55 gallon drum?
a 6000 gallon tank?

What restrictions would you meet when you are finnished and want to empty the tank and clean up?
I have built and used electrolytic tanks in all those sizes .
THe big job was moving the residue from the big tank.
I dug a trench and covered it just to keep it away from my dog.
probably would need to do the same with a large molasses tank.
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Old 02-20-2012, 02:57 AM
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While molasses works well with steel it does not do so well with cast iron.
I had to weld a cast iron manifold from a Dodge V8 fire engine.

It was heavily carbonised up inside so OK we'll try soaking in in a 10 to water and molasses mix. Nearly a week later when we remembered to go and look at the manifold it was like a piece of sponge.We think the molasses water mix ate all the saturated carbon from the casting.

Oz
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Old 02-20-2012, 03:14 AM
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Quote:
Originally Posted by OZWELDER View Post
While molasses works well with steel it does not do so well with cast iron.
I had to weld a cast iron manifold from a Dodge V8 fire engine.

It was heavily carbonised up inside so OK we'll try soaking in in a 10 to water and molasses mix. Nearly a week later when we remembered to go and look at the manifold it was like a piece of sponge.We think the molasses water mix ate all the saturated carbon from the casting.

Oz
Hmmm, eats Cast iron. Makes it a nonstarter for lathe restoration as every lathe I've ever seen larger than a Sherline or Taig is made of cast iron or cast steel (I can't tell the diffeerence without sophisticated or destructive testing), not mild steel.
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Old 02-20-2012, 03:48 AM
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Quote:
Originally Posted by matthew_g View Post
Everyone has heard how molasses dissolves rust,
I've never heard of it. Thank you. I'm gonna have to try it - got lots of rusty stuff out behind the barn.
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Old 02-20-2012, 08:45 AM
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It makes sense that Molasses produces acetic acid, which is vinegar.
So why not just soak the rusted part in vinegar?
dirt cheap and alot less messy.
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Old 02-20-2012, 11:21 AM
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I know from experience what it costs to build run and cleanup after a 6000 gallon tank. I have no access to bulk molasses and would like an approximate cost.
The big tank I built ran all summer and processed a couple of tons of steel and cast iron like my 13 footy long lathe bed and the frame of an 8X10 tilt deck trailer. There are pictures of it here and at

Bill's Antique Gas Engines

Http://antique-engines.com/

You will need to dig a little to get to the derusting page but bill is a pretty neet guy and the page is worth a look .
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Old 02-20-2012, 02:29 PM
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Default Have you tried....?

Very Interesting Terry! You made me look up a word. 'Pong'. I had never seen it before not preceded by 'ping'.

Since the whole point of the exercise is to produce acetic acid, I wonder if you have tried just using that directly. You can get it at the local supermarket. It's sold under its common name - vinegar.

I don't know if it'll clean rust. You could try it on a small piece. If it works you might save the fermenting and stinking uh - ponging - and make the cleanup a bit easier.

DrBob
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Old 02-20-2012, 03:13 PM
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Vinegar cleans rust just great. Leaves a dark coating on the metal if left in for a long time.
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Old 02-20-2012, 11:20 PM
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Quote:
Originally Posted by DrBob View Post
Very Interesting Terry! You made me look up a word. 'Pong'. I had never seen it before not preceded by 'ping'.

Since the whole point of the exercise is to produce acetic acid, I wonder if you have tried just using that directly. You can get it at the local supermarket. It's sold under its common name - vinegar.

I don't know if it'll clean rust. You could try it on a small piece. If it works you might save the fermenting and stinking uh - ponging - and make the cleanup a bit easier.

DrBob
Dr.Bob,
How about using phosphoric acid? Minute amounts in soft drinks. Coke sure cleans the ring out of the toilet bowl!
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