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Large Parts, Evapo-Rust & Vacuum bags

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SkinnyB

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I have some larger items to de rust at some point. So I am either going to need a large container and gallons of evapo-rust or use the recommend method of using paper towels covered in the rust remover. I had the idea of placing the part in a vacuum bag then sucking out the air, filling with evapo-rust and trying that. Not sure if its been done before or if it was going to work but was a new idea for me! This is how I got on:

Thought I would try some smaller but still on the large side parts first. My idea is to use a vacuum bag which seals around the part. This will then be my container and use a lot less liquid than trying to find a container to fill up.

I didn't have any 'proper' vacuum bags so I improvised with some plastic bags and pipe. I would recommend getting the correct size vacuum bags for your parts. Bin bags were not ideal and had a few holes in.

My first try was also to use paper towels as well as a bag. Although it did work in some areas... A few points:

All the paper needs to be saturated and be pressed against the surface.
I had a few less saturated spots which actually meant the rust stuck to the paper towel and was left on the part. It needed a firm chisel to remove it.
Clean up is a lot messier.
Lots of rusty paper towels stuck to the metal.
Retrieval of liquid is a pain
All the evapo-rust I want to reuse is in the paper towel. Id have to squeeze it all off

paper towel
IMG_6255 by jamie skinner, on Flickr

Bag and evaporust poured in
IMG_6257 by jamie skinner, on Flickr

Vacuumed the air out.
IMG_6258 by jamie skinner, on Flickr

Part after a few days, as you can see some areas worked some did not where there wasn't enough liquid.
IMG_6286 by jamie skinner, on Flickr

Second attempt and things I changed:
Swapped to heavier duty bags
Used a pvc pipe to suck air out of and pour in evapo-rust.
Elastic bands to hold plastic once vacuumed.
No paper towel

Placed in a box just in case it leaked.
1 Place part in bag.
2 Suck air out
3 Elastic bands
4 Suck a little more air out
5 Pour in evapo-rust until bag is full to the top.

IMG_6302 by jamie skinner, on Flickr

After 24 hours I opened it up and seemed to have gone well.

IMG_6311 by jamie skinner, on Flickr

I am pleased to say this worked very well. But I would recommend on some vacuum bags instead of bin liners...
Picture is just before painting, cleaned up with a wire brush and cleaning products.
Will have to try this on the big parts now!

Overall:
Very easy to retrieve the liquid after.
Used a lot less of the solution.
Meant I didn't have to buy lots of solution just to cover the parts. (I know you can do one side then flip the part over if you don't have enough. Didn't fancy it though.)
Great for awkward shaped parts



IMG_6314 by jamie skinner, on Flickr

Here was the other part I was also doing.
Unfortunately the bag leaked a bit so didn't get the very top part. Worked on the rest very well though.

IMG_6313 by jamie skinner, on Flickr
 

AndyT

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Interesting idea, and good of you to share the experiment. I wonder if it would be easier with some big zip-lock freezer bags? They are fairly heavy weight and watertight so you could have the part with enough liquid to slosh around a bit, and you could see how it was getting on.
One possible problem would be if the chemical action gives off any gas - the sealed bag would inflate a bit. Does evapo-rust do that, like acids do?
 

Demusss

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You could try heavy duty black bin bags.

Or, put your large part in a container large enough. Then fill the gaps with some objects. I used plastic bottles filled with water. Then fill the container with your derusting solution.

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