Rust remover effect on metal parts (The DIY EDTA based solution)

[rjenkinsgb]

This rust remover solution was mentioned in another thread, and I thought I would do an experiment to see what effect it had if metal parts were left in it for rather longer than required.

The mix is five grams of tetrasodium EDTA per 100ml of deionesed water, plus a tiny amount of citric acid to bring it to around ph 6.5 - 7

I've also used disodium EDTA, which seems to work pretty much the same; these are used in such as cosmetics, so not toxic, though I'd not inhale any dust, on principle.

 

I normally soak parts in it for between 30 mins and a couple of hours, depending on the level of rust - and generally use it for tools and such as keyless mechanism parts, rather than movement train wheels.

For this experiment, I used a couple of items from a big clock part collection I got a while ago.

They were suspended part way in the solution; the one with the single thick wheel was at roughly 45' with the wheel half in the liquid, and the other was vertical with around 3/4 of the pinion submerged.

 

This is the result after something over nine hours; the first two photos are the parts straight out of the solution, with just a rinse under the tap:

 

And this is after drying and removing loose residue with a paint brush. They were in quite a bad way, rust scale and pitting in places, which is why I used those parts. You can still see the heavy rust on top of the small pinion, where it was not in the liquid.

The pivots and steel pinion leaves do now have a matt surface; I don't know how much the size would change after re-polishing them.

The brass wheel has obvious colour changes, more coppery where it was immersed, but still shiny rather than matt.

This was using a fresh mix of the solution for this test & I may have added a bit too much citric acid.

 

For comparison, this is a more normal use - a lathe bed from ebay, which had significant surface rust. Around one hour in the solution and it looks vastly better! The slight "marbling" is probably due to me initially trying to use a cloth wrapped around it & soak that; once I realised that was not working evenly I made a crude trough from cardboard lines with a bin bag, so it was fully immersed.

And after; dried then oiled and thoroughly cleaned off, to avoid further rust.

The stuff does definitely work very well, under appropriate circumstances.

[LittleWatchShop]

Good timing.  I recently acquired the small shop of a deceased watchmaker.  There is some rust. As an example, I have 50+ staking punches that have varying degrees of rust.  None bad, however.  My standard procedure is to chuck on to a drill and spin while holding the stake with 600 grit sandpaper.  Works very well, but time consuming.  Been thinking about a chemical solution.

I also have tons of watch screws that have varying amounts of rust.  A chemical method may be the only way for these tiny items.