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Ultrasonics and citric acid

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gerry madden29/06/2020 18:31:42
252 forum posts
132 photos

Hi all,

I'm currently renovating an OMT toolmakers microscope that I have recently bought.

Lots of the adjustment knobs and screwheads are rusty. I'm cleaning them up by alternating them between dunks in citric acid and spells in the ultrasonic cleaner. The acid does most of the work but the u/s cleaner initially degreases and then removes the heavier layers of rust. The process is slow...well too slow for I'm just wondering if I can sensibly put my acid mix in the u/s cleaner to speed things up a little ?

I've not heard of anyone doing this before and cant think of any pitfalls, but just thought I'd check with others who may have better knowledge in such matters.


Baz29/06/2020 18:39:48
724 forum posts
2 photos

I have used citric acid in the ultrasonic cleaner for descaling injectors with no problems.

Andy Carlson29/06/2020 19:35:37
432 forum posts
132 photos

You didnt say if you were making it hot or cold. Hot will speed up the reaction.

Old School29/06/2020 19:49:07
406 forum posts
39 photos

Yes you can citric acid and a little washing up liquid and do it hot you will get good results, change the solution regularly

Ed Duffner29/06/2020 19:49:18
840 forum posts
94 photos

Could you put the acid inside a container (jar?) then lower the jar into the cleaner fluid? Supported well so the acid cannot spiil into the cleaner solution?

I'm not sure how well ultrasonic waves pass through container walls. Might be worth a try. It seems to work for some of the resin 3D printing people.


Robert Atkinson 229/06/2020 20:05:20
1209 forum posts
20 photos

Ed's suggeston is good and standard practice for cleaning small items in a ultrasonic cleaner. A glass laboratory beaker works well. Use hot water in the taank and cleaner, citric acid in this case in the beaker. Ideally float the beaker with a collar of closed cell foam. A thin (cheap) pressed stainless steel cat's food bowl works well too.

For non-ferrous alloys a dilute solution of ammonia with a drop of washng up liquid works well.

Robert G8RPI.

Neil Wyatt29/06/2020 20:19:47
19037 forum posts
734 photos
80 articles

I've got some concentrated derusting fluid for my ultrasonic cleaner that I'm sure contains citric acid.

I usually use it at about 50C


pgk pgk29/06/2020 21:57:28
2563 forum posts
293 photos

I posted the link to this vid by Tom Lipman on a rusty renovation before...


When using ultrasonics the intensity of bath types varies, I once used an ultrasonic probe to clean a cheapo watch and the hands and numerals fell off...


Nigel Graham 230/06/2020 00:41:14
2136 forum posts
29 photos

I am surprised the sound waves actually pass through any intervening beaker or pan wall, rather than being reflected from it, making me wonder if the work-pieces are simply being pickled. Any vibrations that manage to negotiate the barrier would almost certainly be attenuated by it.

The ultrasonic cleaner I used at work - itself based on ultrasonics - had a stainless-steel work-basket nearly as large as the tank, and I would never put the work in a solid-walled secondary container unless advised in the operating-manual. Ours did not even mention it; and it is hard to see where it might be "standard practice" unless for some particular make and type of ultrasonic cleaner (jewellery or horology trade perhaps?).

These tools are otherwise meant to be used with the work-pieces immersed directly: suspended, in the basket supplied with the appliance, or just laid in the tank. I would use suspension for small items. All you need do is ensure the additives will not harm the tank.

Clive Hartland30/06/2020 07:21:49
2820 forum posts
40 photos

The use of a container in the ultrasonic liquid was standard as far as we were concerned when cleaning oil/grease from optical componebts. I observed the liquid in the container agitating quite happily and would watch as the dirt came out of the parts we could not reach to clean. I have at times used a small quantity of solvent in the container if needed making sure the main liquid was not contaminated.

Further to this we used an aqueous solution called Micro, no connection but it is good stuff. ask for a sample if you contact them and only a 2% solution needed.

Rusted parts need pre-treatment of course.

Graham Stoppani30/06/2020 07:32:09
124 forum posts
26 photos
Posted by Neil Wyatt on 29/06/2020 20:19:47:

I've got some concentrated derusting fluid for my ultrasonic cleaner that I'm sure contains citric acid.

I usually use it at about 50C


I run my ultrasonic tank at 65C, so in the same ball park as Neil. As a side note, if you've put fresh liquid in your tank and are waiting for it to come up to temperature, its worth running the bath empty to degas it while it warms. This will increase the effectiveness of the bath.


Brian Baker 130/06/2020 08:25:49
196 forum posts
36 photos

Greetings, just remember that hot Citric Acid solution in the eye is not nice.



Danny M2Z30/06/2020 08:41:22
963 forum posts
2 photos

My ultrasonic cleaner has a stainless steel tank and I regularly use a solution of citric acid in it to clean used brass cartridge cases before re-loading them.

The results in 10 minutes are better than when I previously used a vibrating tumbler full of crushed walnut shells running for hours. After use I flush the u/s cleaner tank with tap water and it's still working well after 6 years.

* Danny M *

Edited By Danny M2Z on 30/06/2020 08:41:58

gerry madden30/06/2020 22:49:37
252 forum posts
132 photos

Good advice as always. Thanks for your mass of useful info.


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