Useing Citric acid

Would it be safe to use citric acid in a ultra sonic cleaner?

Yes.

I use a citric acid-based pickle in my ultrasonic bath - the combination of warmth and vibration cleans up after silver soldering very effectively. I have two bottles of solution made up. One for steel and one for copper/brass.

Dave and Nealeb thank you very much for our help

What strength do you use for each solution Neal?

It should be. The baths are normally of stainless-steel. Usually they are used with detergents, which are alkaline rather than acid.

However it would be wise to clean the bath well after using for any metals that may have carried swarf particles; as some metals including mild-steel can react against the stainless-steel, causing pitting.

Yes, me too.

IanT

Citric acid can be used to passivate stainless steel which is particularly important if it is used in a marine enviroment.

Sorry - can't remember off hand. I'll try to remember to check the label on the packet when I'm next in the workshop. I'm sure that there are recommendations online, though - it's commonly-enough used.

It does appear to put some kind of coating on steel but whatever it is, it seems to take paint well enough, and does not interfere with subsequent silver-soldering.

Thanks, I can get plenty of it as my son works in the food industry but I don't want to 'overcook it', it's what I tend to do

Over the last year or so I've become a convert to using citric acid instead of other acids such hydrochloric and sulphuric after doing a comparison on some rusty nuts from one of my motorcycles. I did a post about it at the time so wont repeat myself here. I hadn't considered using it in my ultrasonic bath but will give it a go based on the comments above.

A simple way to stop cross contamination in an ultrasonic bath is to use glass jars placed in the basket to hold the pieces (if small enough) to be cleaned and fill the jars with whatever solution you use for cleaning. You then fill the bath with water up to the usual height. Using this method you can, if desired, use different cleaning agents at the same time. It also has the benefit of keeping your bath protected from any more aggressive solutions you might want to experiment with.

A simple test to prove that the glass jars do not interfere with the cleaning process is to place one part in a jar and one part directly in the tank and compare the outcomes.

I have used citric acid pickle for years in the ultrasonic bath after annealing my cartridge brass in a molten salt bath with excellent results. The only other thing I do after the pickle is to rinse in clean water then immerse in a tub containing disolved household washing soda to neutralise any remaining vestiges of acid.

A glass jar works perfectly for avoiding having to clean out the tank, but often even easier is a polythene bag (keep open end above waterline). Or use a bit of plywood with a 50mm hole that fits on top of the tank to allow you to push sheet polythene through, put on parts and whatever cleaning fluid, run cleaning cycle, then cleanly discard the debris. You can fit a pin into a bit of rod to punch a few pinholes in the polythene to decant any reuseable fluid.

Thank you everybody for help and advice i shall be trying some in near future.Graham

I've never measured it, but the answer for me is 'surprisingly weak'!

It doesn't seem to need to be very concentrated to work well.

Neil