Citric acid pickling strength?

[chrisb]

What sort of strength citric acid solution is recommended for picking a copper boiler for a clean up?

[flyingfox]

Hi Chris, I use a level table spoon per litre for boiler pickling, and that is as strong as you need. high temperatures help the process, and if making a boiler, I add some more Citric Acid towards the end of the boiler build.

Regards

Brian B

[racinjason]

I mix mine really strong and use it for cleaning all the silver soldered parts, my new boiler came out spotless in few hours from cold it doesn't burn but stings in a cut.
cheers Jason.

[kipford]

I use 20g/lt into hot water. Works fine.

[chrisb]

Thanks for the input guys. It’s given me a ball park strength to start with.

[Greg]

Hi,

So I've been building a 3/12" gauge boiler. Just the caulking left. Done with high temp plumbers solder (3% silver). I obviously need to clean it after caulking.


My pickle had been sulphuric acid until now, but I was worried about it eating the soft solder, so I thought I'd use citric acid instead, because I thought it'd be gentler. 


I've never used if before with a boiler, but thought it was week. So I thought I need plenty of poweder.


So my mix was 4x100g of citric acid mixed into  to 6 litres of water. Used warm water to help get it mixed in. I thought that shouldn't be too weak. 


Well in a few hours the copper wasn't that much cleaner, but all my solder softr had turned into grey mush   So 60+ grams per litre is too strong for soft solder. I don't know if it liked the tin, lead or silver in it.

Although I felt it was still slow to clean the copper, so I'm wondering if perhaps I return to using sulphuric acid?

Greg

[flyingfox]

Greetings Greg, that was mighty a strong concentration, and it would have worked a lot better hot. The excess acid actually pacifies the copper and makes it more difficult to clean.
regards
Brian B

[Greg]

Yes not good outcome.

So how do people get their new boilers looking so spotless? After removal from the pickle can the copper rubbed with some light abrasive material to finish cleaning it up?

[simplyloco]

Nov 2, 2023 9:59:29 GMT Greg said:

Yes not good outcome.

So how do people get their new boilers looking so spotless? After removal from the pickle can the copper rubbed with some light abrasive material to finish cleaning it up?

Brillo Pads!

[Greg]

Nov 2, 2023 10:44:44 GMT simplyloco said:

Nov 2, 2023 9:59:29 GMT Greg said:

Yes not good outcome.

So how do people get their new boilers looking so spotless? After removal from the pickle can the copper rubbed with some light abrasive material to finish cleaning it up?

Brillo Pads!

Thanks. That sounds easy. I thought they'd scratch thet copper up a bit much.

[simplyloco]

Nov 2, 2023 11:30:29 GMT Greg said:

Nov 2, 2023 10:44:44 GMT simplyloco said:

Brillo Pads!

Thanks. That sounds easy. I thought they'd scratch that copper up a bit much.

It all depends on what sort of finish is required, and whether the boiler will be covered. If you want shiny then there's always Solvol Autosol...!
John

[flyingfox]

I use a green scouring pad.
regards
Brian B

[jo479]

Make sure ALL your soldering is complete before using the Brillo Pad

[Greg]

Thanks all for the advice.

I have some of the green scouring pads, so I'll go with them until all the leaks are sorted.

[stevep]

Scotchbrite is what I use.

[doubletop]

Mine eventually ends up as a saturated solution with a cake of crystals in the bottom. It starts off in a large plastic container with a lid but more citric acid gets added over time. If I do a small volume mix in hot water for say fittings that all gets chucked in the bigger bin when finished. As it is organic a bit of bleach in the mix to ward off mould growth. Every few years the liquid is drained off and what remains allowed to dry out and the crust in the bottom removed to start again.

Pete

[cupalloys]

Wow!

In my day, 10gm of salt per litre of water worked remarkably well removing flux residue.

It was cheap and cheerful and when it was spent, it was tipped down the drain and fresh solution made.

Do not attempt to clean the boiler until all the brazing is completed
and tested - but why would you?

Oxide removal is the function of the flux not the model maker!

Or have the basic principles of successful silver soldering changed?

If not, get the book from CuP Alloys.

Keith

[chrisb]

Thanks Keith, I am cleaning up an older boiler rather than making a new one.