# Pickling agent for copper



## K27fireman (Jul 19, 2008)

I am building a copper boiler 3" in dia and I need a Pickling agent, so what do you guys use to CLean copper before you Silver Solder?

Thanks, Jeff


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## Guest (Feb 7, 2009)

Sulphuric acid, diluted of course, is the first choice of most boiler builders. Citric acid will also work but is less aggresive and therefore less effective. It can also be considerably more costly. Muriatic acid, a dilution of hydrochloric acid used to clean masonry, can also be used, again further diluted. Muriatic is at least as effective as sulphuric and is cheap but tends to load up with dissolved oxides more quickly and becomes ineffective after a few boilers.


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## Shaymaker (Feb 15, 2008)

*Sulphuric acid will eat your shoes, your trousers, the wooden floor and, eventually, eat away your boiler. The only reason it's ever recommended is "because that's the way we've always done it".*

*In the UK, I use a kettle descaler called Ataka, which is Formic Acid, but any weak acid will do. * 
Mike

When I previewed this, the font got smaller and smaller - weird!


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## David BaileyK27 (Jan 2, 2008)

I have a large bucket of dilute sulphuric acid, I top it up about every 3-4 years and have had it now for over 20 years, would not use anyhtin else. 
David Bailey


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## highpressure (Jan 2, 2008)

Hello David. You were missed at Diamondhead this year. I also use Sulphuric acid (out of an old auto battery). I made my MIX in 1968 when I started my first ride on engine. It is still in the same container and I have had to add less than a quart of water in all of those years. *BE SURE TO KEEP IT IN A COVERED CONTAINER, *as the evaporating part will eat up everything in the room where you have it stored. Use eye protection in case of splashing. I'm sure one of the more educated beings out there will be able to explain this in detail.


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## Guest (Feb 7, 2009)

>>Sulphuric acid will eat your shoes, your trousers, the wooden floor and, eventually, eat away your boiler. 

Of course it will, if you use it undiluted and the boiler is left soaking for weeks. I think the board recognises that some care, caution, and responsibility is required to avoid injury and damage. 

>>The only reason it's ever recommended is "because that's the way we've always done it". 

Or, . . . . if it was discovered long ago that it does its job very well, as well as anything else, is freely available at a reasonable cost, has a long shelf life, and can be safely disposed of.


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## David BaileyK27 (Jan 2, 2008)

Yes Larry, I have an airtight cover for it.
David Bailey


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## Shaymaker (Feb 15, 2008)

Posted By Curmudge on 02/07/2009 12:02 PM
>>Sulphuric acid will eat your shoes, your trousers, the wooden floor and, eventually, eat away your boiler. 

Of course it will, if you use it undiluted and the boiler is left soaking for weeks. I think the board recognises that some care, caution, and responsibility is required to avoid injury and damage. 

>>The only reason it's ever recommended is "because that's the way we've always done it". 

Or, . . . . if it was discovered long ago that it does its job very well, as well as anything else, is freely available at a reasonable cost, has a long shelf life, and can be safely disposed of.



I wrote what I did based on long experience, having had my shoes, trousers and workshop floor attacked by _dilute_ sulphuric acid many years ago. Since then, I've always used something a little safer. As for "care, caution and responsibility", I'm still alive and in one piece after a lifetime in industry, so I reckon I know a little about that too.

The old time "experts" were not alway right.

Mike


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## K27fireman (Jul 19, 2008)

So what would the ratio be for say a gallon of water?


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## Taperpin (Jan 6, 2008)

I have used Swimming pool acid [dilute] for some years now..easy to buy in pool shops and no fumes in the shop// the current jar will seeme out! 

Gordon.


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## xo18thfa (Jan 2, 2008)

Posted By K27fireman on 02/07/2009 1:17 PM
So what would the ratio be for say a gallon of water?

Use about 10-12 parts water and one part sulfuric acid. I got sulfuric acid from Home Depot. They had a heavy duty clogged drain opener was 89% acid. I works great. Keep the mix in a tightly covered container. I store mine outside. The fumes are corrosive will eat everything in site. If you get this stuff on your skin, clean it off quickly under running water. Otherwise you get a very irritating itch. After silver soldering, let the part cool down to room temp. Pickle copper for about 15 minutes, then clean off under running water with a brass brush. Boy, does it look nice.

Bob


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## Ora Banda (Jan 2, 2008)

Hi, Bob


My preferred solution is citric acid, you can usually pick it up in the grocery store in powered form... it is generally used as a food additive to give a sour taste to candy etc. It is totally safe. It may take a little longer in the pickle bath but is totally safe. Worth a try.


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## K27fireman (Jul 19, 2008)

Thanks, John 

What's the ratio of Acid per gallon of water ?


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## Chris Scott (Jan 2, 2008)

Posted By Shaymaker on 02/07/2009 1:17 PM
Posted By Curmudge on 02/07/2009 12:02 PM
>>Sulphuric acid will eat your shoes, your trousers, the wooden floor and, eventually, eat away your boiler. 

Of course it will, if you use it undiluted and the boiler is left soaking for weeks. I think the board recognises that some care, caution, and responsibility is required to avoid injury and damage. 

>>The only reason it's ever recommended is "because that's the way we've always done it". 

Or, . . . . if it was discovered long ago that it does its job very well, as well as anything else, is freely available at a reasonable cost, has a long shelf life, and can be safely disposed of.


I wrote what I did based on long experience, having had my shoes, trousers and workshop floor attacked by _dilute_ sulphuric acid many years ago. Since then, I've always used something a little safer. As for "care, caution and responsibility", I'm still alive and in one piece after a lifetime in industry, so I reckon I know a little about that too.

The old time "experts" were not alway right.

Mike




...and some people are just lucky.


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## Ora Banda (Jan 2, 2008)

Hi, Jeff... sorry... didn't realize it was you who started the thread when I posted my last reply...


If you search "Citrus Acid Pickle" on Google you'll find lots of info... used extensively by jewelers. Most recommend to start with 1 part citric acid powder to 10 parts warm water. My mix is more likely to be 1:20.. just experiment a bit to find what works best for you, citric acid powder is cheap... and again, is totally safe... great piece of mind.


The pickle does actually work best when it is warm but I've had good results at room temperature. I mixed up a gallon and keep it in a brown glass pitcher jar... it can be reused several times and I keep a small amount in a small screw top glass jar for every day use when making boiler fittings etc.


PS... One hard lesson that I learned was that you MUST wash the pickle off your workpiece thoroughly before starting heating it again for another soldering operation. I failed to do this when making a small gas tank and the citric residue ended up baking to a hard carbon glaze inside the tank... impossible to remove... I had to scrap the tank.


Here is a photo of one of my projects that has been done exclusively using citric acid pickle.









 


Hope this helps.


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## K27fireman (Jul 19, 2008)

Impressive looking boiler, and thanks for the tips.


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## steamboatmodel (Jan 2, 2008)

I usually use Citric Acid, but have in a pinch (Some one emptied the pail down the drain) used plain white vinegar. It doesn't work as fast, just as Citric doesn't work as fast as Sulphuric, but it does work. 
Regards, 
Gerald. 
PS the only drawback to using vinegar is you wand Fish and Chips when through.


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## David Leech (Dec 9, 2008)

Posted By K27fireman on 02/07/2009 9:56 AM
 
 
I am building a copper boiler 3" in dia and I need a Pickling agent, so what do you guys use to CLean copper before you Silver Solder?
 
Thanks, Jeff


Hi Jeff,
I may be wrong here, but your original question appears to be asking how to clean the copper BEFORE solver soldering.
I know NOTHING about this part of our hobby, but my understanding, as has been pointed out by others, the term PICKLING is with regards to cleaning up the part AFTER silver soldering.
As to before, I would think (and I again point out that I have little knowledge here) that a good mechanical clean with paper, or wire wool is sufficient, as in the same way with soft solder, the flux will do most of the work in making sure that the silver solder can do it's job.
If I am wrong, I am sure that one or more of you will correct me.
All the best,
David Leech, 
Delta, Canada


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## Ed Hume (Jan 3, 2008)

The cleaning before soldering should remove any oils, for example by using mild detergent and then flushing with water. I'll use an ultrasonic bath for small parts. 


All those comments on pickling agents are not in vain. Just before soldering, it is good to dip the pieces in your pickling bath - it removes the little oxide tarnish and activates the surface for soldering. Rinse thoroughly, flux, and solder soon after fluxing. Then use your pickling bath again.


Dilute sulphuric acid is what I use - battery acid diluted in half. If you want to have a safer form of sulphuric acid, you can buy Sparex from jeweler's supply houses.


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## xo18thfa (Jan 2, 2008)

Posted By Ora Banda on 02/07/2009 4:58 PM
Hi, Bob


My preferred solution is citric acid, you can usually pick it up in the grocery store in powered form... it is generally used as a food additive to give a sour taste to candy etc. It is totally safe. It may take a little longer in the pickle bath but is totally safe. Worth a try. 


Hi John: I will look for it in the store. Nice looking boiler. How have you been?? How are those 7/8 projects coming?

Bob


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## Ora Banda (Jan 2, 2008)

Hi, Bob...


Yes, I've been silent for a while now. My move back home to Melbourne form Singapore went well... my attention has been on home renovation and building the workshop and not much progress on the locos. The workshop is taking longer than I expected to set up but I'm getting there. My model engineering tools have had to make way for carpentry and brick laying stuff!


 










My wife keeps saying if I didn't build the workshop to microscopic engineering tolerances... it would have been finished way sooner ! All good fun though. Just as soon as work on the locos start again I'll post.


How about yourself? What are you working on?


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## AsterUK (Jan 2, 2008)

Sulphuric acid makes the best pickle and also the best means of cleaning parts prior to silver soldering. Citric acid and clear vinegar work too but a 10% solution of Sulphuric Acid is fast and more effective at removing the remains of the flux too. (I find citric and vinegar pretty useless).

However, I make no excuse for saying that when diluting any inorganic acid like Sulphuric Acid, always add acid to water[/b] [/b]never the other way about. The act of dilution is a very exothermic reaction. That means a lot of heat is generated. If you add water to concentrated acid then the reaction is extremely unpleasant - hot acid is likely to spit everywhere.

Please always store concentrated acid and diluted pickle in a safe place away from children and pets. Its not nice stuff to have around but its darned effective as a cleaner and pickle for silver soldering so dilute, store and use with care. 
As an afterthought. I am pretty useless at soft soldering but i find silver soldering to be a most satisfying job. With a little care with cleaning component parts first and then the careful application of flux and finally heating up to a dull red and watching the silver solder 'flash' round the joint is a pleasure. But the best bit comes when you take the item out of the pickle and see the copper and brass parts shining brightly and a neat meniscus of silver keeping all the parts together. Almost as a good as a steam-up and a cold day! 
Andrew


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## Slick (Jan 3, 2008)

Great topic and an excellent education......thanks fellows.


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## Ed Hume (Jan 3, 2008)

As I built the boiler for my gauge 1 Climax, I posted many photos on flickr. There are 115 photos in the set -


http://www.flickr.com/photos/edhume3/sets/72157604664938888/





In this photo I am using copper tongs with a 10% sulphuric bath. I do have eye protection on but I am somewhat casual about gloves. I am right next to a sink and fully prepared to rinse off quickly if I splash my hand. A covered plastic container like this one is big enough for gauge 1 boiler work.

By the way the copper sulphate will plate out rapidly on tool steel or mild steel but not stainless steel. This provides a quick test for stainless - dip it in and see if copper plates to it.


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## HMeinhold (Jan 2, 2008)

We switched to citric acid a couple of years ago and have no problems. Copper/brass gets shiny and the residues of flux (we use the commercial stuff from McMaster) dissolves fairly easily. Though diluted sulphuric acid worked faster, we find it very annoying, as even tiny splashes develop holes in clothing, usually days/weeks after the soldering session. 
Regards


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## AsterUK (Jan 2, 2008)

Ed Hume said - ”By the way the copper sulphate will plate out rapidly on tool steel or mild steel but not stainless steel. This provides a quick test for stainless - dip it in and see if copper plates to it.”

That’s a very useful tip Ed, thanks. Basically that is why is worth being a member of MLS for those simple tips which come in handy.

Henner mentions the problems with handling dilute Sulphuric Acid as a pickle. I have found that using tongs at arms length is the best way to go. When the boiler or work piece comes out of the pickle then put it into a bucket of water straight away to rinse. Having water available in case of a splash is good practice. I wear old clothes and work in the garden when I am doing a bit of Silver Soldering. I wear eye protection and generally get everything organized before starting the work in hand. I mix up fresh flux each time and work with the lower temperature solders like ‘Easy-Flo”. Now that Cadmium is banned from Silver Solder in Europe, it doesn’t ‘flash’ round a joint as easily but it still works well enough for me. 
Andrew


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## gwscheil (Aug 6, 2008)

Yep, old lab rats could quickly identify which sweatshirt was worn on the sulphuric acid day in the lab. After a few days on cotton and many other textiles, everything looks normal until wash day. Then major moth attack - holes everywhere a tiny drop made contact. Diluted and cool, sulphuric is slow acting on organic matter - including human beings. Heated, or concentrated above about 70%, it shows a powerful affinity to water and will dehydrate anything it contacts. I still remember the high school demonstration of pouring some concentrated sulphuric into a beaker filled with table sugar - in seconds it turned to solid black carbon - stripped the water right out of the sugar, that is why it is called a carbo-hydrate, a hydrated carbon atom skeleton. Below about 70%, sulphuric has enough water of hydration to stop the dehydrating action, but the strong acid attack remains.

And yes, sulphuric acid is the most dangerous one when adding to water due to the hydration action. SLOW addition of acid to water, preferably in an ice bath, is called for. The other common mineral acids do not generate the tremendous heat of hydration, but the same rule applies. Adding a small amount of water to concentrated sulphuric generates enough heat to flash the water to steam, splashing acid everywhere.

So, goggles and protective clothing are strongly advised. Fumes include assorted sulfur oxides - all toxic and corrosive. Without a fume hood, maintain plenty of fresh air unless you happen to have a respirator fitted with acid fume cartridges. And do not forget that any acid reacting with metals generates hydrogen gas - iron filings and mineral acid are still used as hydrogen generators.


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## Havoc (Jan 2, 2008)

A pair of inox BBQ tongs is nice to have next to the pickle bath. But don't use them for anything else afterwards. 

Regarding HCl, this might be usable for this, but I won't allow it inside the workshop. It rusts everything even if kept in a closed container.


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## K27fireman (Jul 19, 2008)

Ed, the first thing that comes to mind is WOW! You are a Master. 
Thanks!


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## Steve Shyvers (Jan 2, 2008)

Ed - Thanks for the boiler fabrication photos. Nice to see how it's really supposed to be done! 

For pickling I use sulfuric acid from the hardware store plumbing section, but the dilution I mix is probably between 1:20 and 1:30 with water. It's not overly aggressive but it works. I wear eye protection and old clothes. I really need to find some more rigid tongs than the plastic BBQ tongs I currently have. They don't grip well - not rigid enough - and large parts can slip when fishing them out of the pickle causing the acid solution to splash. I need to do better as it's not something to be casual about. 

The pickle is stored outdoors in a covered rectangular plastic container that fits inside a black plastic battery box. I used to keep the pickle in a container with a plastic gasketed cover, but the gasket disintegrated over time. Thanks to George's post I now know why. 

Steve


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## HMeinhold (Jan 2, 2008)

Here is a silver soldered fitting I did today. Pickling was done with citric acid for about 15min. Tube diameter is 5/32". All traces of flux are gone: 










Regards


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## JoelB (Jan 3, 2008)

I realize that this comment is "off thread", but I've also found that pickling brass or copper parts is a good prep for painting. Brass, especially, takes paint more readily when cleaned this way beforehand. I've got some sodium bisulfate (purchased from Sulphur Springs many years ago) that works great.


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