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Post by Garry Coles on Mar 9, 2007 19:47:10 GMT
Hi everyone Question about pickling. I have 2.5 Lt's of full strength (98%) sulphuric acid, and having read one of my ME books, it suggests diluting at 10%. Is this correct for all pickling before and after silver soldering. Also will one of the large 25 lt plastic water containers be OK to store it in. The container I mean is the one that is the same shape and size as a jerry can. Also how long will the solution keep. Cheers Garry
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Post by alanstepney on Mar 9, 2007 20:12:08 GMT
It keeps for ages. I have a container of dilute acid that is several years old, and still works. I store it in glass, plus one particular plastic container, as some plastics arent suitable (so I am told). The plastic one I have originally held acid, but what the plastic is I have no idea. (Or maybe it doesnt matter, I'm sure the chemists here will know.)
a 10% strength will work fine, and even 5% is OK albeit much slower.
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Post by Tel on Mar 10, 2007 7:28:33 GMT
Nip along to the pub and scrounge one of the 20 litre plastic drums the refill spirits arrive in - they are properly rated 'hazardous' containers. Unless, of course, you want to buy a full one of, say, Glenfiddich, and empty it the hard way.
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Post by Shawki Shlemon on Mar 10, 2007 9:36:56 GMT
I use 20 Lr paint container with cover ,to be safely covered when not in use .It keeps for years. When it become blue or better dark blue is full of copper sulfate and becomes not so active. the change is not affected by time but with use .Don't forget add acid to water and slowly .
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Post by Deleted on Mar 10, 2007 13:56:25 GMT
Take Real care with neat sulphric.
Cant stress the safety aspect enough, ALWAYS very slowly add acid to water not the other way round.
I spent a very unhappy and uncomfortable week in an eye hospital a good few years back with sever acid burns.
Don't be butch, put on the safety goggles wear rubber gloves at the very least, do not fall into the trap of thinking it looks like water so it's not going to harm me.
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Noddy
Statesman
Posts: 672
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Post by Noddy on Mar 11, 2007 19:29:47 GMT
Sulphuric keeps indeffinately, it won't evaporate.
Two cautions about plastic containers:
As you add the acid to water, it gets hot (do it the wrong way around and the steam generated will spatter acid everywhere). you don't want a container which will go all soft with the heat, and it isn't difficult to get the mixture boiling!
Most plastic containers should be ok as long as you label them well enough to avoid mistakes, but strong acids will reduce nylon to a jelly.
Hope this helps Keith
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Post by alanstepney on Mar 11, 2007 21:15:32 GMT
One other safety point, the fumes off sulphuric eats clothes wonderfully. Best used with plenty of ventilation, or preferably outdoors, but not where children or animals can get at it.
As for splashes, I always use goggles, on the basis that I only have two eyes and want to keep both of them.
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Noddy
Statesman
Posts: 672
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Post by Noddy on Mar 11, 2007 22:43:36 GMT
Let me second Alan's comments about goggles. My Brother got a face full of a weak acid 18 months ago. But for some very prompt action by the guy who was working for him in getting a water hose into his face then the guy having a GPS in the car to find the route to get him to the Eye infirmary (he went to the local A&E first and they said "not here", the eye infirmary was about an hours drive!), he would have lost his sight.
That was a weak acid (propionic acid, used as a grain preservative, it is like working with tear gas!)
Saying as you have the Sulphuric, you may as well use it, but Citric is a lot easier to get (about £8 for a 20kg bag), none poisonous, and won't burn holes in your clothes or you.
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Post by modeng2000 on Mar 12, 2007 7:53:19 GMT
Noddy,
Where would I look for citric acid please? So far I have been using plumbing drain cleaner (sulphuric acid)for pickling.
John
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Noddy
Statesman
Posts: 672
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Post by Noddy on Mar 12, 2007 10:46:29 GMT
In small quantities, boots, tesco or sainsbury (look in the cooking ingredients area). The bulk bags came from an agricultural chemist. I'll call my brother and find out which one, then post. Keith
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Post by Deleted on Mar 12, 2007 11:45:23 GMT
I get my citric acid from the local home brew shop in 2kg bags for around £2.50. So far I have only used small amounts for pickling fairly small parts so I just put three or four tablespoon fulls to each gallon of water and it works fine as long as you are not in a rush, (I usually leave the parts in the pickle for several hours or overnight). As has been pointed out it is a lot safer to use than sulphuric acid but it does not seem to keep as well. The best plan is to get a batch of parts ready to silver solder, mix fresh solution, pickle to clean, solder and back into the pickle overnight to clean off the old flux and residue.
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Post by the_viffer on Mar 12, 2007 13:38:31 GMT
Modeleng2000
I understand that 20 years ago and more Doug Hewson (then trading as 3H) supplied stabilised sulphuric acid as sold as by janitorial suppliers but over the long term found that it caused problems with the joints.
My recollection might be wrong. [/i]
I imagine Doug is a little touchy about the subject of silver soldered joints these days but it might be worth dropping him a line and seeing if he knows of a problem with it.
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Noddy
Statesman
Posts: 672
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Post by Noddy on Mar 12, 2007 14:19:15 GMT
Hi Valcook, if you mix the stuff stronger, the bugs won't live in it. During the foot & mouth, the footbath outside my old man's gate lasted about a year before peoples feet carrying it away and the rain diluted it enough to get algae growing in it.
Keith
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Post by modeng2000 on Mar 12, 2007 14:33:55 GMT
It looks like I'll be using citric acid from now on. Certainly it is much safer than sulphuric. I note that dilute citric acid is what is supplied by Superdrug for descaling kettles.
John
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Post by the_viffer on Mar 12, 2007 14:45:40 GMT
It looks like I'll be using citric acid from now on. Certainly it is much safer than sulphuric. I note that dilute citric acid is what is supplied by Superdrug for descaling kettles. John That is interesting John. Most of the kettle descaler I've seen uses either sulphamic acid (which is a good bit different from sulphuric acid) or formic acid. I've had a lot of success with citric.
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Post by havoc on Mar 12, 2007 21:05:52 GMT
Yep, these days descaler is often citric acid. Only problem I find is that I never felt 100% sure that that is all there is in it.
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