I want to move away form strong acids and use citric acid for pickling after silver solder. I under stand that citric acid is supplied as a powder by brewing shops. What ratio weight powder to water should i be using?
Thanks Mike
Add only as much powder as will dissolve in the water. A weaker solution will take longer to be effective, while it isn't possible to make a more concentrated solution because it is saturated. Sorry to be vague but it really doesn't matter exactly how concentrated the solution is.
By the way, be prepared for some odd questions when you buy citric acid. Apparently is used by junkies in preparing one or other of the more powerful drugs.
Cliff.
I can no longer buy it in bulk here. Seemingly dealers use it to "cut" drugs.
Thanks guys I will see how much they will sell me then.
Mike
Citric acid pickles vary from about 5% to 25% citric acid w/v - that's
50 to 250 grams per liter - usually jewellers use around 150-200 g/l. They work much better when hot. They are still going to be slower than the strong acid pickles though.(The solubility of citric acid in room temperature water is about 750 grams per liter. A saturated solution is not usually used - it would use a lot of citric acid, and it doesn't dissolve some things as fast as a
25% solution)- Peter Fairbrother
You can get single kilos on eBay for about a fiver including postage. Makes a gallon or so.
5kg is about £16, 25kg is about £50, again including carriage.If you want ton lots let me know offlist.
-- Peter Fairbrother
I use a saturated solution. I source the citric acid from eBay in 5Kg packets. It is also an excellent de-ruster for assemblies, and the rust is converted into a water soluble citrate that flushes out of threads etc thus freeing them. If you use phosphoric acid as a de-ruster the resulting phosphate is insoluble.
AWEM
Greetings Mike, In the USA I use a product called "Citrisurf" for pickling stainless steel after welding in order to passivate the surface. It is, as the name implies, a citric acid based product. I dunno if it's available in the UK but you might want to try a welding supply to see. The stuff is not straight citric acid and there are different formulations for different types of pickling. I sue the stuff because it is so much safer than the nitric acid solutions I used before. Cheers, Eric
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