Citric acid

[Bigfrawg]

How many kilos do I need for frame forks and 4 pairs of bars ?

[Picklez]

If you can fit them all in one paddling pool (1m diameter, £5-£8 from eBay/Amazon etc.) at once then 0.5kg will do you sir 

I actually did my last F&F with 0.25kg (I think from memory the rough recommendation in the old sticky was 250g per 40L of water), but didn't fill with enough water to cover the whole frame, so turned it after 24hours, doing a side at a time. Still worked ok. But for the price of the CA you might as well buy a kilo, use half and fill the pool with enough water to cover all the parts, then have some in stock for next time. There'll always be a next time, I actually find myself looking around for things to clean up now 

[Bigfrawg]

Thank you sir , I was way out thinking about getting 5 kilos lol

[Avro]

I use 100g of citric acid granules per litre water.
Leave the parts in the solution (a heated solution will speed up the reaction) until you are happy or the fizz has stopped. If the fizz has stopped then the reaction is complete or the reagent has been exhausted. If the parts still look rusty then add some more citric to add reagent. Do not worry about leaving the parts in for too long, it is all chemistry! Just use your eye. It is more about balancing the amount of rust with the reagent, there is no rule.

[Picklez]

Hi guys, just reread Clint's original thread on the subject (stickie in Tech & Resto section, and a great read), which is what I based my quantities on:

http://www.radbmx.co.uk/forum/index.php/topic,178383.25.html

I only double checked, and offer the additional post here, as obviously you've received slightly conflicting information, and whilst neither is wrong information, it might help explain a little more.

Basically, my early recollection was slightly inaccurate, Clint's original advice was to use approximately 250g (0.25kg) of citric acid for 20L of water, not the 40L I stated. So, when I did my frame I ended up using 0.5kg of CA for a planned 40L of water. But, because I didn't subsequently also fill my pool with lots of tins, bricks, bottles, etc. (to artificially raise the water level to make sure the whole frame was submerged) I ended up only covering just over half the submerged frame height. Hence soaking it for 24hrs on one side then another 24 hours on the second side.

So, as a minimum, you'll want to:

Get hold of a 1m diameter pool, or similar.
Put all your proposed parts in
(And if not filling the pool with additional items in the gaps to save on absolute water volume & CA) Put in ~1kg of CA crystals, I used these ones, but plenty of other sellers available:
https://www.ebay.co.uk/itm/CITRIC-ACID-2KG-BAG-100-Anhydrous-Powder-GMO-Free-BP-FCC-Food-Grade/183511231815'ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Then fill the pool with water to cover all your components and wait for the chemistry to take effect, around 12-24 hours depending how bad the parts are to start with.

It's also worthwhile having an old toothbrush to hand, to rub over the bad areas every couple of hours, to loosen off any of the 'dissolving' corrosion.

As I mention, neither answer you received is wrong, it's simply a matter of the stronger the concentration the quicker the process, I've personally experimented a bit, and found that as strong as 50g/litre strips all rust of concern in a couple of hours.

Have fun