.

Have you got an Asian food shop close to you.? (That's Asian food, not owned by) They are usually open late.

2 I know of in Warrington both sell quite big bags of citric acid crystals for a couple of quid. – No idea what they use it for.

Nick

Edited By Nick_G on 25/02/2017 17:12:42

Peter – for rusty steel I use cheapo malt vinegar. About 26p a bottle for the "value" stuff last time I looked. Chuck your stuff in and check after 24 hours. When it looks good and black wire brush it, rinse with boiling water – it will dry in seconds – then lube to stop it going home again. Thats the way I do it.

Rik

Citric acid can be pretty potent if you heat it up.

Below is a link to a paper showing how citric relates to other acids.

**LINK**

The tests describe weight loss in standardised steel test subjects at different concentrations and temperatures.

At room temperature citric is so benign and in any case cheap, I don't really understand why one would use anything else for small parts fabrication. With large objects like whole boilers it is different, I accept that up front.

If you get citric nice and hot, you can dunk a small steel silver soldered assembly into the acid and see the oxide layer just "pop off" in just a few minutes. It is literally left floating in the acid like a lizard shedding it's skin.

I use a stainless pan I bought in Sainsburys. I have a temperature controlled hotplate and a thermocouple inside an Inconel shell suspended in the acid by a spider. The thermocouple allows the hotplate to directly control the temperature of the acid.

I made the acid up using de-ionised water (for lead acid batteries) and I bought industrial cooking citric acid granules, from e-bay. The first batch I actually made on the kitchen cooker, and I just kept stirring the granules in until no more would dissolve.

I regularly filter the acid into a plastic container for storage, with Rombouts coffee percolator filters. You lose water by evaporation, so I just top it up each time I use it with the DI water. I originally made my current pickle about two years ago, and it still works nicely now.

I typically use it at around 65-70deg C.

The thing I like about citric is that it does the job. When it is cold even if you spill the whole thing, the only problem you have is a sticky mess that you have to clear up.

Watch out when it's hot though!

Edited By Andy Ash on 26/02/2017 00:15:09