Citric Acid Bath - HELP

[Ken Werner]

I bought some citric acid powder, and am wondering what concentration to use for de-rusting iron. To process tomatoes, it's 1/2 tspn / quart. Can those who've used it describe the mix? TIA.

[Mark Berenbrok]

Try this.

http://lumberjocks.com/WayneC/blog/1439

[Prashun Patel]

I've used varying concentrations. A 5-10% solution is a good place to start. I've gone as aggressive as 25%, but it tends to settle out, and you should really watch it often and remove it when it's done. With a weaker solution it's not so critical.

The way I've settled into for minor rusting is to do 5%. Soak. Wait for bubbles to stop. Remove. Rinse. Rub oxidation with brass bristle brush. Then I recharge more concentrated and repeat as necessary.

[Jon Toebbe]

I don't usually worry about it too much, honestly. Pour some hot water into a bucket, dump in some acid crystals and stir. When the water looks a bit yellow-ish and smells a bit, you're good to go. Citric acid is a pretty mild rust remover, so it's pretty hard to overdo it.

It's mild enough that you don't really need to wear gloves to handle the tools you're de-rusting (as long as you don't have any cuts -- stings like, well, a weak acid bath, DAMHIKT :o ). Give things a scrub with an old toothbrush every few hours to keep things moving along, and be ready to oil things the instant you pull them out and get them dry.

[Rick Rutten]

Where may I find powdered Citric Acid?

Thanks,
Rick

[Roger Newby]

Where may I find powdered Citric Acid?

Thanks,
Rick


Health food stores and home brew suppliers....kind of an anomaly isn't it?:D

[Rick Rutten]

Thanks Roger.

I though you were being redundant

Rick

[David G Baker]

Ken,
I use phosphoric acid or muriatic acid for chemical rust removal. I also use washing soda and electrolysis for non chemical rust removal.

[Ken Werner]

Muriatic acid? Pretty strong stuff, how do you dilute it? Also - at the health food store citric acid was a bit pricey - $3.50 for 5 ounces. Any other cheaper sources? Thanks to all who jumped in on this.

[Niels Cosman]

ken,
I have stopped using acids all together for restoration. I find Evapo-rust followed by some wirebrushing is far superior and safer. You should give it a shot, you wont go back. You can get small bottles at auto-zone and bigger containers at industrial supply places (ala MSC, HF, i think).

also am not sure if this is true, but, i have heard that acids can cause microscopic pitting that can damage iron and steel parts and make rusting more prevalent in the future.

You dont need much, but you have to submerge the entire part.
I de-rusted a #8 sole in a plastic bag rapped in rubberbands to displace the wasted volume.

good luck!

[Will Boulware]

Out of curiosity, what's the advantage of citric acid vs. phosphoric, etc.? I recently used Bob Smalser's tutorials and cleaned up several tools with phosphoric acid (prep and prime). Worked like a charm. I have no complaints. Does citric acid offer any benefits? Is it easier to clean up or less hazardous, etc? I found no problems with what I used, just curious as to whether there was a better way I hadn't tried.

[Jim Koepke]

Out of curiosity, what's the advantage of citric acid vs. phosphoric, etc.? I recently used Bob Smalser's tutorials and cleaned up several tools with phosphoric acid (prep and prime). Worked like a charm. I have no complaints. Does citric acid offer any benefits? Is it easier to clean up or less hazardous, etc? I found no problems with what I used, just curious as to whether there was a better way I hadn't tried.

Citric acid is fairly mild. One member here reported using a powdered lemon aide product as his source.

I am not sure I would feel as safe with phosphoric acid as with a mild citric acid solution. Of course if the dilution were about the same it would likely be as safe. It probably has to do with normally consuming foods with citric acid or vinegar that make them seem more acceptable.

Ken, $3.50 for 5 ounce package does seem a bit on the high side. I think I bought a couple of pounds for less than that at a wine making supply store.

Looking on the net, a search for > citric acid crystals < indicates one of the costs may be that a lot of it is food grade. One source shows 2 Lbs. at $12.95 with free shipping. That is the same as the 5 Lbs without free shipping.

Either prices have gone up in 3 years or there are better places to buy smaller amounts.

How much for a gallon of cheap vinegar?

jim

[David Cefai]

Citric acid will dissolve rust but not iron. Sulphuric (muriatic) and most other common acids will attack and dissolve iron too even when (especially when) dilute.

Phosphoric acid above 25% will not noticably attack iron but leaves an ugly grey coating which is actually protective. It can easily be sanded/wirebrushed off.40-50% is a good concentration roughly a 1:1 dilution of acid with water.

Warning: When diluting phosphoric and sulphuric acid pour the acid into the water not vice versa or the mixture may boil over - it gets very hot.

Naval jelly is phosphoric acid mixed with a gel. Sulphuric acid is Battery acid (when you can find it).

Incidentally I have used citric acid to descale electric kettles.

[Mike Brady]

EvapORust is citric acid. For the emersion times we are talking about, citric will do no harm to the metal or japanning used in tool making. The only ill effect that I have ever experienced with citric acid is that some steels used as springs such as in a traditional caliper can be broken during the process that frees hyrdrogen in the derusting process. Electrolysis can fry the japanning rather quickly, but doesn't appear to hurt metal. These are fairly crudely made tools. There is not there to be damaged other than some wood parts (braces).

[David Cefai]

If Citric Acid causes problems there is something else you can try - an Ammonium Citrate salt.

This is Citric Acid partially neutralised with Ammonia. What you lose in acidity you partially regain in a "chelating" effect (like calgon works)

Make up your Citric Acid solution. Then add household ammonia slowly to the acid. Try a 1+3 mix initially. The liquid will turn green when it starts dissolving rust. You will need to experiment.

Alternatively you can try calgon - slow but sure.

[David Keller NC]

ken,
also am not sure if this is true, but, i have heard that acids can cause microscopic pitting that can damage iron and steel parts and make rusting more prevalent in the future.
good luck!

In general, the acid to stay away from as far as pitting steel is Muriatic (Hydrochloric) acid. The presence of the chloride ion in this acid has a special mechanism that causes pitting in carbon/iron alloys (i.e., steel).

The strong mineral acids (sulfuric, hydrochloric, hydrofluoric, hydroiodic, etc...) will erode both rust and iron; the weak acids (acetic, citric, etc...) will generally erode only rust.

[Ryan Baker]

Just get a can of Barkeeper's Friend (oxalic acid) at any local store for about $2-3. It does a great job of cleaning rust off of iron.

[Christian Castillo]

Do all acids result in hydrogen embrittlement? I tend to use Evapo-Rust on anything that cuts because the website specifically states the Evaporust doesn't cause it to happen. I'm interested in using acid for things that don't require edge retention, but if I could switch over to say, citric acid, I would rather prefer that as Evaporust is expensive.