Citric Acid Strength

[GregLaROCHE]

Five years ago I bought five pounds of citric acid in powder form. I rinse my brass in it for a few minutes, watching what what’s going on and when I notice a change I wash and rinse them off. I have no idea how strong the solution is, but because I have so much of it, I’m sure I errored on the strong side.
Yesterday I was cleaning up an old barrel and couldn’t get some rust out of some pitting. I decided to try citric acid on it. I have used hydro caloric acid on rusted steel many times, however I never used it on any guns, fearing it would etch the metal too much.
I’ve heard of others using citric acid to remove rust, but it doesn’t seem to doing much for me.
I scrubbed the barrel well with dish detergent rinsed an put it in the acid bath. Could there still be oil mixed with the rust in the pitting keeping the acid from getting to it?

What ratios do you mix powdered acid to water and how long do you soak to remove rust?

Thanks

[JonB_in_Glencoe]

The Citric powder I bought is 100% pure.
I mix 3 tablespoons per gallon of water for passivating rifle brass (which includes removing tarnish). I heat the citric acid water mix in a crock pot to a near boiling...heat makes it work faster...when the citric water mix turns blueish-green, it's lost it's power. BUT, then it can be used to darken (copper plate) steel. I've read it's copper plating, and you can kind of see a copperish hue, but mostly it's black. I've darkened some cheap steel china tools that didn't have any finish, the darkening/plating inhibits rust.

I've never tried to remove rust from steel.

[GregLaROCHE]

Well I sure have been mixing it to strong, as I had assumed I was. How long do you leave the brass in the acid?

[GOPHER SLAYER]

The acid used in swimming pools will remove all rust on steel in a few minutes. You can no longer buy that acid in California, but you can in Arizonia. Rinse well and then oil. I have been using it for years with no problems. Works great on brass too, just don't leave it too long. Just a few minutes.

[GregLaROCHE]

The acid used in swimming pools will remove all rust on steel in a few minutes. You can no longer buy that acid in California, but you can in Arizonia. Rinse well and then oil. I have been using it for years with no problems. Works great on brass too, just don't leave it too long. Just a few minutes.

That’s the acid I’ve used in the past on rough pieces of steel. I’ve been afraid it might etch the surface too much to easily polish up. Have you used it on guns before?
Maybe I need to look into the electrolysis method. I’ve always been wondering about it, but I’ve already got so many projects going. Maybe someone has done it and can say it’s easy and not too time consuming.

[Handloader109]

Electrolysis works well, but you have to have a non electronic battery charger or just use a battery. Get the cathode and anode right.
For smaller parts get a qt or gallon of evaporust from HF. Degrease first and then drop in. Won't hurt base metal only rust.

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[blackthorn]

Citric acid will work well on iron/steel. I had 2 CHEAP moulds ($5 for both) that were lightly rust covered. Soaked them in a mild citric acid solution for a couple of days and they came out as if they were "in the white". Citric acid will not damage iron/steel!

[Scrounge]

Electrolysis works well, but you have to have a non electronic battery charger or just use a battery. Get the cathode and anode right.
For smaller parts get a qt or gallon of evaporust from HF. Degrease first and then drop in. Won't hurt base metal only rust.

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OP is in France, kind of a long drive to get EvapoRust. Though there are several competitors that are nearly as good and something like it should be available there. It's just kinda pricy! I've done electrolytic rust removal (ERR) on machine tools, and it works great, and is pretty cheap. You can use lower currents for delicate items. For bicycle frames and machine tools parts that are not precision surfaces, a 12VDC battery charger at 10amps works a treat, as the Brits say. Might be a bit too quick for finely made objects. If you're not in a hurry, 2amps works well, too, on larger items, it's just slower. Nice thing about the process is that you do not need to degrease the parts. Sodium Carbonate is the active ingredient, and I use about a tablespoon full per gallon of water. It's a moderately strong base, and wearing gloves is recommended, but as long as you wash your hands in clear water it's not absolutely necessary. Some folks use Lye (Sodium Hydroxide) as their base, and it would definitely need gloves, and face shield, and that sort of thing. I would not use it that way myself. Whatever you use, it will turn the grease and oil in to soluble soap, softens paint, and converts the rust into ferric oxide that is black, and will need to be scrubbed off. I've done that with my finger tips, plastic scrub brushes, and fine Scotch Brite. The process is not recommended for parts that have dissimilar metal or wooden components. I've built myself a roughly 100 gallon tank long enough to dunk my South Bend Heavy 10L bed into for ERR, but once again, probably not getting it done this year. the tank is two 55-gallon drums with the tops cut out and "stitched" together with SS deck screws. Was going to use iron or SS wire, but the screws seemed to be easier to do. All in, I believe I've got about $60 in all the various sized tanks I've used, from a gallon to 55-gallon, and with enough RTV to seal the 100 gallon tank. I buy Arm & Hammer Washing Soda, which is about $5 for a box with enough to do goodly sized drum. Sodium Carbonate is also used to adjust pH in swimming pools. The smaller parts have mostly been through the 5-gallon drum of EvapoRust. One of these days I'll get the whole thing through some rust removal process and then it will be time to put it back together.

Also note that if you can't find sodium carbonate, you can convert sodium bicarbonate to sodium carbonate by baking it. IIRC, 140 degrees F for a few hours will do the job. Info should be available on the Internet...

Bill

[jonp]

Small battery charger, giant nail or something like it, a cheap tub and some salt. Cleaned cast iron frying pans like that

[JonB_in_Glencoe]

Well I sure have been mixing it to strong, as I had assumed I was. How long do you leave the brass in the acid?

5 min when I do the first few batches of brass.
after that, I leave the brass in longer, like 15 minutes, since acid solution gets weaker.

When I've done the darkening/plating of cheap steel tools with spent acid solution, I leave them in there for an hour or so (on full heat). I check them often for the darkening progress and pull them out, when I get the finish I like.

[blackthorn]

Several years ago, I acquired a small cast iron pot (looks like a small witch's kettle) I think was originally a casting pot. It looks like it will hold about 15 lbs. of lead. Anyway, this pot had obviously been left out in the elements and it was caked heavily with rust. I put it in a small pail, covered it with warm/hot water with about a tablespoon of citric acid mixed in. The pot had a "bail" handle and I put the pot in the water with the handle standing up. After 3 days I checked the project and, looking down, the rust was hanging off the bail like Spanish moss off a tree. The solution cleaned the rust off that pot right down to bare metal. It does NOT do any damage to the base object, but it does remove ALL the rust, including any bluing.

[Bmi48219]

The acid used in swimming pools will remove all rust on steel in a few minutes…...

This thread has piqued my interest. I’ve used a proprietary form of Citric Acid in my pool to remove mineral stains in the finish on occasion and muriatic acid weekly as needed to balance the Ph.
Which pool acid does post #4 refer to?

[blackthorn]

There is a 47 page "stickie" in the "Cast Boolits" forum on this site! 4th stickie from the top. Enjoy!

[john.k]

Im right now experimenting with rust removal...........I got an antique motorbike engine on ebay for 99c..........its worth a lot,but is frozen from having water in it........and impossible to get apart because of solid rusted roller bearings...........I dont want to bust the crankcases......like what happened to a 1936 motor I tried to get apart...........I borrowed some Evaporust ,and have one component in it for a test run.....been over a week,the stuff has certainly removed rust ,but the part is still frozen solid.

[ulav8r]

I found a couple of shackles in my dad's shop, they were so rusted that I could not budge the threaded pins. I let them soak in white vinegar for 3 days then removed the pins without using a wrench.

[john.k]

I only need to free up one side ,and the cases can be separated ,and the flywheel assy pulled apart...Unfortunately the roller main bearings were shielded with thrust washers to stop oil from running out,which makes penetration by a rust buster problematic.......The cases are cast aluminium ,and must not be damaged ......Some of the things that dissolve rust quickly,dissolve aluminium even quicker .

[Scrounge]

Im right now experimenting with rust removal...........I got an antique motorbike engine on ebay for 99c..........its worth a lot,but is frozen from having water in it........and impossible to get apart because of solid rusted roller bearings...........I dont want to bust the crankcases......like what happened to a 1936 motor I tried to get apart...........I borrowed some Evaporust ,and have one component in it for a test run.....been over a week,the stuff has certainly removed rust ,but the part is still frozen solid.

For EvapoRust to work, you must degrease the parts. Any grease or oil keeps the solution from working on that area. I bought a 5gal bucket to work on my South Bend Heavy 10L lathe. Electrolytic rust removal will remove grease, oil, and paint, but it also destroys dissimilar metals. Babbit bearings, brass or aluminum trim, etc., get eaten. You also need line of sight to the rusty area from the anode. Bearings tend to have grease or oil in them, so you need to try to remove it. ERR will do it for you, but can cause other problems. For big parts, folks usually use a piece of sheet steel or sections of rebar connected together, but you can use iron wire, mesh, or other shapes as well or instead. You can also reorient the part. One of the things I've done, using a 55gal plastic drum with the top cut out, is to drop a piece of sheet steel into the bottom of the drum, with a wire connecting it to the anode, along with the sections of rebar around the sides of the drum. Hang the part off a sturdy beam and suspend it in the middle of the drum, instead of letting it sit on the bottom.

Might also consider hot tanking it to get the grease and oil off the bearings and such. A scrub brush and some dish detergent might be the ticket, too, if you can reach those bearings.

Bill

[john.k]

Ive considered all possibilities.......and certainly wont rush it .........what I actually need is a strong reducing agent,that will react with rust.....most are dangerous chemical s like methyl hydrazine,which may react explosively with rust............The endgame will be to remove one of the mainshafts ,either by machining ....or using the oxy.

[sparkyv]

What ratios do you mix powdered acid to water and how long do you soak to remove rust?

I use about 30:1 warm or hot water to CA. The warm water hastens dissolution of the CA. Bubbling should be observed after a few minutes of metal immersion. It may take a few hours for light surface rust to a few days if rust is heavier. More CA can be added if needed. Also if rust is heavy, scrubbing a few times and reimmersion can help. Ultrasonication speeds up the process. It won't harm the metal.