Technical Tech: Simple rust removal with citric acid

I want to share the process as I know it for fast, cheap and easy rust removal using powdered citric acid. I've seen folks using molasses, vinegar, electrolysis and expensive store bought products to remove rust. I leaned about citric acid from my brother a few years ago and have never looked back. Here is the process Ive used with great success, hope this can help my fellow Hambers. step 1 I bought this 5lb bag of powdered citric acid online for about 16$ shipped. For these parts I'll use about 3 cups dissolved in warm water then added to my 5 gallon bucket. A big rubbermaid tote works well for this also. Im not to scientific with the measurments this stuff is cheap enough.
Here are the parts and some small hand tools I'll be de rusting. Normally I'd give these a quick pressure wash first but my washer wouldn't cooperate so I did these as is. .

Once your acid is mixed dump it in the bucket, where your parts are already covered in water.


Now it's as easy as letting them soak, 24 hours is usually plenty, sometimes I leave the worst parts in longer. The Citric acid is mild enough it won't damage anything but the rust.
Now after your soak pull out your parts and they dont look impressive just yet.

If you have a pressure washer use it here. If not, a wire or nylon bristle brush will clean off all of the loosened rust. Give it a quick wash and your parts should look like this. this is after a grand total of maybe 5 minutes with a wire brush. The rust will literally just scrub right off. Its that easy ! When im finished with the acid bath, I neutralize it with a cup of baking soda then dump it out in my side yard. It doesnt even hurt the grass. The acid is so mild it doesnt burn your hands or put off any odor. I did all of this batch in my garage with no problems at all. Also I've painted parts that have held up very well for several years after this process. Hope this helps you guys. If anyone else wants to add to this thread feel free to do so.

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I've done painted parts also, it works great for stripping rust and not affecting the paint. Also great for bringing ol rusty swap meet/garage sale tools back to life. I'd bet it would work well to restore old signs also.

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I use a bigger tank. The last pic was left untreated for 3 months.

 

I use Citric acid as well. Works great. You want to use oxalic acid if you want to preserve old paint and chrome while just removing the rust. I have had citric acid take poor paint off and oxalic acid revive paint I never knew was under the orange. YMMV

 

Thank you for sharing this. I’ve looked at all the othe ways to remove rust, but this looks way easy and cheap. I’m going to give it a try on some really rusty seat brackets.

 

Post pics here when you do.

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There are loads of citric acid threads on here, but nice to people finding it on their own. I've been using it for a while now. I have a big tote that I drop springs, control arms, etc into. I picked up an under-bed tote for soaking the front of my '59 Ford hood to get the rust off it. I strapped the hood to my deck so it would not roll away. Very important, you have to neutralize the acid or it will remain caustic. I use a 1-lb box of baking soda to 5 gallons of water. Which is the same ratio I use for the acid to water. And remember this, AAA.. always add acid. Which means don't add water to the acid, add the acid to the water. A basic chemistry 101 thing.

 

I've had great success with oxalic acid, especially on chrome pieces. Also white vinegar (5%) on smaller rusty parts. I will definitely try the citric acid if I need to do bigger parts. Very good presentation, thanks.

 

Thanks for sharing that info

 

But every body thinks molasses is better. Which stinks. Can you imagine how bad this would stink. I keep it year round. I use $50 dollars worth in the spring with a new supply of water. Then I make a new batch in late July. I use a leaf blower to stir it up a bit. Also use a tank heater in the winter. It slow acting then. The grille below was pretty rusty also.

 

Agreed, the reason I wanted to share this. I still hear so many guys using molasses. I can't imagine the smell, storage and disposal of a giant tub of rusty nasty leftover molasses. I wanted folks first hand to see how easy this method is.

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"Do as you oughta, add acid to water" This was from 7th grade science class. Never forgot it!

 

I bought a bag of citric acid from Amazon a few years ago. I had little success with it, but perhaps I mixed it improperly. If you please, what is the final ratio of citric acid to water that you have found most effective?

 

Food grade. It is the same stuff to make Kool-Aid with. Cleaning dirty chrome parts takes about 15 minutes. Rusty items,(I do a lot of seat frames) I leave in for about a week. The bumper above, I left in for about a month. Depends on how fresh my batch is. Sometimes I forget about parts I have in the tank. I think I have about 35 pounds in my tank. I hose off larger parts off at the car wash.

 

Quote O/P: "For these parts I'll use about 3 cups dissolved in warm water then added to my 5 gallon bucket."

 

Thanks, I revised the post to add acid to the water. @tubman I used 3 cups to the 5 gallons of water. If I had a bigger container I wouldn't hesitate to add the whole 5lb bag as its so cheap and can be used effectively for several months. If your mix doesnt seem to be working well just add more until it does. Most of the sellers on Ebay have a sample sized bag on up to 50lbs. The stuff I bought is listed as "food grade".

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For a slightly different "bible-story"...I had a flathead bare block that wasn't rusted much...but had
obscene-terrible calcium/hard water thick buildup throughout the block's water passages. After reading extensively about removing hard-water deposits ....VINEGAR was cheapest most common remedy suggested. I took empty motor oil quart plastic bottles.... and with caps tightly secured I put them
everywhere in block I could to take up space. (In the cylinders / crank area / cam valley, etc. )
Then I picked engine up by front cover end with cherry picker.... and put engine into triple 4-mil contractor garbage bags. (Leave top open) Then I wrapped entire garbage-bagged block with nearly a roll of DUCT TAPE. (To keep water from breaking through garbage bag) Wrap tape on garbage bags as TIGHT to the block as you can. I then lowered block into a 40-gallon plastic Rubbermaid tote.
With top of block water passages showing where water pumps normally would be I filled block with
white distilled Vinegar from grocery store @ $2.50 per gallon. I was shocked...but it took 11 gallons
to fill block to top. I let the Vinegar work for 5 days. I lifted engine a few feet, then punctured garbage bag. I was shocked at the "light brown slime" that came out of engine. I pressure washed block and the
water passages were incredibly CLEAN. I let the Vinegar sit in tote a few days and was amazed how much calcium SLUDGE came out of the engine. I kept skimming off the top and refilled the dirty vinegar back into their empty jugs. The last 4 gallons of Vinegar I poured off was like tan maple-syrup.
I couldn't believe how much mineral deposits I got out of my flathead block for a little time and $28.00
worth of vinegar. I will do this to ANY bare-block future engine I build.

 

I use 1 pound per 5 gallons of water, seems to work fast enough. I give things a few days in it, maybe longer. The more crud you scrape off the part first, the better it works and the solution stays cleaner.

 

I love this stuff. Been doing parts for a few years now. A guy doesn't have to be spot on for measurement just pour some in the h20 and let it do it's job.
The o.p. Said it doesn't hurt your hands but if you have a small cut or scrape you will know right where it is when you get the mixture on it.

 

Dumb question here ,if you heat the solution would it work faster/better?

 

Heat always makes chemical reactions work faster.

 

that's cool

 

There is a place in Council Bluffs that does this full time. They heat the solution to almost a boil. Really speeds up the process.

 

One more safety item I will mention, always add caustic to water also. I have seen a couple pretty good eruptions from mixing it in reverse. Caustic soda beads. You also want to keep the water temp on the moderate side, one of those eruptions actually happened when the hand mixed beads into extremely hot water.

 

So, I get that the parts need to be neutralized with baking soda after soaking in acid.
Do I just soak parts in another tub with baking soda/water solution and then rinse with clean water after? If so, how long do I need to neutralize?

 

@Bugguts I've done this for years by just washing the parts very thoroughly w clean water then dry with compressed air. After that just following the usual paint prep steps and my parts have held up perfectly well. I only neutralize my acid bath before I dump it in the grass as to not leave a dead spot in the yard. If you wanted to, im sure a 10 minute soak in baking soda bath would neutralize any remaining acid leftovers if there were any concerns.

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Disposal at least is easy, Mollasses is Non-toxic, diluted down a bit it would perfect for turfgrass or lawns. Iron deficiency too is common in plants. It's all good to me, whatever works.

 

I like to degrease the parts first. Oil skim on the water can create a barrier that coats parts and prevents acid penetration

 

@George G Agreed, this stuff wont really cut through grease well at all.

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