Tech: Using Oxalic acid to remove rust

This trick was discovered many years ago by beer can collectors to clean up cans dug out of old dumps. My thought was, since it works on cans why not try it on car parts. I’ve heard of similar stuff like using muratic acid or electrolysis but they seem very messy and cumbersome.

Oxalic acid is fairy mild stuff. It can be found at your local chemical supply house and is very cheap. I got a 50 lb. bag of it for 94 cents a pound. At one time it was sold in little cardboard tubes in the hardware store under the name wood bleach but I haven’t seen it in years. Check the internet and eBay for smaller quantities.

It comes in crystal form and is white (might want to label the container if you have in the car in case you get pulled over!).



For this test, I took a few items I found in the car parts dump I posted last fall to see if I could fix em up. I also grabbed a few rusty model A parts I got at a yard sale recently.


This headlight ring had spent 70 years buried in a trash pile. It’s stainless so it’s not rusted but over the years a hard film of rust has gotten stuck to it. You could remove it with polish but that would take some effort so I’ll try the acid.



A 70 year old Pennzoil can. If it cleans up OK, it’ll look cool in the garage.



Two rusty Model A sill plates. On thin parts like this, sandblasting could mess them up but not the acid.



I don’t even know what this is, I dug it up.



Other odds and ends to be cleaned.



You have to play around with the acid to get the ratio right. For my test here, I decided to mix three tablespoons of acid with each gallon of water. Some people use warm to hot water but cold water is just fine. The amount of time you soak things is a trial and error type of operation as well. I’d start out with things you’re not too fond of like I did.

Clean as much rust and dirt off as you can with a toothbrush before putting whatever you want to clean in the acid.

Use a polypropylene or polyethylene plastic (milk jug plastic) bucket or tub to put your solution in. Most buckets you buy are made of either of these plastics.

The nice thing about this is that paint more or less can tolerate being dipped in the acid. This is good for stuff like old license plates etc.

Check on your items every hour or so to see how they are doing. You can always redip stuff later.



Looking better eh?


Once you feel it’s ready remove them and rise with plain water. Some people use a baking soda and water bath to make sure the acid is neutralized but a good water rinse is good enough.

After three hours of soaking I decided to take the head light ring and the cans out as they were looking a lot nicer. The headlight ring cleaned up perfectly. A light wipedown with a towel and a rinse gave me this shine. The spring loaded mechanism on the bottom is free and works well now and the three retaining springs on the back are fine as well. This could soak some more to completely remove the remaining rust from the hardware.








The cans did really well. Amazing condition of this 1938 Pabst can!





Since the car parts still looked a little rusty, I left them in overnight. In the morning I was busy and didn’t have time to fool with them until I got home that evening. There was a layer of green crud on everything that rinsed off easily.


The sill plates were a surprise as they were blue, not brown or black like I thought. The edge had been cleaned down to bare metal.






All trace of rust was gone from this license plate bracket.



These door hinges still had a little rust but a few seconds with some scotch brite would have them in shiny steel. Or just dip them in the acid for longer. Most of what you see in this photo is grey steel.



Lastly, my whutzit turns out to be painted black. You couldn’t see any of the paint when I started and I thought it was just bare cast iron. There is still some rust on it so more soaking in fresh acid would clean it completely.



What I would use this for as it pertains to cars is for thin sheet metal part or items that have paint on them that you’d like to preserve and clean off the rust. You may have to soak multiple times to get all the rust off but it sure beats sanding. It’s also going to work great for those old signs you find at the flea market for your garage wall.


To get rid of the used acid, stir in a little baking soda and you can pour right down the kitchen sink (while the wife is out shopping)

 

Wow, those are very impressive results!-MIKE

 

I want a swimmin' pool full of that stuff!

 

Thanks. I am always looking for ways to kill rust and this is yet another one to try (and I will).
Not to rain on the parade at all but just to make everyone aware... there are concerns with ANY chemical.
Read warning labels.
Here is a link to the MSDS for it:
http://www.jtbaker.com/msds/englishhtml/o6044.htm

 

That very useful information. Thanks Fiat 128

 

that's really cool, i'll have to find some for sure.

this part from the MSDS worries me a little...or gives me ideas, i'm not sure which

"Fire:
Oxalic Acid is a combustible solid below 101C (215F)
Explosion:
Reacts explosively with strong oxidizing materials and some silver compounds. "

 

Give you ideas???? Scary.
Shall we beware of little "booms" in your area?

 

FWIW, there is a product called Barkeeper's Friend that contains Oxalic acid..great for cleaning up stainless steel. Most grocery stores carry it.

 

probably...i never really grew out of that playing with explosives thing. made a tennis ball cannon that would break the sound barrier once, i make little rockets both air and solid fuel powered at the shop for fun all the time too. i do have a pretty good idea what i'm doing though since i have a pretty good understanding of general chemistry. there have been accidents, but i still have all my limbs and extremities

 

Sorry fiat128 ... we won't hijack your thread but skajaquada just makes me think of FAR too many "episodes" in my past.

 

It's not that dangerous guys. I have been a member of the BCCA (brewery collectibles club of america) for 25 years. Currently there are 4,000 or so members and at one time there were over 35,000 members. They have been around since 1971 and not once has anyone had an explosion or fire. Most all of them have this stuff

I think grain dust is more dangerous. Use it logically and don't mix it with "strong oxidizers". Most of you have gas, fertilizers, acytalene etc. in your shop and manage not to hurt yourselves.

I've used it for years with no problem.

 

Good to know. How about fumes?
How do you neutralize it after?

"Most of you have gas, fertilizers, acytalene etc. in your shop and manage not to hurt yourselves." You don't know us very well!

 

When mixed as described it does not give off alot of fumes. I've seen alot of guys keep the soak inside closed garages but I keep mine outside on the patio just in case. I try not to huff hard over the container just in case too. Bleach is much worse to breath the fumes, it will really screw you up.

I hurt myself worse with an angle grinder than the stuff that burns.

 

Excellent! Thanks for the info.
I'm going away for a week. When I come back.. I'm gonna try this.
I've done the molasses trick and the electrolysis thing too. They all seem to have their places so this hopefully will too.

 

Cool, finally found one of our hardware stores that had the stuff! Dug this thread up in a search since it has been covered a bit recently

 

Lucky you. I wish I could find that stuff here.
The stores here want to sell natural, "green" stuff.
All I've found was watered-down stuff in deck-wash.

 

All of that and also an excellent radiator/block flush. I believe this was the stuff that made up radiator flush solutions in the old days. GM still used this in their commercial radiator flushes, if I'm not mistaken.

 

As he mentioned, it is sold as wood bleach. Check your local hardware store.

 

Thanks but .. this has been talked about in a number of threads.
I can't get wood bleach with oxalic acid around here. Only natural stuff.
Save the planet-type stuff. Not eat the rust-type stuff.
I'll just keep using molasses. I work slowly anyway.

 

I think the issue has more to do with the fact that nobody knows what it is so it is seldom used anymore! I found it with the paint and spackling.

 

Look on ebay, there's a lot of different suppliers. I don't know about shipping to Canada though.

 

You certainly do have a point there.
The deck wash that has a small amount in it clearly lists it on the label but the people at the store swore they had zero oxalic acid in the building.

Someday I'll find some. I tried 1 city and 1 town so far. Maybe I'm going about it all wrong. I'll go to an old town that doesn't have the modern stuff....

Ya.. shipping across the border for chemicals (especially a white powdered acid!! ) is tough.

 

I have gotten similar results with white vinegar. I also found that if the vinegar leaks on to a nice concrete garage floor and is allowed to stand overnight, it eats the smooth top surface of the concrete!

 

What does it do to cam bearings and such?

 

I used a small tub of it in my cooling system a couple of years ago with great results. I drained/flushed the system, filled with water/wood bleach and drove it around that way for ten days. Drained/flushed/refilled again and no more cooling problems. If you are having a hard time finding it try the local/independant hardware stores, I had no luck with Lowes/Home Cheapo type places.

 

grab some old ones and soak them in a small bucket of them. local machine shop must have a few laying around they could spare.

 

I got 5lbs on Egay pretty cheap. It came inside a priority mail envelope inside another envelope to save on packaging costs though Didn't bother me, but I could imagine what would happen if it busted open in transit.

 

check dry cleaner supplies in your area. it is used in bath form to remove rust. just a heads up though, if made too concentrated this stuff will give you a nasty chemical burn. i do not reccomend putting bare hands into it. i also needs to be neutralized to help causing future problems. this is acid. if left to long without neutralizing it will cause other damage. heat will accelerate the process.

 

Thanks for another possible source....
Yes. Acid is just that acid. Safety is an issue.

 

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