Thread: Rust removal Citric Acid

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I’ve been cleaning up the old tools I brought back,( I figure there are probably 200-300 pounds of stuff all together). There are a lot of commercial products on the market (Navel Jelly and Evaporust come to mind) but at the price they get for them this would turn into a pretty expensive project. I’ve also read about using electrolysis but really didn;t want to go thru all that right now.

In the past when I had something that was pretty rusty I wanted to clean up, I’d just steal a little vinegar from the house and soak the part for a day or two and was good to go. The down side to using vinegar, especially in the summer time in an open containers is that the smell can get pretty intense and the colder the weather the slower it seems to work.

I recently read about using citric acid for rust removal and figured I’d give it a try. The citric acid is odorless and pretty cheap so I bought 5 pounds in powdered form and figured I’d give it a try. Vinegar and citric acid are both also biodegradable so that’s a plus too.

As I wanted to compare the results to the vinegar I’d been using I figured why not do a head to head test. I started off with a pair of thread dies that had about the same amount of rust on them.



One went into a container with vinegar (left) and the other went into a container with water and about a 5% mix of citric acid (Right).



It’s been a little cool here, mid 60s during the days and mid 40s at night so I knew going into it the vinegar wouldn’t work quite as fast as it does in the summer but figured it would have the same effect on the citric acid. I was really surprised at the results after 12 hours.

The vinegar (left) was working a little but the citric acid had really taken off.




After 24 Hours the vinegar was slowly working but not near as well as I expected or as the citric acid.





At 48 hours the die soaked in citric acid was about as clean as it was going to get but the one soaked in vinegar still has a long way to go.



I set the one back in the vinegar just to see how long it will take to finally be ready.



The one from the citric acid soak was washed off and wire wheeled, then shot with a light coat of silver paint.






So while I plan on keeping citric acid around from this point on. If I don’t have any readily available I would still use vinegar if time is not important. For the most part I guess the wife’s won’t have to wonder where her vinegar keeps disappearing to in the future.

I’m really glad this die cleaned up so well, you never know when you’ll need a die this size to cut some 1/4 X 20 threads.

Wow, neat comparison Mike!!! Heard of using citric acid but never had tried it, works great.

How about a vinegar, citric acid, moleasses comparison on three similar parts?

Most of those brand name products you mentioned early on are phosphoric acid primarily. You can buy it fairly inexpensively without having to pay for the commercial/retail packaging and brand name. The citric acid you used looks to have worked just as well however. Does it leave a conversion layer (like the iron phosphate left by phosphoric acid) that resists new rusting?

Bob if left alone it will flash rust within a few minuets after it's removed from the solution. I normally pull the parts, rinse with water, then hit it with carb or brake cleaner (or WD 40 if I'm not going to eventually paint it). If I'm going to paint it I'll hit it real quick with a wire wheel then shoot it.

I`ve used the molasses (so I can dump t in the far corner of the yard....) and have also used old brake fluid also works well .

Where did you get it?