With one natural ingredient, it’s easy to remove rust from heavily corroded antiques, artifacts, and tools.
A few months after I sold my first horse, I was walking through the pasture and found a shoe he’d lost sometime in the year before. Looking at it, I thought it would be a nice keepsake- and something I could use to create an equestrian project with sentimental value- but it was covered with layers of rust.
I’d been experimenting all winter with using citric acid to clean rust off garden tools that I, in my distractability, tend to leave out in the elements. As it turns out, the basic combination of citric acid, water, and time completely removes rust from metal. I was pretty thrilled, especially after trying and mostly failing to remove rust from tools with caustic chemicals. A common ingredient in canning recipes, citric acid is an organic acid a little stronger than vinegar, depending on the concentration you mix it in.
2020 Update: I’ve loved reading your feedback on this article and how many of you have found this tutorial useful! A lot of the comments have suggested replacing citric acid with vinegar and soaking a little longer, and I wondered it this would work as well, so I recently did some experiments. At the bottom, you’ll find a price breakdown (spoiler: there’s a clear winner) and some important safety information on using alternative household chemicals other than the very safe one described in this tutorial below.
Supplies You’ll Need for No Scrub Rust Removal:
- A bucket or plastic container large enough to hold your rusted object(s)
- Very hot water
- A surface treatment for raw metal. Oil or clear coat varnish works.
- Pure Citric Acid – You can buy this wherever canning supplies are sold, however, the pricing on citric acid sold for canning includes a huge markup. As of spring 2020, Ball brand citric acid is priced over $1/ounce but a 5 lb bag of food-grade Citric Acid is 21¢/ounce.
My advice is to order in bulk and don’t worry about having too much – it’s SO handy for cleaning! A tablespoon of Citric Acid is great for boosting dishwasher detergent, descaling coffee makers, getting grime off pots and pans, removing hard water stains, and general cleaning. You can use it in cooking too- soaking cut apples in a weak citric acid solution to prevent browning, or adding a tablespoon to bone broth at the beginning of the cooking process to help break down bone and transfer nutrients into your broth.
With one safe, natural ingredient, it’s easy to remove years of rust from antiques, artifacts, and rusty tools- all with no scrubbing required.
Total time to remove rust 1 hour
– A bucket or plastic container large enough to hold your rusted object(s)
– Very hot water
– A post-rust removal protectant for raw metal. Oil or clear coat varnish works.
– Pure Citric Acid – You can buy this wherever canning supplies are sold, however, the pricing on citric acid sold for canning includes a huge markup. As of 2020, Ball brand citric acid is priced over $1/ounce but a 5 lb bag of food-grade Citric Acid is more than 75% cheaper, at 21¢/ounce.
Prepare Acid Bath
It sounds intense, but Citric Acid in the following concentration is very safe- just a little more punch than average household vinegar. Scoop the powdered citric acid carefully into your bucket. I add about 1/3rd cup of powdered citric acid per gallon of water, but you can use slightly more or less depending on how rusty your object is and how quickly you need results.
Fill your bucket with very hot water and stir to dissolve the citric acid powder completely into the water. There should be no grit remaining at the bottom of the bucket.
Submerge Rusty Item in Solution
Being careful not to splash the citric acid solution, place your rusty object in the solution. In this image, I’m de-rusting a found old horse shoe and I’ve tossed in some rusty bolt cutters.
Allow Rusty Object to Soak
After 10-15 minutes you’ll see bubbles forming on the surface of the object as the acid reacts with the rust and creates tiny gas bubbles. When the bubbles rise to the surface and the water turns yellow, you’ll know the solution is working.
Continue soaking your object until you see visible results. Some items will be rust free in hours, while others may take a full day or multiple soaks. After a day you may want to remix your citric acid solution, because it will slowly lose acidity as it breaks down the rust. If you are a fan of instant gratification as I am, you may want to do a bit of scrubbing to speed the process.
Speed the Rust-Removal Process with an (Optional) Scrub
Continue soaking your object until you see visible results. After a day you may want to remix your citric acid solution (it will slowly lose acidity as it breaks down the rust) And if you are a fan of instant gratification (as I am), you may want to do a bit of scrubbing to speed the process.
The above image is how my rusty objects looked after 2 hours in the solution and a quick wipe with a paper towel.
Remix & Resoak if Needed
To remove all rust with absolutely no scrubbing, just remix and soak until no rust remains (you may still need to wipe with a rag or run under running water to remove loosened rust particles from grooves).
When finished, the solution is safe to discard down a drain- the chemical reaction that dissolves the rust will have neutralized the acid, making it harmless for most household pipes (if any pieces of rust have broken off and settled at the bottom of the bucket, do NOT put these down a drain, and instead discard in the garbage).
Seal the Rust Free Metal
When you are pleased with your object’s new finish, dry it completely. The metal may seem “dirty” and transfer dark marks on your hands when touched- this is normal for steel and iron with no protective coating. Make sure the object is totally dry (10 minutes in a 300-degree oven works great as long as long the item is 100% metal with no plastic grips or heat-sensitive parts) and then add a protective finish.
IMPORTANT: You MUST protect the finish. If left uncoated, the unprotected metal will rust again almost instantly. To prevent new rust from forming, You can apply clear coat / lacquer, spray with cooking oil and wipe away the excess, or jump over to my tutorial for creating an antique gold finish (which looks great AND prevents rust).
Scrubbing is optional but speeds the process up significantly. The acid will loosen before it completely dissolves the rust, so much of the rust can be effortlessly wiped off after an hour or two in the solution.
In this photo you can see the yellow-tinge the solution takes on as it is working, as well as the loosened rust sediment that will settle in the bucket.
2020 Update: Vinegar vs Citric Acid
Since published, this article has traveled far and wide and collected a lot of feedback comments- many advising to “just use vinegar” was a comparable technique. Recently, I decided to do a side by side comparison of vinegar vs citric acid in my kitchen. Without repeating the entire rust removing process (difficult to compare with scrutiny, since no two objects rust exactly alike) I ordered some pH testing strips.
To be the “better” rust-removing solution, the winner would need to be 1. higher in acidity, 2. lower in cost, or 3. both. My suspicion was that citric acid would win by a landslide, but my experiment progressed.
I mixed one cup of citric acid solution at the concentration recommended above (.33 cup per gallon, or in this case, the ratio scaled down to 1 tsp citric acid to 1 cup water) and tested it against a leading name brand of undiluted white vinegar.
RESULT #1: ACIDITY
At the recommended dilution, Citric Acid solution is slightly more acidic than vinegar– matching the scale in my pH testing kit at a pH of 3, compared to the name brand distilled white vinegar at pH 4. (Interestingly, according to the internet, the pH of distilled white vinegar should be between 2-3, meaning either my name-brand vinegar was weak or, more likely, my pH testing kit was not lab-accurate. Even if this is the case, I anticipate the values relative to other values read by the same test strips should generate accurate comparisons)
But how do they measure up in terms of cost? Read on
DON’T combine vinegar and add salt to remove rust.
Comments on this post have casually suggested “heating vinegar and then adding salt” to create a rust-busting cleaning solution- but this is VERY unsafe. Combining salt and vinegar creates Hydrochloric Acid. Combining heated vinegar with salt creates hydrochloric acid fumes, which are toxic and potentially fatal in large doses. Unlike citric acid neutralized through rust-dissolving, hydrochloric acid is also difficult to dispose of safely. A simple-language Wikipedia article explains this.
RESULT #2: Cost of Vinegar vs Citric Acid
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