Removing Rust With Citric Acid




This is one of the easiest, safest, and least abrasive ways to remove surface rust from old steel tools.

  • Citric Acid Powder  (available at drug stores or grocery stores as a health food supplement or a baking ingredient)
  • Warm Water
  • Container
  • Scouring Pad / Brass Brush
  • Rusty Parts
  • Rubber gloves are a good idea
  • Don't splash it in your eyes
  • Do a test before trying this on something important - I've noticed it caused a swan chisel to turn very slightly yellow.
  • Do not try this on something like a saw blade with an etching you want to preserve - it might disappear.
Other Ways to Remove Rust:
Wire Wheel on a Grinder - this is probably the quickest way to remove rust, but it's still abrasive, so be careful around logos you want to keep.
Electrolysis - works well, but you have to be careful with batteries and water. not for the novice.
Sandblasting - very quick, but can leave a rough finish depending on the media. requires masking on painted parts.
Sanding - tedious and dirty and removes metal, but it works. sanding in very tight places can be impossible.

Advantages to using Citric Acid:
  • Does not remove painted finishes.
  • Less messy.
  • Requires nothing you don't already have in the kitchen.
  • Can be poured down the sink (citric acid is the main ingredient of some biodegradable cleaners).
  • Way cheaper than sandpaper.

Step 1: Clean the Parts

The rust on this wood plane wasn't too bad. The chip breaker was the worst part, but it was mostly just thick surface rust.
  • The first step is to clean off any dirt with water and a sponge.

Step 2: Prepare the Solution

  • Find a container that is large enough for the parts to lay down flat. This way you only need to cover them with a shallow pool of water.
  • Place the parts in the container and cover them with warm water.
  • Add the citric acid powder and stir it in. Experiment with the proportions here. I used probably a 1/2 ounce of citric acid with 15 ounces of water.

Step 3: Wait, Scrub, Wait, Scrub

  • After a few minutes small air bubbles will form on the part from the chemical reaction.
  • After 30 minutes or 1 hour you may see flakes of rust in the solution.
  • Scrubbing the parts with a scouring pad or brass brush will speed things up.
  • There will be a black haze on the part, but it will scrub away.
  • The blade and most of the screws were ready to come out after 1 1/2 hours.
  • Add more citric acid to the solution if needed.
  • Wait, scrub, wait, scrub until the rust is gone.
I left the chip breaker in for 7 hours with no damage. A very lightly rusted part should be rust free after 30 minutes and some scrubbing. A moderately rusty part only needs 2-4 hours depending on how often you scrub it.

The solution can be poured down the sink when you're finished.

Step 4: Oil the Parts

  • After removing the parts from the solution, rinse them off with water and dry them thoroughly.
  • Oil everything or the rust will reappear when the parts get wet. I used camelia oil, made for rust prevention, but any oil is better than nothing.
What's really nice about this process is that the rust is removed even in hard to reach places, and it helps preserve the original markings without over-restoring the part. The finish is a little bit dull straight out of the acid, but can easily be shined up with fine steel wool or fine sandpaper.

Step 5: Before / After

The before and after results are pretty dramatic considering how little you need to scrub the parts.

I wanted to share it here because it would have saved me countless hours of sanding over the years!

2 People Made This Project!


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184 Discussions


3 months ago

Great instructable. My experiences with it:
1. Don't get bogged down in the exact ratio of citric acid (I used food grade powder from Amazon). On a couple of occasions, I used a higher concentration than the author: about 1:8 to 1:10, measuring both the powder and the water in a typical measuring cup. It worked great although I never saw much bubbling at all.
2. I used a small brass-bristled brush and as the author says: Scrub, Wait, Scrub some more. Or just be patient and leave in longer; but scrubbing is definitely going to speed the process.
3. My biggest challenge was finding a container that was long enough and shallow so that I didn't have to use loads of solution. Finally came up with a flimsy plastic one that some pastries came in. Used it for about 10 items.

Discovered that some old tools had lettering embedded in them that I didn't even know was there!

The photograph of the two angles says it all concerning the finish. I cannot help but notice what appears to be significant shrinkage of the treated angle; it's now about 1/3 smaller than the untreated angle.

7 replies

Citric acid doesn't shrink metal. That's silly.

The first image of the two squares is a photoshop, there is only one square. I put two pictures together, so any size difference you see is because of that. Nowhere near 1/3rd smaller though.

I forgot I wrote that. I kill me! (never mind). Good instructible but I admit having trouble and no luck finding citric acid in retail stores. I know of a pharmacy that compounds chemicals and medicines--surely they'd have citric acid as I have a use for some gentle rust removal in a safe compound like citric acid and water. Pax!


Reply 3 years ago

Concentrated Lemon Juice does very nicely, just don't dilute it too much, or even at all. You can find it at any food store as it is commonly used in stuff needing.... lemon juice.


Reply 3 years ago

Anywhere that sells supplies for canning fruits, jam/jelly, etc. -- things like mason jars & lids, labels, canning funnels.... will have citric acid. Hardware stores that have a good selection often carry this stuff -- call around to your local Ace or TruValue franchise, maybe Target or WalMart.

The cheapest place I've found citric acid is the Indian grocery store, it's with the spices. A good grocery store should sell it as well.


2 years ago

Amazing process! Thanks for the hints.


2 years ago

Great Demo! For small items, using this technique in a ultrasonic cleaner speeds the process
dramatically. I place the citric acid solution in a secondary plastic
container with your parts and surround that with warm water in the cleaner. Monitor so as to not go too long. This works great for brass parts as well.


Reply 3 years ago

Not as fast a citric acid (I speak from exirience), but it gets the job done.


Reply 4 years ago on Introduction

WD-40 eventually causes rust since it contains alcohol which attracts moisture.


Reply 4 years ago on Introduction

Just looked at a can of WD40 I happen to have in the shop. There is no alcohol listed, plus it is described as "drives out moisture" hence the name "WD40" where "WD" stands for "water displacement". It is also called "flammable" because of the propellant used but once it is out of the can and on a surface I have NEVER seen it burn (in fact my son just tried to light a small puddle of the stuff to see what happens. - nothing.)


Reply 3 years ago

I know it contains petroleum products, I used it to start an engine. It's also good for flooded engines.