3 Ways to Remove Rust from Iron
Rust. One of the most formidable enemies of antique collectors the world over. Not only is rust visually unappealing, it’s a bona fide antique killer!
Given enough time, oxygen, and water (moisture), an iron object will inevitably transform to rust and disintegrate. The longer rust is allowed to persist, the more it devours its host.
Over the years, I’ve tried dozens of rust removal techniques; everything from good ole’ fashion elbow grease to harsh chemicals. Having restored hundreds of iron objects, I’ve settled on three inexpensive, non-toxic methods that have produced the best results.
Acid, specifically citric acid (more on that later) and acetic acid, is a natural and inexpensive way to remove rust. Depending on source materials and type, vinegar contains anywhere between 5 to 20% acetic acid by volume.
If you’re dealing with small iron objects, vinegar is a great way to remove rust. White spirit vinegar is packed with the most acetic acid; more than white distilled vinegar and apple cider vinegar. This, and its low cost, make it the perfect choice for eradicating stubborn rust.
When soaking iron objects in vinegar, I prefer to use an inexpensive (throwaway) plastic container. When filling the container with vinegar, pour enough in so that it fully covers the object, with about an inch of vinegar suspended above the object. To avoid the noxious odor, cover the container with Saran Wrap.
Depending on the level of corrosion, the object will need to soak for at least a day. Heavily encrusted objects can take more than a week to breakdown. When the vinegar has done its job, the rust becomes paste like; so much so that it can be removed with the smear of a finger.
Warning: Check on the object periodically. After the vinegar has dislodged the rust, it will begin to eat good metal!
Once the rust has been removed and the object wiped clean, you will then need to take additional preservation measures. More on that later.
2. Lemon or Lime Juice
Have salt? Check. Lime? Check.
Bad news: you’re one ingredient shy of a margarita. Good news: you have the ingredients to a great rust remover!
To remove rust using this technique, start by vigorously rubbing salt on the rusted object. Once coated with salt, place the object into a shallow container. Next, squeeze the lemon or lime juice onto the salted object and let it rest for several hours. Do not throw away the lemons/limes, as the will come in handy later!
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After the object has soaked for a few hours, it will need to be scrubbed clean. To mitigate additional damage to the object, first try to remove the rust by using the rinds of the lemon/lime. It’s coarse enough to gently remove the rust without scuffing-up the remaining good metal.
Depending on the depth of corrosion, you may need something coarser. If so, try using a scouring pad or fine steel wool. If a few stubborn spots remain; and as a last resort, grab a wood chisel! A wood chisel is much softer than a metal chisel, allowing you to chip away at the rust without causing damage to the good metal.
Warning: Much like the vinegar method, after the citric acid has removed the rust, it will begin to eat good metal. Check the status of the object frequently!
Once the rust has been removed and the object wiped clean, you’re just a few steps away from a fully restored iron antique. More on that later… I promise.
In addition to being one of the most reliable forms of rust removal, electrolysis has to be the most interesting of all the methods I’ve used.
“Lysis” is a Greek word that translates to the “disintegration: breaking down” of cells. With electrolysis, electricity is used to break down bonds through the aid of electric current. Cool stuff right?
While I’ve used a variety of setups over the years, I’ve come to use the following with the most success. Here’s what you’ll need:
- 12v DC battery charger (do not use a trickle charger)
- Large, thick plastic bucket
- Copper refrigerator line for sacrificial electrodes
- Arm & Hammer laundry soda (not to be confused with baking soda)
- Distilled water
First, coil the copper refrigerator line around the inside of the bucket without allowing it to touch itself. Crimp the ends of the line flat, as one end will be attached to the positive terminal, while the other crimped end will prevent water from getting inside the line. This copper line will conduct the electricity within the bucket.
In order for the electricity to pull the rust away from the iron object, an electrolyte must present in the water bath. This is where the laundry soda comes in.
To gauge how much of an electrolyte bath you’ll need, place the iron object into the center of the copper coiled plastic bucket. Your laundry soda bath will need to completely cover the object.
Next, prepare the bath by dissolving the laundry soda into hot water. You’ll need to add 1 to 2 teaspoons of washing soda per 5 cups of water, or 1/2 cup of washing soda per 5 gallons of water. Pour the solution into the bucket and stir until dissolved.
Now for the fun part. But wait, first a disclaimer: make sure the battery charger is unplugged!
Okay, now we can have fun.
Connect the negative terminal to the rusty object and the positive terminal to the copper line. The positive terminal connection MUST be outside the washing soda bath!
Plug the charger in, turn it on, and let the fun begin! You’ll know within a matter of seconds if you’re setup is working properly, as you should immediately begin to see bubbles emanating from the object. If no bubbles appear, turn the charger off, unplug it, and recheck your connections.
How long you subject the object to electrolysis, is dependent on how corroded it is. The more corrosion, the longer it should sit in the bath. To gauge progress, simply turn off the charger, unplug it, disconnect the terminals, and then remove the object from the bath. If the electrolysis is complete, the rust will no longer be present, or it can easily be removed by hand. If not yet complete, simply return the item to the bath, reconnect the terminals, plug in the charger, turn it on, and let it rest a little longer.
The best part about the electrolysis method is that once the rust has been removed from the iron object, it doesn’t attack or compromise the remaining “good” metal.
Regardless of which rust removal technique you employ, you will need to follow it up with a two-step preservation process.
Step 1: Rust Converter
Once the object has completely dried, I lightly spray the surface with a rust converter. This conceals the existence of any small pockets of rust and prevents future corrosion.
Step 2: Hot Wax
For iron objects that will be displayed versus being used (like tools), I follow up the rust converter treatment with a “hot wax” coating, using a dark brown Briwax.
To open the pores in the metal and to force trapped moisture to the surface, place the object underneath a heat lamp. Once the object becomes heated, simply apply the wax to the warm iron. The wax will melt on contact, and seep deep into the pores of the metal. Once cooled, the wax acts as a shield against moisture and oxygen.
I prefer my iron antiques to a have a smooth shine, so I brush/buff the waxed surface with a shoeshine brush, followed by a soft terry cloth.
So there you have it! Three tried-and-true rust removal techniques for iron antiques!
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