Step 1: Remove any heavy rust
Removing the heavy rust first reduces the amount of time the parts need to spend in the derusting bath. A fine wire wheel (this one is sold at Home Depot for less than $10) on an inexpensive bench grinder will do the trick. When doing small parts, a pair of Japanese Engineering pliers will hold the parts securely and keep fingers out of harms way. These pliers are essential for holding screws and other round things at the wire wheel. Depending on how many parts I have to do, sometimes I'll run less heavily rusted parts on the wire wheel as well, just to make the later steps go faster. NOTE: DO THIS OUTDOORS AND WEAR A FACE SHIELD AND DUST MASK. The wire wheel can throw broken wires at you without warning and getting one in the eye would really cut into your productivity that day. The dust coming off the parts is nasty and you don't want it all over your shop or in your lungs. |
Step 1: Results
The wire wheel does a great job on the accessible portions of the parts. The inside corners will need to be done by the derusting bath. The wire wheel also removes some of the crusted ink but it's not great for that because the ink can just get smeared around instead of coming off. To get the crusty, old ink off we'll need some chemistry. |
Step 2: Degreasing/ink removal
Old ink is most easily removed using a alkaline cleaner such as Purple Power. Many other brands sell essentially the same product. The important ingredient is lye (sodium hydroxide). Lye attacks the ink chemically, breaking up the cured (oxidized and cross-linked) oil binder. Soaking parts in concentrated cleaner overnight will generally dissolve all the cured ink. A scrub with a bristle brush will easily remove the remains of the ink. If the crust is really thick or the cleaner as been used many times, after a first soak and scrub, the parts can be rinsed and given another soak. NOTE: Take the safety warnings on this type of degreaser seriously. You don't want it on your skin and you really, really don't want it in your eyes. |
Step 2: Results
These parts had one overnight soak, followed by brushing, rinsing, and blowing dry with compressed air. There is still ink in the corners of some parts, but mostly they are clean of ink. The clean parts can go into the derusting bath while the others go back into the degreaser for another soak. Note how some of the parts now look much more rusty than they did after wire brushing. The newly visible rust was hiding under the old ink. |
Step 3: Derusting bath
The parts are soaked in bath of Evapo-rust, one of many similar products that use a mild organic reducing chemical to remove the red rust (actually, the red rust is converted to black rust). The advantage of this method over soaking in vinegar, etc. is that Evapo-rust has no effect on sound metal whereas acids like vinegar can etch (and in extreme cases cause pitting) of the steel surface. Electrolytic rust removal also works great, but nothing's easier than just dumping the parts into a bucket of Evapo-rust. They don't give the stuff away, but it lasts a long time. After the parts have soaked in the Evapo-rust for a couple/few/several hours, I take them out, scrub them with a bristle brush, rinse them, and inspect them for any residual rust. Any parts that still have rust on them go back in the bath for another couple of hours. In theory, you can get Evapo-rust on your skin without ill effects, but I wear gloves when working with it because my hands get beat up enough as it is when I'm working in the shop. The label also claims "safe on eyes" but if you're working in the shop, you're already wearing your safety glasses, right? |
Surprise! No picture here. There isn't even time to get a good picture of the parts before they can start to re-rust. |
Step 3: Results
After the parts come out of the derusting bath, the surfaces are very clean and very susceptible to re-rusting. I blow them dry immediately with compressed air. Waiting even a minute or two invites flash rust on all the nice, clean surfaces you worked so hard to create. |
Step 4: Oiling
Even though the parts have been dried with compressed air, there's still a chance they will start to rust very quickly. To prevent the flash rust, and to give the parts a thin film of oil for long term rust protection, I brush on a liberal coat of light machine oil (like sewing machine oil) diluted in odorless mineral spirits at about a 5:1 solvent:oil ratio. I don't like WD-40 for this because it has a waxy residue that can make parts sticky. After the parts dry, they can be rubbed with a rag to remove any excess oil. |