How not to de-rust your bike chain
a null hypothesis for one way of derusting a bike chain which worked and simultaneously failed hard. 2025-03-04.
- Spontaneously start late at night
- Go: “ah, I’m out of degreaser? I’ll skip that and go ahead with the next step”
Please: never skip a degreasing step. I exhort you. The result will be a rust-free chain (!) but with every milimeter2 of surface area enmired and enmuckened, to such an astonishing degree that the degreaser that was—in fact—there all along cannot be used to clean it off. The only unimpacted areas were, ironically, the little bits of chain that were previously rusted but now cleared of it.
The water, combined with whatever muck left on the chain and that which was released from the rust being eaten by the acid, seemed to have acted as a dispersal agent for last year’s lubricant. Add to that the lengthy bath duration (citric acid is great for removing rust but seems to act slowly, so time helps) and the ample time spread the mutated lubricant everywhere.
Oh, here are the notes from what I was intending to do where each “shaker” is an old jam jar of sufficient volume.
Remove the chain from the bike, then pass it into the first shaker.
- Part 0: shaker of degreaser
- Part 1: shaker of high % citric acid solution
- Part 2: shaker of alkaline solution (baking soda + water)
- (Part 3: shaker of water (?))
Finally:
- Dry the chain
- Reattach it to the bike
- Relube it
And my research notes & snippets:
It’s not because of the water. If you had 100% acetic acid it would be even faster. Acid makes steel flash rust, which is why you are supposed to neutralize it afterwards with an alkaline solution. Baking soda + water for example. If you don’t, it will rust almost immediately. First acid solution, when the rust is gone, move the parts directly to the alkaline solution. Do not mix the solutions, that’s the same as just washing it in water.
and,
Naturally, you can use pure, concentrated acetic acid, but white vinegar costs less per liter, and is just as effective. In fact, you can even use food-grade apple cider vinegar and it’ll do the trick. The process is roughly the same as with most acids — pour, submerge, let it sit, rinse, and if needed, repeat.
and also,
There are alternatives. One trick is to get the chloride, sulfate, or nitrate into solution by using a compound other than the acid. For instance, adding sodium chloride to a solution of citric acid should make the citric acid more aggressive, and yet, won’t change the pH. (One reason for this is that FeCl3 is more soluble than the iron citrate.)
Concentration of citric acid: 14g dry citric acid to 400ml water. Based on Instructables: Removing Rust with citric acid
Citric acid wash anything that has bad rusting, especially if you think there is rust inside the crank. Mix 1-2 table spoons of citric acid for each gallon of water. Soak overnight or longer if needed. Rust comes right off. I’ve done full frames in the bathtub before. Works really well.
What I did do that seems to have worked (only a repeat with better step-adherence will tell):
- Using dry citric acid + water as a rust removal agent (with a heavy concentration of citric acid; in my notes I wrote “14g to 400ml water” but I dosed without measuring)
- Creating a bath of water and bicarbonate of soda, to neutralize the acid left on the chain once removed from the acid bath
- Wearing gloves and goggles to be safe and doing my experiments in a bathroom :)
After researching how to remove rust for a bit, citric acid seemed to be the best way to remove rust for my particular context and it’s something that I usually have a lot of at home for decalcifying my electric kettle. For lighter rust on household goods, acetic acid seems to work great too (if slower).
Fail or not, letting the chain rest a night in the acid bath did, after all, remove the rust.
Anyway so now I’m buying a new chain but I’m one bike-life lesson more prosperous than before. Actually two, depending on how the following goes in practice: when looking around a bit for what degreaser to top up my stash with, I found instructions for creating your own. Seems promising, too. Reproduced in full below but caveat emptor, I haven’t tried it yet:
How to DIY homemade bike chain degreaser
I am an industrial chemist, and manufacture commercial-grade degreasers and other cleaners.
[source: bicycles.stackexchange.com]
Firstly, there are 3 main parts to a degreaser:
- Alkaline booster, to increase the pH, allowing the dirt, grease and grime to be effectively removed, for faster cleaning
- Solvent, to cut through tough grime and grease, as well as extract grime and grease from hard-to-get areas
- Surfactant, to hold grime and grease in the cleaning solution, preventing it from depositing back on the bikes surface once lifted off by the solvent and the alkaline solution
(there are also other components in professional degreasers, such as water softeners, hydro-tropes, anionic and ionic surfactants, specific application solvents, etc…)
The main source of the above 3 parts can be from using baking soda as a alkaline booster, methylated spirit as a solvent (I would use methylated spirit because it is water-soluble), and a small amount of dish-washing liquid as a surfactant.
An example formulation by volume would be:
- 50% Methylated Spirit
- 40% Water (H20)
- 5% Sodium Bicarbonate (Baking Soda)
- 5% Dish-washing Liquid
note: “add baking soda to the water and methylated spirits and mix before adding anything else should help “
The methylated spirit and the sodium bicarbonate will work together to extract and lift the dirt/grime/grease, and the dish-washing liquid will work as a surfactant to stop it from depositing back on the bike again.
The dish washing liquid will also act as a wetting agent and a foam booster.
EDIT —-
Please also note, that the methylated spirit will prevent (or nearly prevent) any foam or the like from forming. If you want foam, you will have to substitute the methylated spirits with a mild solvent that is hydrophilic and not oil-based (lipophilic).