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I picked a girl's mountain bike out of a dumpster . It looks very excellent except for a chain that is so rusted that each link needs to worked free.

Name is Techno Lite , 26" wheels, 15 speed Shimano, center pull brakes Lee Chi.

I know it is not the caliber of bike that most posters here have, but I have a 11 year old granddaughter that could ride it ; a "starter" bicycle to see if it is something she would be interested in. My guess is some one rode on a salt water beach then put it in a garage for years without rinsing it; the chain was essentially solid.

Question: Should I oil the chain and work it free or buy a new chain ?

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    A new chain costs from 15 to 30 euro/dollar/pounds. Just buy a new chain (make sure to get a compatible one) and toss the old one.
    – Grigory Rechistov
    Dec 4, 2018 at 21:10
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    Chains are consumables - it can possibly be saved by soaking in solvents then lubricating. Otherwise replace. At the same time check brake pads and gear/brake cables and tyres, which are also consumables and subject to aging.
    – Criggie ♦
    Dec 4, 2018 at 21:41
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    Also, 15 speed and centerpull brakes sounds like a bike that dates from the 90s. While that's not a bad thing, some kids are put off by little things like squeaks or tears in saddle etc. Even colour can be a turnoff.
    – Criggie ♦
    Dec 4, 2018 at 21:44
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    If the chain is stretched/elongated it may be not worth saving. I've saved one that was surface rusted but almost completely unused. It may never be great, but its worth a go at recovery,
    – Criggie ♦
    Dec 5, 2018 at 1:15
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    @Grigory less than £/€/$ 10 for a (2-3x) 5/6 speed chain. I paid £6 for one for my 3x6 beater bike, and that wasn't even the cheapest
    – Chris H
    Dec 5, 2018 at 8:10

3 Answers 3

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If the chain isn't worn (which it probably is not, kids bikes don't get high mileage) it might be worth trying to save, but you may end up spending more compared to getting a new one.

Penetrating oil, a wire brush and a lot of effort may free it up enough and get it reasonably clean.

Removing the rust chemically is problematic. Something strong enough to work with the chain in place may damage paint or plastics. There are safe products such as Vapo-Rust but the chain would need to be removed and soaked for an extended period of time. Also, new chains for 10 or 15 speed bikes are inexpensive. Instead of buying chemicals, just buy a chain.

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  • "Wood brightener" can be sprayed on (I keep a small spray bottle of it in my toolkit) and will not damage most finishes. One caveat, though, it that since the anodized coating often used on aluminum is essentially a variant of rust, the stuff will remove that.
    – Daniel R Hicks
    Dec 5, 2018 at 2:14
  • @DanielRHicks oxalic acid won't react with the thick layer of Al2O3 formed in anodising, because Al binds much more strongly to O than Fe does (higher reactivity, thermite exploits this). I'd still suggest taking the chain off if you're going to try oxalic acid because the native oxide layer that forms naturally on scratches aluminium is thinner and more porous. That's less likely to protect the metal from the acid.
    – Chris H
    Dec 5, 2018 at 8:09
  • @ChrisH - Have you tried it?
    – Daniel R Hicks
    Dec 5, 2018 at 12:40
  • @DanielRHicks no. I checked the reactivity, but I've got some experience with anodising and acids that ties up with this fairly typical discussion (e.g. you need a strong alkaline solution to strip anodising). But as every old frame will have scratches I don't suggest the experiment. And if you're going to describe an oxide of one metal as a variant of rust, then you're also describing gemstones (sapphire = Al2O3, same compound as in anodising) and the white bit of white paint (TiO2) as variants of rust.
    – Chris H
    Dec 5, 2018 at 12:52
  • I have had good results with "Coca Cola Light" believe it or not. I have free lot's of sutff with it, It worked even better than WD-40 and some penetraiting oils. It think it works because of the acid mixed in the drink, like phosphoric and carboxilic acid.
    – dmb
    Jan 14, 2019 at 14:34
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Such question reminds me of one of the Sheldon Brown's April Fools Day articles on chain cleaning. In short:

  • disassemble each link by driving the pins out
  • clean each part individually and thoroughly
  • lubricate the moving parts
  • reassemble (reverse of disassembly)

With his sets including the chain break tool, all chemicals and some replacement parts, ranging in price from $69,95 to $249,95 you're good to go.

But let's get serious - as many say, it can be done. It only depends on economy, i.e. your imaginary hourly rate. Be prepared to spend couple (2-3) hours on cleaning the chain and making it work more or less properly. And all this in hope that the chain has proper dimensions (is not overstretched).

To give you some indication on what can be done have a look at the small part of the chain that I cleaned last weekend:
enter image description here
It's a piece of chain that started rusting in the early '70s. After soaking it in phosphoric acid[1] for about a quarter and then cleaning, lightly sanding (120 grit if I'm not mistaken) and polishing it with some paste for a following quarter it's the result I got. And it's only 5 out of more than a hundred links.

Was it worth? Financially not. And I wouldn't put this chain on a bike (reliability and the ease of maintenance).
I did it because a) it's a respected vintage brand from where I come from, this chain has some interesting history and I was making a key-chain (pun intended) for someone to keep this as memorabilia.

[1] - phosphoric acid is a hazardous substance with corrosive characteristics. At moderate concentrations phosphoric acid solutions are irritating to the skin. Contact with concentrated solutions can cause severe skin burns and permanent eye damage.

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  • Phosphoric acid is good stuff for cleaning up rust. But it also happily dissolves skin, damages most paints and rubbers. and tends to covert the red/brown rust into a harder black iron oxide which may interfere with the smooth flexing of the chain. And the costs come into it too. But the acid can be used on other parts like spot treating frame rust, or handlebars/stems/bolts .
    – Criggie ♦
    Dec 5, 2018 at 10:43
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    @Criggie - you're right, certain precautions are necessary when using phosphoric acid (even diluted). For me it is obvious, but for the society where writing "caution, the content is hot" on coffee cups is customary I should add a suitable disclaimer.
    – Mike
    Dec 5, 2018 at 10:51
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    I've cleaned up a badly rusted chain after about 15 minutes drenched (via spray) in oxalic acid solution, followed by 2-3 minutes with a chain washer. The trick is to NOT lubricate it before attempting this, so that the ox acid can do its work.
    – Daniel R Hicks
    Dec 5, 2018 at 12:50
  • That's not a pun, they're both literally chains. I'm reporting you to the joke police. honk honk
    – Monica Apologists Get Out
    Dec 5, 2018 at 20:52
  • Plus for saving old chain from Bydgoszcz.
    – krzyski
    Jan 15, 2019 at 12:30
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If there's loose rust, of course you should remove it; a wire brush is all that needs. The real problem is inside the pin joints, and usually a penetrating oil (or WD-40, or kerosene) can rinse that out. After the joints are free, blot dry and put on a real lube (I've liked drip bottle Tri-Flow, White Lightning gets good reports, too).

The little solid microbeads get into the pin area and stay; even after most of the oil washes off, and despite surface rust, the chain can work fine for years of commuting.

Oxalic acid (depending on time and concentration) can etch the bearing surfaces, or remove the black oxide (not much rust protection in black oxide, but it's better than bare metal); I'd avoid that. Yes, it dissolves rust, but even an infrequently lubed chain ought not to need that.

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  • You've never seen a chain that was so rusty it didn't flex?
    – Daniel R Hicks
    Jan 14, 2019 at 12:59
  • @DanielRHicks Frozen chains, rusty or not, respond to cleaning; the flex was restored by washing out grit, not by reducing visible rust. The stuff I saw in the bottom of the kerosene jar was road grit.
    – Whit3rd
    Jan 14, 2019 at 22:19
  • You've clearly never seen a rusty chain.
    – Daniel R Hicks
    Jan 14, 2019 at 22:38
  • That's not clear. I'm in Seattle, commuted for years on wet roads and have enjoyed normal chain function with and without rust.
    – Whit3rd
    Jan 15, 2019 at 1:19
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    You've never seen a chain that was apparently cleaned with a hose and soapy water, then left out in the weather for a year. It's bright red and doesn't flex at all.
    – Daniel R Hicks
    Jan 15, 2019 at 1:32

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