Rust removal?

[noparlpf]

Does anybody have tips for removing rust from steel? Preferably with a brief explanation of the chemistry. There are a bunch of suggestions all over the internet but some seem to be suggesting acids, some seem to be suggesting bases, some seem completely made up, and I don't remember enough inorganic chem from undergrad three years ago.

Edit: I'm trying to get rust out of my bike gears and it's pretty tough to get down in between them with any of the brushes or scouring pads I have on hand.

[Lord Torath]

I think the best (most effective) methods are mechanical, not chemical. Depends on just what you're trying to remove the rust from, of course, and how rusty it is. SSPC-SP-5 White Metal Blast or SSPC-SP-10 Near White Metal Blast both work very well at removing rust. They are surface preparations, however, and are intended to be followed by a protective coating or paint, and will not protect a surface or prevent rust by themselves. Power tools (grinders, needle guns, etc) and hand tools (wire brushes, chisels) are also effective.

[noparlpf]

I think the best (most effective) methods are mechanical, not chemical. Depends on just what you're trying to remove the rust from, of course, and how rusty it is. SSPC-SP-5 White Metal Blast or SSPC-SP-10 Near White Metal Blast both work very well at removing rust. They are surface preparations, however, and are intended to be followed by a protective coating or paint, and will not protect a surface or prevent rust by themselves. Power tools (grinders, needle guns, etc) and hand tools (wire brushes, chisels) are also effective.

I'm trying to get rust out of some bike parts and not everything is reachable with brushes or scouring pads. I just edited the OP too.

I'm also just kind of curious about the chemistry now.

Another idea that might be worthwhile is a rust converter (I think I saw that some solution with tannic acid converts rust to an inert compound that won't continue to rust, but would also benefit from a coat of paint over it) but that would also mean going to the bigger hardware store the next town over and I don't want to do that this weekend.

[Lord Torath]

Okay, that clears things up a bit. We're going to have to wait for the Chemists in the Playground to show up. I passed Chem 101, and that's about it. I just took a course on corrosion, so I can tell you how it happens (different parts of the metal have different electrical potentials, up to about half a volt in steel, and when you connect the exterior with an electrolyte, it creates a circuit in the metal, with a cathode and an anode, and the anode corrodes in the process, oxidizing into rust). But we didn't cover rust removal in chemical terms.

[noparlpf]

I was also thinking of rigging a makeshift electrolysis chamber in the garage, but my mum vetoed it. Even though I was just going to use a 5v power supply.

[BlueHerring]

I've always used lemon juice (citric acid) to initially get the rust off, followed by wiping it off with a wet paper towel. In general, don't use too much acid without wiping it off, since you don't want it to corrode. I can't actually say much about citric acid on the actual inorganic chem side, but since it's a weak acid, and you're not using it in extreme concentrations, it should be fine.

I usually try to avoid acids for cleaning things, but the bike chain is the main exception to that rule.

[cobaltstarfire]

I would usually just use WD40, with one of the little spray straws, spin the chain and spray WD40 on it, and switch back and forth through all the gears.

Wipe off any extra WD40, then coat the chain with the chain oil/wax/grease of your choice (don't overdo it) while spinning the chain and go through the gears again.


Can't give you any sciency info on that, but that's how I took care of my bike chain when I lived in a dorm and my bike lived out in the elements. I'd have to clean it once a month because of dust/dirt build up in the summer, but once I started actually maintaining my chain it never seriously rusted again.

[Lord Torath]

I would usually just use WD40, with one of the little spray straws, spin the chain and spray WD40 on it, and switch back and forth through all the gears.

Wipe off any extra WD40, then coat the chain with the chain oil/wax/grease of your choice (don't overdo it) while spinning the chain and go through the gears again.Don't skip the bolded part. A buddy of mine soaked his chain in WD40, stripping all the grease. He dried it, installed it on his bike, and then broke it within 2 days as it rusted. :smallsigh:

[aspi]

I'd always try a mechanical approach before a chemical one, since any kind of acid that you use will also attack the iron. So it's somewhat complicated to find the proper balance. Afterwards, when you rinse it off, it'll also be wet (and if it's hard to clean it will be hard to dry off), which will encourage new rust to form

A mechanical alternative that should work even for parts that are hard to reach is sand. Just put the parts in a box with fine sand (and some extra room) and shake it for a while. The rust is much softer than the iron and will be ground away. A couple of friends of mine who are into LARP say that this is the easiest way of cleaning rusted chain mail. And if it works for something that intricate I'd be surprised if it didn't work for bike parts.

[Xuc Xac]

A couple of friends of mine who are into LARP say that this is the easiest way of cleaning rusted chain mail. And if it works for something that intricate I'd be surprised if it didn't work for bike parts.

The traditional method of cleaning mail was putting it in a barrel of sand and rolling it down a hill.