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I use a D-Lock to secure my bike (along with other locks.) But every lock I've had has developed rust in the prongs and lock mechanism, that is messy and eventually seizes up.

The problem can be delayed and reduced by oiling with WD-40 and wiping off the prongs, but I feel like it ought to be possible to get a D-Lock that just isn't ferrous and thus doesn't rust in the first place.

But I can't immediately find such a product by googling.

  • a Is there any reason that such a lock shouldn't exist?
  • Are there any particular search terms I should use? (Or does anyone have a specific product recommendation?)
  • Does anyone else have alternative solutions to the problem?
  • Stainless steel would be the best bet for the exposed parts as most non-ferrous metals are quite soft (and the others expensive). Some stainless steels can be hardened quite well. – Chris H Feb 4 '17 at 22:17
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    Isn't hardened stainless steel quite brittle? Wouldn't it be susceptible to liquid nitrogen / hammer attacks? – RoboKaren Feb 4 '17 at 22:24
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    @RoboKaren is up to something. Locks ought to be hard such that they are difficult to saw through and ductile enough that they resist attacks with levers and hammers. A slow rusting steel might be chose over a stainless steel. – gschenk Feb 4 '17 at 22:44
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    The problem is that the lock mechanism itself is the part most likely to freeze up, and it's hard to protect a mechanism of such complexity and precision from getting crud in it and seizing. It's generally made of brass and other relatively corrosion-resistant metals, but there are too many tiny pieces that can get stuck by an even tinier bit of grit. – Daniel R Hicks Feb 4 '17 at 23:11
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    I spray graphite in my locks periodically into the cylinder, and Triflow into the U-end. Seems to keep them working fine. Nothing will last without lubrication and cleaning in a wet/salty environment. – Batman Feb 5 '17 at 3:40
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This doesn't answer your question about non-ferrous locks, but rather the pre-question of why your locks feel like they're "rusting."


First of all, you shouldn't use WD-40. It's OK for its primary purpose of driving water out of thing (Water Displacing Formula #40) - but it leaves a thin sheen of light oil. This is ok for door hinges, but when used on locks, it attracts dirt and grit, which can actually make the lock worse.

(The internal mechanism of most quality locks is brass, which shouldn't "rust" -- what you're most probably feeling as "rust" is the dirt and grit that's gotten into the mechanism. Even if the body were made of titanium, you'd still likely make the locking mechanism out of brass because of its ability to be precisely machined and its self-lubricating properties).

Use a dry lubricant for the internal mechanisms of locks. Locksmiths prefer graphite, which you can get at your hardware store. Or you can use PTFE based dry chain lubricant if you have it - but do make sure it doesn't leave a greasy film, some do.


For the rest of the U-lock body, you can use anything you like to prevent rust. Paint, nail polish, plastidip, sugru, silicone oil, Boeshield, etc. etc.

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  • No, it really is rust .... I'm not "feeling" it ... I'm looking at it. It's rust. For sure, this is probably ALSO some grime but the majority of it is definitely rust. Apart from anything else ... it's Orange! And when I clean the superficial stuff off, I can see the rusting corroded sections on the D-prongs. Will try alternative lubricants, though. – Brondahl Feb 5 '17 at 15:32
  • The prongs might rust as they're part of the body and are made of metal. The latch might also be made of steel. But the internal lock mechanism is usually brass in high end locks. – RoboKaren Feb 5 '17 at 16:12
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This won't help with cosmetic surface rust, but you should consider how the dirty water that gums up the mechanism gets in there. If you can lock up so that water would drain out rather than into the keyhole and latch hole, that would help. Under cover is even better but sometimes that's not an option. Riding along you have to consider water flicked up as well. In fact that's the worst sort as it's usually got tiny bits of grit in it. Many frame mounts for locks don't help in this regard as they put the lock in places that get very wet with spray.

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