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I'm using my bike to commute between my work and home (~10km). In the middle of my trip I have to use a ferry and have to put my bike on the deck.

Within 2 weeks of the trip I could see my cassette and some nuts started to rust. Frame is aluminium and I didn't see any rusty spots on it. Since I've never used my bike this much in salty/humid environment I don't know anything how to protect it from rusting.

Is there any grease that I should use for nuts and other open steel surfaces to prevent rust?

Or should I just gently wash my bike every day after coming home ?

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    Consider washing down your bike when you get home. The salt runoff will make grass sad, so do it over a concrete or gravel area.
    – Criggie ♦
    Sep 24, 2018 at 9:33

2 Answers 2

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Rust on a cassette or even a chain is quite normal in this kind of surroundings is quite inevitable. Also it has little impact other than visual. More frequent wiping and greasing of the chain is one of the few remedies. Buy the cheapest cassettes so that it won't hurt your wallet too much if you have to replace more often than usual.

What is far more insidious would be rust or corrosion on hidden places like the insides of tubes for a steel or aluminium bike. Or the kind of corrosion that will fuse parts such as bolts. So you should take bits apart more frequently and apply a thin coat of grease where metal touches metal. You should also apply spray wax to the insides of the frame.

Keep an eye on seat-post, stem and handlebar. And get stainless and coated brake and shift cables.

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    +1 for mentioning that aluminum is susceptible to corrosion.
    – mattnz
    Sep 23, 2018 at 20:59
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    @mattnz Since when? I learned that aluminium rust (oxide) forms a smooth thin layer that's actually harder than aluminium and protects the aluminium below from further rust and even scratches.
    – Nobody
    Sep 24, 2018 at 21:39
  • Keep in mind that no all parts of the frame have to be made of aluminium, the bottom bracket and other highly stressed parts most likely will be steel
    – Lars Beck
    Sep 25, 2018 at 6:02
  • @Nobody: I think aluminium tends to act as a galvanic anode for other, electrically connected metal parts.
    – Michael
    Sep 25, 2018 at 14:57
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The cassette and chain are some of the hard parts to deal with as nuts and bolts can usually be replaced by stainless steel versions (eBay for small quantities of odd sizes. You can every get titanium skewers.

I have a cheap bike that lives outside all the time, though a few km from the sea. I use a light spray oil with PTFE (GT85) on the chain, gears and derailleurs, taking the opportunity to do that when the bike is nice and dry. Just be careful to avoid braking surfaces. This isn't the highest performance lubricant for chains, but on that bike I don't care, and it's much better than the more common WD40, that goes gummy after a while (and is therefore unsuitable as a lubricant, though useful for freeing up stuck parts of you're desperate)

You won't keep the rust away completely, as there are steel bits you can't swap out for stainless, so if this is a valuable bike I suggest you get a cheap (second hand) commuter and save this one for best.

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  • WD-40 should never be used as a chain lubricant.
    – Batman
    Sep 23, 2018 at 18:50
  • @Batman that's what I said
    – Chris H
    Sep 23, 2018 at 19:25
  • Considering if there will be galvanic corrosion between stainless steel nuts and aluminium frame.
    – Efe Can
    Sep 24, 2018 at 6:08
  • @EfeCan it's possible, but IME (I've got some experience of galvanic corrosion in cooling systems and a lab experiment) stainless on aluminium is acceptable, unlike brass on aluminium. This is despite the galvanic series suggesting otherwise, which may have something to do with aluminium's natural passivating oxide layer
    – Chris H
    Sep 24, 2018 at 6:59
  • ...or maybe cheap stainless parts are unpassivated 304
    – Chris H
    Sep 24, 2018 at 7:05

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