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Protecting wheel rim from salt-induced corrosion

Posted: 2 Apr 2024, 10:16pm
by ElCani
I recently experienced a highly inconvenient failure of a Ryde Andra 40 rim on my cargo bike. Here’s what happened:

Having repaired my first rear wheel puncture (after two years of using the bike), I realised that a roadside fix would be fairly difficult, thanks to the level of effort involved in removing the rear wheel. As a result, I decided to replace the rear tyre (a Schwalbe Pickup) slightly earlier (it had done maybe 6000km and was about 70% worn) than I normally would, to reduce the risk of punctures.

This went fine until the new tyre wouldn’t seat properly, leading to me using the standard trick of over-pressuring (to maybe 80 psi) in an attempt to get the last bit of the bead to pop into place. But, instead of that happening, the entire rim bed split. Bugger. All is finally well again after I bought an “identical” rim and rebuilt the wheel (after having to buy special “reducer” nipples when it turned out the new rim had smaller nipple holes than the old, astonishing?).

Anyway, the old rim was clearly badly weakened by salt-corrosion (there was about two tablespoons of white powder in the tyre when I took it off), and I would like to somehow protect the new rim from suffering the same fate. The bike is used daily through the Swedish winter in a city where the roads are salted. Washing the bike in winter is pretty difficult due to freezing temperatures. So… very far from ideal conditions!

Anybody got any ideas?

Cheers.
IMG_2735.jpeg

Re: Protecting wheel rim from salt-induced corrosion

Posted: 2 Apr 2024, 11:06pm
by 531colin
What gauge are the spokes, and is it possible the rim was drilled out to fit oversize nipples breaching the anodising and letting corrosion start?

Re: Protecting wheel rim from salt-induced corrosion

Posted: 2 Apr 2024, 11:45pm
by slowster
How does your experience compare with that of other cyclists in the city? Is it pretty much par for the conditions, or is it an outlier?

It might be worthwhile enquiring in some local bike shops. The mechanics should be able to say if it's just something to be expected, or tell you what measures they take to protect against corrosion.

Brucey has recommended in the past using Waxoyl - search.php?keywords=waxoyl+nipples&term ... mit=Search.

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 6:59am
by PT1029
You say " over-pressuring (to maybe 80 psi)", how 80psi was it?
That said, even if more than 80psi, the rim should hold up.
A friend had a similar experience, but he admitted that some months before he had tried tubeless tyres that would not seal, so he inflated the tyre to "200 psi"(!) to try to get them to seal. It didn't fail immediately, but some months later.

The rim looks not too bad (ignoring the split of course), so I am guessing it is internal corrosion in the hollow section. If you use waxoil or some such, I guess you will need to seal it from contaminating the inner tube.
Or may be a periodic dab of oil on the outside at each spoke/nipple hole, and seal the hollow section internally at the valve hole. That might keep the water out. If sealing the valve hole hollow section, it might be worth making the seal removable in case you loose a spoke nipple in the rim at some point.

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 7:46am
by rogerzilla
Is it a hub brake?

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 7:48am
by Paulkentuk
For a set of mag alloy motorcycle rims, exposed to salt through the English winter, I used to apply a light smear of Castrol LM grease ahead of winter.

Once the overnight temperatures increased in Spring, and the April rain washed the salt away, a quick wash with a rag and warm soapy water, restored the rims appearance.

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 11:29am
by Cyclothesist
I take it the rim has corroded from the tyre/inner tube side from salt water ingress rather than from the outside of the rim? If so why not paint the inside of the rim with a couple of coats of waterproof varnish?

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 2:15pm
by Cyclothesist
Another thought - are you sure it was salt water ingress that caused it and not your sealant? If you're running tubeless then some sealants are alkaline and can corrode unprotected aluminium. Some rim manufacturers specify what sort of dealant to use.

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 4:29pm
by rareposter
Cyclothesist wrote: 3 Apr 2024, 2:15pm Another thought - are you sure it was salt water ingress that caused it and not your sealant? If you're running tubeless then some sealants are alkaline and can corrode unprotected aluminium. Some rim manufacturers specify what sort of dealant to use.
Sealant is nowhere near harsh enough to corrode aluminium plus it shouldn't (under normal conditions) be on the rim anyway, it's contained within the airtight rim tape and the tyre. Modern tubeless wheels are made near enough airtight on that side anyway, there's no possibility of sealant leaking through into the rim bed and spoke nipples.

Much more likely to be salt water, road grime etc penetrating the wheel rim from around the wheel nipples.

If the wheel has a hub or disc brake, you can spray the rim with some sort of protectant like silicone wax or GT85.
Do NOT do that on rim brake wheels!

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 5:10pm
by 531colin
What does it look like without the rim tape?
Is there a single continuous crack or several cracks originating at ( or involving) individual drillings in the inner wall of the rim?
Andra rims have been around a long time, any reports of similar failures?

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 6:09pm
by Cyclothesist
rareposter wrote: 3 Apr 2024, 4:29pm
Cyclothesist wrote: 3 Apr 2024, 2:15pm Another thought - are you sure it was salt water ingress that caused it and not your sealant? If you're running tubeless then some sealants are alkaline and can corrode unprotected aluminium. Some rim manufacturers specify what sort of dealant to use.
Sealant is nowhere near harsh enough to corrode aluminium plus it shouldn't (under normal conditions) be on the rim anyway, it's contained within the airtight rim tape and the tyre. Modern tubeless wheels are made near enough airtight on that side anyway, there's no possibility of sealant leaking through into the rim bed and spoke nipples.

Much more likely to be salt water, road grime etc penetrating the wheel rim from around the wheel nipples.

If the wheel has a hub or disc brake, you can spray the rim with some sort of protectant like silicone wax or GT85.
Do NOT do that on rim brake wheels!
Looking at the photo posted by the OP the rim tape is ruptured over one spokehead and torn longitudinally either side of the valve hole. No way does it look gas tight let alone water tight. If the cause is salt water permeation down the spoke holes I'd expect corrosion at the spoke nipple holes with cracking around them and spokes pulling through.

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 6:21pm
by 531colin
My recollection of this old thread has been bugging me.....viewtopic.php?t=40617&hilit=twins&start=15

shows it is possible to design a rim which will fail by fatigue cracking....apparently from some stress raiser within the hollow section.

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 6:25pm
by geocycle
The white powder on the picture looks like dried tubeless sealant? Might not be corrosion but the overinflated tyre opened another weakness. Cargo bikes can be heavy which might have caused the initial crack?

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 6:28pm
by Cyclothesist
geocycle wrote: 3 Apr 2024, 6:25pm The white powder on the picture looks like dried tubeless sealant? Might not be corrosion but the overinflated tyre opened another weakness. Cargo bikes can be heavy which might have caused the initial crack?
80psi doesn't even touch overinflation.

Re: Protecting wheel rim from salt-induced corrosion

Posted: 3 Apr 2024, 6:30pm
by 531colin
I'm guessing its a small wheel, so there are 3 holes close together....valve hole and the adjacent spoke holes.

There is also a LOT of cracking just adjacent to the bead seat, where the corners of the box section are....in the general run of events, I wouldn't expect this bit of the rim to be particularly highly stressed?.....eg. it isn't supporting spoke tension.

Be interesting to see photos of all round the rim, without rim tape.