Internal corrosion on Tubeless rims

[Mecnic]

I have been involved in and around bike shops for the last 7 years and have seen alot of thing from dumb to strange but this, this is a first, see pics.

 

It seems the sealent has eaten away the matel of the rims resulting in it looking like swiss cheese and it's on both the front and rear wheel and not just on one spot on the rim, it seems everywhere where the black coating is scratched its started to eat away at the rim from the inside

 

What's your opinion?

 

My theory is either the client cleaned hs rims with some volatile solvent or corrosive liguid of sorts or he made some odd mix of home brew sealent and it caused one huge chemical reaction almost like it became corrosive?

Edited October 12, 2010 by Mecnic

[Capricorn]

how bout some in-focus images with proper close ups/macro shots

[Johan Bornman]

Very common. I recently had it on a Dura Ace tubeless wheel. Unfortunately the orginal owner sold the wheel to a sucker who didn't look carefully. We don't know what was used in there to eat the rim.

 

Most of these rims are anodised and anodising can be removed by something caustic (alkaline).

 

Maybe someone here can measure the pH of some common sealants. Who has access to a lab? Steynja, your phone is ringing...Tring tring, tring tring.

[Capricorn]

still would appreciate the better photos. not everyone knows asmuch as jB

Edited October 12, 2010 by Capricorn

[Brighter-Lights]

A friend of mine had the same thing happened to his Crossmax SL wheel and he just used Stans... what I do know, is that anything caustic dissolves anodising easily.

[Mecnic]

how bout some in-focus images with proper close ups/macro shots

 

They were just quickly snapped on my phone, will take some proper pics tomorrow it at my LBS,

 

Its odd that sealent is capable of this but as JB said would be interesting to see what the PH of some sealents are

[dcal]

Ammonia is the answer

Use ammonia-free sealant

[montyzuma]

I had it happen to a pair of Crossmax's - occurred around valve hole & from what I can see in the pics above it seems to be the case there too. My theory is the electrolytic potental between the brass or steel of the valve and the Alu rim in the prescence of a weak acid (the ammonia in the sealant), where the weak acid on it's own wouldn't be strong enough to corrode the alu.

 

Any chemists out there to refine the theory?

[Capricorn]

ammonia is acidic or caustic?

 

but that sounds a better theory than just straight blaming alkalinity of the sealant. If were that straightforward, should be happening more often. then again...

[mach7-7]

I have the same issue with my Cervino Expert tubeless rims. They are coming up to the 3 year age mark and are also corroding around the valve( where the sealant accumulates due to it drying out from constant inflation).. As I treat my bike and accessories with care, and have only used Stan's sealant since the rims were new, I have to direct the cause at the Ammonia that is used in the sealant. While I beleive that Stans is very good, I see no reason why they cannot start manufacturing their products without Ammonia like other brands do..

 

Its a shame, as when the corrosion eventually makes the metal thin, it will probably be time for a new tubeless wheelset upgrade...Unless I get brave and try some alumnium welding / brazing...

[Mecnic]

Apparently Stans has released an ECO Version, I suppose this is ammonia free but will have to check

[Weight Weenie]

Apparently Stans has released an ECO Version, I suppose this is ammonia free but will have to check

 

It does say 'non-corrosive' on the bottle

[Mecnic]

It does say 'non-corrosive' on the bottle

 

 

Maybe Stans knows about this problem.

 

Who knows maybe, Stans like Asbestos, was at the time, a good idea and they didn't quite know what exactly it all does like eating rims and destroying the enviornment.