Corrosion in Aluminium Frames

[mrjemm]

Took a BB out of my MTB this week... water came out. It was red with (I assume) rust. This being an Al frame, I am going on the assumption the rust came from the BB, which feels a little rough, so got a new one. Will need to check for corrosion inside though I guess. Being the frame I naively had powder-coated (before I knew about the baking potentially causing tempering questions, as per another thread some time ago), I am perhaps damned anyway...

Am another that uses white (I believe) teflon based grease for general use, and not copper, but I think some other anti seize grease (Park brand?) on threaded applications.

[Valbrona]

Copper anti-seize assembly grease is much of a muchness. I just happen to use the Finish Line stuff.

[Brucey]

Copper anti-seize assembly grease is much of a muchness. I just happen to use the Finish Line stuff.

I'm sure that the finish line stuff is OK but you can't assume it is all the same otherwise. The copper solids content varies from less than 5% to over 40%, the thickener type can vary, and some have graphite in and others don't. I think you can buy inferior anti-seize, just like you can buy inferior anything else. At its worst a 'copper grease' could be a soap-thickened grease (that actually promotes corrosion and seizure between some metals) with a little bit of copper in it.

A good budget choice IMHO is Comma and my favourite is the Rocol stuff.

cheers

[bod]

I had a Cannondale that rotted from the inside of the seat tube. It was a bit weird as there was no damage and nothing in contact with that part of the tube. Shame, it was a nice bike.
matt

[Valbrona]

Took a BB out of my MTB this week... water came out. It was red with (I assume) rust. This being an Al frame, I am going on the assumption the rust came from the BB, which feels a little rough, so got a new one. Will need to check for corrosion inside though I guess. Being the frame I naively had powder-coated (before I knew about the baking potentially causing tempering questions, as per another thread some time ago), I am perhaps damned anyway....

Water can get down a seat tube through the smallest gap by capillary action. I routinely use a thin, sprayable anti-seize compound on seat posts (Loctite), but in your scenario I would perhaps try a smear of anti-seize grease. With grease you can get slippage, which can result in the user over-torqueing the binder bolt ... so be careful.

And depending of what type of BB we are talking, you can get protective sleeves.

Plenty of steel frames have a drain hole in the BB shell, as I am sure you know.

[Brucey]

I had a Cannondale that rotted from the inside of the seat tube. It was a bit weird as there was no damage and nothing in contact with that part of the tube. Shame, it was a nice bike.
matt

out of interest, what model was it? How old was it/what use had it had? DId it have mudguards?

cheers

[bod]

Hi Brucey,
It was a F800 from about 1999. It had mudguards for half it's life but it did quite a bit mileage, maybe 100k?
Matt

[Brucey]

I guess it could have been road salt inside the seat tube; a little may have got in there and just humidity inside the tube would then be enough to cause the corrosion to nibble away at the tubing from then on.

Mind you if you got 100K out of it that isn't a bad life, and I'm not saying that a steel frame would have done any better if it was salt inside the frame that caused the rotting; it'd have to be a really good corrosion proofing agent to resist that.

cheers

[breakwellmz]

Does anyone use Aluminium Graphite grease?

[ChrisButch]

For many years I've used Shimano's own-brand assembly compound. This is white in colour, but I've no idea what its metal base is. Anybody know?

[JohnW]

I always just used the same grease for everything that needed greasing on my bike. So is the consensus to use special anti-seize grease for seatposts, threads etc. ?

Assembly greases have a different function from lubricating greases.

For assembly grease - and that's on everything, threads et al I use Millers Oils "BLACK MOLY MILLERGREASE D180". I've used it for over 25 years. I started using it when I learned that the fire brigade use it for assembling their water-pumps and all permanently underwater tackle.

Since I started using it, I've never had anything seize - seat-posts, stems, BB threads........nothing - and for 15 of those years I had a work bike that did 20 miles a day in all weathers without fail - you know how it is, frost, rain, snow, salt......everything that winter could throw at it - and never actually overhauled nor serviced it except where safety was an issue and to liberally apply oil - how I abused that faithful old friend, and yet, when it came to removing years of crud and finally stripping it down, it came apart like a dream. Nothing had seized. I rebuilt it, and it then got nicked from the cellar at work.

Previously, for - well - 40 years-ish - I'd always used the same grease that I used for lubricating, and if I didn't reassemble and re-grease from time to time, I did have problems - especially with BB cups. Most things were steel in those days, but alloy seat-posts in steel frames did have to be watched........and taken out and re-greased occasionally. The same with handlebar stems.

Currently, for bearings, I'm using "Weldtide Cycle grease with Teflon" - it's quite a rich red colour. We don't grease bottom bracket bearings any more - they're sealed and lubricated for their life. I find the stuff very satisfactory, and I only clean and re-grease wheel bearings when the rim needs replacing - about 10,000 miles with current rims.

I've been recommended, and actually bought but not yet used, some "FINISH LINE Teflon Grease" - which is white and the information on the tube seems to suggest that it's the best thing that the world has ever known for greasing bearings and for use in assembling threads, posts etc.

Comments on the experience of users requested.............

I have known just one cycling colleague have trouble with assembly (or rather dis-assembly) when he'd use copper-slip. That was in his bottom bracket - alloy cups (it was a modern-ish type sealed unit) in a steel frame. It set solid - I saw it. I've no idea why. We did get it out, but it took two of us and we put so much leverage in that I was afraid of twisting the frame. All was well though, including the threads in the frame, but the threads on the alloy cups had corroded almost away. The BB cartridge was up for replacement anyway.