|   White corrosion spots on '96 polished alum frame. Cause? | Mr Magoo
Jan 16, 2002 12:16 PM | | I started riding my old hardtail for snow rides. 'Been using the new FS since April. Actually felt good. Still dialed. The bike was stored on hooks in the rafters of the 'rustic' garage. I noticed white splotches all over the frame. Like salt. Looks like it can be polished off. Oxydation? The alum equiv. of rust? Any compromise to structural integrity? |
| Oxidation | BH
Jan 16, 2002 12:24 PM | | Yes, its corrosion. If the corrosion is only on the surface it should be OK. Deep corrosion will reduce the structural integrity of the frame. Just lightly polish them out and put a good coat of wax over the whole frame and store it inside, if you can. |
| re: White corrosion spots on '96 polished alum frame. Cause? | The Notorious R.O.B.
Jan 16, 2002 2:50 PM | | It is called "uniform etch" or "pitting" corrosion. It is a product of the electrochemical corrosion cell. The electrochemical corrosion cell consists of 3 parts. A "Cathode" (steel bolts or any other dissimilar metal parts on the bike), an "Anode" (the weaker metal; ie: your frame), the "metal path" (bike frame) and an electrolyte (moisture, dew, condensation, etc...) Because the steel bolts and what not are made of a more "noble" metal, hydroxyl ions are actually removed from the Anodic, or weaker metal (frame) and are carried through the electrolyte and deposited on the Cathode (steel parts). In essence, your frame's Aluminum is slowly being "eaten away" by the corrosion process....Any pits deeper than , say, .010" (ten-thousanths of an inch)should be looked at more seriously, especially if the frame's covered with them. Start with "0000" (four-ought) stainless steel wool, available at any hardware store, and a GOOD metal polish, such as Mother's mag and aluminum polish, and start rubbing. Don't worry, the wool is only rough enough to remove the corrosion deposits, and after the corrosion is gone, you can just keep polishing by hand with the polish alone. Touch-up the shine once in a while with the polish. And remember, a highly polished metal surface resists corrosion better.---Hope it helps.
I hope we've all learned something here...Class dismissed!
The notorious R.O.B.
12 yr. Aircraft Structural Repair Craftsman, U.S. Air Force
and
3 yr. Bike shop mechanic. |
| SHOW OFF!! :-) (nm) | Squash
Jan 16, 2002 5:07 PM | | |
| BFD!!! | Wwwwaspinatuh
Jan 16, 2002 5:14 PM | | |
| re: BFD!!! | Raid
Jan 17, 2002 9:50 PM | | It's "BVD", and if you'd pull your head out, you'd see more than those three letters.
Hope this helps! |
| Well said. Should I bolt zinc plates on? Cool science. | Mr Magoo
Jan 16, 2002 7:30 PM | | Sounds like yachting speak. We bolted zinc collars to the shafts and zinc plates to the rudders. Further, I did a cathode/anode demo in seawater for my sons science project. I think the key in my case is ambient moisture in that garage. I've been meaning to put a cupola on top. Yes, the stuff buffs away with Mothers mag wheel polish on a rag. Thanks for placing the electrolysis effect on (not so) dry land.
Mr Magoo
24 year accountant and controller
30 year yacht yard assistant and sailboat racer |
| Just the man I want to talk to! | Noah
Jan 16, 2002 11:07 PM | | I'm right now polishing my old IBOC. I got all the paint off, and I've been sanding/steel wooling it down to shinyness. I was going to buff it tomorrow and see how it looks, then probably clear coat it. Am I sanding/wooling my frame down to nothing? It's already quite thick aluminum and I'm not too worried about it. how should I coat it to make sure it stays pretty after I've buffed it? Thanks.
Noah |
| agree.. | Hammerheadbikes
Jan 17, 2002 6:42 AM | | I do the same, start with 0000 steel wool to "clean it up" and then polish it out with Mothers...
0000 steel wool is the finest and it won't hurt the metal
I have used it to polish guitar frets for years....
Charles
Hammerheadbikes |
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