# Help! Corrosion on Aluminum frame...



## Puzman (Apr 1, 2004)

I have a Yeti 575, Raw finish, that's about 5 yrs old, and has some corrosion on the frame (see photos). It's no longer under warranty, so I'm trying to figure out what to do. As I see it, options are:

1) leave it alone
2) try to remove it and then protect the frame from further corrosion.

What would y'all do? Any ideas on how to get rid of this? I'd like to do this relatively painlessly and inexpensively if possible...


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## Zoke2 (Nov 16, 2007)

This should do the trick


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## Puzman (Apr 1, 2004)

tried it, doesn't work


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## nemhed (May 2, 2010)

It looks to me like it is corroding underneath a clear-coat. Which might explain why it won't polish away. I've seen similar corrosion on clear coated aluminum motorcycle parts and aluminum car wheels. If that's the case the clear-coat would need to be completely removed in order to get rid of the corrosion, then you would have to choose between leaving it truly "raw" and maintaining that or repainting/powdercoating. As always, JMHO, YRMV:thumbsup: .


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## Puzman (Apr 1, 2004)

OK, how do you get rid of clear coat, and then how do you get rid of corrosion? The best suggestion I've seen by googling was to sand with fine-grit emery paper soaked in mineral spirits.


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## nemhed (May 2, 2010)

Puzman said:


> OK, how do you get rid of clear coat, and then how do you get rid of corrosion? The best suggestion I've seen by googling was to sand with fine-grit emery paper soaked in mineral spirits.


Well, this all depends on how much of a project you want to make of this. You could use a small wire wheel on a Dremel tool to remove the clear-coat and corrosion in just the affected areas then reapply a clear coat. You could also experiment with various grits to try to match the brushed finish on the rest of the frame. You could also use a chemical stripper on the whole frame, clean up the corrosion, then refinish or leave raw. I don't know what alloy your frame is but some are much more prone to corrosion than others. In your photo the bolt heads also appear to be rusting, maybe the result of salt spray?


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## farrisw1 (Jul 22, 2009)

Are the bolts aluminum also? If they are of a different alloy than the frame maybe your experiencing some type of dissimilar metal corrosion around the heads....


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## nemhed (May 2, 2010)

farrisw1 said:


> Are the bolts aluminum also? If they are of a different alloy than the frame maybe your experiencing some type of dissimilar metal corrosion around the heads....


Good point. I'm guessing those bolts are chrome plated steel. Now would be a great time to clean and lube everything and replace the bolts with stainless hardware.


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## g34343greg (Dec 16, 2010)

paint stripper will take the clear off with ease.

the engine cases on my 73 Honda motorcycle were polished and cleared over, but the clearcoat had yellowed over time. i stripped it all of, then sanded with progressively finer grits of sandpaper and then started polishing. it shines like chrome now, but you really need to keep after it. you can always spray some more clear on once you have it where you want it. it will haze up pretty quickly if exposed to moisture.


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## Psycho Mike (Apr 2, 2006)

Aluminum corrosion is an aesthetic thing...thankfully it generally self-inhibits other than the surficial. Might look bad, but at least it's not like rusted steel where you don't know how far it has gone into the metal.

Once you get the clear coat off, it shouldn't take much elbow grease and a little Mother's to get it shiny again. Biggest thing will be protecting it again...clearcoats can be tricky to match as not all of them are really "clear."


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## playdead (Apr 17, 2009)

put some "tefgel" on the fasteners.


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## Darkstar187 (Sep 6, 2010)

If it were me.. i would take the bike apart and just have it blasted and powdercoated. if you like the raw look and good powdercoating place can clean up the frame and re clear coat it.


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## GFAthens (Sep 10, 2009)

Darkstar187 said:


> If it were me.. i would take the bike apart and just have it blasted and powdercoated. if you like the raw look and good powdercoating place can clean up the frame and re clear coat it.


+1 on that. If you're the really handy sort, you mmay be able to get the clearcoat and everything looking perfect, but I can't imagine myself being able to get things back to 100% Aesthetically, which is important since this is really just an aesthetic issue.


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## accutrax (Mar 22, 2008)

reminds me on my good old gt zaskar le (polished ali frame..)....got some corrosion around the BB from saltspray..at first it did not look to serious..but some time later there was no way anymore to stop it ..tried everything, metalpolish, sandpaper, sandblasting, covering with thick grease...
best way for me would be , as mentioned before, sandblasting and powdercoating....


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## ThreeD (Feb 7, 2008)

Darkstar187 said:


> If it were me.. i would take the bike apart and just have it blasted and powdercoated. if you like the raw look and good powdercoating place can clean up the frame and re clear coat it.


I agree. It may be more than what you want to spend but.....
If I had the choice and really liked the bike I would spend the extra $$ and get it sand blasted. They do it with baking soda now and won't hurt the frame material. The positive side is you get to choose whatever color you want for the frame. It'll look like a brand new bike. A big plus is you'll know it was completely cleaned of any corrosion.


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## manabiker (Jul 18, 2010)

I have plenty of experience with automotive wheels with the same problem.
I would disassemble, wear a mask/rubber gloves, use Oven Cleaner to remove coating, then deal with the corrosion, you could sand or polish, then paint or clearcoat, or polish every year to keep shine, the fasteners are metal, metal, and aluminum together create oxidaiton, and make nuts, and bolts in that area impossible to unfasten, use antiseize when reassembling. Good Luck


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## danbo (Oct 16, 2005)

Had the same thing on my 575, but a I broke the frame before it was that bad. I scraped it off and made sure I could remove the bolts to service the shock and bearings.


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## Philius413 (Apr 22, 2010)

When I was researching the best way to strip my frame & go raw, all the literature I found & the metal experts & bike builders I talked to stated that aluminum, unlike steel, actually hardens as it oxidizes. So you shouldn't have any issues with it weakening. That being said, you should still replace &/or grease the bolts so they don't seize up. But unless you just don't like the look of it, you don't need to spend a ton having it powder coated--the spotting shouldn't jeopardize the strength or rigidity of the frame, but actually do the opposite.


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## Philius413 (Apr 22, 2010)

I forgot to comment on the "corrosion" in the pics. I think you'll find that is mostly the clear coat making it look like it is corroding (except the bolts, which should probably be replaced), but once you strip it with a good spray on (if you decide to go that route), the aluminum underneath will be just fine.


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## sean salach (Sep 15, 2007)

If it's oxidation, and it hardens, wont that make it more brittle?

If you're storing the bike near pool chemicals, or any other chems that could give off corrosive vapors, stop doing so.

http://www.keytometals.com/Article14.htm

.


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## JSD303 (Jun 15, 2006)

As pointed out in the Yeti thread by eatdrinkride - this thread and the pics seem to be carbon copy of this earlier thread:

http://forums.mtbr.com/showthread.php?t=141784&highlight=raw+corrosion

Coincidence?


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## nemhed (May 2, 2010)

JSD303 said:


> As pointed out in the Yeti thread by eatdrinkride - this thread and the pics seem to be carbon copy of this earlier thread:
> 
> http://forums.mtbr.com/showthread.php?t=141784&highlight=raw+corrosion
> 
> Coincidence?


Good catch! Is someone playing games?


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## Puzman (Apr 1, 2004)

Pics are identical- not playing games, just too lazy to take pictures of my own bike , which has the same corrosion problem as in the previous thread


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## frehgv (Dec 1, 2010)

I always thought that corrosion was a bright red or orange colour am i right or wrong


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## Blurr (Dec 7, 2009)

Does Aluminum Rust?

Aluminum is actually very prone to corrosion. However, aluminum corrosion is aluminum oxide, a very hard material that actually protects the aluminum from further corrosion. Aluminum oxide corrosion also looks a lot more like aluminum, so it isn't as easy to notice as rusted iron.


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## MTBeing (Jan 11, 2012)

That looks to be a finish corrosion, not a material one. 


Sent from my mountain bike while crashing


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## beerrun (Jul 31, 2007)

I live near an ocean, really close, and my bike does that same thing although as mentioned above, purely cosmetic, nothing to worry about when you're screaming downhill. Save your pennies for a new Yeti, and keep the old one clean at least.


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## 426h (Jul 13, 2006)

nemhed said:


> Good point. I'm guessing those bolts are chrome plated steel. Now would be a great time to clean and lube everything and replace the bolts with stainless hardware.


That is exactly what you should *not* do. Your frame will be a sacrificial anode.
Galvanic corrosion - Wikipedia, the free encyclopedia


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## Yeti_Rider (Dec 26, 2003)

frehgv said:


> I always thought that corrosion was a bright red or orange colour am i right or wrong


corrosion and oxidation are sort of similar things.

Rust is bright red or orange.

steel rusts.

rust is a form of corrosion.

most metals corrode.

aluminum corrodes, or more specifically oxidized. it's a surface oxidation and doesn't penetrate the base metal very much at all. But, the oxidization is very strong.

anodizing is "colored" oxidation for aluminum. you actually intentionally oxidize the part to protect it. aluminum sailboat masts are anodized for protection against the salt water.

the problem with rust on a ferrous (iron) part is that it penetrates the metal and will continue to cause damage if it is simply covered or painted over.


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## Guerdonian (Sep 4, 2008)

426h said:


> That is exactly what you should *not* do. Your frame will be a sacrificial anode.
> Galvanic corrosion - Wikipedia, the free encyclopedia


I worked at a sub-sea engineering firm where I actually had to calculate the degredation of Aluminum Structures that were left in the ocean for decades. A bicycle frame will fatigue and crack LONG before it become compromised from galvanic corrosion.

As mentioned many times already this is a purely aesthetic issue. Scratches, rivets, welds, crevices, etc.. provide focal points for the "corrosion" to start. If you banged the frame from a wrench, scratched it from a fall, etc.. and are exposed to lots of salty mist, or moist air, then the first place that oxidation will show is the scratch exposing the raw metal. Thus I am going to +1 on the "under the clear coat" argument, of some slight oxidization.

Edit: The type of Aluminum corrosion that was a concern (tested in salt spray chambers) looked like a crystal grow kit i had as a kid. Fatigue related to heat treat and weld penetration is a MUCH bigger concern for Aluminum than oxidization.


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## apsteve (Sep 11, 2012)

Hi all,

We got a bike in for paint stripping which we have done but the seat receiver tube looks like swiss cheese. I know this wasn't caused by our paint stripper as it doesn't attack aluminum. I'm pretty sure I'll need an explanation when I call the customer to pick up his frame. Can anyone explain what is going on here?


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## spsoon (Jul 28, 2008)

Classic bike termite damage.


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## Zanetti (Sep 18, 2005)

apsteve said:


> Hi all,
> 
> We got a bike in for paint stripping which we have done but the seat receiver tube looks like swiss cheese. I know this wasn't caused by our paint stripper as it doesn't attack aluminum. I'm pretty sure I'll need an explanation when I call the customer to pick up his frame. Can anyone explain what is going on here?


Seat tube was/is corroded from the inside. Most likely cause is water ingress from the seat post clamp area.


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## jmmUT (Sep 15, 2008)

apsteve said:


> Hi all,
> 
> We got a bike in for paint stripping which we have done but the seat receiver tube looks like swiss cheese. I know this wasn't caused by our paint stripper as it doesn't attack aluminum. I'm pretty sure I'll need an explanation when I call the customer to pick up his frame. Can anyone explain what is going on here?
> 
> ]


That frame is doomed and should be considered unrideable. Being aluminum, it's not realistically repairable either.


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## stingray4540 (Jun 25, 2009)

OP: looks minimal. 
As has been explained, not all corrosion is bad. In fact when steel gets a "patina" dark gray corrosion, it actually helps protect from the more damaging orange(rust) corrosion. Even if steel gets a surface rust(orange) it won't hurt too much damage if you sand it down and oil it to stop the corrosion process.

Anyways, easiest/cheapest fix for you right now is to take it apart, and sand/steel wool the parts down until you remove the corrosion/oxidization(only the parts in question). Then hit it with some mineral oil. Fresh water bath and mineral oil wipedown after every ride and you will be fine. Or if you want to spend the money, strip it, rub out the oxidization, and re- clearcoat it.
You could also just replace that bolt instead of trying to clean it up.

Honestly though, it's going to take a LONG time before any of that threatens the integrity of your bike, you could probably just leave it and keep an eye on it that it doesn't get a lot worse real fast...


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## nemhed (May 2, 2010)

apsteve said:


> Hi all,
> 
> We got a bike in for paint stripping which we have done but the seat receiver tube looks like swiss cheese. I know this wasn't caused by our paint stripper as it doesn't attack aluminum. I'm pretty sure I'll need an explanation when I call the customer to pick up his frame. Can anyone explain what is going on here?


That brings to mind inter-granular corrosion I've seen on certain types of aircraft aluminum. I have no idea if this is ever an issue with the aluminum alloys typically used in bike frames. I also have no clue why it would be localized in the middle of the seat tube like that.


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## modifier (May 11, 2007)

426h said:


> That is exactly what you should *not* do. Your frame will be a sacrificial anode.
> Galvanic corrosion - Wikipedia, the free encyclopedia


So you are saying that stainless steel causes galvanic corrosion worse than chromed bolts? I find that hard to believe. Any dissimilar metals or even carbon fiber will cause a small electrical current.

If it were my frame I would chemically strip the frame, wash well, polish it out with Scotchbrite pads or what ever you choose, then maybe wax it with car wax and just keep it clean. I have several bare aluminum frames and as long as you keep ahead of it corrosion is not a problem. Buy new bolts too and grease them.


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## Tone's (Nov 12, 2011)

farrisw1 said:


> Are the bolts aluminum also? If they are of a different alloy than the frame maybe your experiencing some type of dissimilar metal corrosion around the heads....


mate, youve nailed it in one, thats exactly whats happening, they are steel bolts poorly plated, they are having a reaction to the alloy helped along by the conditions the bike has been exposed to., these bolts need to be replaced, yeti has dropped the ball and used these steel bolts to save money, you can even see where the plating has gone n they are rusting.
Alloy hates to be butted up with most other metals and will cause the alloy to start corroding in time, if you have an alloy boat and you have ever put a steel bolt though it you will know exactly what i mean.
you will need to replace these bolts with stainless bolts, this is yetis fault n its very poor form on their behalf, i would have thought a company that makes such great bikes would not have made this fundamental error, cheers


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## spsoon (Jul 28, 2008)

modifier said:


> So you are saying that stainless steel causes galvanic corrosion worse than chromed bolts? I find that hard to believe. Any dissimilar metals or even carbon fiber will cause a small electrical current.
> 
> If it were my frame I would chemically strip the frame, wash well, polish it out with Scotchbrite pads or what ever you choose, then maybe wax it with car wax and just keep it clean. I have several bare aluminum frames and as long as you keep ahead of it corrosion is not a problem. Buy new bolts too and grease them.





Tone's L'axeman said:


> mate, youve nailed it in one, thats exactly whats happening, they are steel bolts poorly plated, they are having a reaction to the alloy helped along by the conditions the bike has been exposed to., these bolts need to be replaced, yeti has dropped the ball and used these steel bolts to save money, you can even see where the plating has gone n they are rusting.
> Alloy hates to be butted up with most other metals and will cause the alloy to start corroding in time, if you have an alloy boat and you have ever put a steel bolt though it you will know exactly what i mean.
> you will need to replace these bolts with stainless bolts, this is yetis fault n its very poor form on their behalf, i would have thought a company that makes such great bikes would not have made this fundamental error, cheers


Just want to point out this thread is over a year and a half old


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## Tone's (Nov 12, 2011)

LOL, Oh well, better late than never they say


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## Mountain Cycle Shawn (Jan 19, 2004)

manabiker said:


> use Oven Cleaner to remove coating


Go soak your aluminum frame in, "Oven Cleaner" and let us know how that turns out!


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## modifier (May 11, 2007)

Mountain Cycle Shawn said:


> Go soak your aluminum frame in, "Oven Cleaner" and let us know how that turns out!


I've heard that oven cleaner is a way to clean anodizing off of aluminum. But I have also head you have to watch it and not leave it on too long. Some kind of paint stripper should... er...strip the paint. aka clearcoat.


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## Mountain Cycle Shawn (Jan 19, 2004)

modifier said:


> I've heard that oven cleaner is a way to clean anodizing off of aluminum. But I have also head you have to watch it and not leave it on too long. Some kind of paint stripper should... er...strip the paint. aka clearcoat.


Putting oven cleaner on an aluminum frame for any reason, is way beyond stupid. Paint stripper will strip paint, powder and clear. Wet sanding will take care of ano.


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## Mountain Cycle Shawn (Jan 19, 2004)

apsteve said:


> Hi all,
> 
> We got a bike in for paint stripping which we have done but the seat receiver tube looks like swiss cheese. I know this wasn't caused by our paint stripper as it doesn't attack aluminum. I'm pretty sure I'll need an explanation when I call the customer to pick up his frame. Can anyone explain what is going on here?
> 
> View attachment 723218


Someone at some point used oven cleaner.


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## thegooddoctor (May 16, 2012)

If you do go the route of taking it apart, removing the existing clear (chemical, blasting ...whatever) and re clear coating you will need to pull out the bearings and then mask the areas where press fits and dimensional allowances will be problematic before re-coating with clear coat. You could leave the bearings in and pull and replace them after clear coating but this sounds like it would be hard to do without trashing your new clear coat.


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## Mountain Cycle Shawn (Jan 19, 2004)

I wouldn't clear coat it again. If you want a durable, easy to take care of finish, I would strip it and give it a professional brushed finish. It would be easy to take care of and less damaging to the frame


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