does aluminium rust?

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i've scratch my aluminum frame.
is it going to rust?
what paint shall i use to make it good?
thanks.
:confused:

Originally posted by fabs
i've scratch my aluminum frame.
is it going to rust?
what paint shall i use to make it good?
thanks.
:confused:

Aluminum can oxidize (rust) and as such it's usually annodizide or protected in some fashion. I honestly cannot saywhat the affect would be over the long term but a littletouch up paint to protect the area can't hurt. Look at an old Aluminum Car Wheel Rim or Barbecue and the white powdery substance you may see is oxidized aluminum.


my 2 Cents :)

Snarl is very much correct. I will oxidize if not protected. This is not to say it will ever be a problem of "rusting" like steel. If you keep it clean it will not be a problem. One of my bikes has a polished swingarm and it has never been an issue, as far as oxidation goes. It is not a problem for your bike. Have fun riding it.

K.

Probably not an issue - my old Trek Y22 MTB has a polished aluminum swingarm on the back. While it is clearcoated to keep that nice polished finish, it also has numerous scratches in the clearcoat, from the chain, trail junk, etc... No corrosion is evident.

Any aluminium exposed to air will oxidise (rust) within seconds.

however unlike steel its not a problem because aluminium oxide is the second hardest substance on earth (only diamonds are harder) and the microscopically thin layer of oxide protects the aluminium underneath from further corrosion.

Even polished aluminium has the thin layer of oxide

bottom line, it doesn't matter if you scratch the paint on an aluminium frame

So, hypothetically speaking... is it better to get an unpainted aluminum frame then?

Originally posted by BaCardi
So, hypothetically speaking... is it better to get an unpainted aluminum frame then?

Well .. Yes,and no.
It will be protected from further oxidation, but it won't be as attractive as paint or anodizing.
:)

Thanks all. Very intersting info.
fabs.

On the subject of aluminium frames - what kind of riding life do they have? Does anyone have any experience of their alloy frames going 'soft'. My road racing frame is 3 seasons old now but still feels responsive.

Also, is respraying aluminium OK? Are there any issues surrounding the temperature?

Wouldn't be too concerned with the aluminum rusting, however your brake cable housing ferrules definitely will rust, and can damage the painted surfaces of the frame where the ferrules are held in place on the bike. (real-life Cannondale experience).