I have a 7 year old (already???) Giant road frame made from 6061-T6 aluminium alloy. It has recently developed some small white patches (the bike has a silver finish) up to 4-5mm in diameter on the front of the head tube. I've not crashed the bike, but it has done a lot of miles[1], including some racing and triathlon.
I want to know if this discoloration is just some surface/cosmetic issue or if it is a sign that it is going to fail and make me fall on my face.
Can anyone shed some light on this?
Cheers, Ritch
[1] The frame, stem, handlebars and seatpost are all that is left of the original bike...
It sounds as if the protective finish on the front of the head tube has been chipped in those places where you are seeing the white patches. By your description there is either a layer of anodizing or clear coat over the polished aluminum.
Clean off the white powder which is oxidation. Polish it best you can by hand where you see the pitting. Immediately, clean it with something to remove any oil and grease, then spray a clear coat of acrylic over the spots.
If the pitting isn't too bad that should be all you have to do. If the pitting at these sights is too deep then take it to a bike shop and have them tell you what you should do.
It sounds as if the protective finish on the front of the head tube has been chipped in those places where you are seeing the white patches. By your description there is either a layer of anodizing or clear coat over the polished aluminum.
More likely the latter, and it's quite possible that the oxidation is under the clearcoat, spreading out from small chips in th coating.
Quoted message said:
Clean off the white powder which is oxidation.
To remove oxidation from aluminum, use ammonia solution. If the oxidation in under clearcoat, then the coating must be removed in that area.
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I have a 7 year old (already???) Giant road frame made from 6061-T6 aluminium alloy. It has recently developed some small white patches (the bike has a silver finish) up to 4-5mm in diameter on the front of the head tube. I've not crashed the bike, but it has done a lot of miles[1], including some racing and triathlon.
I want to know if this discoloration is just some surface/cosmetic issue or if it is a sign that it is going to fail and make me fall on my face.
Just a bit of surface oxidation. It happens particularly badly if they use salt on the roads where you live. You can keep polishing it off or have the frame refinished.
