Paint peeling on Alu frame

[PdeB]

Hi all

Has any of you seen this on an aluminium mtb frame? It's right where the seat post goes into the frame.

The frame is only a few years old (2019) and has not been exposed to hazardous conditions. Other than for this, the frame is in an excellent condition. My LBS says I should approach the manufacturer (which I've done), to ask if this is covered by warranty, but if not, I shouldn't worry about it too much.

I do not want to mention the bike brand at this stage as I don't want to jeopardise any potential warranty claim I may have. 

Thanks

[Barry]

26 minutes ago, PdeB said:

Hi all

Has any of you seen this on an aluminium mtb frame? It's right where the seat post goes into the frame.

The frame is only a few years old (2019) and has not been exposed to hazardous conditions. Other than for this, the frame is in an excellent condition. My LBS says I should approach the manufacturer (which I've done), to ask if this is covered by warranty, but if not, I shouldn't worry about it too much.

I do not want to mention the bike brand at this stage as I don't want to jeopardise any potential warranty claim I may have. 

Thanks

Looks like galvanic corrosion . If it is a carbon frame or seat post then it could be a reaction between the carbon and aluminum. Carbon assembly paste would have limited the effects of the reaction.

Edited October 28, 2022 by Barry

[PdeB]

10 minutes ago, Barry said:

Looks like galvanic corrosion . If it is a carbon frame or seat post then it could be a reaction between the carbon and aluminum. Carbon assembly paste would have limited the effects of the reaction.

Both the frame and the seat post are aluminium.

[Barry]

2 minutes ago, PdeB said:

Both the frame and the seat post are aluminium.

What started as a small paint chip could have allowed moisture to get under the paint and it started corrosion. Hi pressure wash can force water and detergent under the paint and if not rinsed off can react with the aluminum. 

[Barry]

The white powdery stuff in the pic is defiantly corrosion. Same as the red color that you would get from steel when rust starts.

[RiverInTheRoad]

It looks like a manufacturing defect. Should be covered under warranty IMO. 

[PdeB]

5 minutes ago, Barry said:

What started as a small paint chip could have allowed moisture to get under the paint and it started corrosion. Hi pressure wash can force water and detergent under the paint and if not rinsed off can react with the aluminum. 

I've had the bike since new and I don't use a high pressure washer or detergent when I wash my bike. I use a normal hose and a damp cloth.

From my understanding (a bit of googling) aluminium does not normally corrode unless it's exposed to salt. 

Surely it is not normal for an aluminium frame which is kept clean and indoors to corrode after only a few years, or am I mistaken?

[Ispeed_V]

Could be as a result of overtightening the seat post clamp?

Nothing a bit of black nail polish cant fix.

[Barry]

1 minute ago, PdeB said:

I've had the bike since new and I don't use a high pressure washer or detergent when I wash my bike. I use a normal hose and a damp cloth.

From my understanding (a bit of googling) aluminium does not normally corrode unless it's exposed to salt. 

Surely it is not normal for an aluminium frame which is kept clean and indoors to corrode after only a few years, or am I mistaken?

Salt and some detergents may cause corrosion.  But if you haven't used anything then tough to explain.

Maybe wait for the manufacturer could well be a factory fault and you score a new frame.

 

[Barry]

Galvanic corrosion is not limited to carbon on aluminum.  It will happen when any dissimilar metals are in contact with each other.  6061 and 7075 could react.

[PdeB]

8 minutes ago, Barry said:

Salt and some detergents may cause corrosion.  But if you haven't used anything then tough to explain.

Maybe wait for the manufacturer could well be a factory fault and you score a new frame.

 

Thank you very much for your insights.

[PdeB]

5 minutes ago, Barry said:

Galvanic corrosion is not limited to carbon on aluminum.  It will happen when any dissimilar metals are in contact with each other.  6061 and 7075 could react.

Noted, although I would hope that the manufacturer would know this and would not mismatch metals when building a bike. The seat post is the original one the bike came out with.

I will wait and see what the manufacturer says. 

[Barry]

As for salt it would be interesting to see if other hubbers can pinpoint salt as a cause of corrosion. The sweat from your body falls on your bike. I have seen it on a bike stem the bike lived on an indoor trainer. 

Edited October 28, 2022 by Barry

[Eldron]

That looks like good old fashioned corrosion caused by poor coating. All the little bumps in the paint around the visible corrosion are spots where the alu is oxidising under the paint.

Do you live near the coast? Salt is terrible for alu.

It is only a surface problem though - a sand blast and respray should sort it out.

[PdeB]

Hi all

Just thought I's give you an update. My warranty claim was approved, although I still don't know exactly why. I guess it is, as most of you suggested, corrosion.

I'm now awaiting a replacement frame. I just hope the replacement is the same colour so it matches my fork.

Thanks for your insights.

[Headshot]

Good to hear.  My Spesh frame also developed similar localized corrosion in the vicinity of the forward shock mount. No damage to frame in that area and very obviously a coating defect. I just peeled off the loose paint, cleaned it and left it unpainted (luckily its not visible unless you try hard)