A nasty surprise. Corrosion of bars.

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Mike Sales
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A nasty surprise. Corrosion of bars.

Postby Mike Sales » 3 Jul 2015, 10:16am

I have just got round to replacing the bar tape on my utility bike. It has been on for years and was getting to be a disgrace.

I uncovered extensive corrosion in the TTT bars under the tape. There is a lot of white powder and flaking of the metal. There is expansion of the bar. It looks unsafe, but I have not done more than a superficial inspection.

I guess this is electrolysis, perhaps caused by the dynamo which is electrically connected to the frame, I think. The tape is Ambrosio Ribbon, which I suppose could have held moisture.

I would like to clean up the mess to assess the damage. What substance will help shift the powder, which is quite solid in places? I expect cleaning will confirm the need to replace.

I have never seen anything quite as bad as this. I would welcome comments.

beardy
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Re: A nasty surprise. Corrosion of bars.

Postby beardy » 3 Jul 2015, 10:55am

Dont blame the dynamo, it happens on bikes without them.

I took the tape off some twenty five year old bars and found the same. Heading for thirty five years old now. :D

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Mick F
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Re: A nasty surprise. Corrosion of bars.

Postby Mick F » 3 Jul 2015, 10:59am

I had the tape off one side of mine a couple of weeks ago. They were as good as new underneath.
Cinelli 64 bought in 1986.

I have no real idea why 'bars should corrode, it must be something to do with the anodising - or lack of it.
Mick F. Cornwall

beardy
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Re: A nasty surprise. Corrosion of bars.

Postby beardy » 3 Jul 2015, 11:00am

I would expect that it is rain and sweat getting through the bar tape. Then being held there.

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NUKe
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Re: A nasty surprise. Corrosion of bars.

Postby NUKe » 3 Jul 2015, 11:14am

try a plastic pan scourer should remove the loose stuff. if its still not satifactory try wet and dry paper in a fine grade.
NUKe
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Mick F
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Re: A nasty surprise. Corrosion of bars.

Postby Mick F » 3 Jul 2015, 11:16am

Trouble is, it will happen again.
If you clean them off with abrasives, any anodising will go. It'll just be bare alu with sticky tape over it.
Mick F. Cornwall

beardy
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Re: A nasty surprise. Corrosion of bars.

Postby beardy » 3 Jul 2015, 11:23am

I think that they were just bare aluminium with bar tape over it in the first place.

Brucey
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Re: A nasty surprise. Corrosion of bars.

Postby Brucey » 3 Jul 2015, 11:30am

I hold with the 'sweat hypothesis'. It could be that rainwater + adhesive + crevice can cause corrosion too. I also think that corrosion is worst on aluminium bars that are not anodised, but I've occasionally seen it on anodised bars too. Once it starts, it carries on, even if the bike is 'dry stored'. [I pulled one set of bars out of a bone dry shed and the bar tape had warty bumps all over because of the corrosion beneath... :shock: ]

If you can get one of those small (suede brush size) stainless steel brushes that will shift the white powdery stuff which is mostly aluminium oxide. If you use a (weakly) acidic treatment (eg jenolite) on the corroded areas, then rinse well, that should passivate them such that unless water is added, little further corrosion should occur.

However if there is any doubt about the integrity of the bars you should really replace them; if they break at the wrong time, it can cause a nasty accident.

Because I have seen bar corrosion so often, I now routinely apply a base layer of tape (eg parcel tape) to the bars in order to prevent such corrosion. Since I've done that I've seen little if any such corrosion occur, even on bars that live outdoors.

On bars with a reinforced centre sleeve, I think it is worthwhile using tape to seal the join so that water cannot get in the gap so easily.

On bikes that do a lot of miles, removing all the tape and inspecting the bars ought (ideally) to be done every year.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

mercalia
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Re: A nasty surprise. Corrosion of bars.

Postby mercalia » 3 Jul 2015, 11:40am

Acid rain?

Mike Sales
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Re: A nasty surprise. Corrosion of bars.

Postby Mike Sales » 3 Jul 2015, 11:44am

I have retaped many pairs of bars professionally. I have seen corrosion, but I don't think I have ever seen anything near as bad as these.

Mike Sales
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Re: A nasty surprise. Corrosion of bars.

Postby Mike Sales » 3 Jul 2015, 3:12pm

Thanks for your thought, all.

LWaB
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Re: A nasty surprise. Corrosion of bars.

Postby LWaB » 3 Jul 2015, 7:23pm

Several years ago, when I was a bike shop mechanic in Oz, I replaced the padded plastic tape (with perforations along the centreline of the tape) on a set of Cinelli bars. The rider's sweat had encouraged corrosion at the base of the perforations. Salty water, unprotected aluminium and oxygen isn't a good mix. I could push a spoke completely through the handlebars! The bars got replaced at the same time as the tape.

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georgew
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Re: A nasty surprise. Corrosion of bars.

Postby georgew » 4 Jul 2015, 8:43am

Brucey wrote:Because I have seen bar corrosion so often, I now routinely apply a base layer of tape (eg parcel tape) to the bars in order to prevent such corrosion. Since I've done that I've seen little if any such corrosion occur, even on bars that live outdoors.

On bars with a reinforced centre sleeve, I think it is worthwhile using tape to seal the join so that water cannot get in the gap so easily.

On bikes that do a lot of miles, removing all the tape and inspecting the bars ought (ideally) to be done every year.

cheers


I do think that this is a good idea. The Tow ball of my car continually rusted until I completely covered it with Duct tap. Now all that's needed is a squirt of WD40 to remove the adhesive before use.