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SR Sakae Handlebar Corrosion Failure 35+ Years

SR Sakae Modolo handlebar; 2018 picture, handlebar probably from 1990:

[handlebar.SR-Modolo.failhb8a.jpg]   [handlebar.SR-Modolo.failhb8b.jpg]  
Photos courtesey of Yellow Jersey.

Damage was discovered when unwrapping handlebar tape; large amounts of white aluminum oxide fell off. Photos show a tool placed through the largest of several holes caused by corrosion through the handlebar.

Damage was discovered during maintenance. Rider was not injured.

Service history is unknown.

Not-corroded areas show the handlebar is a dark color, which may be anodizing or paint. Such layers can resist corrosion, but minor surface damage is common -- including scratches during installation of brake levers, etc., as well the bike falling over, etc.

Further, once a protective layer is damaged, it might trap corrosive elements and speed up corrosion.

Corrosion can be sped up by environmental conditions including high humidity and/or salt exposure, which is common both near oceans and in places that salt the streets in winter. Further, sweat is salty and thus corrosive, so riders who frequently sweat a lot also report corrosion of assorted bike parts, even in regions that are dry and otherwise far from salt.

The corroded area of the handlebars includes an area where riders often place their hands. Thus, using gloves may reduce this kind of corrosion. However, note the brake in one picture has several steel fasteners that are corroded. The brake is newer than the handlebars, so has had less time to corrode. The bicycle shown here is not otherwise visibly corroded.

Aluminum alloys vary greatly in resistance to corrosion. Unfortunately, it is hard to make an alloy which is both high-strength and highly corrosion-resistance. At the same time, a typical reason to use a high-strength aluminum is to build lighter handlebars with thinner walls. Thinner walls mean a given degree of corrosion hurts handlebar strength more than the same corrosion on a thick wall.

The following table shows some alloys and some trade-offs between them

alloy formability weldability machining corrosion resistance heat treating strength
1100 excellent excellent good excellent no low
2011 good poor excellent poor yes high
2024 good poor fair poor yes high
3003 excellent excellent good good no medium
5052 good good fair excellent no medium
6061 good good good excellent yes medium
6063 good good fair good yes medium
7075 poor poor fair average yes high

From [] as of 2018/06.

For example, the 2011 and 2024 alloys are high strength but have poor corrosion resistance. 7075 alloy raises corrosion resistance to "average" (which might still be worse than "good"), but is not very formable so may be a poor choice for handlebars.

Note also that "corrosion resistance" depends on more than just the alloy, and so is a complicated issue. Corrosion depends on humidity, chemical exposure (e.g., salt, acid, etc.), other kinds of metals nearby, how heavily the structure is loaded, and other factors. That said, the table does suggest some of the challenges in making a handlebar that is both light and durable.

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