Hydrogen Embrittlement on a Classic Frameset
Guys, I may need some help with my paranoia...
I'm really wanting to purchase a new, classic, Cinelli Supercorsa frameset, but I've always been wary of the chroming process.
In fact, way back in 1983, I purchased a Gios Super Record frameset with one of the key considerations being there was NO chrome on it (and I loved the fact it came in its own, ultra-protective, styrofoam case!).
Meanwhile, I've always wanted a Supercorsa, but the potential corrosion issue because of the extensive chroming on the frame has kept me away.
In short, I'm aware of the required clean-up/follow-up process after the plating, to prevent the embrittlement issue, but have always been afraid that procedure would not be executed properly - especially when you consider how hard it is to rinse and drain areas such as the fork ends, etc.
In fact, I wonder if the process is done with any care at all, as the pressure to keep costs down seem to encourage half-assing steps such as this - especially when they are 'hidden'.
Anyway, I just wanted to get some opinions and see if I'm being too anal about the whole corrosion issue, or not...
The Gimlet Eye
Originally Posted by Jimbolina
I have framesets in my garage that date back to the 1960's that are either fully or partially chromed.
There is no corrosion on any of theose.
You are assuming that a company that has been employing a well-understood industrial process for generations, on both a mass-production and hand-craft scale, producing expensive products that it knows consumers will expect to use for many years, is going to do it wrong to save a couple of bucks, and thereby increase the likelihood of premature failure of its products. That does not sound like a reasonable fear to me.
I agree with the previous posts. Cinelli has been turning out chrome Supercorsas by the thousands for years, and know how to clean the frames and bake them to prevent hydrogen embrittlement. Your concerns are unfounded IMHO.
Or you could just get a nice new carbon fiber bike that'll just explode anyway!
buy the Cinelli Supercorsa, build it, ride it. Shouldn't have to think too much about it.
Unless they outsourced production. Then expect exactly that.
Originally Posted by JCavilia
The issue you are referring to is Hydrogen Charging, which is caused by the disassociation of hydrogen during the plating process. This is a particular issue in the high strength steels (>160ksi) which are typically used as fasteners (and are routinely plated). The failure mechanism is brittle which, in bolts, can occur suddenly hours or days after final torquing. In other words, three things are necessary for Hydrogen Embrittlement 1) Hydrogen, 2) Susceptible Microstructure, and 3) Tensile Stress.
1. Hydrogen is present in plating processes. So that little guy is going to be there unless they did a post plating bake (discussed later)
2. Susceptible microstructures are those that contain features which hydrogen can permeate more rapidly and affect more strongly. In plain carbon and alloy steels this is generally the residual austenite and martensite boundaries. High strength steels are particularly susceptible to hydrogen embrittlement because Martensite (and its precursor, austenite) are abundant.
3. Tensile stress. Depending on the welding method, there may be some residual tensile stresses in the regions which are plated. If tensile stresses exceed some value (which is generally pretty low) cracks can develop at room temperature leading to failure of the weldment without warning.
Now, as it pertains to bicycle frames...
-First, what tubing is this frame? If it is one of the very high strength frames (essentially a form of Chrome Moly Steel), it COULD have some martensite in the weld regions which may be susceptible to hydrogen embrittlement.
-Residual stresses are likely very low due to the geometry of bicycle frame tubing.
Also, hydrogen can be completely eliminated from the microstructure by baking the parts at 3-400 degrees F for 4-24 hours (depending the alloy/process). Is this frame powder coated or painted? If powder coated, i would expect the baking process to eliminate much of the Hydrogen as a side benefit.
All in all, I think its a very low risk that you see your bicycle frame fall to pieces from Hydrogen Embrittlement. While some of the newer 400 series stanless steels may be susceptible, i do not believe the prevailing tensile stresses to be high enough to allow cracks to propagate. Furthermore, my metallurgist side would expect any plating shop who is plating carbon steel parts to bake the parts when completed, as a matter of course (especially if they knew they could posses strengths in excess of 160ksi). a 400 degree bake is cheap insurance.
Hope this helps some.
"Late to bed, early to rise, work like hell and advertise." -Von Braun
Excellent responses, guys!
The frame should be fine, unless you are fat. If you're over 180, you might want to look at a more modern oversized tubeset. (unless you plan to just ride easy)
If your opinion differs from mine, ..........Too bad.
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