Andy's brother John has a master's in Metalurgical engineering and "is in every sense of the word an expert in materials, and corrosion" accroding to Andy.
Bummer about your rollerski - I saw the wreckage on Nordic Ski Racer. But, wasn't that a fairly old failure?
If I may add my own to cents:
The failure was consistent with tensile overload on the bottom off the rollerski. Given the manner in which these skies are worn I would expect the bottom side of the ski to be in tension. The crack appears to have propagated from the bottom of the ski toward the top. The ski appears to be made out of aluminum, therefore, I would not expect environmental attack to be an issue (unless of course you found super alkaline caustic solution to leave the skies in). If I had to guess, based on the two pictures that I saw.
I would suppose that you had dinged the ski several times on the bottom going over little bumps here and there. These dings led to an incipient crack or stress concentrator from which a crack grew due to the cyclical loading associated with the skiing motion. The crack eventually grew to reach a length critical for the load being applied and you were left with a broken ski. Recommendations:
Have fun, John