Falanx

I'll never understand the fascination with chromium plating steel. It's a corrosion nightmare, and while when perfect, it increases the fatigue life of a component just as any surface hardening treatment would, it's too frequently imperfect to warrant performing.

Right, to address a number of metallurgical considerations;

Hydrogen embrittlement - while it is true to say that the plating process releases hydrogen, and the temperatures involved encourage diffusion of hydrogen into the substrate where it collects over time at grain boundaries in the typical hydrogen embrittlement phenomenon in steels, all reputable plating shops perform a hydrogen bake-out as the final thermochemical step in the process to eliminate this deleterious behaviour.

It is not true to say that all steels suffer from hydrogen embrittlement when plated in an acid bath, nor do those that do suffer, to the same extent, but in essentially all cases, the substrate will be damaged. The diffusivity of hydrogen into a steel is based upon its crystal structure, and the degree of embrittlement on the (usually) inverse relationship between strength and remaining ductility in the substrate.

For reference, the bakeout needs to progress at no more than 250 degrees celsius, much less than 400 degrees, unless the figures you quote are in farenheit.

Heat Treatment - no presently used heat-treated/thermophilic/whatever you want to call it steel for bicycle frames is tempered or aged at 200-250 degrees celsius. That's spring-temper range, and as such, the steel would have unnacceptably low elongation to failure figures. They aren't tempered at just above that value either, as the 300 degree celsius area is also know as the temper embrittlement or blue brittleness zone, associated with the decomposition of martensite to free carbide and ferrite.

There is no technical reason why chromium plating of Reynolds 853 without associated hydrogen embrittlement or damage to the careful heat-treatent isn't practical and practicable when you approach it with sound materials science. What I'm more concerned about is the deleterious effect such a cathodic layer would have on the corrosion performance of the steel when compromised.