Overdue update!

[Niels V]

Sadly I can not give you definite answer to those answers to that, eg. not sure if its cast or forged.
actually this the wiki article not to bad https://en.wikipedia.org/wiki/Hydrogen_embrittlement and its also worth maybe checking out the references.

[Andrew Rowe]

And he only wanted to clean the parts...........!

[Niels V]

Yes there are always pro and cons to any treatment process.
For something like engine parts I personally would lean towards, water polishing or dry ice blasting, as these would leave a minimum of residue.

I am not sure about how the production process or materials of the Flathead crankshaft, something like case hardened journals could be susceptible hydrogen embrittlement.

Sadly I cannot ask my professor in surface treatment and material science any more.

[Lynn Eades]

The process of re chroming or indeed chrome plating can cause hydrogen embrittlement. Any process that increases hydrogen at the surface of a metal weakens the metal and can lead to premature failure. The process of increasing nitrogen at the surface toughen the metal (nitriding) I think hydrogen embrittlement can happen to a range of "ordinary" steels which would include a cast steel crank.