http://www.micromy.com/eng/micronite.htm
Won't increase the strength of the overall material, just the surface.
You will never get a CAST crank to the overall strength level of a forged or billet unit.
Corrosion isn't an issue with most Automotive engines.......... unless antifreeze is intoduced.
Basic high school chemistry.
Along the lines like nitriding or hard chroming. Haven't had it done in years but it used to cost $500.00 to hard chrome. Then add the price of the crank.
But personally Synthetic oil with coated bearings would be cheaper and do an equivilant job?