Well I have been doing some research and I also have some first hand experience with hard chrome. I was none too impressed with Armoloy. I had S&W revolvers in .357 Mag, .41 Mag, and .44 Mag I hated the cleaning process I had to go through after shooting and thought hard chroming would help so I had em all Armoloyed. But the vapor honing that Armoloy does just gives grime a place to hold on to. If I didnt clean every tiny crevice it would rust (not bad though) and any where it wore due to friction it would self polish bright spots. I am no fan of revolvers or Armoloy and I sold em all. I even sold the nickle plated 686 because I didnt like the bright shiny nickle even though it never rusted.
As for chrome there is 3 types. There is thin film coating. This is whats done on top of nickle to help get rid of nickles yellowish cast and does not help much at all. Then there is a "flake chrome" like whats used in chrome lined pistons. The surface looks like the desert (cracked and flaky) and is designed to hold oil well but is not good at resisting corrosion. This is the type that wont stop corrosion you cited. Finally there is a 100 hour salt spray even thick coated hard chrome. This is what I want to use.
My idea is this... I am going to hard chrome EVERYTHING in my upper and lower recievers. Bolt/carrier, trigger group, mag release assembly, bolt catch assembly, and an ambi safety. This will make it more corrosion resistant than the raw steel as well as giving it less friction. Then I will coat in a Teflon or Moly based finish to make it all black again, make it impervious to corrosion and add lubricating qualities to make it quick to clean up. The parts that rub together will eventually be the only parts that have exposed hard chrome. This will be better than the normally exposed steel after the parkerizing wears away since its more corrosion resistant and slicker. The rest of the parts will be maintenance free (not need to be protected to stop rust) and I can use a minimum of non-particulate accumulating lube on the parts that rub together to stop the buildup of carbon and dust thus improving reliablity.
As far as the chrome lined bolt carrier wearing out the upper reciever after the Teflon/Moly finish has worn away, I will have a moly dry lube on the upper reciever to help slow this and even if it does wear it out its not an expensive part and it wont wear out before my barrel so I will just get a new upper reciever when it time to replace my barrel so its a non issue to me.
What do you guys think? I know its expensive but my preban is only half way built up and I already have over $2000 in her. I expect it to go past the $4000 mark by the time I am done. I just have one simple goal... To creat the ultimate AR. Cost be damned!