The method of protection of NCP uses Fluoride vs Chromate. Chromate, especially Cr6+ has been proven to have nasty side effects. While Fluoride ions are NOT heavy metals and thus allows them to advertise as "no chrome or other hazardous heavy metals", you may want to read an MSDS sheet and search the internet about Fluorosis and what it can do to you...really BAD for your bones and irreversible.
As a Metallurgist & Chemical Engineer who has worked on aerospace coating development projects I would MUCH rather deal with chromates than with Fluoride.
Chromates can be nasty, but they require long term, repeated exposure. Much of the hype about them is just that, hype. I have had my clothing soaked by chromic acid plating solution, had plating solution splashed into my mouth, had open sores get solution in them - I am not only still here but have never had any effects of heavy metal toxicity. No, I wouldn't recommend playing with them but the reality is very far from the boogie-man that hex chrome has been made out to be.
We had painters who regularly got blood tests because they were always sanding on primed cadmium plating that had a chromate conversion coating (and the primer had chromate, too). Invariably, if their heavy metal levels got too high it was the cadmium that forced them to retire from painting and find another occupation (usually became inspectors with all of those years of experience) not the chrome.
Now fluoride, especially in an acidic solution, THAT scares the jeepers out of me. I had to work with those solutions at my plating gig, too, but I was VERY, VERY, VERY careful with them. Sulfuric/Hydrofluoric Acid activating baths were used on both the chrome and nickel plating lines. We RESPECTED those tanks and the horrors they contained.
Heck, we had (alkaline) cyanide solutions, too. No big deal there provided that you didn't wear gold jewelry while on that line and NEVER put acid into the bath. The klaxons for the cyanide gas detection system were loud enough to wake the dead.
As to protecting aluminum from corrosion without using chromates, there are a lot of ways to skin that cat. But that's for another topic.
