tough stuff
Even if you get resistant hardware, may I suggest you give 'em a shot of spray paint?
There are some really fantastic products on the market, these days.
Alternately, a dab of grease on the threads 'n heads might stave off that old brown powder.
Yes, it'll collect dust 'n bugs...
We had a member a while back who runs a hardware supply business.
He offered to set us up with some sort of super-fantastic
metal-coating treatment that should withstand anything short of Armageddon.
You might find him by searching the FTA (and subforums).
I don't recall the coating, but it was something he did for hardware he supplied to... Edmund Scientific....??
If I remember, he would send the parts out for a passivation, coating, or treatment.
Not sure if it was zinc chromate or something more exotic,
but it was bonded to the metal, not some temporary paint or grease.
As a last resort, if you can determine the
finish you want on your hardware, you might search the internet for hardware supply stores with that key word.
I know we have some industrial supply stores around Los Angeles, and I'm sure you could find some around your nearest large city.