As has been posted here a few times (search is your friend), Ruger failed to treat the SS frames (and other parts) by chemical passivation methods for wayyy too long. They relied on mechanical passivation, i.e., media blasting, which is known to be inferior for most stainless alloys.
In the latter method especially, free ferrites (iron) open to the surface will oxidize and begin to show visible corrosion, which is obviously not quality nor value to the end customers. Actually, a good cleaning and wipe-down with quality oil like G96 or MR7 will all-but remove the spots and will prevent any "rapid" re-rusting of the remaining surface ferrite. But no one intended to pay good money for rust, right?
Ruger knew better and gambled with quality in favor of margin. I understand the RCCA went all the way to the top. I have yet to read that for myself.
Chemical passivation is normal & customary in their manufacturing world and cheap to process, except that it takes a few minutes to run material in batches. They simply chose to skip it.
Standard answer again - Send 'em back for correction on their dime. Everyone of them.
