Define corrosion?
Or better yet post a picture of what you are seeing?
You do realize it's highly recommended to flush the radiators before putting them into service anyway, but there are various levels of corrosion some being actual dried left over flushing liquid that dried that Koolance did before shipping, (which is usually white).
Green corrosion however could be bad and left over from acid based solder flux in the manufacturing process, that can usually be cleaned out with a white vinegar flush?
Corrosion that is actually pitting the metal is extremely bad, but I don't see how that could be happening if the rads are new?
So what exactly are you seeing?