Second picture looks like casting slag, possibly. The first one appears to be on a machined surface. That is odd-can it be scraped off? Is that a new part?
It is certainly material from the casting process. I'm just surprised at the amount of it. I'd think that would cause some kind of disturbance in the flow of the coolant.
Wire brush and brake clean wouldn't get it. I was able to use a piece of scrap metal and scarp of whatever it was. It appears it was used to cover/fill pitting.
This is a new housing just received from Mancini today.