aluminum oxide coating?

[jorrow]

Ive found these knuckle cases with good numbers that have some sort of thick oxide coating that have been applied to them. It is silver in color and has the feel of heavy course paint overspray or corrosion, but it is not. Ive been hesitant to try to blast it off less it be harmful to the aluminum. and paint stripper bothers me too. This stuff is really tough not like paint at all...it fills in much of the case numbers but they are still legible...it is sprayed on the case hardware as well ...anybody have any ideas what has gone on here? Jeff

[Rubone]

They sound like they are aluminum metal sprayed, a coating I saw often in the late'60s, early '70s on heads and cylinders. It is a molten metal process done with a torch and pressurized metal particles. Not sure how to remove it though!
Hopefully someone here can help.
Robbie