What's the matte finish on a Cinelli 1E stem?
I got one of these, and while the matte silver finish is OK, it doesn't say "aluminum alloy" to me. So, doing a bit of alu refinishing work, I dunked it into some Drano wherein a seatpost was having its clear anodized finish cooked off. Virtually nothing happened, except that the submerged part got a tiny bit foggy after about 10 minutes (meanwhile, the seatpost was done). So, I rubbed it with a bit of the wet-or-dry sandpaper I was using to refinish the seatpost; again, virtually nothing happened -- but it is some sort of coating, because it finally started to rub off on the sharper arrises around the bar openings. Is it a paint? I guess I'll break out the methylene chloride paint stripper next.
It's anodizing, but tough anodizing. Drain cleaner is not going to do it. You need to buy proper anodizing remover to get that stuff off.
The later Cinelli stems use a very thick type of anodizing and are usually poorly finished underneath. They take a lot of work to make look nice.